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  1. ARM - AMIE Gan Island - Data Plots

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Gan Related Links amie.png 34h AMIE Home cindy.png 50h CINDY2011 dynamo.png 34h DYNAMO ARM Data Discovery Browse Data Outreach News & Press Blog Backgrounder (PDF, 1.2MB) Education Flyer (PDF, 2.0MB) Images ARM flickr site Official AMIE Logo AMIE Gear Experiment Planning Steering Committee AMIE-MANUS Proposal Abstract AMIE-GAN Proposal Abstract Meetings Cloud Life Cycle Working Group Deployment Operations Science Plan - TWP Manus Site (PDF, 2.1 MB) Science Plan - Gan Island Site (PDF, 2.0

  2. ARM - News from the Gan Island Deployment

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    News from the Gan Island Deployment Related Links amie.png 34h AMIE Home cindy.png 50h CINDY2011 dynamo.png 34h DYNAMO ARM Data Discovery Browse Data Outreach News & Press Blog Backgrounder (PDF, 1.2MB) Education Flyer (PDF, 2.0MB) Images ARM flickr site Official AMIE Logo AMIE Gear Experiment Planning Steering Committee AMIE-MANUS Proposal Abstract AMIE-GAN Proposal Abstract Meetings Cloud Life Cycle Working Group Deployment Operations Science Plan - TWP Manus Site (PDF, 2.1 MB) Science

  3. ARM - Field Campaign - AMIE-Gan Ancillary Disdrometer

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    govCampaignsAMIE-Gan Ancillary Disdrometer Campaign Links Field Campaign Report ARM Data Discovery Browse Data Related Campaigns ARM MJO Investigation Experiment on Gan Island 2011.10.01, Long, AMF Comments? We would love to hear from you! Send us a note below or call us at 1-888-ARM-DATA. Send Campaign : AMIE-Gan Ancillary Disdrometer 2012.01.01 - 2012.02.10 Lead Scientist : Mariko Oue For data sets, see below. Abstract As part of the AMIE-Gan campaign, an ancillary disdrometer for comparison

  4. GaN: Defect and Device Issues

    SciTech Connect (OSTI)

    Pearton, S.J.; Ren, F.; Shul, R.J.; Zolper, J.C.

    1998-11-09

    The role of extended and point defects, and key impurities such as C, O and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

  5. ARM MJO Investigation Experiment on Gan Island (AMIE-Gan) Science Plan

    SciTech Connect (OSTI)

    Long, CL; Del Genio, A; Deng, M; Fu, X; Gustafson, W; Houze, R; Jakob, C; Jensen, M; Johnson, R; Liu, X; Luke, E; May, P; McFarlane, S; Minnis, P; Schumacher, C; Vogelmann, A; Wang, Y; Webster, P; Xie, S; Zhang, C

    2011-04-11

    The overarching campaign, which includes the ARM Mobile Facility 2 (AMF2) deployment in conjunction with the Dynamics of the Madden-Julian Oscillation (DYNAMO) and the Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011) campaigns, is designed to test several current hypotheses regarding the mechanisms responsible for Madden-Julian Oscillation (MJO) initiation and propagation in the Indian Ocean area. The synergy between the proposed AMF2 deployment with DYNAMO/CINDY2011, and the corresponding funded experiment on Manus, combine for an overarching ARM MJO Investigation Experiment (AMIE) with two components: AMF2 on Gan Island in the Indian Ocean (AMIE-Gan), where the MJO initiates and starts its eastward propagation; and the ARM Manus site (AMIE-Manus), which is in the general area where the MJO usually starts to weaken in climate models. AMIE-Gan will provide measurements of particular interest to Atmospheric System Research (ASR) researchers relevant to improving the representation of MJO initiation in climate models. The framework of DYNAMO/CINDY2011 includes two proposed island-based sites and two ship-based locations forming a square pattern with sonde profiles and scanning precipitation and cloud radars at both island and ship sites. These data will be used to produce a Variational Analysis data set coinciding with the one produced for AMIE-Manus. The synergy between AMIE-Manus and AMIE-Gan will allow studies of the initiation, propagation, and evolution of the convective cloud population within the framework of the MJO. As with AMIE-Manus, AMIE-Gan/DYNAMO also includes a significant modeling component geared toward improving the representation of MJO initiation and propagation in climate and forecast models. This campaign involves the deployment of the second, marine-capable, AMF; all of the included measurement systems; and especially the scanning and vertically pointing radars. The campaign will include sonde

  6. Ge doped GaN with controllable high carrier concentration for...

    Office of Scientific and Technical Information (OSTI)

    Ge doped GaN with controllable high carrier concentration for plasmonic applications Citation Details In-Document Search Title: Ge doped GaN with controllable high carrier...

  7. High Voltage GaN Schottky Rectifiers

    SciTech Connect (OSTI)

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  8. Conductivity based on selective etch for GaN devices and applications thereof

    DOE Patents [OSTI]

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

    This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

  9. Highly transparent ammonothermal bulk GaN substrates

    SciTech Connect (OSTI)

    Jiang, WK; Ehrentraut, D; Downey, BC; Kamber, DS; Pakalapati, RT; Do Yoo, H; D'Evelyn, MP

    2014-10-01

    A novel apparatus has been employed to grow ammonothermal (0001) gallium nitride (GaN) with diameters up to 2 in The crystals have been characterized by x-ray diffraction rocking-curve (XRC) analysis, optical and scanning electron microscopy (SEM), cathodoluminescence (CL), and optical spectroscopy. High crystallinity GaN with FWHM values about 20-50 arcsec and dislocation densities below 1 x 10(5) cm(-2) have been obtained. High optical transmission was achieved with an optical absorption coefficient below 1 cm(-1) at a wavelength of 450 nm. (C) 2014 Elsevier B.V. All rights reserved.

  10. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect (OSTI)

    Jeganathan, K. E-mail: jagan@physics.bdu.ac.in; Purushothaman, V.; Debnath, R.; Arumugam, S.

    2014-05-15

    We report an intrinsic ferromagnetism in vertical aligned GaN nanowires (NW) fabricated by molecular beam epitaxy without any external catalyst. The magnetization saturates at ?0.75 emu/gm with the applied field of 3000 Oe for the NWs grown under the low-Gallium flux of 2.4 10{sup ?8} mbar. Despite a drop in saturation magnetization, narrow hysteresis loop remains intact regardless of Gallium flux. Magnetization in vertical standing GaN NWs is consistent with the spectral analysis of low-temperature photoluminescence pertaining to Ga-vacancies associated structural defects at the nanoscale.

  11. Properties of H, O and C in GaN

    SciTech Connect (OSTI)

    Pearton, S.J.; Abernathy, C.R.; Lee, J.W.

    1996-04-01

    The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at {ge} 450 C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until > 800 C, and its diffusivity is relatively high ({approximately} 10{sup {minus}11} cm{sup 2}/s) even at low temperatures (< 200 C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30--40 meV. It is essentially immobile up to 1,100 C. Carbon can produce low p-type levels (3 {times} 10{sup 17} cm{sup {minus}3}) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

  12. Refractive index of erbium doped GaN thin films

    SciTech Connect (OSTI)

    Alajlouni, S.; Sun, Z. Y.; Li, J.; Lin, J. Y.; Jiang, H. X.; Zavada, J. M.

    2014-08-25

    GaN is an excellent host for erbium (Er) to provide optical emission in the technologically important as well as eye-safe 1540 nm wavelength window. Er doped GaN (GaN:Er) epilayers were synthesized on c-plane sapphire substrates using metal organic chemical vapor deposition. By employing a pulsed growth scheme, the crystalline quality of GaN:Er epilayers was significantly improved over those obtained by conventional growth method of continuous flow of reaction precursors. X-ray diffraction rocking curve linewidths of less than 300 arc sec were achieved for the GaN (0002) diffraction peak, which is comparable to the typical results of undoped high quality GaN epilayers and represents a major improvement over previously reported results for GaN:Er. Spectroscopic ellipsometry was used to determine the refractive index of the GaN:Er epilayers in the 1540 nm wavelength window and a linear dependence on Er concentration was found. The observed refractive index increase with Er incorporation and the improved crystalline quality of the GaN:Er epilayers indicate that low loss GaN:Er optical waveguiding structures are feasible.

  13. Structural defects in GaN revealed by Transmission Electron Microscopy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Liliental-Weber, Zuzanna

    2014-09-08

    This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Lastly, some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

  14. Structural defects in GaN revealed by Transmission Electron Microscopy

    SciTech Connect (OSTI)

    Liliental-Weber, Zuzanna

    2014-04-18

    This paper reviews the various types of structural defects observed by Transmission Electron Microscopy in GaN heteroepitaxial layers grown on foreign substrates and homoepitaxial layers grown on bulk GaN substrates. The structural perfection of these layers is compared to the platelet self-standing crystals grown by High Nitrogen Pressure Solution. Defects in undoped and Mg doped GaN are discussed. Some models explaining the formation of inversion domains in heavily Mg doped layers that are possible defects responsible for the difficulties of p-doping in GaN are also reviewed.

  15. This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

    DOE Patents [OSTI]

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

    This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

  16. Growth and Band Offsets of Epitaxial Lanthanide Oxides on GaN...

    Office of Scientific and Technical Information (OSTI)

    M.T.T., 60 (6) (2012) 3 Jon Ihlefeld, Sandia National Laboratories Electronic Materials ... Undoped GaN Undoped AlGaN Doped AlGaN 2D Electron Gas Enhancement Mode (nominally ...

  17. Dislocation confinement in the growth of Na flux GaN on metalorganic...

    Office of Scientific and Technical Information (OSTI)

    Dislocation confinement in the growth of Na flux GaN on metalorganic chemical vapor deposition-GaN Citation Details In-Document Search Title: Dislocation confinement in the growth ...

  18. Low temperature thin film transistors with hollow cathode plasma-assisted atomic layer deposition based GaN channels

    SciTech Connect (OSTI)

    Bolat, S. E-mail: aokyay@ee.bilkent.edu.tr; Tekcan, B.; Ozgit-Akgun, C.; Biyikli, N.; Okyay, A. K. E-mail: aokyay@ee.bilkent.edu.tr

    2014-06-16

    We report GaN thin film transistors (TFT) with a thermal budget below 250?C. GaN thin films are grown at 200?C by hollow cathode plasma-assisted atomic layer deposition (HCPA-ALD). HCPA-ALD-based GaN thin films are found to have a polycrystalline wurtzite structure with an average crystallite size of 9.3?nm. TFTs with bottom gate configuration are fabricated with HCPA-ALD grown GaN channel layers. Fabricated TFTs exhibit n-type field effect characteristics. N-channel GaN TFTs demonstrated on-to-off ratios (I{sub ON}/I{sub OFF}) of 10{sup 3} and sub-threshold swing of 3.3?V/decade. The entire TFT device fabrication process temperature is below 250?C, which is the lowest process temperature reported for GaN based transistors, so far.

  19. Hybrid device based on GaN nanoneedles and MEH-PPV/PEDOT:PSS polymer

    SciTech Connect (OSTI)

    Shin, Min Jeong; Gwon, Dong-Oh; Lee, Chan-Mi; Lee, Gang Seok; Jeon, In-Jun; Ahn, Hyung Soo; Yi, Sam Nyung; Ha, Dong Han

    2015-08-15

    Highlights: • A hybrid device was demonstrated by using MEH-PPV, PEDOT:PSS, and GaN nanoneedles. • I–V curve of the hybrid device showed its rectification behaviour, similar to a diode. • EL peak originated by the different potential barriers at MEH-PPV and GaN interface. - Abstract: A hybrid device that combines the properties of organic and inorganic semiconductors was fabricated and studied. It incorporated poly[2-methoxy-5-(2-ethylhexyloxy)- 1,4-phenylenevinylene] (MEH-PPV) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as organic polymers and GaN nanoneedles as an inorganic semiconductor. Layers of the two polymers were spin coated on to the GaN nanoneedles. The one peak in the electroluminescence spectrum originated from the MEH-PPV layer owing to the different potential barriers of electrons and holes at its interface with the GaN nanoneedles. However, the photoluminescence spectrum showed peaks due to both GaN nanoneedles and MEH-PPV. Such hybrid structures, suitably developed, might be able to improve the efficiency of optoelectronic devices.

  20. Intrinsic polarization control in rectangular GaN nanowire lasers

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Li, Changyi; Liu, Sheng; Luk, Ting S.; Figiel, Jeffrey J.; Brener, Igal; Brueck, S. R. J.; Wang, George T.

    2016-02-01

    In this study, we demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444kW/cm2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control overmore » the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.« less

  1. High active nitrogen flux growth of GaN by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    McSkimming, Brian M. Speck, James S.; Chaix, Catherine

    2015-09-15

    In the present study, the authors report on a modified Riber radio frequency (RF) nitrogen plasma source that provides active nitrogen fluxes more than 30 times higher than those commonly used for plasma assisted molecular beam epitaxy (PAMBE) growth of gallium nitride (GaN) and thus a significantly higher growth rate than has been previously reported. GaN films were grown using N{sub 2} gas flow rates between 5 and 25 sccm while varying the plasma source's RF forward power from 200 to 600 W. The highest growth rate, and therefore the highest active nitrogen flux, achieved was ∼7.6 μm/h. For optimized growth conditions, the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 × 3 μm) on the order of 1 nm. Secondary ion mass spectroscopy impurity analysis demonstrates oxygen and hydrogen incorporation of 1 × 10{sup 16} and ∼5 × 10{sup 17}, respectively. In addition, the authors have achieved PAMBE growth of GaN at a substrate temperature more than 150 °C greater than our standard Ga rich GaN growth regime and ∼100 °C greater than any previously reported PAMBE growth of GaN. This growth temperature corresponds to GaN decomposition in vacuum of more than 20 nm/min; a regime previously unattainable with conventional nitrogen plasma sources. Arrhenius analysis of the decomposition rate shows that samples with a flux ratio below stoichiometry have an activation energy greater than decomposition of GaN in vacuum while samples grown at or above stoichiometry have decreased activation energy. The activation energy of decomposition for GaN in vacuum was previously determined to be ∼3.1 eV. For a Ga/N flux ratio of ∼1.5, this activation energy was found to be ∼2.8 eV, while for a Ga/N flux ratio of ∼0.5, it was found to be ∼7.9 eV.

  2. GaN Initiative for Grid Applications (GIGA)

    SciTech Connect (OSTI)

    Turner, George

    2015-07-03

    For nearly 4 ½ years, MIT Lincoln Laboratory (MIT/LL) led a very successful, DoE-funded team effort to develop GaN-on-Si materials and devices, targeting high-voltage (>1 kV), high-power, cost-effective electronics for grid applications. This effort, called the GaN Initiative for Grid Applications (GIGA) program, was initially made up of MIT/LL, the MIT campus group of Prof. Tomas Palacios (MIT), and the industrial partner M/A Com Technology Solutions (MTS). Later in the program a 4th team member was added (IQE MA) to provide commercial-scale GaN-on-Si epitaxial materials. A basic premise of the GIGA program was that power electronics, for ubiquitous utilization -even for grid applications - should be closer in cost structure to more conventional Si-based power electronics. For a number of reasons, more established GaN-on-SiC or even SiC-based power electronics are not likely to reach theses cost structures, even in higher manufacturing volumes. An additional premise of the GIGA program was that the technical focus would be on materials and devices suitable for operating at voltages > 1 kV, even though there is also significant commercial interest in developing lower voltage (< 1 kV), cost effective GaN-on-Si devices for higher volume applications, like consumer products. Remarkable technical progress was made during the course of this program. Advances in materials included the growth of high-quality, crack-free epitaxial GaN layers on large-diameter Si substrates with thicknesses up to ~5 μm, overcoming significant challenges in lattice mismatch and thermal expansion differences between Si and GaN in the actual epitaxial growth process. Such thick epilayers are crucial for high voltage operation of lateral geometry devices such as Schottky barrier (SB) diodes and high electron mobility transistors (HEMTs). New “Normally-Off” device architectures were demonstrated – for safe operation of power electronics circuits. The trade-offs between lateral and

  3. Nanostructural engineering of nitride nucleation layers for GaN substrate dislocation reduction.

    SciTech Connect (OSTI)

    Koleske, Daniel David; Lee, Stephen Roger; Lemp, Thomas Kerr; Coltrin, Michael Elliott; Cross, Karen Charlene; Thaler, Gerald

    2009-07-01

    With no lattice matched substrate available, sapphire continues as the substrate of choice for GaN growth, because of its reasonable cost and the extensive prior experience using it as a substrate for GaN. Surprisingly, the high dislocation density does not appear to limit UV and blue LED light intensity. However, dislocations may limit green LED light intensity and LED lifetime, especially as LEDs are pushed to higher current density for high end solid state lighting sources. To improve the performance for these higher current density LEDs, simple growth-enabled reductions in dislocation density would be highly prized. GaN nucleation layers (NLs) are not commonly thought of as an application of nano-structural engineering; yet, these layers evolve during the growth process to produce self-assembled, nanometer-scale structures. Continued growth on these nuclei ultimately leads to a fully coalesced film, and we show in this research program that their initial density is correlated to the GaN dislocation density. In this 18 month program, we developed MOCVD growth methods to reduce GaN dislocation densities on sapphire from 5 x 10{sup 8} cm{sup -2} using our standard delay recovery growth technique to 1 x 10{sup 8} cm{sup -2} using an ultra-low nucleation density technique. For this research, we firmly established a correlation between the GaN nucleation thickness, the resulting nucleation density after annealing, and dislocation density of full GaN films grown on these nucleation layers. We developed methods to reduce the nuclei density while still maintaining the ability to fully coalesce the GaN films. Ways were sought to improve the GaN nuclei orientation by improving the sapphire surface smoothness by annealing prior to the NL growth. Methods to eliminate the formation of additional nuclei once the majority of GaN nuclei were developed using a silicon nitride treatment prior to the deposition of the nucleation layer. Nucleation layer thickness was determined

  4. Synthesis, morphology and optical properties of GaN and AlGaN semiconductor nanostructures

    SciTech Connect (OSTI)

    Kuppulingam, B. Singh, Shubra Baskar, K.

    2014-04-24

    Hexagonal Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) nanoparticles were synthesized by sol-gel method using Ethylene Diamine Tetra Acetic acid (EDTA) complex route. Powder X-ray diffraction (PXRD) analysis confirms the hexagonal wurtzite structure of GaN and Al{sub 0.25}Ga{sub 0.75}N nanoparticles. Surface morphology and elemental analysis were carried out by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The room temperature Photoluminescence (PL) study shows the near band edge emission for GaN at 3.35 eV and at 3.59 eV for AlGaN nanoparticles. The Aluminum (Al) composition of 20% has been obtained from PL emission around 345 nm.

  5. Electrical and optical properties of carbon-doped GaN grown by MBE on MOCVD GaN templates using a CCl4 dopant source

    SciTech Connect (OSTI)

    Armitage, Rob; Yang, Qing; Feick, Henning; Park, Yeonjoon; Weber, Eicke R.

    2002-04-15

    Carbon-doped GaN was grown by plasma-assisted molecular-beam epitaxy using carbon tetrachloride vapor as the dopant source. For moderate doping mainly acceptors were formed, yielding semi-insulating GaN. However at higher concentrations p-type conductivity was not observed, and heavily doped films (>5 x 10{sup 20} cm{sup -3}) were actually n-type rather than semi-insulating. Photoluminescence measurements showed two broad luminescence bands centered at 2.2 and 2.9 eV. The intensity of both bands increased with carbon content, but the 2.2 eV band dominated in n-type samples. Intense, narrow ({approx}6 meV) donor-bound exciton peaks were observed in the semi-insulating samples.

  6. Tunnel-injection GaN quantum dot ultraviolet light-emitting diodes

    SciTech Connect (OSTI)

    Verma, Jai; Kandaswamy, Prem Kumar; Protasenko, Vladimir; Verma, Amit; Grace Xing, Huili; Jena, Debdeep

    2013-01-28

    We demonstrate a GaN quantum dot ultraviolet light-emitting diode that uses tunnel injection of carriers through AlN barriers into the active region. The quantum dot heterostructure is grown by molecular beam epitaxy on AlN templates. The large lattice mismatch between GaN and AlN favors the formation of GaN quantum dots in the Stranski-Krastanov growth mode. Carrier injection by tunneling can mitigate losses incurred in hot-carrier injection in light emitting heterostructures. To achieve tunnel injection, relatively low composition AlGaN is used for n- and p-type layers to simultaneously take advantage of effective band alignment and efficient doping. The small height of the quantum dots results in short-wavelength emission and are simultaneously an effective tool to fight the reduction of oscillator strength from quantum-confined Stark effect due to polarization fields. The strong quantum confinement results in room-temperature electroluminescence peaks at 261 and 340 nm, well above the 365 nm bandgap of bulk GaN. The demonstration opens the doorway to exploit many varied features of quantum dot physics to realize high-efficiency short-wavelength light sources.

  7. Ultra High p-doping Material Research for GaN Based Light Emitters

    SciTech Connect (OSTI)

    Vladimir Dmitriev

    2007-06-30

    The main goal of the Project is to investigate doping mechanisms in p-type GaN and AlGaN and controllably fabricate ultra high doped p-GaN materials and epitaxial structures. Highly doped p-type GaN-based materials with low electrical resistivity and abrupt doping profiles are of great importance for efficient light emitters for solid state lighting (SSL) applications. Cost-effective hydride vapor phase epitaxial (HVPE) technology was proposed to investigate and develop p-GaN materials for SSL. High p-type doping is required to improve (i) carrier injection efficiency in light emitting p-n junctions that will result in increasing of light emitting efficiency, (ii) current spreading in light emitting structures that will improve external quantum efficiency, and (iii) parameters of Ohmic contacts to reduce operating voltage and tolerate higher forward currents needed for the high output power operation of light emitters. Highly doped p-type GaN layers and AlGaN/GaN heterostructures with low electrical resistivity will lead to novel device and contact metallization designs for high-power high efficiency GaN-based light emitters. Overall, highly doped p-GaN is a key element to develop light emitting devices for the DOE SSL program. The project was focused on material research for highly doped p-type GaN materials and device structures for applications in high performance light emitters for general illumination P-GaN and p-AlGaN layers and multi-layer structures were grown by HVPE and investigated in terms of surface morphology and structure, doping concentrations and profiles, optical, electrical, and structural properties. Tasks of the project were successfully accomplished. Highly doped GaN materials with p-type conductivity were fabricated. As-grown GaN layers had concentration N{sub a}-N{sub d} as high as 3 x 10{sup 19} cm{sup -3}. Mechanisms of doping were investigated and results of material studies were reported at several International conferences providing

  8. Influence of growth temperature and temperature ramps on deep level defect incorporation in m-plane GaN

    SciTech Connect (OSTI)

    Armstrong, A. M.; Kelchner, K.; Nakamura, S.; DenBaars, S. P.; Materials Department, University of California, Santa Barbara, California 93106 ; Speck, J. S.

    2013-12-02

    The dependence of deep level defect incorporation in m-plane GaN films grown by metal-organic chemical vapor deposition on bulk m-plane GaN substrates as a function of growth temperature (T{sub g}) and T{sub g} ramping method was investigated using deep level optical spectroscopy. Understanding the influence of T{sub g} on GaN deep level incorporation is important for InGaN/GaN multi-quantum well (MQW) light emitting diodes (LEDs) and laser diodes (LDs) because GaN quantum barrier (QB) layers are grown much colder than thin film GaN to accommodate InGaN QW growth. Deep level spectra of low T{sub g} (800?C) GaN films grown under QB conditions were compared to deep level spectra of high T{sub g} (1150?C) GaN. Reducing T{sub g}, increased the defect density significantly (>50) through introduction of emergent deep level defects at 2.09?eV and 2.9?eV below the conduction band minimum. However, optimizing growth conditions during the temperature ramp when transitioning from high to low T{sub g} substantially reduced the density of these emergent deep levels by approximately 40%. The results suggest that it is important to consider the potential for non-radiative recombination in QBs of LED or LD active regions, and tailoring the transition from high T{sub g} GaN growth to active layer growth can mitigate such non-radiative channels.

  9. Localized tip enhanced Raman spectroscopic study of impurity incorporated single GaN nanowire in the sub-diffraction limit

    SciTech Connect (OSTI)

    Patsha, Avinash E-mail: dhara@igcar.gov.in; Dhara, Sandip; Tyagi, A. K.

    2015-09-21

    The localized effect of impurities in single GaN nanowires in the sub-diffraction limit is reported using the study of lattice vibrational modes in the evanescent field of Au nanoparticle assisted tip enhanced Raman spectroscopy (TERS). GaN nanowires with the O impurity and the Mg dopants were grown by the chemical vapor deposition technique in the catalyst assisted vapor-liquid-solid process. Symmetry allowed Raman modes of wurtzite GaN are observed for undoped and doped nanowires. Unusually very strong intensity of the non-zone center zone boundary mode is observed for the TERS studies of both the undoped and the Mg doped GaN single nanowires. Surface optical mode of A{sub 1} symmetry is also observed for both the undoped and the Mg doped GaN samples. A strong coupling of longitudinal optical (LO) phonons with free electrons, however, is reported only in the O rich single nanowires with the asymmetric A{sub 1}(LO) mode. Study of the local vibration mode shows the presence of Mg as dopant in the single GaN nanowires.

  10. Surfactant assisted growth of MgO films on GaN

    SciTech Connect (OSTI)

    Paisley, E. A.; Shelton, T. C.; Collazo, R.; Sitar, Z.; Maria, J.-P.; Christen, H. M.; Biegalski, M. D.; Mita, S.

    2012-08-27

    Thin epitaxial films of <111> oriented MgO on [0001]-oriented GaN were grown by molecular beam epitaxy and pulsed laser deposition using the assistance of a vapor phase surfactant. In both cases, surfactant incorporation enabled layer-by-layer growth and a smooth terminal surface by stabilizing the {l_brace}111{r_brace} rocksalt facet. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100 Multiplication-Sign reduction in leakage current density for the surfactant-assisted samples. These data verify numerous predictions regarding the role of H-termination in regulating the habit of rocksalt crystals.

  11. Anisotropy of two-photon absorption and free-carrier effect in nonpolar GaN

    SciTech Connect (OSTI)

    Fang, Yu; Zhou, Feng; Yang, Junyi; Wu, Xingzhi; Xiao, Zhengguo; Li, Zhongguo; Song, Yinglin

    2015-03-30

    We reported a systematic study about the anisotropic optical nonlinearities in bulk m-plane and a-plane GaN crystals by Z-scan and pump-probe with phase object methods under picosecond at 532 nm. The two-photon absorption coefficient, which was measured as a function of polarization angle, exhibited oscillation curves with a period of π/2, indicating a highly polarized optical third-order nonlinearity in both nonpolar GaN samples. Furthermore, free-carrier absorption revealed stronger hole-related absorption for E⊥c than for E//c probe polarization. In contrast, free-carrier refraction was found almost isotropic due to electron-related refraction in the isotropic conduction bands.

  12. Performance and breakdown characteristics of irradiated vertical power GaN P-i-N diodes

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    King, M. P.; Armstrong, A. M.; Dickerson, J. R.; Vizkelethy, G.; Fleming, R. M.; Campbell, J.; Wampler, W. R.; Kizilyalli, I. C.; Bour, D. P.; Aktas, O.; et al

    2015-10-29

    Electrical performance and defect characterization of vertical GaN P-i-N diodes before and after irradiation with 2.5 MeV protons and neutrons is investigated. Devices exhibit increase in specific on-resistance following irradiation with protons and neutrons, indicating displacement damage introduces defects into the p-GaN and n- drift regions of the device that impact on-state device performance. The breakdown voltage of these devices, initially above 1700 V, is observed to decrease only slightly for particle fluence <; 1013 cm-2. Furthermore, the unipolar figure of merit for power devices indicates that while the on-resistance and breakdown voltage degrade with irradiation, vertical GaN P-i-Ns remainmore » superior to the performance of the best available, unirradiated silicon devices and on-par with unirradiated modern SiC-based power devices.« less

  13. Catalyst and its diameter dependent growth kinetics of CVD grown GaN nanowires

    SciTech Connect (OSTI)

    Samanta, Chandan [Department of Physics, Indian Institute of Technology Kanpur (India)] [Department of Physics, Indian Institute of Technology Kanpur (India); Chander, D. Sathish [Department of Physics, Indian Institute of Technology Kanpur (India) [Department of Physics, Indian Institute of Technology Kanpur (India); Department of Mechanical Engineering, Indian Institute of Technology Kanpur (India); Ramkumar, J. [Department of Mechanical Engineering, Indian Institute of Technology Kanpur (India)] [Department of Mechanical Engineering, Indian Institute of Technology Kanpur (India); Dhamodaran, S., E-mail: kdams2003@gmail.com [Department of Physics, Indian Institute of Technology Kanpur (India)

    2012-04-15

    Graphical abstract: GaN nanowires with controlled diameter and aspect ratio has been grown using a simple CVD technique. The growth kinetics of CVD grown nanowires investigated in detail for different catalysts and their diameters. A critical diameter important to distinguish the growth regimes has been discussed in detail. The results are important which demonstrates the growth of diameter and aspect ratio controlled GaN nanowires and also understand their growth kinetics. Highlights: Black-Right-Pointing-Pointer Controlled diameter and aspect ratio of GaN nanowires achieved in simple CVD reactor. Black-Right-Pointing-Pointer Nanowire growth kinetics for different catalyst and its diameters were understood. Black-Right-Pointing-Pointer Adatoms vapor pressure inside reactor plays a crucial role in growth kinetics. Black-Right-Pointing-Pointer Diffusion along nanowire sidewalls dominate for gold and nickel catalysts. Black-Right-Pointing-Pointer Gibbs-Thomson effect dominates for palladium catalyst. -- Abstract: GaN nanowires were grown using chemical vapor deposition with controlled aspect ratio. The catalyst and catalyst-diameter dependent growth kinetics is investigated in detail. We first discuss gold catalyst diameter dependent growth kinetics and subsequently compare with nickel and palladium catalyst. For different diameters of gold catalyst there was hardly any variation in the length of the nanowires but for other catalysts with different diameter a strong length variation of the nanowires was observed. We calculated the critical diameter dependence on adatoms pressure inside the reactor and inside the catalytic particle. This gives an increasing trend in critical diameter as per the order gold, nickel and palladium for the current set of experimental conditions. Based on the critical diameter, with gold and nickel catalyst the nanowire growth was understood to be governed by limited surface diffusion of adatoms and by Gibbs-Thomson effect for the palladium

  14. Hafnium nitride buffer layers for growth of GaN on silicon

    DOE Patents [OSTI]

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16

    Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 {character pullout}m. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.

  15. Analysis of the carbon-related 'blue' luminescence in GaN

    SciTech Connect (OSTI)

    Armitage, R.; Yang, Q.; Weber, E.R.

    2004-09-24

    The properties of a broad 2.86 eV photoluminescence band in carbon-doped GaN were studied as a function of C-doping level, temperature, and excitation density. The results are consistent with a C{sub Ga}-C{sub N} deep donor-deep acceptor recombination mechanism as proposed by Seager et al. For GaN:C grown by molecular-beam epitaxy (MBE) the 2.86 eV band is observed in Si co-doped layers exhibiting high n-type conductivity as well as in semi-insulating material. For low excitation density (4 W/cm{sup 2}) the 2.86 eV band intensity decreases as a function of cw-laser exposure time over a period of many minutes. The transient behavior is consistent with a model based on carrier diffusion and charge trapping-induced Coulomb barriers. The temperature dependence of the blue luminescence below 150 K was different for carbon-contaminated GaN grown by metalorganic vapor phase epitaxy (MOVPE) compared to C-doped MBE GaN.

  16. Theoretical and experimental study of dynamics of photoexcited carriers in GaN

    SciTech Connect (OSTI)

    Shishehchi, Sara; Bellotti, Enrico; Rudin, Sergey; Garrett, Gregory A.; Wraback, Michael

    2013-12-21

    We present a theoretical and experimental study of the sub-picosecond dynamics of photo-excited carriers in GaN. In the theoretical model, interaction with an external ultrafast laser pulse is treated coherently and to account for the scattering mechanisms and dephasing processes, a generalized Monte-Carlo simulation is used. The scattering mechanisms included are carrier interactions with polar optical phonons and acoustic phonons, and carrier-carrier Coulomb interactions. We study the effect of different scattering mechanisms on the carrier densities. In the case that the excitation energy satisfies the threshold for polar optical scattering, phonon contribution is the dominant process in relaxing the system, otherwise, carrier-carrier mechanism is dominant. Furthermore, we present the temperature and pulse power dependent normalized luminescence intensity. The results are presented over a range of temperatures, electric field, and excitation energy of the laser pulse. For comparison, we also report the experimental time-resolved photoluminescence studies on GaN samples. There is a good agreement between the simulation and experiment in normalized luminescence intensity results. Therefore, we show that we can explain the dynamics of the photo-excited carriers in GaN by including only carrier-carrier and carrier-phonon interactions and a relatively simple two-band electronic structure model.

  17. Formation of manganese {delta}-doped atomic layer in wurtzite GaN

    SciTech Connect (OSTI)

    Shi Meng; Chinchore, Abhijit; Wang Kangkang; Mandru, Andrada-Oana; Liu Yinghao; Smith, Arthur R.

    2012-09-01

    We describe the formation of a {delta}-doped manganese layer embedded within c-plane wurtzite gallium nitride using a special molecular beam epitaxy growth process. Manganese is first deposited on the gallium-poor GaN (0001) surface, forming a {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign reconstructed phase. This well-defined surface reconstruction is then nitrided using plasma nitridation, and gallium nitride is overgrown. The manganese content of the {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign phase, namely one Mn per each {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign unit cell, implies that the MnGaN alloy layer has a Mn concentration of up to 33%. The structure and chemical content of the surface are monitored beginning from the initial growth stage up through the overgrowth of 20 additional monolayers (MLs) of GaN. An exponential-like drop-off of the Mn signal with increasing GaN monolayers, as measured by Auger electron spectroscopy, indicates that the highly concentrated Mn layer remains at the {delta}-doped interface. A model of the resultant {delta}-doped structure is formulated based on the experimental data, and implications for possible spintronic applications are discussed.

  18. Vertical GaN power diodes with a bilayer edge termination

    SciTech Connect (OSTI)

    Dickerson, Jeramy R.; Allerman, Andrew A.; Bryant, Benjamin N.; Fischer, Arthur J.; King, Michael P.; Moseley, Michael W.; Armstrong, Andrew M.; Kaplar, Robert J.; Kizilyalli, Isik C.; Aktas, Ozgur; Wierer, Jr., Jonathan J.

    2015-12-07

    Vertical GaN power diodes with a bilayer edge termination (ET) are demonstrated. The GaN p-n junction is formed on a low threading dislocation defect density (104 - 105 cm-2) GaN substrate, and has a 15-μm-thick n-type drift layer with a free carrier concentration of 5 × 1015 cm-3. The ET structure is formed by N implantation into the p+-GaN epilayer just outside the p-type contact to create compensating defects. The implant defect profile may be approximated by a bilayer structure consisting of a fully compensated layer near the surface, followed by a 90% compensated (p) layer near the n-type drift region. These devices exhibit avalanche breakdown as high as 2.6 kV at room temperature. In addition simulations show that the ET created by implantation is an effective way to laterally distribute the electric field over a large area. This increases the voltage at which impact ionization occurs and leads to the observed higher breakdown voltages.

  19. Vertical GaN power diodes with a bilayer edge termination

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Dickerson, Jeramy R.; Allerman, Andrew A.; Bryant, Benjamin N.; Fischer, Arthur J.; King, Michael P.; Moseley, Michael W.; Armstrong, Andrew M.; Kaplar, Robert J.; Kizilyalli, Isik C.; Aktas, Ozgur; et al

    2015-12-07

    Vertical GaN power diodes with a bilayer edge termination (ET) are demonstrated. The GaN p-n junction is formed on a low threading dislocation defect density (104 - 105 cm-2) GaN substrate, and has a 15-μm-thick n-type drift layer with a free carrier concentration of 5 × 1015 cm-3. The ET structure is formed by N implantation into the p+-GaN epilayer just outside the p-type contact to create compensating defects. The implant defect profile may be approximated by a bilayer structure consisting of a fully compensated layer near the surface, followed by a 90% compensated (p) layer near the n-type driftmore » region. These devices exhibit avalanche breakdown as high as 2.6 kV at room temperature. In addition simulations show that the ET created by implantation is an effective way to laterally distribute the electric field over a large area. This increases the voltage at which impact ionization occurs and leads to the observed higher breakdown voltages.« less

  20. Spectroscopic and magnetic properties of Mn doped GaN epitaxial films grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Vidyasagar, R.; Lin, Y.-T.; Tu, L.-W.

    2012-12-15

    Graphical abstract: We report here that micro-Raman scattering spectrum for Mn doped GaN thin film has displayed a new peak manifested at 578 cm{sup −1}, by which it is attributed to interior LVM originated by the incorporation of Mn ions in place of Ga sites. Mn doped GaN thin film also showed the typical negative magnetoresistance up to ∼50 K, revealing that the film showed magnetic ordering of spins below 50 K. Display Omitted Highlights: ► GaN and Mn doped GaN single phase wurtzite structures grown by PAMBE. ► The phase purity of the epilayers investigated by HRXRD, HRSEM and EDX. ► The red shift in near band edge emission has been observed using micro-PL. ► A new peak related LVM at 578 cm{sup −1} in micro-Raman scattering measurements confirmed Mn doped into GaN. ► Negative-magnetoresistance investigations have showed that the film has T{sub c} < 50 K. -- Abstract: Spectroscopic and magnetic properties of Mn doped GaN, and GaN epitaxial films have been investigated by employing micro-photoluminescence, micro-Raman, and temperature dependent magneto-resistance measurements. The HR-XRD profiles have shown that the epitaxial films are in hexagonal wurtzite structures. Morphology and composition of the films have been examined by field emission scanning electron microscopy, and energy-dispersive X-ray analysis. Micro-photoluminescence spectrum displayed a dominant near band edge emission at 362 nm, which is assigned to near band edge transition within the hexagonal structure of GaN. Raman scattering profiles showed a new vibrational mode at 578 cm{sup −1}, which is attributed to the vacancy-related local vibrational mode of Mn occupying the Ga site. Temperature dependent negative magnetoresistance measurements provide a direct evidence of magnetic ordering below 50 K for the Mn doped GaN thin film.

  1. Multicycle rapid thermal annealing optimization of Mg-implanted GaN: Evolution of surface, optical, and structural properties

    SciTech Connect (OSTI)

    Greenlee, Jordan D.; Feigelson, Boris N.; Anderson, Travis J.; Hite, Jennifer K.; Mastro, Michael A.; Eddy, Charles R.; Hobart, Karl D.; Kub, Francis J.; Tadjer, Marko J.

    2014-08-14

    The first step of a multi-cycle rapid thermal annealing process was systematically studied. The surface, structure, and optical properties of Mg implanted GaN thin films annealed at temperatures ranging from 900 to 1200?C were investigated by Raman spectroscopy, photoluminescence, UV-visible spectroscopy, atomic force microscopy, and Nomarski microscopy. The GaN thin films are capped with two layers of in-situ metal organic chemical vapor deposition -grown AlN and annealed in 24 bar of N{sub 2} overpressure to avoid GaN decomposition. The crystal quality of the GaN improves with increasing annealing temperature as confirmed by UV-visible spectroscopy and the full widths at half maximums of the E{sub 2} and A{sub 1} (LO) Raman modes. The crystal quality of films annealed above 1100?C exceeds the quality of the as-grown films. At 1200?C, Mg is optically activated, which is determined by photoluminescence measurements. However, at 1200?C, the GaN begins to decompose as evidenced by pit formation on the surface of the samples. Therefore, it was determined that the optimal temperature for the first step in a multi-cycle rapid thermal anneal process should be conducted at 1150?C due to crystal quality and surface morphology considerations.

  2. Utilization of native oxygen in Eu(RE)-doped GaN for enabling device compatibility in optoelectronic applications

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Mitchell, Brandon; Timmerman, D.; Poplawsky, Jonathan D.; Zhu, W.; Lee, D.; Wakamatsu, R.; Takatsu, J.; Matsuda, M.; Guo, Wei; Lorenz, K.; et al

    2016-01-04

    The detrimental influence of oxygen on the performance and reliability of V/III nitride based devices is well known. However, the influence of oxygen on the nature of the incorporation of other co-dopants, such as rare earth ions, has been largely overlooked in GaN. Here, we report the first comprehensive study of the critical role that oxygen has on Eu in GaN, as well as atomic scale observation of diffusion and local concentration of both atoms in the crystal lattice. We find that oxygen plays an integral role in the location, stability, and local defect structure around the Eu ions thatmore » were doped into the GaN host. Although the availability of oxygen is essential for these properties, it renders the material incompatible with GaN-based devices. However, the utilization of the normally occurring oxygen in GaN is promoted through structural manipulation, reducing its concentration by 2 orders of magnitude, while maintaining both the material quality and the favorable optical properties of the Eu ions. Furthermore, these findings open the way for full integration of RE dopants for optoelectronic functionalities in the existing GaN platform.« less

  3. Ab initio study on noncompensated CrO codoping of GaN for enhanced solar energy conversion

    SciTech Connect (OSTI)

    Pan, Hui; Gu, Baohua; Eres, Gyula; Zhang, Zhenyu

    2010-03-01

    We describe a novel photocatalyst obtained by codoping GaN with CrO, according to a new "noncompensated" codoping concept based on first-principles calculations. The approach enables controllable narrowing of the GaN band gap with significantly enhanced carrier mobility and photocatalytic activity in the visible light region and thus offers immense potential for application in solar energy conversion, water splitting, and a variety of solar-assisted photocatalysis. Our calculations indicate that the formation energy for the cation doping is greatly reduced by noncompensated codoping with an anion. Although Cr doping alone can split the band gap with the formation of an intermediate band, the mobility is low due to carrier trapping by the localized states. The first-principles calculations also demonstrate that CrO codoping of GaN shifts the Fermi level into the conduction band resulting in high carrier density and mobility.

  4. Fundamental Bulk/Surface Structure Photoactivity Relationships of Supported (Rh2-yCryO3)/GaN Photocatalysts

    SciTech Connect (OSTI)

    Phivilay, Somphonh; Roberts, Charles; Puretzky, Alexander A; Domen, Kazunari Domen; Wachs, Israel

    2013-01-01

    ABSTRACT. The supported (Rh2-yCryO3)/GaN photocatalyst was examined as a model nitride photocatalyst system to assist in the development of fundamental structure photoactivity relationships for UV activated water splitting. Surface characterization of the outermost surface layers by High Sensitivity-LEIS and High Resolution-XPS revealed for the first time that the GaN support consists of a GaOx outermost surface layer and a thin film of GaOxNy in the surface region. HR-XPS also demonstrates that the supported (Rh2-yCryO3) mixed oxide nanoparticles (NPs) exclusively consist of Cr+3 and Rh+3 cations and are surface enriched for the supported (Rh2-yCryO3)/GaN photocatalyst. Bulk analysis by Raman and UV-vis spectroscopy show that the bulk molecular and electronic structures, respectively, of the GaN support are not perturbed by the deposition of the (Rh2-yCryO3) mixed oxide NPs. The function of the GaN bulk lattice is to generate photoexcited electrons/holes, with the electrons harnessed by the surface Rh+3 sites for evolution of H2 and the holes trapped at the Ga oxide/oxynitride surface sites for splitting of water and evolving O2. These new structure-photoactivity relationships for supported (Rh2-yCryO3)/GaN also extend to the best performing visible light activated supported (Rh2-yCryO3)/(Ga1-xZnx)(N1-xOx) photocatalyst.

  5. Properties of radio-frequency-sputter-deposited GaN films in a nitrogen/hydrogen mixed gas

    SciTech Connect (OSTI)

    Miyazaki, Takayuki; Takada, Kouhei; Adachi, Sadao; Ohtsuka, Kohji

    2005-05-01

    GaN films have been deposited by reactive sputtering in nitrogen gas at pressures from 0.08 to 2.70 Pa with and without the addition of hydrogen gas. X-ray diffraction (XRD), Fourier transform infrared (FTIR), optical absorption, and photoluminescence (PL) spectroscopy have been used to characterize the sputter-deposited GaN films. The XRD pattern reveals that the GaN films deposited in nitrogen gas at pressures lower than 0.53 Pa are polycrystals with the (0001) texture ({alpha}-GaN), while those deposited at or above 1.07 Pa display mixed crystalline orientations or an amorphous-like nature. The GaN:H films deposited in nitrogen/hydrogen mixed gas, on the other hand, show an amorphous or amorphous-like nature. The FTIR spectra indicate that the GaN:H films show peaks arising from hydrogen-related bonds at {approx}1000 and {approx}3200 cm{sup -1}, in addition to the GaN absorption band at {approx}555 cm{sup -1}. The optical absorption spectra at 300 K indicate the fundamental absorption edges at {approx}3.38 and {approx}3.7 eV for the highly oriented {alpha}-GaN and amorphous GaN:H films, respectively. PL emission has been observed from sputter-deposited {alpha}-GaN films at temperatures below 100 K. The GaN:H films also show strong band-edge and donor-acceptor pair emissions. The PL emission in the GaN:H film may arise from crystalline GaN particles embedded in the amorphous GaN matrix.

  6. Electroreflectance study of the effect of {gamma} radiation on the optical properties of epitaxial GaN films

    SciTech Connect (OSTI)

    Belyaev, A. E.; Klyui, N. I. Konakova, R. V.; Lukyanov, A. N.; Danilchenko, B. A.; Sveshnikov, J. N.; Klyui, A. N.

    2012-03-15

    Experimental data on the electroreflectance spectra of {gamma}-irradiated epitaxial GaN films on sapphire are reported. The irradiation doses are 10{sup 5}-2 Multiplication-Sign 10{sup 6} rad. The theoretical electroreflectance spectra calculated on the basis of a model of three types of transitions are in agreement with experimental data with reasonable accuracy. The energies and broadenings of the transitions derived in the context of the model give grounds to infer that, in the GaN films, there are internal stresses dependent on the {gamma}-irradiation dose.

  7. Nanoscale size dependence parameters on lattice thermal conductivity of Wurtzite GaN nanowires

    SciTech Connect (OSTI)

    Mamand, S.M.; Omar, M.S.; Muhammad, A.J.

    2012-05-15

    Graphical abstract: Temperature dependence of calculated lattice thermal conductivity of Wurtzite GaN nanowires. Highlights: Black-Right-Pointing-Pointer A modified Callaway model is used to calculate lattice thermal conductivity of Wurtzite GaN nanowires. Black-Right-Pointing-Pointer A direct method is used to calculate phonon group velocity for these nanowires. Black-Right-Pointing-Pointer 3-Gruneisen parameter, surface roughness, and dislocations are successfully investigated. Black-Right-Pointing-Pointer Dislocation densities are decreases with the decrease of wires diameter. -- Abstract: A detailed calculation of lattice thermal conductivity of freestanding Wurtzite GaN nanowires with diameter ranging from 97 to 160 nm in the temperature range 2-300 K, was performed using a modified Callaway model. Both longitudinal and transverse modes are taken into account explicitly in the model. A method is used to calculate the Debye and phonon group velocities for different nanowire diameters from their related melting points. Effect of Gruneisen parameter, surface roughness, and dislocations as structure dependent parameters are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves. It was observed that Gruneisen parameter will decrease with decreasing nanowire diameters. Scattering of phonons is assumed to be by nanowire boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. At high temperatures and for dislocation densities greater than 10{sup 14} m{sup -2} the lattice thermal conductivity would be limited by dislocation density, but for dislocation densities less than 10{sup 14} m{sup -2}, lattice thermal conductivity would be independent of that.

  8. Impact of the GaN nanowire polarity on energy harvesting

    SciTech Connect (OSTI)

    Gogneau, Noelle Galopin, Elisabeth; Guilet, Stephane; Travers, Laurent; Harmand, Jean-Christophe; Chrétien, Pascal; Houzé, Frédéric

    2014-05-26

    We investigate the piezoelectric generation properties of GaN nanowires (NWs) by atomic force microscopy equipped with a Resiscope module for electrical measurements. By correlating the topography profile of the NWs with the recorded voltage peaks generated by these nanostructures in response to their deformation, we demonstrate the influence of their polarity on the rectifying behavior of the Schottky diode formed between the NWs and the electrode of measurement. These results establish that the piezo-generation mechanism crucially depends on the structural characteristics of the NWs.

  9. Mechanism of the GaN LED efficiency falloff with increasing current

    SciTech Connect (OSTI)

    Bochkareva, N. I.; Voronenkov, V. V.; Gorbunov, R. I.; Zubrilov, A. S.; Lelikov, Y. S.; Latyshev, F. E.; Rebane, Y. T.; Tsyuk, A. I.; Shreter, Y. G.

    2010-06-15

    The quantum efficiency of GaN LED structures has been studied at various temperatures and biases. It was found that an efficiency falloff is observed with increasing current density and, simultaneously, the tunnel component of the current through the LED grows and the quasi-Fermi levels reach the mobility edge in the InGaN active layer. It is shown that the internal quantum efficiency falloff with increasing current density is due to the carrier leakage from the quantum well as a result of tunnel transitions from its band-tail states to local defect-related energy levels within the energy gaps of the barrier layers.

  10. Surfactant assisted growth of MgO films on GaN

    SciTech Connect (OSTI)

    Paisley, Elisibeth A.; Shelton, T C; Mita, S; Gaddy, Brian E.; Irving, D L; Christen, Hans M; Sitar, Z; Biegalski, Michael D; Maria, Jon Paul

    2012-01-01

    Thin epitaxial films of <111> oriented MgO on [0001]-oriented GaN were grown by molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) using the assistance of a vapor phase surfactant. In both cases, surfactant incorporation enabled layer-by-layer growth and a smooth terminal surface due to stabilizing the {111} rocksalt facet. MBE growth of MgO in water terminates after several monolayers, and is attributed to saturation of surface active sites needed to facilitate the Mg oxidation reaction. MgO films prepared by PLD grow continuously, this occurs due to the presence of excited oxidizing species in the laser plasma eliminate the need for catalytic surface sites. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly two order of magnitude reduction in leakage current density for the smoother surfactant-assisted samples. Collectively, these data verify numerous predictions and calculations regarding the role of H-termination in regulating the habit of MgO crystals.

  11. The effect of N-polar GaN domains as Ohmic contacts

    SciTech Connect (OSTI)

    Xie, J.; Mita, S.; Collazo, R.; Rice, A.; Tweedie, J.; Sitar, Z.

    2010-09-20

    Transfer line method measurements revealed that if the Ohmic contact regions were replaced by N-polar GaN, the contact resistance could be reduced from 0.71 {Omega} mm (or {rho}{sub c}=4x10{sup -6} {Omega} cm{sup 2}) to 0.24 {Omega} mm for a {approx}200 nm thick Si-doped GaN layer. The reduction in contact resistance was largely due to the {approx}10{sup 19} cm{sup -3} free carriers in N-polar source/drain regions as measured by Hall effect. Secondary ion mass spectroscopy confirmed that oxygen doping in the N-polar region was more than three orders of magnitude greater than that in the Ga-polar region that was explained by the large difference in the adsorption energy for oxygen ({approx}1.3 eV/atom) between the N- and Ga-polar surfaces during the metalorganic chemical vapor deposition.

  12. Enhanced UV detection by non-polar epitaxial GaN films

    SciTech Connect (OSTI)

    Mukundan, Shruti; Chandan, Greeshma; Mohan, Lokesh; Krupanidhi, S. B.; Roul, Basanta; Shetty, Arjun

    2015-12-15

    Nonpolar a-GaN (11-20) epilayers were grown on r-plane (1-102) sapphire substrates using plasma assisted molecular beam epitaxy. High resolution x-ray diffractometer confirmed the orientation of the grown film. Effect of the Ga/N ratio on the morphology and strain of a-GaN epilayers was compared and the best condition was obtained for the nitrogen flow of 1 sccm. Atomic force microscopy was used to analyze the surface morphology while the strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by reciprocal space mapping technique. UV photo response of a-GaN film was measured after fabricating a metal-semiconductor-metal structure over the film with gold metal. The external quantum efficiency of the photodetectors fabricated in the (0002) polar and (11-20) nonpolar growth directions were compared in terms of responsivity and nonpolar GaN showed the best sensitivity at the cost of comparatively slow response time.

  13. Excitation mechanisms of Er optical centers in GaN epilayers

    SciTech Connect (OSTI)

    George, D. K.; Hawkins, M. D.; McLaren, M.; Vinh, N. Q.; Jiang, H. X.; Lin, J. Y.; Zavada, J. M.

    2015-10-26

    We report direct evidence of two mechanisms responsible for the excitation of optically active Er{sup 3+} ions in GaN epilayers grown by metal-organic chemical vapor deposition. These mechanisms, resonant excitation via the higher-lying inner 4f shell transitions and band-to-band excitation of the semiconductor host, lead to narrow emission lines from isolated and the defect-related Er optical centers. However, these centers have different photoluminescence spectra, local defect environments, decay dynamics, and excitation cross sections. The photoluminescence at 1.54 μm from the isolated Er optical center which can be excited by either mechanism has the same decay dynamics, but possesses a much higher excitation cross-section under band-to-band excitation. In contrast, the photoluminescence at 1.54 μm from the defect-related Er optical center can only be observed through band-to-band excitation but has the largest excitation cross-section. These results explain the difficulty in achieving gain in Er doped GaN and indicate approaches for realization of optical amplification, and possibly lasing, at room temperature.

  14. Growth modes of InN(000-1) on GaN buffer layers on sapphire

    SciTech Connect (OSTI)

    Liu, Bing; Kitajima, Takeshi; Chen, Dongxue; Leone, Stephen R.

    2005-01-24

    In this work, using atomic force microscopy and scanning tunneling microscopy, we study the surface morphologies of epitaxial InN films grown by plasma-assisted molecular beam epitaxy with intervening GaN buffer layers on sapphire substrates. On smooth GaN buffer layers, nucleation and evolution of three-dimensional InN islands at various coverages and growth temperatures are investigated. The shapes of the InN islands are observed to be predominantly mesa-like with large flat (000-1) tops, which suggests a possible role of indium as a surfactant. Rough GaN buffer layers composed of dense small GaN islands are found to significantly improve uniform InN wetting of the substrates, on which atomically smooth InN films are obtained that show the characteristics of step-flow growth. Scanning tunneling microscopy imaging reveals the defect-mediated surface morphology of smooth InN films, including surface terminations of screw dislocations and a high density of shallow surface pits with depths less than 0.3 nm. The mechanisms of the three-dimensional island size and shape evolution and formation of defects on smooth surfaces are considered.

  15. Impact of defects on the electrical transport, optical properties and failure mechanisms of GaN nanowires.

    SciTech Connect (OSTI)

    Armstrong, Andrew M.; Aubry, Sylvie; Shaner, Eric Arthur; Siegal, Michael P.; Li, Qiming; Jones, Reese E.; Westover, Tyler; Wang, George T.; Zhou, Xiao Wang; Talin, Albert Alec; Bogart, Katherine Huderle Andersen; Harris, C. Thomas; Huang, Jian Yu

    2010-09-01

    We present the results of a three year LDRD project that focused on understanding the impact of defects on the electrical, optical and thermal properties of GaN-based nanowires (NWs). We describe the development and application of a host of experimental techniques to quantify and understand the physics of defects and thermal transport in GaN NWs. We also present the development of analytical models and computational studies of thermal conductivity in GaN NWs. Finally, we present an atomistic model for GaN NW electrical breakdown supported with experimental evidence. GaN-based nanowires are attractive for applications requiring compact, high-current density devices such as ultraviolet laser arrays. Understanding GaN nanowire failure at high-current density is crucial to developing nanowire (NW) devices. Nanowire device failure is likely more complex than thin film due to the prominence of surface effects and enhanced interaction among point defects. Understanding the impact of surfaces and point defects on nanowire thermal and electrical transport is the first step toward rational control and mitigation of device failure mechanisms. However, investigating defects in GaN NWs is extremely challenging because conventional defect spectroscopy techniques are unsuitable for wide-bandgap nanostructures. To understand NW breakdown, the influence of pre-existing and emergent defects during high current stress on NW properties will be investigated. Acute sensitivity of NW thermal conductivity to point-defect density is expected due to the lack of threading dislocation (TD) gettering sites, and enhanced phonon-surface scattering further inhibits thermal transport. Excess defect creation during Joule heating could further degrade thermal conductivity, producing a viscous cycle culminating in catastrophic breakdown. To investigate these issues, a unique combination of electron microscopy, scanning luminescence and photoconductivity implemented at the nanoscale will be used in

  16. Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Novikov, S. V.; Ting, M.; Yu, K. M.; Sarney, W. L.; Martin, R. W.; Svensson, S. P.; Walukiewicz, W.; Foxon, C. T.

    2014-10-01

    In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 9×10²⁰ cm⁻³. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 3×10¹⁹ cm⁻³ and mobilities of ~1 cm²/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

  17. Highly c-axis oriented GaN films grown on free-standing diamond substrates for high-power devices

    SciTech Connect (OSTI)

    Zhang, D. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China) [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Bian, J.M., E-mail: jmbian@dlut.edu.cn [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Qin, F.W.; Wang, J.; Pan, L. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China) [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Zhao, J.M. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)] [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Zhao, Y.; Bai, Y.Z. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China) [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Du, G.T. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)] [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2011-10-15

    Highlights: {yields} GaN films are deposited on diamond substrates by ECR-PEMOCVD. {yields} Influence of deposition temperature on the properties of samples is investigated. {yields} Properties of GaN films are dependent on the deposition temperature. -- Abstract: GaN films with highly c-axis preferred orientation are deposited on free-standing thick diamond films by low temperature electron cyclotron resonance plasma enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). The TMGa and N{sub 2} are applied as precursors of Ga and N, respectively. The quality of as-grown GaN films are systematically investigated as a function of deposition temperature by means of X-ray diffraction (XRD) analysis, Hall Effect measurement (HL), room temperature photoluminescence (PL) and atomic force microscopy (AFM). The results show that the dense and uniformed GaN films with highly c-axis preferred orientation are successfully achieved on free-standing diamond substrates under optimized deposition temperature of 400 {sup o}C, and the room temperature PL spectra of the optimized GaN film show a intense ultraviolet near band edge emission and a weak yellow luminescence. The obtained GaN/diamond structure has great potential for the development of high-power semiconductor devices due to its excellent heat dissipation nature.

  18. Effect of ZnO seed layer on the morphology and optical properties of ZnO nanorods grown on GaN buffer layers

    SciTech Connect (OSTI)

    Nandi, R. Mohan, S. Major, S. S.; Srinivasa, R. S.

    2014-04-24

    ZnO nanorods were grown by chemical bath deposition on sputtered, polycrystalline GaN buffer layers with and without ZnO seed layer. Scanning electron microscopy and X-ray diffraction show that the ZnO nanorods on GaN buffer layers are not vertically well aligned. Photoluminescence spectrum of ZnO nanorods grown on GaN buffer layer, however exhibits a much stronger near-band-edge emission and negligible defect emission, compared to the nanorods grown on ZnO buffer layer. These features are attributed to gallium incorporation at the ZnO-GaN interface. The introduction of a thin (25 nm) ZnO seed layer on GaN buffer layer significantly improves the morphology and vertical alignment of ZnO-NRs without sacrificing the high optical quality of ZnO nanorods on GaN buffer layer. The presence of a thick (200 nm) ZnO seed layer completely masks the effect of the underlying GaN buffer layer on the morphology and optical properties of nanorods.

  19. Influence of the adatom diffusion on selective growth of GaN nanowire regular arrays

    SciTech Connect (OSTI)

    Gotschke, T.; Schumann, T.; Limbach, F.; Calarco, R.; Stoica, T.

    2011-03-07

    Molecular beam epitaxy (MBE) on patterned Si/AlN/Si(111) substrates was used to obtain regular arrays of uniform-size GaN nanowires (NWs). The silicon top layer has been patterned with e-beam lithography, resulting in uniform arrays of holes with different diameters (d{sub h}) and periods (P). While the NW length is almost insensitive to the array parameters, the diameter increases significantly with d{sub h} and P till it saturates at P values higher than 800 nm. A diffusion induced model was used to explain the experimental results with an effective diffusion length of the adatoms on the Si, estimated to be about 400 nm.

  20. Monolithic single GaN nanowire laser with photonic crystal microcavity on silicon

    SciTech Connect (OSTI)

    Heo, Junseok; Guo Wei; Bhattacharya, Pallab

    2011-01-10

    Optically pumped lasing at room temperature in a silicon based monolithic single GaN nanowire with a two-dimensional photonic crystal microcavity is demonstrated. Catalyst-free nanowires with low density ({approx}10{sup 8} cm{sup -2}) are grown on Si by plasma-assisted molecular beam epitaxy. High resolution transmission electron microscopy images reveal that the nanowires are of wurtzite structure and they have no observable defects. A single nanowire laser fabricated on Si is characterized by a lasing transition at {lambda}=371.3 nm with a linewidth of 0.55 nm. The threshold is observed at a pump power density of {approx}120 kW/cm{sup 2} and the spontaneous emission factor {beta} is estimated to be 0.08.

  1. Demonstration of forward inter-band tunneling in GaN by polarization engineering

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram; Park, Pil Sung; Rajan, Siddharth

    2011-12-05

    We report on the design, fabrication, and characterization of GaN interband tunnel junction showing forward tunneling characteristics. We have achieved very high forward tunneling currents (153 mA/cm{sup 2} at 10 mV, and 17.7 A/cm{sup 2} peak current) in polarization-engineered GaN/InGaN/GaN heterojunction diodes grown by plasma assisted molecular beam epitaxy. We also report the observation of repeatable negative differential resistance in interband III-Nitride tunnel junctions, with peak-valley current ratio of 4 at room temperature. The forward current density achieved in this work meets the typical current drive requirements of a multi-junction solar cell.

  2. Resonant energy transfer between Eu luminescent sites and their local geometry in GaN

    SciTech Connect (OSTI)

    Timmerman, Dolf; Wakamatsu, Ryuta; Tanaka, Kazuteru; Lee, Dong-gun; Koizumi, Atsushi; Fujiwara, Yasufumi

    2015-10-12

    Eu-doped GaN is a solid state material with promising features for quantum manipulation. In this study, we investigate the population dynamics of Eu in ions in this system by resonant excitation. From differences in the emission related to transitions between the {sup 5}D{sub 0} and {sup 7}F{sub 2} manifold in the Eu ions, we can distinguish different luminescence sites and observe that a resonant energy transfer takes place between two of these sites which are in proximity of each other. The time constants related to this energy transfer are on the order of 100 μs. By using different substrates, the energy transfer efficiency could be strongly altered, and it is demonstrated that the coupling between ions has an out-of-plane character. Based on these results, a microscopic model of this combined center is presented.

  3. Efficient Switches for Solar Power Conversion: Four Quadrant GaN Switch Enabled Three Phase Grid-Tied Microinverters

    SciTech Connect (OSTI)

    2012-02-13

    Solar ADEPT Project: Transphorm is developing power switches for new types of inverters that improve the efficiency and reliability of converting energy from solar panels into useable electricity for the grid. Transistors act as fast switches and control the electrical energy that flows in an electrical circuit. Turning a transistor off opens the circuit and stops the flow of electrical current; turning it on closes the circuit and allows electrical current to flow. In this way a transistor can be used to convert DC from a solar panel into AC for use in a home. Transphorm’s transistors will enable a single semiconductor device to switch electrical currents at high-voltage in both directions—making the inverter more compact and reliable. Transphorm is using Gallium Nitride (GaN) as a semiconductor material in its transistors instead of silicon, which is used in most conventional transistors, because GaN transistors have lower losses at higher voltages and switching frequencies.

  4. Method of growing GaN films with a low density of structural defects using an interlayer

    DOE Patents [OSTI]

    Bourret-Courchesne, Edith D.

    2003-01-01

    A dramatic reduction of the dislocation density in GaN was obtained by insertion of a single thin interlayer grown at an intermediate temperature (IT-IL) after the growth of an initial grown at high temperature. A description of the growth process is presented with characterization results aimed at understanding the mechanisms of reduction in dislocation density. A large percentage of the threading dislocations present in the first GaN epilayer are found to bend near the interlayer and do not propagate into the top layer which grows at higher temperature in a lateral growth mode. TEM studies show that the mechanisms of dislocation reduction are similar to those described for the epitaxial lateral overgrowth process, however a notable difference is the absence of coalescence boundaries.

  5. Performance and breakdown characteristics of irradiated vertical power GaN P-i-N diodes

    SciTech Connect (OSTI)

    King, M. P.; Armstrong, A. M.; Dickerson, J. R.; Vizkelethy, G.; Fleming, R. M.; Campbell, J.; Wampler, W. R.; Kizilyalli, I. C.; Bour, D. P.; Aktas, O.; Nie, H.; Disney, D.; Wierer, Jr., J.; Allerman, A. A.; Moseley, M. W.; Kaplar, R. J.

    2015-10-29

    Electrical performance and defect characterization of vertical GaN P-i-N diodes before and after irradiation with 2.5 MeV protons and neutrons is investigated. Devices exhibit increase in specific on-resistance following irradiation with protons and neutrons, indicating displacement damage introduces defects into the p-GaN and n- drift regions of the device that impact on-state device performance. The breakdown voltage of these devices, initially above 1700 V, is observed to decrease only slightly for particle fluence <; 1013 cm-2. Furthermore, the unipolar figure of merit for power devices indicates that while the on-resistance and breakdown voltage degrade with irradiation, vertical GaN P-i-Ns remain superior to the performance of the best available, unirradiated silicon devices and on-par with unirradiated modern SiC-based power devices.

  6. Elimination of surface band bending on N-polar InN with thin GaN capping

    SciTech Connect (OSTI)

    Kuzmík, J. Haščík, Š.; Kučera, M.; Kúdela, R.; Dobročka, E.; Adikimenakis, A.; Mičušík, M.; Gregor, M.; Plecenik, A.; Georgakilas, A.

    2015-11-09

    0.5–1 μm thick InN (0001) films grown by molecular-beam epitaxy with N- or In-polarity are investigated for the presence of native oxide, surface energy band bending, and effects introduced by 2 to 4 monolayers of GaN capping. Ex situ angle-resolved x-ray photo-electron spectroscopy is used to construct near-surface (GaN)/InN energy profiles, which is combined with deconvolution of In3d signal to trace the presence of InN native oxide for different types of polarity and capping. Downwards surface energy band bending was observed on bare samples with native oxide, regardless of the polarity. It was found that the In-polar InN surface is most readily oxidized, however, with only slightly less band bending if compared with the N-polar sample. On the other hand, InN surface oxidation was effectively mitigated by GaN capping. Still, as confirmed by ultra-violet photo-electron spectroscopy and by energy band diagram calculations, thin GaN cap layer may provide negative piezoelectric polarization charge at the GaN/InN hetero-interface of the N-polar sample, in addition to the passivation effect. These effects raised the band diagram up by about 0.65 eV, reaching a flat-band profile.

  7. GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Lin, Yong; Leung, Benjamin; Li, Qiming; Figiel, Jeffrey J.; Wang, George T.

    2015-07-14

    In this study, ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on (11¯02) r-plane sapphire substrates. Dislocation free [112¯0] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar {101¯0} side facets, which appear due to a decrease in relative growth rate of the {101¯0} facets to the {101¯1} and {101¯1} facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal–organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an ordermore » of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.« less

  8. Transistors for Electric Motor Drives: High-Performance GaN HEMT Modules for Agile Power Electronics

    SciTech Connect (OSTI)

    2010-09-01

    ADEPT Project: Transphorm is developing transistors with gallium nitride (GaN) semiconductors that could be used to make cost-effective, high-performance power converters for a variety of applications, including electric motor drives which transmit power to a motor. A transistor acts like a switch, controlling the electrical energy that flows around an electrical circuit. Most transistors today use low-cost silicon semiconductors to conduct electrical energy, but silicon transistors don’t operate efficiently at high speeds and voltage levels. Transphorm is using GaN as a semiconductor material in its transistors because GaN performs better at higher voltages and frequencies, and it is more energy efficient than straight silicon. However, Transphorm is using inexpensive silicon as a base to help keep costs low. The company is also packaging its transistors with other electrical components that can operate quickly and efficiently at high power levels—increasing the overall efficiency of both the transistor and the entire motor drive.

  9. GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy

    SciTech Connect (OSTI)

    Lin, Yong; Leung, Benjamin; Li, Qiming; Figiel, Jeffrey J.; Wang, George T.

    2015-07-14

    In this study, ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on (11¯02) r-plane sapphire substrates. Dislocation free [112¯0] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar {101¯0} side facets, which appear due to a decrease in relative growth rate of the {101¯0} facets to the {101¯1} and {101¯1} facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal–organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an order of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.

  10. Electronic and optical device applications of hollow cathode plasma assisted atomic layer deposition based GaN thin films

    SciTech Connect (OSTI)

    Bolat, Sami Tekcan, Burak; Ozgit-Akgun, Cagla; Biyikli, Necmi; Okyay, Ali Kemal

    2015-01-15

    Electronic and optoelectronic devices, namely, thin film transistors (TFTs) and metalsemiconductormetal (MSM) photodetectors, based on GaN films grown by hollow cathode plasma-assisted atomic layer deposition (PA-ALD) are demonstrated. Resistivity of GaN thin films and metal-GaN contact resistance are investigated as a function of annealing temperature. Effect of the plasma gas and postmetallization annealing on the performances of the TFTs as well as the effect of the annealing on the performance of MSM photodetectors are studied. Dark current to voltage and responsivity behavior of MSM devices are investigated as well. TFTs with the N{sub 2}/H{sub 2} PA-ALD based GaN channels are observed to have improved stability and transfer characteristics with respect to NH{sub 3} PA-ALD based transistors. Dark current of the MSM photodetectors is suppressed strongly after high-temperature annealing in N{sub 2}:H{sub 2} ambient.

  11. Characterization of GaN nanowires grown on PSi, PZnO and PGaN on Si (111) substrates by thermal evaporation

    SciTech Connect (OSTI)

    Shekari, Leila; Hassan, Haslan Abu; Thahab, Sabah M.; Hassan, Zainuriah

    2012-06-20

    In this research, we used an easy and inexpensive method to synthesize highly crystalline GaN nanowires (NWs); on different substrates such as porous silicon (PSi), porous zinc oxide (PZnO) and porous gallium nitride (PGaN) on Si (111) wafer by thermal evaporation using commercial GaN powder without any catalyst. Micro structural studies by scanning electron microscopy and transmission electron microscope measurements reveal the role of different substrates in the morphology, nucleation and alignment of the GaN nanowires. The degree of alignment of the synthesized nanowires does not depend on the lattice mismatch between wires and their substrates. Further structural and optical characterizations were performed using high resolution X-ray diffraction and energy-dispersive X-ray spectroscopy. Results indicate that the nanowires are of single-crystal hexagonal GaN. The quality and density of grown GaN nanowires for different substrates are highly dependent on the lattice mismatch between the nanowires and their substrates and also on the size of the porosity of the substrates. Nanowires grown on PGaN have the best quality and highest density as compared to nanowires on other substrates. By using three kinds of porous substrates, we are able to study the increase in the alignment and density of the nanowires.

  12. Carrier and photon dynamics in a topological insulator Bi{sub 2}Te{sub 3}/GaN type II staggered heterostructure

    SciTech Connect (OSTI)

    Chaturvedi, P.; Chouksey, S.; Banerjee, D.; Ganguly, S.; Saha, D.

    2015-11-09

    We have demonstrated a type-II band-aligned heterostructure between pulsed laser deposited topological insulator bismuth telluride and metal organic-chemical-vapour deposited GaN on a sapphire substrate. The heterostructure shows a large valence band-offset of 3.27 eV as determined from x-ray photoelectron spectroscopy, which is close to the bandgap of GaN (3.4 eV). Further investigation using x-ray diffraction, Raman spectroscopy, and energy-dispersive x-ray spectrum reveals the stoichiometric and material properties of bismuth telluride on GaN. Steady state photon emission from GaN is found to be modulated by the charge transfer process due to diffusion across the junction. The time constant involved with the charge transfer process is found to be 0.6 ns by transient absorption spectroscopy. The heterostructure can be used for designing devices with different functionalities and improving the performance of the existing devices on GaN.

  13. TEM studies of laterally overgrown GaN layers grown on non-polarsubstrates

    SciTech Connect (OSTI)

    Liliental-Weber, Z.; Ni, X.; Morkoc, H.

    2006-01-05

    Transmission electron microscopy (TEM) was used to study pendeo-epitaxial GaN layers grown on polar and non-polar 4H SiC substrates. The structural quality of the overgrown layers was evaluated using a number of TEM methods. Growth of pendeo-epitaxial layers on polar substrates leads to better structural quality of the overgrown areas, however edge-on dislocations are found at the meeting fronts of two wings. Some misorientation between the 'seed' area and wing area was detected by Convergent Beam Electron Diffraction. Growth of pendeo-epitaxial layers on non-polar substrates is more difficult. Two wings on the opposite site of the seed area grow in two different polar directions with different growth rates. Most dislocations in a wing grown with Ga polarity are 10 times wider than wings grown with N-polarity making coalescence of these layers difficult. Most dislocations in a wing grown with Ga polarity bend in a direction parallel to the substrate, but some of them also propagate to the sample surface. Stacking faults formed on the c-plane and prismatic plane occasionally were found. Some misorientation between the wings and seed was detected using Large Angle Convergent Beam Diffraction.

  14. Radiation-induced defects in GaN bulk grown by halide vapor phase epitaxy

    SciTech Connect (OSTI)

    Duc, Tran Thien; Pozina, Galia; Son, Nguyen Tien; Janzn, Erik; Hemmingsson, Carl; Ohshima, Takeshi

    2014-09-08

    Defects induced by electron irradiation in thick free-standing GaN layers grown by halide vapor phase epitaxy were studied by deep level transient spectroscopy. In as-grown materials, six electron traps, labeled D2 (E{sub C}0.24?eV), D3 (E{sub C}0.60?eV), D4 (E{sub C}0.69?eV), D5 (E{sub C}0.96?eV), D7 (E{sub C}1.19?eV), and D8, were observed. After 2?MeV electron irradiation at a fluence of 1??10{sup 14?}cm{sup ?2}, three deep electron traps, labeled D1 (E{sub C}0.12?eV), D5I (E{sub C}0.89?eV), and D6 (E{sub C}1.14?eV), were detected. The trap D1 has previously been reported and considered as being related to the nitrogen vacancy. From the annealing behavior and a high introduction rate, the D5I and D6 centers are suggested to be related to primary intrinsic defects.

  15. Enhanced stability of Eu in GaN nanoparticles: Effects of Si co-doping

    SciTech Connect (OSTI)

    Kaur, Prabhsharan; Sekhon, S. S.; Zavada, J. M.; Kumar, Vijay

    2015-06-14

    Ab initio calculations on Eu doped (GaN){sub n} (n = 12, 13, and 32) nanoparticles show that Eu doping in nanoparticles is favorable compared with bulk GaN as a large fraction of atoms lie on the surface where strain can be released compared with bulk where often Eu doping is associated with a N vacancy. Co-doping of Si further facilitates Eu doping as strain from an oversized Eu atom and an undersized Si atom is compensated. These results along with low symmetry sites in nanoparticles make them attractive for developing strongly luminescent nanomaterials. The atomic and electronic structures are discussed using generalized gradient approximation (GGA) for the exchange-correlation energy as well as GGA + U formalism. In all cases of Eu (Eu + Si) doping, the magnetic moments are localized on the Eu site with a large value of 6μ{sub B} (7μ{sub B}). Our results suggest that co-doping can be a very useful way to achieve rare-earth doping in different hosts for optoelectronic materials.

  16. Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

    SciTech Connect (OSTI)

    Lee, June Key E-mail: hskim7@jbnu.ac.kr; Hyeon, Gil Yong; Tawfik, Wael Z.; Choi, Hee Seok; Ryu, Sang-Wan; Jeong, Tak; Jung, Eunjin; Kim, Hyunsoo E-mail: hskim7@jbnu.ac.kr

    2015-05-14

    Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by ∼35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region.

  17. High-power blue laser diodes with indium tin oxide cladding on semipolar (202{sup }1{sup }) GaN substrates

    SciTech Connect (OSTI)

    Pourhashemi, A. Farrell, R. M.; Cohen, D. A.; Speck, J. S.; DenBaars, S. P.; Nakamura, S.

    2015-03-16

    We demonstrate a high power blue laser diode (LD) using indium tin oxide as a cladding layer on semipolar oriented GaN. These devices show peak output powers and external quantum efficiencies comparable to state-of-the-art commercial c-plane devices. Ridge waveguide LDs were fabricated on (202{sup }1{sup }) oriented GaN substrates using InGaN waveguiding layers and GaN cladding layers. At a lasing wavelength of 451?nm at room temperature, an output power of 2.52?W and an external quantum efficiency of 39% were measured from a single facet under a pulsed injection current of 2.34?A. The measured differential quantum efficiency was 50%.

  18. Performance enhancement of GaN metalsemiconductormetal ultraviolet photodetectors by insertion of ultrathin interfacial HfO{sub 2} layer

    SciTech Connect (OSTI)

    Kumar, Manoj E-mail: aokyay@ee.bilkent.edu.tr; Tekcan, Burak; Okyay, Ali Kemal E-mail: aokyay@ee.bilkent.edu.tr

    2015-03-15

    The authors demonstrate improved device performance of GaN metalsemiconductormetal ultraviolet (UV) photodetectors (PDs) by ultrathin HfO{sub 2} (UT-HfO{sub 2}) layer on GaN. The UT-HfO{sub 2} interfacial layer is grown by atomic layer deposition. The dark current of the PDs with UT-HfO{sub 2} is significantly reduced by more than two orders of magnitude compared to those without HfO{sub 2} insertion. The photoresponsivity at 360?nm is as high as 1.42 A/W biased at 5 V. An excellent improvement in the performance of the devices is ascribed to allowed electron injection through UT-HfO{sub 2} on GaN interface under UV illumination, resulting in the photocurrent gain with fast response time.

  19. Highly mismatched crystalline and amorphous GaN(1-x)As(x) alloys in the whole composition range

    SciTech Connect (OSTI)

    Yu, K. M.; Novikov, S. V.; Broesler, R.; Demchenko, I. N.; Denlinger, J. D.; Liliental-Weber, Z.; Luckert, F.; Martin, R. W.; Walukiewicz, W.; Foxon, C. T.

    2009-08-29

    Alloying is a commonly accepted method to tailor properties of semiconductor materials for specific applications. Only a limited number of semiconductor alloys can be easily synthesized in the full composition range. Such alloys are, in general, formed of component elements that are well matched in terms of ionicity, atom size, and electronegativity. In contrast there is a broad class of potential semiconductor alloys formed of component materials with distinctly different properties. In most instances these mismatched alloys are immiscible under standard growth conditions. Here we report on the properties of GaN1-xAsx, a highly mismatched, immiscible alloy system that was successfully synthesized in the whole composition range using a nonequilibrium low temperature molecular beam epitaxy technique. The alloys are amorphous in the composition range of 0.17GaN to ~;;0.8 eV at x~;;0.85. The reduction in the band gap can be attributed primarily to the downward movement of the conduction band for alloys with x>0.2, and to the upward movement of the valence band for alloys with x<0.2. The unique features of the band structure offer an opportunity of using GaN1-xAsx alloys for various types of solar power conversion devices.

  20. Ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy on semipolar GaN (2021) substrates

    SciTech Connect (OSTI)

    Sawicka, M.; Grzanka, S.; Skierbiszewski, C.; Turski, H.; Muziol, G.; Krysko, M.; Grzanka, E.; Sochacki, T.; Siekacz, M.; Kucharski, R.

    2013-03-18

    Multi-quantum well (MQW) structures and light emitting diodes (LEDs) were grown on semipolar (2021) and polar (0001) GaN substrates by plasma-assisted molecular beam epitaxy. The In incorporation efficiency was found to be significantly lower for the semipolar plane as compared to the polar one. The semipolar MQWs exhibit a smooth surface morphology, abrupt interfaces, and a high photoluminescence intensity. The electroluminescence of semipolar (2021) and polar (0001) LEDs fabricated in the same growth run peaks at 387 and 462 nm, respectively. Semipolar LEDs with additional (Al,Ga)N cladding layers exhibit a higher optical output power but simultaneously a higher turn-on voltage.

  1. Ar{sup +}-irradiation-induced damage in hydride vapor-phase epitaxy GaN films

    SciTech Connect (OSTI)

    Nakano, Yoshitaka Ogawa, Daisuke; Nakamura, Keiji; Kawakami, Retsuo; Niibe, Masahito

    2015-07-15

    The authors have investigated the electrical characteristics of hydride vapor-phase epitaxy GaN films exposed to Ar{sup +} irradiation, employing Schottky barrier diodes. The Ar{sup +} irradiation tends to largely increase the effective carrier concentration in the near surface region of GaN up to ∼25 nm, due to the generation of donor-type N vacancy defects, compared to the original value before the irradiation. More interestingly, acceptor-type deep-level defects are found to be formed at ∼2.1, ∼2.9, and ∼3.2 eV below the conduction band in the subsequently deeper region, in which Ga vacancies introduced by the Ar{sup +} irradiation are considered to be in-diffused and immediately combined with hydrogen. These N vacancies and hydrogenated Ga vacancies formed are dominantly responsible for changing the depth profiles of the effective carrier concentration via the carrier generation, the carrier trapping, and/or carrier compensation.

  2. Effect of Fe-doping on nonlinear optical responses and carrier trapping dynamics in GaN single crystals

    SciTech Connect (OSTI)

    Fang, Yu; Yang, Junyi; Yang, Yong; Zhou, Feng; Wu, Xingzhi; Xiao, Zhengguo; Song, Yinglin

    2015-08-03

    We presented a quantitative study on the Fe-doping concentration dependence of optical nonlinearities and ultrafast carrier dynamics in Fe-doped GaN (GaN:Fe) single crystals using picosecond Z-scan and femtosecond pump-probe with phase object techniques under two-photon excitation. In contrast to the two-photon absorption that was found to be independent on the Fe-doping, the nonlinear refraction decreased with the Fe concentration due to the fast carrier trapping effect of Fe{sup 3+}/Fe{sup 2+} deep acceptors, which simultaneously acted as an efficient non-radiative recombination channels for excess carriers. Remarkably, compared to that of Si-doped GaN bulk crystal, the free-carrier refraction effect in GaN:Fe crystals was found to be enhanced considerably since Fe-doping and the effective carrier lifetime (∼10 ps) could be tuned over three orders of magnitude at high Fe-doping level of 1 × 10{sup 19 }cm{sup −3}.

  3. Strong geometrical effects in submillimeter selective area growth and light extraction of GaN light emitting diodes on sapphire

    SciTech Connect (OSTI)

    Tanaka, Atsunori; Chen, Renjie; Jungjohann, Katherine L.; Dayeh, Shadi A.

    2015-11-27

    Advanced semiconductor devices often utilize structural and geometrical effects to tailor their characteristics and improve their performance. Our detailed understanding of such geometrical effects in the epitaxial selective area growth of GaN on sapphire substrates is reported here, and we utilize them to enhance light extraction from GaN light emitting diodes. Systematic size and spacing effects were performed side-by-side on a single 2” sapphire substrate to minimize experimental sampling errors for a set of 144 pattern arrays with circular mask opening windows in SiO2. We show that the mask opening diameter leads to as much as 4 times increase in the thickness of the grown layers for 20 μm spacings and that spacing effects can lead to as much as 3 times increase in thickness for a 350 μm dot diameter. We also observed that the facet evolution in comparison with extracted Ga adatom diffusion lengths directly influences the vertical and lateral overgrowth rates and can be controlled with pattern geometry. Lastly, such control over the facet development led to 2.5 times stronger electroluminescence characteristics from well-faceted GaN/InGaN multiple quantum well LEDs compared to non-faceted structures.

  4. Strong geometrical effects in submillimeter selective area growth and light extraction of GaN light emitting diodes on sapphire

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Tanaka, Atsunori; Chen, Renjie; Jungjohann, Katherine L.; Dayeh, Shadi A.

    2015-11-27

    Advanced semiconductor devices often utilize structural and geometrical effects to tailor their characteristics and improve their performance. Our detailed understanding of such geometrical effects in the epitaxial selective area growth of GaN on sapphire substrates is reported here, and we utilize them to enhance light extraction from GaN light emitting diodes. Systematic size and spacing effects were performed side-by-side on a single 2” sapphire substrate to minimize experimental sampling errors for a set of 144 pattern arrays with circular mask opening windows in SiO2. We show that the mask opening diameter leads to as much as 4 times increase inmore » the thickness of the grown layers for 20 μm spacings and that spacing effects can lead to as much as 3 times increase in thickness for a 350 μm dot diameter. We also observed that the facet evolution in comparison with extracted Ga adatom diffusion lengths directly influences the vertical and lateral overgrowth rates and can be controlled with pattern geometry. Lastly, such control over the facet development led to 2.5 times stronger electroluminescence characteristics from well-faceted GaN/InGaN multiple quantum well LEDs compared to non-faceted structures.« less

  5. Increased p-type conductivity through use of an indium surfactant in the growth of Mg-doped GaN

    SciTech Connect (OSTI)

    Kyle, Erin C. H. Kaun, Stephen W.; Young, Erin C.; Speck, James S.

    2015-06-01

    We have examined the effect of an indium surfactant on the growth of p-type GaN by ammonia-based molecular beam epitaxy. p-type GaN was grown at temperatures ranging from 700 to 780 °C with and without an indium surfactant. The Mg concentration in all films in this study was 4.5–6 × 10{sup 19} cm{sup −3} as measured by secondary ion mass spectroscopy. All p-type GaN films grown with an indium surfactant had higher p-type conductivities and higher hole concentrations than similar films grown without an indium surfactant. The lowest p-type GaN room temperature resistivity was 0.59 Ω-cm, and the highest room temperature carrier concentration was 1.6 × 10{sup 18} cm{sup −3}. Fits of the temperature-dependent carrier concentration data showed a one to two order of magnitude lower unintentional compensating defect concentration in samples grown with the indium surfactant. Samples grown at higher temperature had a lower active acceptor concentration. Improvements in band-edge luminescence were seen by cathodoluminescence for samples grown with the indium surfactant, confirming the trends seen in the Hall data.

  6. Effect of AlN buffer layer properties on the morphology and polarity of GaN nanowires grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Brubaker, Matt D.; Rourke, Devin M.; Sanford, Norman A.; Bertness, Kris A.; Bright, Victor M.

    2011-09-01

    Low-temperature AlN buffer layers grown via plasma-assisted molecular beam epitaxy on Si (111) were found to significantly affect the subsequent growth morphology of GaN nanowires. The AlN buffer layers exhibited nanowire-like columnar protrusions, with their size, shape, and tilt determined by the AlN V/III flux ratio. GaN nanowires were frequently observed to adopt the structural characteristics of the underlying AlN columns, including the size and the degree of tilt. Piezoresponse force microscopy and polarity-sensitive etching indicate that the AlN films and the protruding columns have a mixed crystallographic polarity. Convergent beam electron diffraction indicates that GaN nanowires are Ga-polar, suggesting that Al-polar columns are nanowire nucleation sites for Ga-polar nanowires. GaN nanowires of low density could be grown on AlN buffers that were predominantly N-polar with isolated Al-polar columns, indicating a high growth rate for Ga-polar nanowires and suppressed growth of N-polar nanowires under typical growth conditions. AlN buffer layers grown under slightly N-rich conditions (V/III flux ratio = 1.0 to 1.3) were found to provide a favorable growth surface for low-density, coalescence-free nanowires.

  7. Study of the effects of GaN buffer layer quality on the dc characteristics of AlGaN/GaN high electron mobility transistors

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Ahn, Shihyun; Zhu, Weidi; Dong, Chen; Le, Lingcong; Hwang, Ya-Hsi; Kim, Byung-Jae; Ren, Fan; Pearton, Stephen J.; Lind, Aaron G.; Jones, Kevin S.; et al

    2015-04-21

    Here we studied the effect of buffer layer quality on dc characteristics of AlGaN/GaN high electron mobility (HEMTs). AlGaN/GaN HEMT structures with 2 and 5 μm GaN buffer layers on sapphire substrates from two different vendors with the same Al concentration of AlGaN were used. The defect densities of HEMT structures with 2 and 5 μm GaN buffer layer were 7 × 109 and 5 × 108 cm₋2, respectively, as measured by transmission electron microscopy. There was little difference in drain saturation current or in transfer characteristics in HEMTs on these two types of buffer. However, there was no dispersionmore » observed on the nonpassivated HEMTs with 5 μm GaN buffer layer for gate-lag pulsed measurement at 100 kHz, which was in sharp contrast to the 71% drain current reduction for the HEMT with 2 μm GaN buffer layer.« less

  8. ALD TiO2-Al2O3 Stack: An Improved Gate Dielectrics on Ga-polar GaN MOSCAPs

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wei, Daming; Edgar, James H.; Briggs, Dayrl P.; Srijanto, Bernadeta R.; Retterer, Scott T.; Meyer, III, Harry M.

    2014-10-15

    This research focuses on the benefits and properties of TiO2-Al2O3 nano-stack thin films deposited on Ga2O3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO2, 7.1 nm Al2O3 and 2 nm Ga2O3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectron spectroscopy (XPS) depth profile, was negligible for GaN pretreated bymore » thermal oxidation in O2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO2-Al2O3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al2O3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 1011 cm-2. The gate leakage current density (J=2.81× 10-8 A/cm2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO2/Al2O3 for serving as the gate oxide on Ga2O3/GaN based MOS devices.« less

  9. Vehicle Technologies Office Merit Review 2014: Advanced Low-Cost SiC and GaN Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction Drives

    Broader source: Energy.gov [DOE]

    Presentation given by APEI Inc. at 2014 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about Advanced low-cost SIC and GaN wide...

  10. Vehicle Technologies Office Merit Review 2015: Advanced Low-Cost SiC and GaN Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction Drives

    Broader source: Energy.gov [DOE]

    Presentation given by APEI Inc. at 2015 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about advanced low-cost SiC and GaN wide...

  11. Role of an ultra-thin AlN/GaN superlattice interlayer on the strain engineering of GaN films grown on Si(110) and Si(111) substrates by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Shen, X. Q.; Takahashi, T.; Matsuhata, H.; Ide, T.; Shimizu, M.; Rong, X.; Chen, G.; Wang, X. Q.; Shen, B.

    2013-12-02

    We investigate the role of an ultra-thin AlN/GaN superlattice interlayer (SL-IL) on the strain engineering of the GaN films grown on Si(110) and Si(111) substrates by plasma-assisted molecular beam epitaxy. It is found that micro-cracks limitted only at the SL-IL position are naturally generated. These micro-cracks play an important role in relaxing the tensile strain caused by the difference of the coefficient of thermal expansion between GaN and Si and keeping the residual strain in the crack-free GaN epilayers resulted from the SL-IL during the growth. The mechanism understanding of the strain modulation by the SL-IL in the GaN epilayers grown on Si substrates makes it possible to design new heterostructures of III-nitrides for optic and electronic device applications.

  12. Polarity characterization by anomalous x-ray dispersion of ZnO films and GaN lateral polar structures

    SciTech Connect (OSTI)

    Shelton, Christopher T.; Sachet, Edward; Paisley, Elizabeth A.; Hoffmann, Marc P.; Rajan, Joseph; Collazo, Ramn; Sitar, Zlatko; Maria, Jon-Paul

    2014-01-28

    We demonstrate the use of anomalous x-ray scattering of constituent cations at their absorption edge, in a conventional Bragg-Brentano diffractometer, to measure absolutely and quantitatively the polar orientation and polarity fraction of unipolar and mixed polar wurtzitic crystals. In one set of experiments, the gradual transition between c+ and c? polarity of epitaxial ZnO films on sapphire as a function of MgO buffer layer thickness is monitored quantitatively, while in a second experiment, we map the polarity of a lateral polar homojunction in GaN. The dispersion measurements are compared with piezoforce microscopy images, and we demonstrate how x-ray dispersion and scanning probe methods can provide complementary information that can discriminate between polarity fractions at a material surface and polarity fractions averaged over the film bulk.

  13. Phase-field simulations of GaN growth by selective area epitaxy on complex mask geometries

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Aagesen, Larry K.; Coltrin, Michael Elliott; Han, Jung; Thornton, Katsuyo

    2015-05-15

    Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. Furthermore, this model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. We found that the model provides a route to optimize masks andmore » processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.« less

  14. Phase-field simulations of GaN growth by selective area epitaxy from complex mask geometries

    SciTech Connect (OSTI)

    Aagesen, Larry K.; Thornton, Katsuyo; Coltrin, Michael E.; Han, Jung

    2015-05-21

    Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. The model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. The model provides a route to optimize masks and processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.

  15. Compositionally graded relaxed AlGaN buffers on semipolar GaN for mid-ultraviolet emission

    SciTech Connect (OSTI)

    Young, Erin C.; Wu Feng; Haeger, Daniel A.; Nakamura, Shuji; Denbaars, Steven P.; Cohen, Daniel A.; Speck, James S.; Romanov, Alexey E.

    2012-10-01

    In this Letter, we report on the growth and properties of relaxed, compositionally graded Al{sub x}Ga{sub 1-x}N buffer layers on freestanding semipolar (2021) GaN substrates. Continuous and step compositional grades with Al concentrations up to x = 0.61 have been achieved, with emission wavelengths in the mid-ultraviolet region as low as 265 nm. Coherency stresses were relaxed progressively throughout the grades by misfit dislocation generation via primary (basal) slip and secondary (non-basal) slip systems. Threading dislocation densities in the final layers of the grades were less than 10{sup 6}/cm{sup 2} as confirmed by plan-view transmission electron microscopy and cathodoluminescence studies.

  16. Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

    SciTech Connect (OSTI)

    Li, X.; Nilsson, D.; Danielsson, Ö.; Pedersen, H.; Janzén, E.; Forsberg, U.; Bergsten, J.; Rorsman, N.

    2015-12-28

    The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) epitaxial layer closest to the substrate and a lower doped layer (3 × 10{sup 16 }cm{sup −3}) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

  17. Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

    SciTech Connect (OSTI)

    Lupina, L.; Zoellner, M. H.; Dietrich, B.; Capellini, G.; Niermann, T.; Lehmann, M.; Thapa, S. B.; Haeberlen, M.; Storck, P.; Schroeder, T.

    2015-11-16

    We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} buffer system a very promising template for the growth of high quality GaN layers on silicon.

  18. Temperature dependent dielectric function and the E{sub 0} critical points of hexagonal GaN from 30 to 690 K

    SciTech Connect (OSTI)

    Kim, Tae Jung Hwang, Soon Yong; Byun, Jun Seok; Barange, Nilesh S.; Park, Han Gyeol; Dong Kim, Young

    2014-02-15

    The complex dielectric function ? and the E{sub 0} excitonic and band-edge critical-point structures of hexagonal GaN are reported for temperatures from 30 to 690 K and energies from 0.74 to 6.42 eV, obtained by rotating-compensator spectroscopic ellipsometry on a 1.9 ?m thick GaN film deposited on a c-plane (0001) sapphire substrate by molecular beam epitaxy. Direct inversion and B-splines in a multilayer-structure calculation were used to extract the optical properties of the film from the measured pseudodielectric function ???. At low temperature sharp E{sub 0} excitonic and critical-point interband transitions are separately observed. Their temperature dependences were determined by fitting the data to the empirical Varshni relation and the phenomenological expression that contains the Bose-Einstein statistical factor.

  19. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy

    SciTech Connect (OSTI)

    Lotsari, A.; Kehagias, Th.; Katsikini, M.; Arvanitidis, J.; Ves, S.; Komninou, Ph.; Dimitrakopulos, G. P.; Tsiakatouras, G.; Tsagaraki, K.; Georgakilas, A.; Christofilos, D.

    2014-06-07

    Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the M-shape dependence of the (112{sup }0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.

  20. Measurement of the hot electron mean free path and the momentum relaxation rate in GaN

    SciTech Connect (OSTI)

    Suntrup, Donald J.; Gupta, Geetak; Li, Haoran; Keller, Stacia; Mishra, Umesh K.

    2014-12-29

    We present a method for measuring the mean free path and extracting the momentum relaxation time of hot electrons in GaN using the hot electron transistor (HET). In this device, electrons are injected over a high energy emitter barrier into the base where they experience quasi-ballistic transport well above the conduction band edge. After traversing the base, high energy electrons either surmount the base-collector barrier and become collector current or reflect off the barrier and become base current. We fabricate HETs with various base thicknesses and measure the common emitter transfer ratio (α) for each device. The mean free path is extracted by fitting α to a decaying exponential as a function of base width and the relaxation time is computed using a suitable injection velocity. For devices with an injection energy of ∼1 eV, we measure a hot electron mean free path of 14 nm and calculate a momentum relaxation time of 16 fs. These values are in agreement with theoretical calculations where longitudinal optical phonon scattering is the dominant momentum relaxation mechanism.

  1. InGaN/GaN tunnel junctions for hole injection in GaN light emitting diodes

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram E-mail: rajan@ece.osu.edu; Akyol, Fatih; Rajan, Siddharth E-mail: rajan@ece.osu.edu

    2014-10-06

    InGaN/GaN tunnel junction contacts were grown using plasma assisted molecular beam epitaxy (MBE) on top of a metal-organic chemical vapor deposition (MOCVD)-grown InGaN/GaN blue (450?nm) light emitting diode. A voltage drop of 5.3?V at 100?mA, forward resistance of 2 10{sup ?2} ? cm{sup 2}, and a higher light output power compared to the reference light emitting diodes (LED) with semi-transparent p-contacts were measured in the tunnel junction LED (TJLED). A forward resistance of 5??10{sup ?4} ? cm{sup 2} was measured in a GaN PN junction with the identical tunnel junction contact as the TJLED, grown completely by MBE. The depletion region due to the impurities at the regrowth interface between the MBE tunnel junction and the MOCVD-grown LED was hence found to limit the forward resistance measured in the TJLED.

  2. Design, fabrication, and performance analysis of GaN vertical electron transistors with a buried p/n junction

    SciTech Connect (OSTI)

    Yeluri, Ramya Lu, Jing; Keller, Stacia; Mishra, Umesh K.; Hurni, Christophe A.; Browne, David A.; Speck, James S.; Chowdhury, Srabanti

    2015-05-04

    The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9?kA/cm{sup 2}) and low ON-resistance (0.4 m? cm{sup 2}) are demonstrated. Non-planar selective area regrowth is identified as the limiting factor to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown voltage with high current will enable GaN vertical transistors with high power densities.

  3. Ultraviolet GaN photodetectors on Si via oxide buffer heterostructures with integrated short period oxide-based distributed Bragg reflectors and leakage suppressing metal-oxide-semiconductor contacts

    SciTech Connect (OSTI)

    Szyszka, A. E-mail: adam.szyszka@pwr.wroc.pl; Haeberlen, M.; Storck, P.; Thapa, S. B.; Schroeder, T.

    2014-08-28

    Based on a novel double step oxide buffer heterostructure approach for GaN integration on Si, we present an optimized Metal-Semiconductor-Metal (MSM)-based Ultraviolet (UV) GaN photodetector system with integrated short-period (oxide/Si) Distributed Bragg Reflector (DBR) and leakage suppressing Metal-Oxide-Semiconductor (MOS) electrode contacts. In terms of structural properties, it is demonstrated by in-situ reflection high energy electron diffraction and transmission electron microscopy-energy dispersive x-ray studies that the DBR heterostructure layers grow with high thickness homogeneity and sharp interface structures sufficient for UV applications; only minor Si diffusion into the Y{sub 2}O{sub 3} films is detected under the applied thermal growth budget. As revealed by comparative high resolution x-ray diffraction studies on GaN/oxide buffer/Si systems with and without DBR systems, the final GaN layer structure quality is not significantly influenced by the growth of the integrated DBR heterostructure. In terms of optoelectronic properties, it is demonstrated thatwith respect to the basic GaN/oxide/Si system without DBRthe insertion of (a) the DBR heterostructures and (b) dark current suppressing MOS contacts enhances the photoresponsivity below the GaN band-gap related UV cut-off energy by almost up to two orders of magnitude. Given the in-situ oxide passivation capability of grown GaN surfaces and the one order of magnitude lower number of superlattice layers in case of higher refractive index contrast (oxide/Si) systems with respect to classical III-N DBR superlattices, virtual GaN substrates on Si via functional oxide buffer systems are thus a promising robust approach for future GaN-based UV detector technologies.

  4. Effects of substrate temperature, substrate orientation, and energetic atomic collisions on the structure of GaN films grown by reactive sputtering

    SciTech Connect (OSTI)

    Schiaber, Ziani S.; Lisboa-Filho, Paulo N.; Silva, Jos H. D. da; Leite, Douglas M. G.; Bortoleto, Jos R. R.

    2013-11-14

    The combined effects of substrate temperature, substrate orientation, and energetic particle impingement on the structure of GaN films grown by reactive radio-frequency magnetron sputtering are investigated. Monte-Carlo based simulations are employed to analyze the energies of the species generated in the plasma and colliding with the growing surface. Polycrystalline films grown at temperatures ranging from 500 to 1000 C clearly showed a dependence of orientation texture and surface morphology on substrate orientation (c- and a-plane sapphire) in which the (0001) GaN planes were parallel to the substrate surface. A large increase in interplanar spacing associated with the increase in both a- and c-parameters of the hexagonal lattice and a redshift of the optical bandgap were observed at substrate temperatures higher than 600 C. The results showed that the tensile stresses produced during the film's growth in high-temperature deposition ranges were much larger than the expected compressive stresses caused by the difference in the thermal expansion coefficients of the film and substrate in the cool-down process after the film growth. The best films were deposited at 500 C, 30 W and 600 C, 45 W, which corresponds to conditions where the out diffusion from the film is low. Under these conditions the benefits of the temperature increase because of the decrease in defect density are greater than the problems caused by the strongly strained lattice that occurr at higher temperatures. The results are useful to the analysis of the growth conditions of GaN films by reactive sputtering.

  5. Photo-induced water oxidation at the aqueous GaN (101¯0) interface: Deprotonation kinetics of the first proton-coupled electron-transfer step

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Ertem, Mehmed Z.; Kharche, Neerav; Batista, Victor S.; Hybertsen, Mark S.; Tully, John C.; Muckerman, James T.

    2015-03-12

    Photoeclectrochemical water splitting plays a key role in a promising path to the carbon-neutral generation of solar fuels. Wurzite GaN and its alloys (e.g., GaN/ZnO and InGaN) are demonstrated photocatalysts for water oxidation, and they can drive the overall water splitting reaction when coupled with co-catalysts for proton reduction. In the present work, we investigate the water oxidation mechanism on the prototypical GaN (101¯0) surface using a combined ab initio molecular dynamics and molecular cluster model approach taking into account the role of water dissociation and hydrogen bonding within the first solvation shell of the hydroxylated surface. The investigation ofmore » free-energy changes for the four proton-coupled electron-transfer (PCET) steps of the water oxidation mechanism shows that the first PCET step for the conversion of –Ga-OH to –Ga-O˙⁻ requires the highest energy input. We further examine the sequential PCETs, with the proton transfer (PT) following the electron transfer (ET), and find that photo-generated holes localize on surface –NH sites is thermodynamically more favorable than –OH sites. However, proton transfer from –OH sites with subsequent localization of holes on oxygen atoms is kinetically favored owing to hydrogen bonding interactions at the GaN (101¯0)–water interface. We find that the deprotonation of surface –OH sites is the limiting factor for the generation of reactive oxyl radical ion intermediates and consequently for water oxidation.« less

  6. Photo-induced water oxidation at the aqueous GaN (1010) interface: Deprotonation kinetics of the first proton-coupled electron-transfer step

    SciTech Connect (OSTI)

    Ertem, Mehmed Z.; Kharche, Neerav; Batista, Victor S.; Hybertsen, Mark S.; Tully, John C.; Muckerman, James T.

    2015-03-12

    Photoeclectrochemical water splitting plays a key role in a promising path to the carbon-neutral generation of solar fuels. Wurzite GaN and its alloys (e.g., GaN/ZnO and InGaN) are demonstrated photocatalysts for water oxidation, and they can drive the overall water splitting reaction when coupled with co-catalysts for proton reduction. In the present work, we investigate the water oxidation mechanism on the prototypical GaN (1010) surface using a combined ab initio molecular dynamics and molecular cluster model approach taking into account the role of water dissociation and hydrogen bonding within the first solvation shell of the hydroxylated surface. The investigation of free-energy changes for the four proton-coupled electron-transfer (PCET) steps of the water oxidation mechanism shows that the first PCET step for the conversion of Ga-OH to Ga-O?? requires the highest energy input. We further examine the sequential PCETs, with the proton transfer (PT) following the electron transfer (ET), and find that photo-generated holes localize on surface NH sites is thermodynamically more favorable than OH sites. However, proton transfer from OH sites with subsequent localization of holes on oxygen atoms is kinetically favored owing to hydrogen bonding interactions at the GaN (1010)water interface. We find that the deprotonation of surface OH sites is the limiting factor for the generation of reactive oxyl radical ion intermediates and consequently for water oxidation.

  7. Mismatch relaxation by stacking fault formation of AlN islands in AlGaN/GaN structures on m-plane GaN substrates

    SciTech Connect (OSTI)

    Smalc-Koziorowska, Julita; Sawicka, Marta; Skierbiszewski, Czeslaw; Grzegory, Izabella

    2011-08-08

    We study the mismatch relaxation of 2-5 nm thin elongated AlN islands formed during growth of AlGaN on bulk m-plane GaN by molecular beam epitaxy. The relaxation of these m-plane AlN layers is anisotropic and occurs through the introduction of stacking faults in [0001] planes during island coalescence, while no relaxation is observed along the perpendicular [1120] direction. This anisotropy in the mismatch relaxation and the formation of stacking faults in the AlN islands are explained by the growth mode of the AlN platelets and their coalescence along the [0001] direction.

  8. Thermal stability of deep level defects induced by high energy proton irradiation in n-type GaN

    SciTech Connect (OSTI)

    Zhang, Z.; Farzana, E.; Sun, W. Y.; Arehart, A. R.; Ringel, S. A.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; McSkimming, B.; Kyle, E. C. H.; Speck, J. S.

    2015-10-21

    The impact of annealing of proton irradiation-induced defects in n-type GaN devices has been systematically investigated using deep level transient and optical spectroscopies. Moderate temperature annealing (>200–250 °C) causes significant reduction in the concentration of nearly all irradiation-induced traps. While the decreased concentration of previously identified N and Ga vacancy related levels at E{sub C} − 0.13 eV, 0.16 eV, and 2.50 eV generally followed a first-order reaction model with activation energies matching theoretical values for N{sub I} and V{sub Ga} diffusion, irradiation-induced traps at E{sub C} − 0.72 eV, 1.25 eV, and 3.28 eV all decrease in concentration in a gradual manner, suggesting a more complex reduction mechanism. Slight increases in concentration are observed for the N-vacancy related levels at E{sub C} − 0.20 eV and 0.25 eV, which may be due to the reconfiguration of other N-vacancy related defects. Finally, the observed reduction in concentrations of the states at E{sub C} − 1.25 and E{sub C} − 3.28 eV as a function of annealing temperature closely tracks the detailed recovery behavior of the background carrier concentration as a function of annealing temperature. As a result, it is suggested that these two levels are likely to be responsible for the underlying carrier compensation effect that causes the observation of carrier removal in proton-irradiated n-GaN.

  9. Donor impurity states and related terahertz range nonlinear optical response in GaN cylindrical quantum wires: Effects of external electric and magnetic fields

    SciTech Connect (OSTI)

    Correa, J. D.; Mora-Ramos, M. E.; Duque, C. A.

    2014-06-07

    We report a study on the optical absorption coefficient associated to hydrogenic impurity interstate transitions in zinc-blende GaN quantum wires of cylindrical shape taking into account the effects of externally applied static electric and magnetic fields. The electron states emerge within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement and external field effects. The nonlinear optical absorption is calculated using a recently derived expression for the dielectric susceptibility, obtained via a nonperturbative solution of the density-matrix Bloch equation. Our results show that this treatment eliminates not only the intensity-dependent bleaching effect but also the change in sign of the nonlinear contribution due to the combined effect of asymmetric impurity location and the applied electric field.

  10. Three-dimensional spectrum mapping of bright emission centers: Investigating the brightness-limiting process in Eu-doped GaN red light emitting diodes

    SciTech Connect (OSTI)

    Ishii, Masashi; Koizumi, Atsushi; Fujiwara, Yasufumi

    2015-08-24

    A pulse-driven emission-spectroscopy mapping technique is used to investigate the bright emission centers in Eu-doped GaN (GaN:Eu) red light emitting diodes (LED). The LEDs are operated in pulse-driven mode, and the emission spectra are acquired for a range of pulse frequencies. This ensemble of emission spectral data yields a three-dimensional mapping that allows the origin of emission lines to be identified by visual inspection. The identification was achieved even for a weak {sup 5}D{sub 0} → {sup 7}F{sub 3} transition in conventional photoluminescence measurements. A peculiar split is observed in the {sup 5}D{sub 0} → {sup 7}F{sub 3} transition for the bright emission center referred to as OMVPE 8. Despite the unique transition at this emission center, the emission efficiencies for the {sup 5}D{sub 0} → {sup 7}F{sub 3} and {sup 5}D{sub 0} → {sup 7}F{sub 2} transitions were identical. This finding indicates that the excitation of the emission centers, rather than the radiative transitions, is the limiting process that determines the GaN:Eu red LED brightness.

  11. Relaxation and critical strain for maximum In incorporation in AlInGaN on GaN grown by metal organic vapour phase epitaxy

    SciTech Connect (OSTI)

    Reuters, Benjamin; Finken, M.; Wille, A.; Kalisch, H.; Vescan, A.; Hollaender, B.; Heuken, M.

    2012-11-01

    Quaternary AlInGaN layers were grown on conventional GaN buffer layers on sapphire by metal organic vapour phase epitaxy at different surface temperatures and different reactor pressures with constant precursor flow conditions. A wide range in compositions within 30-62% Al, 5-29% In, and 23-53% Ga was covered, which leads to different strain states from high tensile to high compressive. From high-resolution x-ray diffraction and Rutherford backscattering spectrometry, we determined the compositions, strain states, and crystal quality of the AlInGaN layers. Atomic force microscopy measurements were performed to characterize the surface morphology. A critical strain value for maximum In incorporation near the AlInGaN/GaN interface is presented. For compressively strained layers, In incorporation is limited at the interface as residual strain cannot exceed an empirical critical value of about 1.1%. Relaxation occurs at about 15 nm thickness accompanied by strong In pulling. Tensile strained layers can be grown pseudomorphically up to 70 nm at a strain state of 0.96%. A model for relaxation in compressively strained AlInGaN with virtual discrete sub-layers, which illustrates the gradually changing lattice constant during stress reduction is presented.

  12. Poole-Frenkel effect on electrical characterization of Al-doped ZnO films deposited on p-type GaN

    SciTech Connect (OSTI)

    Huang, Bohr-Ran; Liao, Chung-Chi; Ke, Wen-Cheng Chang, Yuan-Ching; Huang, Hao-Ping; Chen, Nai-Chuan

    2014-03-21

    This paper presents the electrical properties of Al-doped ZnO (AZO) films directly grown on two types of p-type GaN thin films. The low-pressure p-GaN thin films (LP-p-GaN) exhibited structural properties of high-density edge-type threading dislocations (TDs) and compensated defects (i.e., nitrogen vacancy). Compared with high-pressure p-GaN thin films (HP-p-GaN), X-ray photoemission spectroscopy of Ga 3d core levels indicated that the surface Fermi-level shifted toward the higher binding-energy side by approximately 0.7 eV. The high-density edge-type TDs and compensated defects enabled surface Fermi-level shifting above the intrinsic Fermi-level, causing the surface of LP-p-GaN thin films to invert to n-type semiconductor. A highly nonlinear increase in leakage current regarding reverse-bias voltage was observed for AZO/LP-p-GaN. The theoretical fits for the reverse-bias voltage region indicated that the field-assisted thermal ionization of carriers from defect associated traps, which is known as the Poole-Frenkel effect, dominated the I-V behavior of AZO/LP-p-GaN. The fitting result estimated the trap energy level at 0.62 eV below the conduction band edge. In addition, the optical band gap increased from 3.50 eV for as-deposited AZO films to 3.62 eV for 300 °C annealed AZO films because of the increased carrier concentration. The increasing Fermi-level of the 300 °C annealed AZO films enabled the carrier transport to move across the interface into the LP-p-GaN thin films without any thermal activated energy. Thus, the Ohmic behavior of AZO contact can be achieved directly on the low-pressure p-GaN films at room temperature.

  13. AMIE Gan Island Ancillary Disdrometer Field Campaign...

    Office of Scientific and Technical Information (OSTI)

    Ancillary Disdrometer Field Campaign Report M Oue April 2016 CLIMATE RESEARCH FACILITY DISCLAIMER This report was prepared as an account of work sponsored by the U.S. Government. ...

  14. ARM - Facility News Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    5, 2011 [Facility News] Team Continues Campaign Planning on Gan Island Bookmark and Share Mike Ritsche, technical operations manager for the AMF2, discusses instrumentation specifics with Gan airport and MMS officials. Mike Ritsche, technical operations manager for the AMF2, discusses instrumentation specifics with Gan airport and MMS officials. For its first international field campaign, the second ARM Mobile Facility (AMF2) is scheduled to operate on Gan Island in the Indian Ocean for the ARM

  15. Microsoft Word - Airports.docx

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Airports Blacksburg and the New River Valley are serviced by three local airports; two are private and the other is commercial. For international service, Richmond International and Charlotte Douglas are just a couple of hours drive. Roanoke-Blacksburg Regional Airport is the closest commercial airport with connections to major cities such as Charlotte, Orlando, New York and Chicago. Travel to Roanoke is made even simpler with The Smart Way, a bus service connecting the New River Valley to

  16. AMIE Gan Island Ancillary Disdrometer Field Campaign Report ...

    Office of Scientific and Technical Information (OSTI)

    SMART-R C-band radar, and the National Center for Atmospheric Research (NCAR) dual ... Comparing the disdrometer data with 2DVD data, the raindrop size distribution data will be ...

  17. ARM - Field Campaign - ARM MJO Investigation Experiment on Gan...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    was designed to test several current hypotheses regarding the mechanisms responsible for MJO (Madden-Julian Oscillation) initiation and propagation in the Indian Ocean area. ...

  18. Lu Gan | Center for Bio-Inspired Solar Fuel Production

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    92 2.184 2.149 2.175 2.227 2.284 1993-2016 All Grades - Conventional Areas 2.193 2.187 2.150 2.179 2.231 2.287 1994-2016 All Grades - Reformulated Areas 2.182 2.156 2.138 2.133 2.181 2.249 1994-2016 Regular 2.033 2.025 1.991 2.016 2.068 2.128 1993-2016 Conventional Areas 2.036 2.030 1.993 2.021 2.073 2.132 1993-2016 Reformulated Areas 2.009 1.980 1.965 1.959 2.011 2.080 1994-2016 Midgrade 2.327 2.321 2.285 2.322 2.371 2.424 1994-2016 Conventional Areas 2.322 2.317 2.280 2.320 2.371 2.423

  19. airport | National Nuclear Security Administration

    National Nuclear Security Administration (NNSA)

    airport | National Nuclear Security Administration Facebook Twitter Youtube Flickr RSS People Mission Managing the Stockpile Preventing Proliferation Powering the Nuclear Navy...

  20. Airports & Lodging | Savannah River Ecology Laboratory

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Airports and Lodging AIRPORTS Augusta, GA Augusta Regional Airport (Bush Field) - closest commercial airport; Delta and U.S. Express. Daniel Field - private planes, rentals, or chartered flights. Columbia, SC Columbia Metropolitan Airport - all major carriers; 1.5-2h drive to SREL. Atlanta, GA Hartsfield Airport - all major carriers; 2.5-3 hour drive from Atlanta, GA, to Aiken, SC. LODGING No lodging is available at SREL. However, hotels and motels are available in Aiken, SC, and Augusta, GA.

  1. Beijing Capital International Airport | Open Energy Information

    Open Energy Info (EERE)

    International Airport Jump to: navigation, search Name: Beijing Capital International Airport Place: Beijing, Beijing Municipality, China Zip: 100621 Product: Beijing Capital...

  2. FAA Airport Categories Website | Open Energy Information

    Open Energy Info (EERE)

    Categories Website Jump to: navigation, search OpenEI Reference LibraryAdd to library Web Site: FAA Airport Categories Website Abstract This website lists FAA airport...

  3. Philadelphia International Airport Apron Lighting: LED System...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Philadelphia International Airport Apron Lighting: LED System Performance in a Trial Installation Philadelphia International Airport Apron Lighting: LED System Performance in a ...

  4. LASO Airport Landfill | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    LASO Airport Landfill LASO Airport Landfill The Los Alamos Airport Landfill consists of two inactive solid waste disposal sites [the airport landfill, SWMU 73-001(a) and the debris disposal area (DDA), SWMU 73-001(d)] are located at the Los Alamos County Airport. In late 2006 and early 2007, the Final Remedy landfill cover system was installed at the airport landfill. The Final Remedy design and completion activities for the airport landfill and the DDA are provided in the Remedy Completion

  5. Denver International Airport Photovoltaic System

    Office of Energy Efficiency and Renewable Energy (EERE)

    The Denver International Airport (DIA) features a 2-megawatt (MW) photovoltaic (PV) system. DIA also hosts to a second 1.6-MW system. Denver is a Solar America City.

  6. Tonopah Airport Solar Power Plant | Open Energy Information

    Open Energy Info (EERE)

    Tonopah Airport Solar Power Plant Jump to: navigation, search Name Tonopah Airport Solar Power Plant Facility Tonopah Airport Solar Sector Solar Facility Type Concentrating Solar...

  7. Prescott Airport Solar Plant Solar Power Plant | Open Energy...

    Open Energy Info (EERE)

    Prescott Airport Solar Plant Solar Power Plant Jump to: navigation, search Name Prescott Airport Solar Plant Solar Power Plant Facility Prescott Airport Solar Plant Sector Solar...

  8. Airports & Lodging | Savannah River Ecology Laboratory

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Columbia, SC Columbia Metropolitan Airport - all major carriers; 1.5-2h drive to SREL. Atlanta, GA Hartsfield Airport - all major carriers; 2.5-3 hour drive from Atlanta, GA, to ...

  9. Airports - Local Information - Radiation Effects Facility / Cyclotron

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Institute / Texas A&M University Airports College Station is served locally by Easterwood Airport (5 min. drive), with airports in Austin (2 hr. drive) and Houston (1 hr 45 min. drive) not far away. Easterwood Airport / College Station / Directions George Bush Intercontinental / Houston / Directions Austin-Bergstrom International / Austin / Directions Directional maps are provided as a guide. It is recommended that you use google maps or map quest for more detailed directions. Quick

  10. Implementing Solar Technologies at Airports

    SciTech Connect (OSTI)

    Kandt, A.; Romero, R.

    2014-07-01

    Federal agencies, such as the Department of Defense and Department of Homeland Security, as well as numerous private entities are actively pursuing the installation of solar technologies to help reduce fossil fuel energy use and associated emissions, meet sustainability goals, and create more robust or reliable operations. One potential approach identified for siting solar technologies is the installation of solar energy technologies at airports and airfields, which present a significant opportunity for hosting solar technologies due to large amounts of open land. This report focuses largely on the Federal Aviation Administration's (FAA's) policies toward siting solar technologies at airports.

  11. EECBG Success Story: New San Antonio Airport Terminal Generating...

    Broader source: Energy.gov (indexed) [DOE]

    new photovoltaic system at the San Antonio International Airport. The new photovoltaic system at the San Antonio International Airport. In early 2010, the City of San Antonio's ...

  12. Alternative Fuels Data Center: Airport Shuttles Run on Propane

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    " Don Duvernay, Airport Shuttle General Manager, Louis Armstrong New Orleans International The Louis Armstrong New Orleans International Airport in the Big Easy uses 27 ...

  13. Siting Solar Photovoltaics at Airports: Preprint

    SciTech Connect (OSTI)

    Kandt, A.; Romero, R.

    2014-06-01

    Airports present a significant opportunity for hosting solar technologies due to their open land; based on a 2010 Federal Aviation Administration study, the US Department of Agriculture, and the US Fish and Wildlife Service, there's potential for 116,704 MW of solar photovoltaics (PV) on idle lands at US airports. PV has a low profile and likely low to no impact on flight operations. This paper outlines guidance for implementing solar technologies at airports and airfields, focusing largely on the Federal Aviation Administration's policies. The paper also details best practices for siting solar at airports, provides information on the Solar Glare Hazard Analysis Tool, and highlights a case study example where solar has been installed at an airport.

  14. LEDs Ready for Takeoff at Louisiana Airport

    Broader source: Energy.gov [DOE]

    About 250 lights along the busy taxiway at Hammond Northshore Regional Airport are being replaced with light-emitting diodes (LEDs) with funds from an Energy Efficiency and Conservation Block Grant (EECBG) from the U.S. Department of Energy.

  15. Yeager Airport Hydrogen Vehicle Test Project

    SciTech Connect (OSTI)

    Davis, Williams

    2015-10-01

    The scope of this project was changed during the course of the project. Phase I of the project was designed to have the National Alternative Fuels Training Consortium (NAFTC), together with its partners, manage the Hydrogen Vehicle Test Project at the Yeager Airport in conjunction with the Central West Virginia Regional Airport Authority (CWVRAA) in coordination with the United States Department of Energy National Energy Technology Laboratory (U.S. DOE NETL). This program would allow testing and evaluation of the use of hydrogen vehicles in the state of West Virginia utilizing the hydrogen fueling station at Yeager Airport. The NAFTC and CWVRAA to raise awareness and foster a greater understanding of hydrogen fuel and hydrogen-powered vehicles through a targeted utilization and outreach and education effort. After initial implementation of the project, the project added, determine the source(s) of supply for hydrogen powered vehicles that could be used for the testing. After completion of this, testing was begun at Yeager Airport. During the course of the project, the station at Yeager Airport was closed and moved to Morgantown and the West Virginia University Research Corporation. The vehicles were then moved to Morgantown and a vehicle owned by the CWVRAA was purchased to complete the project at the new location. Because of a number of issues detailed in the report for DE-FE0002994 and in this report, this project did not get to evaluate the effectiveness of the vehicles as planned.

  16. Northern New Mexico regional airport market feasibility

    SciTech Connect (OSTI)

    Drake, R.H.; Williams, D.S.

    1998-06-01

    This report is about the market for airline travel in northern New Mexico. Interest in developing a northern New Mexico regional airport has periodically surfaced for a number of years. The New Mexico State Legislature passed a memorial during the 1998 Second Session calling for the conduct of a study to determine the feasibility of building a new regional airport in NNM. This report is a study of the passenger market feasibility of such an airport. In addition to commercial passenger market feasibility, there are other feasibility issues dealing with siting, environmental impact, noise, economic impact, intermodal transportation integration, region-wide transportation services, airport engineering requirements, and others. These other feasibility issues are not analyzed in any depth in this report although none were discovered to be show-stoppers as a by-product of the authors doing research on the passenger market itself. Preceding the need for a detailed study of these other issues is the determination of the basic market need for an airport with regular commercial airline service in the first place. This report is restricted to an in-depth look at the market for commercial passenger air service in NNM. 20 figs., 8 tabs.

  17. Space-and-Time Resolved Spectroscopy of Single GaN Nanowires

    SciTech Connect (OSTI)

    Upadhya, Prashanth C.; Martinez, Julio A.; Li, Qiming; Wang, George T.; Swartzentruber, Brian S.; Taylor, Antoinette J.; Prasankumar, Rohit P.

    2015-07-01

    Gallium nitridenanowires have garnered much attention in recent years due to their attractive optical and electrical properties. An understanding of carrier transport, relaxation, and recombination in these quasi-one-dimensional nanosystems is therefore important in optimizing them for various applications. We present ultrafast optical microscopic measurements on single GaNnanowires. Furthermore, our experiments, performed while varying the light polarization,excitation fluence, and position, give insight into the mechanisms governing carrier dynamics in these nanosystems.

  18. Negative differential resistance in GaN tunneling hot electron transistors

    SciTech Connect (OSTI)

    Yang, Zhichao; Nath, Digbijoy; Rajan, Siddharth

    2014-11-17

    Room temperature negative differential resistance is demonstrated in a unipolar GaN-based tunneling hot electron transistor. Such a device employs tunnel-injected electrons to vary the electron energy and change the fraction of reflected electrons, and shows repeatable negative differential resistance with a peak to valley current ratio of 7.2. The device was stable when biased in the negative resistance regime and tunable by changing collector bias. Good repeatability and double-sweep characteristics at room temperature show the potential of such device for high frequency oscillators based on quasi-ballistic transport.

  19. LEDs on Semipolar Bulk GaN Substrate with IQE > 80% at 150 A...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    ... program are disseminated to a broader audience at the annual DOE Solid State Lighting R&D Workshops. Communications: Results from this program have been presented in the ...

  20. Growth and Band Offsets of Epitaxial Lanthanide Oxides on GaN...

    Office of Scientific and Technical Information (OSTI)

    Close Cite: Bibtex Format Close 0 pages in this document matching the terms "" Search For Terms: Enter terms in the toolbar above to search the full text of this document for ...

  1. Functional Mn–Mg{sub k} cation complexes in GaN featured by Raman spectroscopy

    SciTech Connect (OSTI)

    Devillers, T. Bonanni, A.; Leite, D. M. G.; Dias da Silva, J. H.

    2013-11-18

    The evolution of the optical branch in the Raman spectra of (Ga,Mn)N:Mg epitaxial layers as a function of the Mn and Mg concentrations, reveals the interplay between the two dopants. We demonstrate that the various Mn-Mg-induced vibrational modes can be understood in the picture of functional Mn–Mg{sub k} complexes formed when substitutional Mn cations are bound to k substitutional Mg through nitrogen atoms, the number of ligands k being driven by the ratio between the Mg and the Mn concentrations.

  2. S3TEC - Thermal Engineering of GaN Semiconductor Devices | Solid...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    will be presented where the temperature of the devices was measured using Raman Spectroscopy while the mechanical deformation was measured by Scanning Joule Expansion Microscopy. ...

  3. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    SciTech Connect (OSTI)

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-05-14

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ?10{sup 17}?cm{sup ?3} to (25)??10{sup 14}?cm{sup ?3}. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ?5??10{sup 13}?cm{sup ?3} versus 2.9??10{sup 16}?cm{sup ?3} in the standard samples, with a similar decrease in the electron traps concentration.

  4. Ultra-short channel GaN high electron mobility transistor-like...

    Office of Scientific and Technical Information (OSTI)

    based on the velocity-field dependence of two-dimensional electron gas (2-DEG) channel accounting for the ballistic electron acceleration and the inter-valley transfer. In...

  5. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOE Patents [OSTI]

    Wang, George T.; Li, Qiming; Creighton, J. Randall

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

  6. Space-and-time resolved spectroscopy of single GaN nanowires

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Upadhya, Prashanth C.; Martinez, Julio A.; Li, Qiming; Wang, George T.; Swartzentruber, Brian S.; Taylor, Antoinette J.; Prasankumar, Rohit P.

    2015-06-30

    Gallium nitridenanowires have garnered much attention in recent years due to their attractive optical and electrical properties. An understanding of carrier transport, relaxation, and recombination in these quasi-one-dimensional nanosystems is therefore important in optimizing them for various applications. We present ultrafast optical microscopic measurements on single GaNnanowires. Furthermore, our experiments, performed while varying the light polarization,excitation fluence, and position, give insight into the mechanisms governing carrier dynamics in these nanosystems.

  7. P-type doping of GaN (Thesis/Dissertation) | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    Authors: Wong, R.K. Publication Date: 2000-04-10 OSTI Identifier: 764386 Report Number(s): LBNL--45553 R&D Project: 513310; TRN: US0100055 DOE Contract Number: AC03-76SF00098 ...

  8. Electronic and structural characteristics of zinc-blende wurtzite biphasic homostructure GaN nanowires

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Jacobs, Benjamin W.; Ayres, Virginia M.; Petkov, Mihail P.; Halpern, Joshua B.; He, Maoqi; Baczewski, Andrew D.; McElroy, Kaylee; Crimp, Martin A.; Zhang, Jiaming; Shaw, Harry C.

    2016-02-01

    Here, we report a new biphasic crystalline wurtzite/zinc-blende homostructure in gallium nitride nanowires. Cathodoluminescence was used to quantitatively measure the wurtzite and zinc-blende band gaps. High-resolution transmission electron microscopy was used to identify distinct wurtzite and zinc-blende crystalline phases within single nanowires through the use of selected area electron diffraction, electron dispersive spectroscopy, electron energy loss spectroscopy, and fast Fourier transform techniques. A mechanism for growth is identified.

  9. Microsoft PowerPoint - Morgantown Muncipal Airport to NETL Morgantown...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Morgantown Site from Morgantown Municipal Airport 1. Exit the airport by TURNING RIGHT onto HARTMAN RUN RD. and proceed to first light (US-119). 2. Turn LEFT onto US-119 SOUTH and...

  10. Microsoft PowerPoint - Pittsburgh International Airport to Morgantown...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Pittsburgh International Airport to Morgantown Site, Morgantown, WV 1. Exit airport on US-60S toward PittsburghI-79S (follow signs to Pittsburgh, proceed 7 miles). 2. Merge onto...

  11. Support EM LA Airport Landfill Cover Project by providing 40000...

    Office of Environmental Management (EM)

    Support EM LA Airport Landfill Cover Project by providing 40000 tons of soil Support EM LA Airport Landfill Cover Project by providing 40000 tons of soil DE-DT0010454-Task-Order-4 ...

  12. Guidelines to improve airport preparedness against chemical and biological terrorism.

    SciTech Connect (OSTI)

    Edwards, Donna M.; Price, Phillip N.; Gordon, Susanna P.; Gadgil, Ashok

    2005-05-01

    Guidelines to Improve Airport Preparedness Against Chemical and Biological Terrorism is a 100-page document that makes concrete recommendations on improving security and assessing vulnerable areas and helps its readers understand the nature of chemical and biological attacks. The report has been turned over to Airports Council International (ACI) and the American Association of Airport Executives (AAAE), two organizations that together represent the interests of thousands of airport personnel and facilities in the U.S. and around the world.

  13. DOE - Office of Legacy Management -- Milwaukee Airport - WI 04

    Office of Legacy Management (LM)

    Milwaukee Airport - WI 04 FUSRAP Considered Sites Site: MILWAUKEE AIRPORT (WI.04 ) Eliminated from further consideration under FUSRAP Designated Name: Not Designated Alternate Name: None Location: Milwaukee Airport , Milwaukee , Wisconsin WI.04-1 Evaluation Year: 1991 WI.04-1 Site Operations: Airport Facility received a shipment of Uranium oxides from Allegheny Ludlow sent to an AEC employee - final destination unknown. WI.04-1 Site Disposition: Eliminated - Limited scope of activities performed

  14. Miami International Airport stormwater NPDES plan

    SciTech Connect (OSTI)

    Perez, A.I.; Goldman, J.Z.; Schmidt, M.F.; Clark, E.E.

    1994-12-31

    Miami International Airport (MIA) is endeavoring to essentially double its traffic volume by the turn of the century. This is a great challenge since the site is already highly developed. Space, safety and other constraints make it difficult to implement conventional detention/retention stormwater practices. Other practices were evaluated to control stormwater quantity/quality, since some of the downstream bodies of water are flood-prone or environmentally sensitive.

  15. Advance in bottle scanning could enhance airport security and benefit

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    passengers Advance in bottle scanning could enhance airport security Advance in bottle scanning could enhance airport security and benefit passengers Los Alamos scientists have advanced a Magnetic Resonance Imaging technology that may provide a breakthrough for screening liquids at airport security. November 25, 2013 MagRay engineer Larry Schultz puts a bottle of surrogate material that mimics home made explosives into the MagRay bottle scanner. MagRay engineer Larry Schultz puts a bottle of

  16. Airport Drive, Missouri: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    Airport Drive, Missouri: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 37.1425588, -94.5107824 Show Map Loading map... "minzoom":false,"mappi...

  17. Airports Soar to New Heights with Alternative Fuels

    Broader source: Energy.gov [DOE]

    A number of airports have adopted the use of alternative fuels and advanced technology vehicles, ranging from gaseous fuels to hybrid cars.

  18. Crowne Plaza Suites MSP Airport - Mall of America

    Office of Environmental Management (EM)

    Airport - Mall of America Bloomington, Minnesota * May 13-15, 2014 Revised Agenda Monday, ... Song Prairie Island Indian Community of Minnesota * Welcome to Minnesota Speaker to be ...

  19. DOE - Office of Legacy Management -- St Louis Airport - MO 01

    Office of Legacy Management (LM)

    - MO 01 FUSRAP Considered Sites St. Louis Airport, MO Alternate Name(s): Airport Site St. Louis Airport Storage Site (SLAPS) Former Robertson Storage Area Robertson Airport MO.01-1 MO.01-2 Location: Brown Road, Robertson, Missouri MO.01-2 Historical Operations: Stored uranium process residues containing uranium, radium, and thorium for the MED and AEC. MO.01-2 MO.01-3 MO.01-4 Eligibility Determination: Eligible MO.01-1 MO.01-7 Radiological Survey(s): Assessment Surveys MO.01-4 MO.01-5 Site

  20. Alternative Fuels Data Center: North Carolina Airport Advances With Plug-In

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    Electric Buses North Carolina Airport Advances With Plug-In Electric Buses to someone by E-mail Share Alternative Fuels Data Center: North Carolina Airport Advances With Plug-In Electric Buses on Facebook Tweet about Alternative Fuels Data Center: North Carolina Airport Advances With Plug-In Electric Buses on Twitter Bookmark Alternative Fuels Data Center: North Carolina Airport Advances With Plug-In Electric Buses on Google Bookmark Alternative Fuels Data Center: North Carolina Airport

  1. The Doral Group Ltd | Open Energy Information

    Open Energy Info (EERE)

    Group Ltd Jump to: navigation, search Name: The Doral Group Ltd. Place: Ramat Gan, Israel Product: Ramat Gan-based investment, development and holding company. References: The...

  2. New MagViz Airport Liquid Analysis System Undergoes Testing

    ScienceCinema (OSTI)

    None

    2010-01-08

    LOS ALAMOS, New Mexico, December 16, 2008?An innovative application of a technology first used for medical imaging may enhance airport security if Los Alamos National Laboratory scientists are successful. Los Alamos technologists have adapted Magnetic Res

  3. Airport Road, Wyoming: Energy Resources | Open Energy Information

    Open Energy Info (EERE)

    Hide Map This article is a stub. You can help OpenEI by expanding it. Airport Road is a census-designated place in Washakie County, Wyoming. It falls under...

  4. Airport Road Addition, Texas: Energy Resources | Open Energy...

    Open Energy Info (EERE)

    Hide Map This article is a stub. You can help OpenEI by expanding it. Airport Road Addition is a census-designated place in Brooks County, Texas.1 References ...

  5. DOE - Office of Legacy Management -- St Louis Airport Site Vicinity...

    Office of Legacy Management (LM)

    Louis. The properties are associated with the St. Louis Airport Site. The Manhattan Engineer District (MED), a predecessor agency of the U.S. Department of Energy (DOE), acquired ...

  6. Crowne Plaza Suites MSP Airport - Mall of America

    Office of Environmental Management (EM)

    Crowne Plaza Suites MSP Airport - Mall of America Bloomington, Minnesota | May 13-15, 2014 ... While you're in Minnesota, you'll experience three days of dynamic programming - starting ...

  7. EECBG Success Story: LEDs Ready for Takeoff at Louisiana Airport

    Broader source: Energy.gov [DOE]

    About 250 lights along the taxiway at Hammond Northshore Regional Airport in Louisiana are being replaced with light-emitting diodes (LEDs) with funds from an Energy Efficiency and Conservation Block Grant (EECBG). Learn more.

  8. New airport liquid analysis system undergoes testing at Albuquerque

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    International Sunport New airport liquid analysis system New airport liquid analysis system undergoes testing at Albuquerque International Sunport A new tool that distinguishes potential-threat liquids from the harmless shampoos and sodas a regular traveler might take aboard an aircraft. December 16, 2008 Los Alamos National Laboratory sits on top of a once-remote mesa in northern New Mexico with the Jemez mountains as a backdrop to research and innovation covering multi-disciplines from

  9. NNSA, Romania Launch Radiation Detection System at International Airport

    National Nuclear Security Administration (NNSA)

    near Bucharest | National Nuclear Security Administration | (NNSA) NNSA, Romania Launch Radiation Detection System at International Airport near Bucharest July 22, 2015 Today, the U.S. Embassy in Bucharest, the National Nuclear Security Administration (NNSA) and Romania's Ministry of Internal Affairs celebrated the commencement of operations of the radiation detection system located at Henri Coandă International Airport near Bucharest. To mark the occasion, U.S. Embassy Chargé d'Affaires

  10. Central airport energy systems using alternate energy sources

    SciTech Connect (OSTI)

    Not Available

    1982-07-01

    The purpose of this project was to develop the concept of a central airport energy system designed to supply energy for aircraft ground support and terminal complex utility systems using municipal waste as a fuel. The major task was to estimate the potential for reducing aircraft and terminal fuel consumption by the use of alternate renewable energy sources. Additional efforts included an assessment of indirect benefits of reducing airport atmospheric and noise pollution.

  11. DOE - Office of Legacy Management -- St Louis Airport Site Vicinity

    Office of Legacy Management (LM)

    Properties - 017 Site Vicinity Properties - 017 FUSRAP Considered Sites Site: St. Louis Airport Site Vicinity Properties (017) FUSRAP Active Site. More information at http://www.mvs.usace.army.mil/Home.aspx Designated Name: Berkeley, MO, Site Vicinity Properties Alternate Name: None Location: Berkeley, Missouri Evaluation Year: Added to FUSRAP by Congress in 1984 Site Operations: Contaminated by materials from St Louis Airport site Site Disposition: USACE is actively remediating the site

  12. Direct transparent electrode patterning on layered GaN substrate by screen printing of indium tin oxide nanoparticle ink for Eu-doped GaN red light-emitting diode

    SciTech Connect (OSTI)

    Kashiwagi, Y. Yamamoto, M.; Saitoh, M.; Takahashi, M.; Ohno, T.; Nakamoto, M.; Koizumi, A.; Fujiwara, Y.; Takemura, Y.; Murahashi, K.; Ohtsuka, K.; Furuta, S.

    2014-12-01

    Transparent electrodes were formed on Eu-doped GaN-based red-light-emitting diode (GaN:Eu LED) substrates by the screen printing of indium tin oxide nanoparticle (ITO np) inks as a wet process. The ITO nps with a mean diameter of 25?nm were synthesized by the controlled thermolysis of a mixture of indium complexes and tin complexes. After the direct screen printing of ITO np inks on GaN:Eu LED substrates and sintering at 850?C for 10?min under atmospheric conditions, the resistivity of the ITO film was 5.2?m??cm. The fabricated LED up to 3?mm square surface emitted red light when the on-voltage was exceeded.

  13. World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport | Department

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    of Energy World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport June 10, 2015 - 1:30pm Addthis World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport Sunita Satyapal Director, Fuel Cell Technologies Office What looks like a golf cart

  14. Phase-Field Simulations of GaN Growth by Selective Area Epitaxy on Complex Mask Geometries

    SciTech Connect (OSTI)

    Aagesen, Larry K.; Coltrin, Michael Elliott; Han, Jung; Thornton, Katsuyo

    2015-05-15

    Three-dimensional phase-field simulations of GaNgrowth by selective area epitaxy were performed. Furthermore, this model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. We found that the model provides a route to optimize masks and processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.

  15. Electrical spin injection using GaCrN in a GaN based spin light emitting diode

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D.; Adari, R.; Sankaranarayan, S.; Kumar, A.; Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S.

    2013-12-09

    We have demonstrated electrical spin-injection from GaCrN dilute magnetic semiconductor (DMS) in a GaN-based spin light emitting diode (spin-LED). The remanent in-plane magnetization of the thin-film semiconducting ferromagnet has been used for introducing the spin polarized electrons into the non-magnetic InGaN quantum well. The output circular polarization obtained from the spin-LED closely follows the normalized in-plane magnetization curve of the DMS. A saturation circular polarization of ?2.5% is obtained at 200?K.

  16. Airport Viz - a 3D Tool to Enhance Security Operations

    SciTech Connect (OSTI)

    Koch, Daniel B

    2006-01-01

    In the summer of 2000, the National Safe Skies Alliance (NSSA) awarded a project to the Applied Visualization Center (AVC) at the University of Tennessee, Knoxville (UTK) to develop a 3D computer tool to assist the Federal Aviation Administration security group, now the Transportation Security Administration (TSA), in evaluating new equipment and procedures to improve airport checkpoint security. A preliminary tool was demonstrated at the 2001 International Aviation Security Technology Symposium. Since then, the AVC went on to construct numerous detection equipment models as well as models of several airports. Airport Viz has been distributed by the NSSA to a number of airports around the country which are able to incorporate their own CAD models into the software due to its unique open architecture. It provides a checkpoint design and passenger flow simulation function, a layout design and simulation tool for checked baggage and cargo screening, and a means to assist in the vulnerability assessment of airport access points for pedestrians and vehicles.

  17. DOE to Build Hydrogen Fuel Test Facility at West Virginia Airport...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    to Build Hydrogen Fuel Test Facility at West Virginia Airport DOE to Build Hydrogen Fuel Test Facility at West Virginia Airport March 25, 2009 - 1:00pm Addthis Washington, DC - The ...

  18. Alternative Fuels Data Center: St. Louis Airport Relies on Biodiesel and

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    Natural Gas Vehicles St. Louis Airport Relies on Biodiesel and Natural Gas Vehicles to someone by E-mail Share Alternative Fuels Data Center: St. Louis Airport Relies on Biodiesel and Natural Gas Vehicles on Facebook Tweet about Alternative Fuels Data Center: St. Louis Airport Relies on Biodiesel and Natural Gas Vehicles on Twitter Bookmark Alternative Fuels Data Center: St. Louis Airport Relies on Biodiesel and Natural Gas Vehicles on Google Bookmark Alternative Fuels Data Center: St. Louis

  19. AVTA: Airport Ground Support Equipment Specifications and Test Procedures |

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Department of Energy Airport Ground Support Equipment Specifications and Test Procedures AVTA: Airport Ground Support Equipment Specifications and Test Procedures eGSE America Electric Baggage Tow Tractor (EBTT) Technical Specifications (136.16 KB) eGSE America Electric Aircraft PushBack Tractor (EAPT) Technical Specifications (85.7 KB) eGSE America Electric Aircraft Cargo Conveyor (EACC) Technical Specifications (76.64 KB) ETA-GAC001 Control, Close-out, and Storage of Documentation (76.84

  20. Hydrogen Production and Dispensing Facility Opens at W. Va. Airport |

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Department of Energy Hydrogen Production and Dispensing Facility Opens at W. Va. Airport Hydrogen Production and Dispensing Facility Opens at W. Va. Airport August 19, 2009 - 1:00pm Addthis Major General Allen Tackett of the National Guard's 130th Airlift Wing dispenses the first fill-up of hydrogen fuel from the Yeager facility. Major General Allen Tackett of the National Guard's 130th Airlift Wing dispenses the first fill-up of hydrogen fuel from the Yeager facility. Washington, D.C. -- A

  1. Combined Retrieval, Microphysical Retrievals and Heating Rates

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Feng, Zhe

    2013-02-22

    Microphysical retrievals and heating rates from the AMIE/Gan deployment using the PNNL Combined Retrieval.

  2. Combined Retrieval, Microphysical Retrievals and Heating Rates

    DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]

    Feng, Zhe

    Microphysical retrievals and heating rates from the AMIE/Gan deployment using the PNNL Combined Retrieval.

  3. Integrating repositories with fuel cycles: The airport authority model

    SciTech Connect (OSTI)

    Forsberg, C.

    2012-07-01

    The organization of the fuel cycle is a legacy of World War II and the cold war. Fuel cycle facilities were developed and deployed without consideration of the waste management implications. This led to the fuel cycle model of a geological repository site with a single owner, a single function (disposal), and no other facilities on site. Recent studies indicate large economic, safety, repository performance, nonproliferation, and institutional incentives to collocate and integrate all back-end facilities. Site functions could include geological disposal of spent nuclear fuel (SNF) with the option for future retrievability, disposal of other wastes, reprocessing with fuel fabrication, radioisotope production, other facilities that generate significant radioactive wastes, SNF inspection (navy and commercial), and related services such as SNF safeguards equipment testing and training. This implies a site with multiple facilities with different owners sharing some facilities and using common facilities - the repository and SNF receiving. This requires a different repository site institutional structure. We propose development of repository site authorities modeled after airport authorities. Airport authorities manage airports with government-owned runways, collocated or shared public and private airline terminals, commercial and federal military facilities, aircraft maintenance bases, and related operations - all enabled and benefiting the high-value runway asset and access to it via taxi ways. With a repository site authority the high value asset is the repository. The SNF and HLW receiving and storage facilities (equivalent to the airport terminal) serve the repository, any future reprocessing plants, and others with needs for access to SNF and other wastes. Non-public special-built roadways and on-site rail lines (equivalent to taxi ways) connect facilities. Airport authorities are typically chartered by state governments and managed by commissions with members

  4. Support EM LA Airport Landfill Cover Project by providing 40000 tons of

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    soil | Department of Energy Support EM LA Airport Landfill Cover Project by providing 40000 tons of soil Support EM LA Airport Landfill Cover Project by providing 40000 tons of soil DE-DT0010454-Task-Order-4 Airport Landfill Construction Activities The purpose of this task order (TO) is to support the EM-LA Field Office in replacing the cover at the Los Alamos County Airport Landfill. The new cover design is an evapotranspiration (ET) cover. Contractor: TSAY Corporation DOE Contracting

  5. Directions to NETL Morgantown Site from Morgantown Municipal Airport

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Exit the airport by TURNING RIGHT onto HARTFEILD RD. and proceed to first light (US-119). 2. Turn LEFT onto US-119 SOUTH and proceed to traffic circle (WV-705). 3. Take the second exit turn RIGHT onto WV-705, proceed in the right lane to 6th traffic light (VAN VOORHIS RD.) 4. Proceed straight through intersection onto BURROUGHS ST. 5. At A 3 ay way stop stop t turn urn R RIGHT IGHT onto onto C COLLINS OLLINS FERR FERRY Y R RD D. 6. Proceed 0.5 miles straight through traffic light. On RIGHT-

  6. Los Alamos Shows Airport Security Technology at Work

    ScienceCinema (OSTI)

    Espy, Michelle; Schultz, Larry; Hunter, James

    2014-06-24

    Los Alamos scientists have advanced a Magnetic Resonance Imaging (MRI) technology that may provide a breakthrough for screening liquids at airport security. They've added low-power X-ray data to the mix, and as a result have unlocked a new detection technology. Funded in part by the Department of Homeland Security's Science and Technology Directorate, the new system is named MagRay. The goal is to quickly and accurately distinguish between liquids that visually appear identical. For example, what appears to be a bottle of white wine could potentially be nitromethane, a liquid that could be used to make an explosive. Both are clear liquids, one would be perfectly safe on a commercial aircraft, the other would be strictly prohibited. How to tell them apart quickly without error at an airport security area is the focus of Michelle Espy, Larry Schultz and their team. In this video, Espy and the MagRay team explain how the new technology works, how they've developed an easy operator interface, and what the next steps might be in transitioning this technology to the private sector.

  7. A major cogeneration system goes in at JFK International Airport. Low-visibility privatization in a high-impact environment

    SciTech Connect (OSTI)

    Leibler, J.; Luxton, R.; Ostberg, P.

    1998-04-01

    This article describes the first major privatization effort to be completed at John F. Kennedy International Airport. The airport owner and operator, the Port Authority of New York and New Jersey, decided to seek private sector involvement in a capital-intensive project to expand and upgrade the airport`s heating and air conditioning facilities and construct a new cogeneration plant. Kennedy International Airport Cogeneration (KIAC) Partners, a partnership between Gas Energy Incorporated of New York and Community Energy Alternatives of New Jersey, was selected to develop an energy center to supply electricity and hot and chilled water to meet the airport`s growing energy demand. Construction of a 110 MW cogeneration plant, 7,000 tons of chilled water equipment, and 30,000 feet of hot water delivery piping started immediately. JFK Airport`s critical international position called for this substantial project to be developed almost invisibly; no interruption in heating and air conditioning service and no interference in the airport`s active operations could be tolerated. Commercial operation was achieved in February 1995.

  8. The Integrated Airport: Building a Successful NextGen Testbed

    ScienceCinema (OSTI)

    Frederick-Recascino, Christina [Embry-Riddle Aeronautical University, Daytona Beach, Florida, United States]; Sweigard, Doug [Lockheed Martin Corporation]; Lester, Wade [ERAU

    2010-01-08

    This presentation will describe a unique public-private partnership - the Integrated Airport - that was created to engage in research and testing related to NextGen Technology deployment.  NextGen refers to the program that will be initiated to modernize the US National Airspace.  As with any major, multi-decade initiative, such as NextGen, integration of work efforts by multiple partners in the modernization is critical for success.  This talk will focus on the development of the consortium, how the consortium plans for NextGen initiatives, the series of technology demonstrations we have produced and plans for the future of NextGen testing and implementation. 

  9. World's First Fuel Cell Cargo Trucks Deployed at Memphis International Airport

    Broader source: Energy.gov [DOE]

    Thanks to R&D funding from the Energy Departments Fuel Cell Technologies Office (FCTO), the Federal Express Hub at the Memphis International Airport in Tennessee has a new 15-vehicle fleet of...

  10. Uranium characterization at the St. Louis Airport Site

    SciTech Connect (OSTI)

    Schilk, A.J.; Hubbard, C.W.; Bowyer, T.W.; Reiman, R.T.

    1995-05-01

    In support of the Department of Energy/Office of Technology Development`s Expedited Site Characterization (ESC) project (coordinated by Ames Laboratory), the Pacific Northwest Laboratory demonstrated two complementary technologies at the St. Louis Airport (SLAP) site that have been designed and optimized for the rapid, in situ quantification of radionuclide contamination in surface soils. The sensors are optimized for the detection of high-energy beta particles or gamma rays emitted from the decay of specific radionuclides of interest. These technologies were demonstrated by measuring the beta and gamma fluxes at several locations within the SLAP site. Measurements were converted to average contamination levels, using detector calibrations performed with spiked samples (beta) or sealed sources (gamma). Additionally, subsurface activity levels were derived from discrete soil samples (provided by the ESC field crew) via gamma-ray spectrometry in a controlled laboratory setting. Since the beta and gamma sensor technologies are intrinsically sensitive to different types of radiation and activity distributions (i.e., surface and shallow subsurface, respectively), the data obtained from the two detectors provide complementary information about the distribution of the contamination. The results reported here suggest that a number of locations within the SLAP site have elevated levels of {sup 211}U, and the differences between the beta and gamma activities indicate that the contamination is largely located near the surface of the soil.

  11. Reliability of AlGaN/GaN high electron mobility transistors on low dislocation density bulk GaN substrate: Implications of surface step edges

    SciTech Connect (OSTI)

    Killat, N. E-mail: Martin.Kuball@bristol.ac.uk; Montes Bajo, M.; Kuball, M. E-mail: Martin.Kuball@bristol.ac.uk; Paskova, T.; Materials Science and Engineering Department, North Carolina State University, Raleigh, North Carolina 27695 ; Evans, K. R.; Leach, J.; Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 ; Li, X.; Özgür, Ü.; Morkoç, H.; Chabak, K. D.; Crespo, A.; Gillespie, J. K.; Fitch, R.; Kossler, M.; Walker, D. E.; Trejo, M.; Via, G. D.; Blevins, J. D.

    2013-11-04

    To enable gaining insight into degradation mechanisms of AlGaN/GaN high electron mobility transistors, devices grown on a low-dislocation-density bulk-GaN substrate were studied. Gate leakage current and electroluminescence (EL) monitoring revealed a progressive appearance of EL spots during off-state stress which signify the generation of gate current leakage paths. Atomic force microscopy evidenced the formation of semiconductor surface pits at the failure location, which corresponds to the interaction region of the gate contact edge and the edges of surface steps.

  12. Visible-light absorption and large band-gap bowing of GaN1-xSbx from first principles

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Sheetz, R. Michael; Richter, Ernst; Andriotis, Antonis N.; Lisenkov, Sergey; Pendyala, Chandrashekhar; Sunkara, Mahendra K.; Menon, Madhu

    2011-08-01

    Applicability of the Ga(Sbx)N1-x alloys for practical realization of photoelectrochemical water splitting is investigated using first-principles density functional theory incorporating the local density approximation and generalized gradient approximation plus the Hubbard U parameter formalism. Our calculations reveal that a relatively small concentration of Sb impurities is sufficient to achieve a significant narrowing of the band gap, enabling absorption of visible light. Theoretical results predict that Ga(Sbx)N1-x alloys with 2-eV band gaps straddle the potential window at moderate to low pH values, thus indicating that dilute Ga(Sbx)N1-x alloys could be potential candidates for splitting water under visible light irradiation.

  13. Investigation of surface-plasmon coupled red light emitting InGaN/GaN multi-quantum well with Ag nanostructures coated on GaN surface

    SciTech Connect (OSTI)

    Li, Yi; Liu, Bin E-mail: rzhang@nju.edu.cn; Zhang, Rong E-mail: rzhang@nju.edu.cn; Xie, Zili; Zhuang, Zhe; Dai, JiangPing; Tao, Tao; Zhi, Ting; Zhang, Guogang; Chen, Peng; Ren, Fangfang; Zhao, Hong; Zheng, Youdou

    2015-04-21

    Surface-plasmon (SP) coupled red light emitting InGaN/GaN multiple quantum well (MQW) structure is fabricated and investigated. The centre wavelength of 5-period InGaN/GaN MQW structure is about 620?nm. The intensity of photoluminescence (PL) for InGaN QW with naked Ag nano-structures (NS) is only slightly increased due to the oxidation of Ag NS as compared to that for the InGaN QW. However, InGaN QW with Ag NS/SiO{sub 2} structure can evidently enhance the emission efficiency due to the elimination of surface oxide layer of Ag NS. With increasing the laser excitation power, the PL intensity is enhanced by 25%53% as compared to that for the SiO{sub 2} coating InGaN QW. The steady-state electric field distribution obtained by the three-dimensional finite-difference time-domain method is different for both structures. The proportion of the field distributed in the Ag NS for the GaN/Ag NS/SiO{sub 2} structure is smaller as compared to that for the GaN/naked Ag NS structure. As a result, the energy loss of localized SP modes for the GaN/naked Ag NS structure will be larger due to the absorption of Ag layer.

  14. HIGH-QUALITY, LOW-COST BULK GALLIUM NITRIDE SUBSTRATES GROWN BY THE ELECTROCHEMICAL SOLUTION GROWTH METHOD

    Broader source: Energy.gov [DOE]

    To develop ESG into a viable bulk growth process for GaN that is more scalable to large-area wafer manufacturing and able to produce cost-effective, high-quality bulk GaN substrates.

  15. ARM - Data Announcements Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the Madden-Julian Oscillation (DYNAMO) and the ARM Madden-Julian Oscillation MJO Investigation Experiment AMIE on Gan Island, or AMIE-Gan field campaign. Due to the lack of a...

  16. Solar IT | Open Energy Information

    Open Energy Info (EERE)

    IT Jump to: navigation, search Name: Solar IT Place: Ramat-Gan, Israel Product: Ramat-Gan-based supplier and assemblier of PV-based systems for domestic and industrial use....

  17. Summary Document: Restoration Plan for Major Airports after a Bioterrorist Attack

    SciTech Connect (OSTI)

    Raber, E

    2007-01-11

    This document provides general guidelines for developing a Restoration Plan for a major airport following release of a biological warfare agent. San Francisco International Airport was selected as the example airport during development of the Plan to illustrate specific details. The spore forming bacterium Bacillus anthracis was selected as the biological agent of primary concern because it is the most difficult of known bioterrorism agents to inactivate and is considered to be one of the agents most likely to be used as a biological weapon. The focus of the Plan is on activities associated with the Characterization, Remediation, and Clearance Phases that are defined herein. Activities associated with the Notification and First-Response Phases are briefly discussed in Appendixes A and B, respectively. In addition to the main text of this Plan and associated appendixes, a data supplement was developed specifically for San Francisco International Airport. Requests for the data supplement must be made directly to the Emergency Planning Operations Division of San Francisco International Airport.

  18. News Item

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Switchable Control of Nanowire Growth SEM images of GaN nanowire arrays illustrating their growth orientations with respect to the GaN crystal structure Scientific Achievement A team of multidisciplinary researchers at the Berkeley Lab's Molecular Foundry used catalyst composition to control the crystallographic growth of GaN nanowires Significance and Impact Manipulating GaN nanostructures offers the ability to custom design bulk material properties in unique ways, potentially leading to new

  19. Assessment and management of aquatic impacts from airport de-icing activities -- The Canadian perspective

    SciTech Connect (OSTI)

    Kent, R.A.; Andersen, D.; Simpson, A.

    1995-12-31

    Historically, aircraft deicing fluids have simply drained from aircraft and runway surfaces into airport drainage systems and invariably end up in surrounding receiving aquatic systems. This led to recent concerns over environmental impacts from glycol-based fluids typically used for deicing aircraft. Glycols from de-icing fluids have been detected at high levels at Canadian airports. Concern not only stems from the high volumes being used at relatively few point sources, but also to the higher toxicity of the formulated de-icing fluids, compared to pure glycols. As a result, significant environmental management efforts have been made at Canadian airports over the last 4 years, including extensive stormwater monitoring, glycol mitigation and pollution prevention plans. Site-specific mitigation plans have been implemented at 15 major Canadian airports which typically include glycol containment, collection and removal. While a reasonable dataset is available on the toxicity of pure glycols, much less information is available on the toxicity of formulated deicers. Furthermore, there have been very few field assessments of the aquatic impacts of de-icing. To date, management regimes developed to address the problem in Canada have focused almost exclusively on glycols and voluntary compliance to discharge limits and receiving water quality guidelines. This approach has resulted in reductions in the quantities of glycols which are released from Canadian airports into the surrounding environment. Currently, government and industry are refining this management system with an examination of new approaches and options such as more holistic airport wastewater quality assessments and toxicity-based guidelines.

  20. Cost Benefit Analysis Modeling Tool for Electric vs. ICE Airport Ground Support Equipment Development and Results

    SciTech Connect (OSTI)

    James Francfort; Kevin Morrow; Dimitri Hochard

    2007-02-01

    This report documents efforts to develop a computer tool for modeling the economic payback for comparative airport ground support equipment (GSE) that are propelled by either electric motors or gasoline and diesel engines. The types of GSE modeled are pushback tractors, baggage tractors, and belt loaders. The GSE modeling tool includes an emissions module that estimates the amount of tailpipe emissions saved by replacing internal combustion engine GSE with electric GSE. This report contains modeling assumptions, methodology, a users manual, and modeling results. The model was developed based on the operations of two airlines at four United States airports.

  1. Microsoft PowerPoint - Pittsburgh International Airport to Morgantown Site Directions.ppt [Compatibility Mode]

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Pittsburgh International Airport to Morgantown Site, Morgantown, WV 1. Exit airport on US-60S toward Pittsburgh/I-79S (follow signs to Pittsburgh, proceed ~7 miles). 2. Merge onto US-22E/US-30E toward Pittsburgh (proceed ~3 miles). 3. Merge onto I-79S toward WASHINGTON, PA (proceed ~25 miles). I-70 East merges with I-79, continue on I-70E/I-79S. 4. Merge RIGHT at Exit 21 onto I-79S toward MORGANTOWN, WV (proceed ~39 miles). 5 T k EXIT 155 STAR CITY EXIT t WV 7 WEST VIRGINIA UNIVERSITY 5. Take

  2. EECBG Success Story: New San Antonio Airport Terminal Generating Clean Power

    Broader source: Energy.gov [DOE]

    In early 2010, the City of San Antonio’s Energy Efficiency and Conservation Block Grant (EECBG) program staff quickly realized a golden opportunity lay right at their fingertips. The opening of the new San Antonio International Airport terminal was just months away and the team knew that a solar photovoltaic (PV) system at the airport would offer a highly visible location to showcase renewable energy technologies, help the city accelerate its “Mission Verde” sustainable development plan and create local jobs. Learn more.

  3. Implementation of alternative bio-based fuels in aviation: The Clean Airports Program

    SciTech Connect (OSTI)

    Shauck, M.E.; Zanin, M.G.

    1997-12-31

    The Renewable Aviation Fuels Development Center at Baylor University in Waco, Texas, was designated, in March 1996, by the US Department of Energy (US DOE) as the national coordinator of the Clean Airports Program. This program, a spin-off of the Clean Cities Program, was initiated to increase the use of alternative fuels in aviation. There are two major fuels used in aviation today, the current piston engine aviation gasoline, and the current turbine engine fuel. The environmental impact of each of these fuels is significant. Aviation Gasoline (100LL), currently used in the General Aviation piston engine fleet, contributes 100% of the emissions containing lead in the USA today. In the case of the turbine engine fuel (Jet fuel), there are two major environmental impacts to be considered: the local, in the vicinity of the airports, and the global impact on climate change. The Clean Airports Program was established to promote the use of clean burning fuels in order to achieve and maintain clean air at and in the vicinities of airports through the use of alternative fuel-powered air and ground transportation vehicles.

  4. Microsoft PowerPoint - To NETL Albany Site from Eugene, Oregon Airport Directions.ppt [Compatibility Mode]

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Eugene, Oregon Airport 1. From the EUGENE AIRPORT take HWY 99 (the airport is located off Hwy 99). 2. Follow HWY 99 NORTH from EUGENE to ALBANY. 3. Outside of EUGENE, HWY 99 splits into HWY 99 EAST and 99 WEST. 4. Take HWY 99 EAST to ALBANY (bear right at intersection). 5. You are nearing ALBANY when you pass under HWY 34. 6. Continue on 99 EAST, PACIFIC BLVD., until it intersects QUEEN AVENUE (there will be a directional sign at intersection for Albany Site). 7. Turn LEFT (WEST) on QUEEN

  5. New Technology Demonstration of the Whole-Building Diagnostician at the Federal Aviation Administration-Denver Airport

    SciTech Connect (OSTI)

    Pratt, Robert G.; Bauman, Nathan N.; Katipamula, Srinivas

    2003-01-17

    This report describes results from an evaluation of the Whole Building Diagnostician's (WBD) ability to automatically and continually diagnose operational problems in building air handlers at the Federal Aviation Administration's Denver airport.

  6. Estimating Traveler Populations at Airport and Cruise Terminals for Population Distribution and Dynamics

    SciTech Connect (OSTI)

    Jochem, Warren C; Sims, Kelly M; Bright, Eddie A; Urban, Marie L; Rose, Amy N; Coleman, Phil R; Bhaduri, Budhendra L

    2013-01-01

    In recent years, uses of high-resolution population distribution databases are increasing steadily for environmental, socioeconomic, public health, and disaster-related research and operations. With the development of daytime population distribution, temporal resolution of such databases has been improved. However, the lack of incorporation of transitional population, namely business and leisure travelers, leaves a significant population unaccounted for within the critical infrastructure networks, such as at transportation hubs. This paper presents two general methodologies for estimating passenger populations in airport and cruise port terminals at a high temporal resolution which can be incorporated into existing population distribution models. The methodologies are geographically scalable and are based on, and demonstrate how, two different transportation hubs with disparate temporal population dynamics can be modeled utilizing publicly available databases including novel data sources of flight activity from the Internet which are updated in near-real time. The airport population estimation model shows great potential for rapid implementation for a large collection of airports on a national scale, and the results suggest reasonable accuracy in the estimated passenger traffic. By incorporating population dynamics at high temporal resolutions into population distribution models, we hope to improve the estimates of populations exposed to or at risk to disasters, thereby improving emergency planning and response, and leading to more informed policy decisions.

  7. Microsoft PowerPoint - Morgantown Muncipal Airport to NETL Morgantown Site Directions.ppt [Compatibility Mode]

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Exit the airport by TURNING RIGHT onto HARTMAN RUN RD. and proceed to first light (US-119). 2. Turn LEFT onto US-119 SOUTH and proceed to next traffic light (WV-705). 3. At light turn RIGHT onto WV-705, proceed in the right lane to 5th traffic light (VAN VOORHIS RD.) 4. Proceed forward through intersection onto BURROUGHS ST. 5 At 3 way stop turn RIGHT onto COLLINS FERRY RD 5. At 3-way stop turn RIGHT onto COLLINS FERRY RD. 6. Proceed 0.5 miles through traffic light. On RIGHT- Arrive US

  8. EA-2000: Proposed Land Transfer to Develop a General Aviation Airport at the East Tennessee Technology Park Heritage Center, Oak Ridge, Tennessee

    Broader source: Energy.gov [DOE]

    DOE is preparing an EA to assess potential environmental impacts of the proposed land transfer to the Metropolitan Knoxville Airport Authority for the development of a general aviation airport at the East Tennessee Technology Park Heritage Center, in Oak Ridge, Tennessee.

  9. Microsoft PowerPoint - To NETL Albany Site from Portland, Oregon Airport (PDX) Directions.ppt [Compatibility Mode]

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Portland, Oregon Airport (PDX) 1. Take the AIRPORT EXIT RD. until it intersects I-205. 2. Follow I-205 SOUTH for 25 MILES to the intersection with I-5 SOUTH (Salem exit). 3. Follow I-5 SOUTH for approximately 60 miles to the 1 st Albany exit, EXIT 234B - ALBANY, PACIFIC BLVD, OREGON HIGHWAY 99. 4. Follow PACIFIC BLVD. to QUEEN AVE. 5. TURN RIGHT (WEST) on QUEEN AVE. 6 The ALBANY SITE is located on the LEFT just past WEST ALBANY HIGH SCHOOL 6. The ALBANY SITE is located on the LEFT just past WEST

  10. Risk-based approach for bioremediation of fuel hydrocarbons at a major airport

    SciTech Connect (OSTI)

    Wiedemeier, T.H.; Guest, P.R.; Blicker, B.R.

    1994-12-31

    This paper describes a risk-based approach for bioremediation of fuel-hydrocarbon-contaminated soil and ground water at a major airport in Colorado. In situ bioremediation pilot testing, natural attenuation modeling, and full-scale remedial action planning and implementation for soil and ground water contamination has conducted at four airport fuel farms. The sources of fuel contamination were leaking underground storage tanks (USTs) or pipelines transporting Jet A fuel and aviation gasoline. Continuing sources of contamination were present in several small cells of free-phase product and in fuel residuals trapped within the capillary fringe at depths 15 to 20 feet below ground surface. Bioventing pilot tests were conducted to assess the feasibility of using this technology to remediate contaminated soils. The pilot tests included measurement of initial soil gas chemistry at the site, determination of subsurface permeability, and in situ respiration tests to determine fuel biodegradation rates. A product recovery test was also conducted. ES designed and installed four full-scale bioventing systems to remediate the long-term sources of continuing fuel contamination. Benzene, toluene, ethylbenzene, and xylenes (BTEX) and total petroleum hydrocarbons (TPH) were detected in ground water at concentrations slightly above regulatory guidelines.

  11. St. Louis Airport site environmental report for calendar year 1989, St. Louis, Missouri

    SciTech Connect (OSTI)

    none,

    1990-05-01

    The environmental monitoring program, which began in 1984, continued during 1989 at the St. Louis Airport Site (SLAPS) in St. Louis County, Missouri. SLAPS and its vicinity properties, including ditches north and south of the site, were designated for cleanup as part of the Formerly Utilized Sites Remedial Action Program (FUSRAP), a United States Department of Energy (DOE) program to identify and decontaminate or otherwise control sites where residual radioactive material remains from the early years of the nation's atomic energy program. The monitoring program at SLAPS measures radon concentrations in air; external gamma dose rates; and uranium, thorium, and radium concentrations in surface water, groundwater, and sediment. Additionally, several nonradiological parameters are measured in groundwater. To assess the potential effect of SLAPS on public health, the potential radiation dose was estimated for a hypothetical maximally exposed individual. This report presents the findings of the environmental monitoring program conducted at the St. Louis Airport Site (SLAPS) during calendar year 1989. 19 refs., 13 figs., 14 tabs.

  12. Simulation to assess the efficacy of US airport entry scrreening of passengers for pandemic influenza

    SciTech Connect (OSTI)

    Mcmahon, Benjamin

    2009-01-01

    We present our methodology and stochastic discrete-event simulation developed to model the screening of passengers for pandemic influenza at the US port-of-entry airports. Our model uniquely combines epidemiology modelling, evolving infected states and conditions of passengers over time, and operational considerations of screening in a single simulation. The simulation begins with international aircraft arrivals to the US. Passengers are then randomly assigned to one of three states -- not infected, infected with pandemic influenza and infected with other respiratory illness. Passengers then pass through various screening layers (i.e. pre-departure screening, en route screening, primary screening and secondary screening) and ultimately exit the system. We track the status of each passenger over time, with a special emphasis on false negatives (i.e. passengers infected with pandemic influenza, but are not identified as such) as these passengers pose a significant threat as they could unknowingly spread the pandemic influenza virus throughout our nation.

  13. Environmental assessment of the thermal neutron activation explosive detection system for concourse use at US airports

    SciTech Connect (OSTI)

    Jones, C.G.

    1990-08-01

    This document is an environmental assessment of a system designed to detect the presence of explosives in checked airline baggage or cargo. The system is meant to be installed at the concourse or lobby ticketing areas of US commercial airports and uses a sealed radioactive source of californium-252 to irradiate baggage items. The major impact of the use of this system arises from direct exposure of the public to scattered or leakage radiation from the source and to induced radioactivity in baggage items. Under normal operation and the most likely accident scenarios, the environmental impacts that would be created by the proposed licensing action would not be significant. 44 refs., 19 figs., 18 tabs.

  14. Beamline 10.3.1

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Trace-element analysis with high spatial resolution (e.g., silicon solar cells, GaN, atmospheric particulates, environmental soil samples, and biological samples) Scientific...

  15. Housing and Construction Holding Company | Open Energy Information

    Open Energy Info (EERE)

    Housing and Construction Holding Company Jump to: navigation, search Name: Housing and Construction Holding Company Place: Ramat-Gan, Israel Zip: 52215 Product: Israel-based...

  16. Light-Emitting Diodes on Semipolar Bulk Gallium Nitride Substrate

    Broader source: Energy.gov [DOE]

    This project is producing high-efficiency semipolar light-emitting diodes (LEDs) on low-defect bulk gallium nitride (GaN) substrates.

  17. Measurement of mean inner potential and inelastic mean free path...

    Office of Scientific and Technical Information (OSTI)

    Authors: Gan, Zhaofeng ; Ahn, Seungho ; Yu, Hongbin ; Smith, David J. ; McCartney, Martha R. Publication Date: 2015-10-01 OSTI Identifier: 1238990 GrantContract Number: ...

  18. ARM - Feature Stories and Releases Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    ARM field campaigns on Gan Island, Maldives and Manus Island, Papua New Guinea will contribute significantly to concurrent national and international research efforts addressing ...

  19. ARM - ARM MJO Investigation Experiment (AMIE)

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    ARM MJO Investigation Experiment (AMIE) ARM field campaigns on Gan Island, Maldives, and Manus Island, Papua New Guinea, will contribute significantly to concurrent national and ...

  20. Field Mapping At Raft River Geothermal Area (1993) | Open Energy...

    Open Energy Info (EERE)

    extension over broad areas of the northern Basin and Range. References Dumitru, T.; Miller, E.; Savage, C.; Gans, P.; Brown, R. (1 April 1993) Fission track evidence for...

  1. Fission track evidence for widespread early to Middle miocene...

    Open Energy Info (EERE)

    major extension over broad areas of the northern Basin and Range. Authors Dumitru, T.; Miller, E.; Savage, C.; Gans, P.; Brown and R. Published Geological Society of America,...

  2. Field Mapping At Northern Basin and Range Geothermal Region ...

    Open Energy Info (EERE)

    extension over broad areas of the northern Basin and Range. References Dumitru, T.; Miller, E.; Savage, C.; Gans, P.; Brown, R. (1 April 1993) Fission track evidence for...

  3. High-Quality, Low-Cost Bulk Gallium Nitride Substrates

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    achieving GaN bulk growth without the limitations of tradi- tional crystal growth methods. ... MEMC technology transfer and marketing staff are coordinating with the research team to ...

  4. Beamline 10.3.1

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    depending on configuration. Sample environment Air and vacuum Scientific applications Trace-element analysis with high spatial resolution (e.g., silicon solar cells, GaN,...

  5. Shikun Binui Arison Group | Open Energy Information

    Open Energy Info (EERE)

    Ramat Gan, Israel Zip: 55215 Product: String representation "Shikun & Binui ... gy and ecology." is too long. References: Shikun & Binui Arison Group1 This article is a stub. You...

  6. Search for: All records | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    Xiao Mei ; Du, Zehui ; Schuh, Christopher A. ; Tamura, Nobumichi ; Gan, Chee Lip April 2016 , Elsevier Prev Next Switch to Detail View for this search SOLR Query Details

  7. ARM - Site Instruments

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    2009-2010 Shouxian, China, 2008 Black Forest, Germany, 2007 Niamey, Niger, 2006 Point Reyes, California, 2005 Instruments : Gan Island, Maldives Active Retired Active instruments...

  8. Beamline 10.3.1

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    resolution (e.g., silicon solar cells, GaN, atmospheric particulates, environmental soil samples, and biological samples) Scientific disciplines Environmental science,...

  9. Resonant energy transfer between Eu luminescent sites and their...

    Office of Scientific and Technical Information (OSTI)

    Resonant energy transfer between Eu luminescent sites and their local geometry in GaN Citation Details In-Document Search Title: Resonant energy transfer between Eu luminescent ...

  10. Intrinsic Semiconductor | Open Energy Information

    Open Energy Info (EERE)

    Intrinsic Semiconductor is a privately held emerging growth company focusing on materials and device technologies based on silicon carbide (SiC) and gallium nitride (GaN)...

  11. Cree Inc | Open Energy Information

    Open Energy Info (EERE)

    North Carolina Zip: 27703 Product: Cree develops and manufactures semiconductor materials and devices based on silicon carbide (SiC), gallium nitride (GaN), silicon (Si) and...

  12. Search for: All records | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    ... Office of Nonproliferation and National Security (NN) (United States) USDOE Office of ... GaN electrodes for electrolysis, water splitting, or photosynthetic process applications. ...

  13. Sandia Energy - Solid-State Lighting

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Energy Efficiency Permalink Gallery Assessment of deep level defects in m-plane GaN grown by metalorganic chemical vapor deposition Energy Efficiency, News, News & Events,...

  14. Growth process for gallium nitride porous nanorods

    DOE Patents [OSTI]

    Wildeson, Isaac Harshman; Sands, Timothy David

    2015-03-24

    A GaN nanorod and formation method. Formation includes providing a substrate having a GaN film, depositing SiN.sub.x on the GaN film, etching a growth opening through the SiN.sub.x and into the GaN film, growing a GaN nanorod through the growth opening, the nanorod having a nanopore running substantially through its centerline. Focused ion beam etching can be used. The growing can be done using organometallic vapor phase epitaxy. The nanopore diameter can be controlled using the growth opening diameter or the growing step duration. The GaN nanorods can be removed from the substrate. The SiN.sub.x layer can be removed after the growing step. A SiO.sub.x template can be formed on the GaN film and the GaN can be grown to cover the SiO.sub.x template before depositing SiN.sub.x on the GaN film. The SiO.sub.x template can be removed after growing the nanorods.

  15. Search for: All records | DOE PAGES

    Office of Scientific and Technical Information (OSTI)

    and shape memory behavior of titania and yttria co-doped zirconia Zeng, Xiao Mei ; Du, Zehui ; Schuh, Christopher A. ; Tamura, Nobumichi ; Gan, Chee Lip April 2016 , Elsevier

  16. Change in equilibrium position of misfit dislocations at the...

    Office of Scientific and Technical Information (OSTI)

    Our results highlight a direct correlation between threading-dislocation density in GaN ... Department of Materials Science and Engineering and Research Institute of Advanced ...

  17. ASU EFRC - Postdoctoral fellows

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Postdoctoral fellows Barun Das Postdoctoral Fellow Bhupesh Goyal Postdoctoral fellow Jackson Megiatto Postdoctoral Fellow Lu Gan Postdoctoral fellow Matthieu Koepf Postdoctoral...

  18. Center for Energy Nanoscience at USC

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    LED Nanowire LEDs GaN based light emitting diodes (LEDs) are a key technology for high brightness LEDs. Although already successful commercially, fundamental physical and device...

  19. Letter Report Yucca Mountain Environmental Monitoring Systems Initiative - Air Quality Scoping Study for Tonopah Airport, Nye County, Nevada

    SciTech Connect (OSTI)

    J. Engelbrecht; I. Kavouras; D. Campbell; S. Campbell; S. Kohl; D. Shafer

    2009-04-02

    The Desert Research Institute (DRI) is performing a scoping study as part of the U.S. Department of Energy's Yucca Mountain Environmental Monitoring Systems Initiative (EMSI). The main objective is to obtain baseline air quality information for Yucca Mountain and an area surrounding the Nevada Test Site (NTS). Air quality and meteorological monitoring and sampling equipment housed in a mobile trailer (shelter) is collecting data at eight sites outside the NTS, including Ash Meadows National Wildlife Refuge (NWR), Tonopah Airport, Beatty, Rachel, Caliente, Pahranagat NWR, Crater Flat, and the Tonopah Airport, and at four sites on the NTS (Engelbrecht et al., 2007a-d). The trailer is stationed at any one site for approximately eight weeks at a time. This letter report provides a summary of air quality and meteorological data, on completion of the site's sampling program.

  20. Letter Report: Yucca Mountain Environmental Monitoring Systems Initiative - Air Quality Scoping Study for Tonopah Airport, Nye County, Nevada

    SciTech Connect (OSTI)

    J. Engelbrecht; I. Kavouras; D Campbell; S. Campbell; S. Kohl, D. Shafer

    2008-08-01

    The Desert Research Institute (DRI) is performing a scoping study as part of the U.S. Department of Energy's Yucca Mountain Environmental Monitoring Systems Initiative (EMSI). The main objective is to obtain baseline air quality information for Yucca Mountain and an area surrounding the Nevada Test Site (NTS). Air quality and meteorological monitoring and sampling equipment housed in a mobile trailer (shelter) is collecting data at eight sites outside the NTS, including Ash Meadows National Wildlife Refuge (NWR), Tonopah Airport, Beatty, Rachel, Caliente, Pahranagat NWR, Crater Flat, and the Tonopah Airport, and at four sites on the NTS (Engelbrecht et al., 2007a-d). The trailer is stationed at any one site for approximately eight weeks at a time. This letter report provides a summary of air quality and meteorological data, on completion of the site's sampling program.

  1. KOH based selective wet chemical etching of AlN, AlxGa1-xN, and GaN crystals: A way towards substrate removal in deep ultraviolet-light emitting diode

    SciTech Connect (OSTI)

    Guo, W; Kirste, R; Bryan, I; Bryan, Z; Hussey, L; Reddy, P; Tweedie, J; Collazo, R; Sitar, Z

    2015-02-23

    A controllable and smooth potassium hydroxide-based wet etching technique was developed for the AlGaN system. High selectivity between AlN and AlxGa1-xN (up to 12 x) was found to be critical in achieving effective substrate thinning or removal for AlGaN-based deep ultraviolet light emitting diodes, thus increasing light extraction efficiency. The mechanism of high selectivity of AlGaN as a function of Al composition can be explained as related to the formation and dissolution of oxide/hydroxide on top of N-polar surface. Cross-sectional transmission electron microscopic analysis served as ultimate proof that these hillocks were not related to underlying threading dislocations. (C) 2015 AIP Publishing LLC.

  2. Electric Ground Support Equipment Advanced Battery Technology Demonstration Project at the Ontario Airport

    SciTech Connect (OSTI)

    Tyler Gray; Jeremy Diez; Jeffrey Wishart; James Francfort

    2013-07-01

    The intent of the electric Ground Support Equipment (eGSE) demonstration is to evaluate the day-to-day vehicle performance of electric baggage tractors using two advanced battery technologies to demonstrate possible replacements for the flooded lead-acid (FLA) batteries utilized throughout the industry. These advanced battery technologies have the potential to resolve barriers to the widespread adoption of eGSE deployment. Validation testing had not previously been performed within fleet operations to determine if the performance of current advanced batteries is sufficient to withstand the duty cycle of electric baggage tractors. This report summarizes the work performed and data accumulated during this demonstration in an effort to validate the capabilities of advanced battery technologies. This report summarizes the work performed and data accumulated during this demonstration in an effort to validate the capabilities of advanced battery technologies. The demonstration project also grew the relationship with Southwest Airlines (SWA), our demonstration partner at Ontario International Airport (ONT), located in Ontario, California. The results of this study have encouraged a proposal for a future demonstration project with SWA.

  3. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    DOE Patents [OSTI]

    Raffetto, Mark; Bharathan, Jayesh; Haberern, Kevin; Bergmann, Michael; Emerson, David; Ibbetson, James; Li, Ting

    2014-06-24

    A flip-chip semiconductor based Light Emitting Device (LED) can include an n-type semiconductor substrate and an n-type GaN epi-layer on the substrate. A p-type GaN epi-layer can be on the n-type GaN epi-layer and a metal ohmic contact p-electrode can be on the p-type GaN epi-layer, where the metal ohmic contact p-electrode can have an average thickness less than about 25 .ANG.. A reflector can be on the metal ohmic contact p-electrode and a metal stack can be on the reflector. An n-electrode can be on the substrate opposite the n-type GaN epi-layer and a bonding pad can be on the n-electrode.

  4. Preliminary assessment report for Virginia Army National Guard Army Aviation Support Facility, Richmond International Airport, Installation 51230, Sandston, Virginia

    SciTech Connect (OSTI)

    Dennis, C.B.

    1993-09-01

    This report presents the results of the preliminary assessment (PA) conducted by Argonne National Laboratory at the Virginia Army National Guard (VaARNG) property in Sandston, Virginia. The Army Aviation Support Facility (AASF) is contiguous with the Richmond International Airport. Preliminary assessments of federal facilities are being conducted to compile the information necessary for completing preremedial activities and to provide a basis for establishing corrective actions in response to releases of hazardous substances. The PA is designed to characterize the site accurately and determine the need for further action by examining site activities, quantities of hazardous substances present, and potential pathways by which contamination could affect public health and the environment. The AASF, originally constructed as an active Air Force interceptor base, provides maintenance support for VaARNG aircraft. Hazardous materials used and stored at the facility include JP-4 jet fuel, diesel fuel, gasoline, liquid propane gas, heating oil, and motor oil.

  5. Public health assessment for St. Louis Airport, Hazelwood Interim Storage/Futura Coatings Company, St. Louis, St. Louis County, Missouri, Region 7. Cerclis No. MOD980633176. Preliminary report

    SciTech Connect (OSTI)

    Not Available

    1994-01-20

    The St. Louis Airport/Hazelwood Iterim Storage/Futura Coatings Company, a National Priorities List site, is in St. Louis County, Missouri. From 1946 to 1973, the site was used to store radioactive materials resulting from uranium processing. High levels of uranium, thorium, radium, and radon were detected in soil, groundwater, and air. The site is still being used to store radioactive materials. The Agency for Toxic Substances and Disease Registry considers the St. Louis Airport site to be an indeterminate public health hazard. Although there are emissions of radon and the presence of thorium in on-site air and off-site soils and the emission of radiation resulting from the presence of these materials is not currently considered a health hazard. At present conditions, the concentration of radon off-site is indistinguishable from background levels. However, in the past, these contaminants may have been present at levels of health concern.

  6. Review of using gallium nitride for ionizing radiation detection

    SciTech Connect (OSTI)

    Wang, Jinghui; Mulligan, Padhraic; Cao, Lei R.; Brillson, Leonard

    2015-09-15

    With the largest band gap energy of all commercial semiconductors, GaN has found wide application in the making of optoelectronic devices. It has also been used for photodetection such as solar blind imaging as well as ultraviolet and even X-ray detection. Unsurprisingly, the appreciable advantages of GaN over Si, amorphous silicon (a-Si:H), SiC, amorphous SiC (a-SiC), and GaAs, particularly for its radiation hardness, have drawn prompt attention from the physics, astronomy, and nuclear science and engineering communities alike, where semiconductors have traditionally been used for nuclear particle detection. Several investigations have established the usefulness of GaN for alpha detection, suggesting that when properly doped or coated with neutron sensitive materials, GaN could be turned into a neutron detection device. Work in this area is still early in its development, but GaN-based devices have already been shown to detect alpha particles, ultraviolet light, X-rays, electrons, and neutrons. Furthermore, the nuclear reaction presented by {sup 14}N(n,p){sup 14}C and various other threshold reactions indicates that GaN is intrinsically sensitive to neutrons. This review summarizes the state-of-the-art development of GaN detectors for detecting directly and indirectly ionizing radiation. Particular emphasis is given to GaN's radiation hardness under high-radiation fields.

  7. Infrastructure Security EXCEPTIONAL SERVICE IN THE NATIONAL INTEREST

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    741P GaN for LED Lighting Displays and High Power Electronics The LED market is one of the fastest growing worldwide, driven by demand for clean solid state lighting, LED displays, and mobile devices. GaN-based materials are essential for white LEDs used in solid state lighting and flat panel displays as well as high power electromics where GaN transistors are emerging as the high power device of choice for military communications and cell phone base stations. Current GaN devices are typically

  8. Event Archives | Solid State Solar Thermal Energy Conversion

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Event Archives Seminar S3TEC - Thermal Engineering of GaN Semiconductor Devices Friday, Jul 22, 2016 12:00 am 3-270 The development of gallium nitride (GaN) on a variety of substrates from SiC to diamond is under development to create high power RF technologies for advanced communications and power electronic devices. In general, GaN devices can accommodate high operational frequencies, high junction... more Seminar Cross Cutting seminar series: Generation, transport and relaxation of

  9. Defect-engineered GaN:Mg nanowire arrays for overall water splitting under violet light

    SciTech Connect (OSTI)

    Kibria, M. G.; Chowdhury, F. A.; Zhao, S.; Mi, Z.; Trudeau, M. L.; Guo, H.

    2015-03-16

    We report that by engineering the intra-gap defect related energy states in GaN nanowire arrays using Mg dopants, efficient and stable overall neutral water splitting can be achieved under violet light. Overall neutral water splitting on Rh/Cr{sub 2}O{sub 3} co-catalyst decorated Mg doped GaN nanowires is demonstrated with intra-gap excitation up to 450?nm. Through optimized Mg doping, the absorbed photon conversion efficiency of GaN nanowires reaches ?43% at 375450?nm, providing a viable approach to extend the solar absorption of oxide and non-oxide photocatalysts.

  10. Vehicle Technologies Office Merit Review 2016: Advanced Low-Cost SiC and

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    GaN Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction Drives | Department of Energy Low-Cost SiC and GaN Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction Drives Vehicle Technologies Office Merit Review 2016: Advanced Low-Cost SiC and GaN Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction Drives Presentation given by Wolfspeed at the 2016 DOE Vehicle Technologies Office and Hydrogen and Fuel Cells Program Annual Merit Review and Peer

  11. Geochemical information for sites contaminated with low-level radioactive wastes: II. St. Louis Airport Storage Site

    SciTech Connect (OSTI)

    Seeley, F.G.; Kelmers, A.D.

    1985-01-01

    The St. Louis Airport Storage Site (SLASS) became radioactively contaminated as a result of wastes that were being stored from operations to recover uranium from pitchblende ores in the 1940s and 1950s. The US Department of Energy is considering various remedial action options for the SLASS under the Formerly Utilized Site Remedial Action Program (FUSRAP). This report describes the results of geochemical investigations, carried out to support the FUSRAP activities and to aid in quantifying various remedial action options. Soil and groundwater samples from the site were characterized, and sorption ratios for uranium and radium and apparent concentration limit values for uranium were measured in soil/groundwater systems by batch contact methodology. The uranium and radium concentrations in soil samples were significantly above background near the old contaminated surface horizon (now at the 0.3/sup -/ to 0.9/sup -/m depth); the maximum values were 1566 ..mu..g/g and 101 pCi/g, respectively. Below about the 6/sup -/m depth, the concentrations appeared to be typical of those naturally present in soils of this area (3.8 +- 1.2 ..mu..g/g and 3.1 +- 0.6 pCi/g). Uranium sorption ratios showed stratigraphic trends but were generally moderate to high (100 to 1000 L/kg). The sorption isotherm suggested an apparent uranium concentration limit of about 200 mg/L. This relatively high solubility can probably be correlated with the carbonate content of the soil/groundwater systems. The lower sorption ratio values obtained from the sorption isotherm may have resulted from changes in the experimental procedure or the groundwater used. The SLASS appears to exhibit generally favorable behavior for the retardation of uranium solubilized from waste in the site. Parametric tests were conducted to estimate the sensitivity of uranium sorption and solubility to the pH and carbonate content of the system.

  12. Developing health-based pre-planning clearance goals for airport remediation following a chemical terrorist attack: Decision criteria for multipathway exposure routes

    SciTech Connect (OSTI)

    Watson, Annetta Paule; Dolislager, Frederick; Hall, Dr. Linda; Hauschild, Veronique; Raber, Ellen; Love, Dr. Adam

    2011-01-01

    In the event of a chemical terrorist attack on a transportation hub, post-event remediation and restoration activities necessary to attain unrestricted facility re-use and re-entry could require hours to multiple days. While timeframes are dependent on numerous variables, a primary controlling factor is the level of pre-planning and decision-making completed prior to chemical release. What follows is the second of a two-part analysis identifying key considerations, critical information and decision criteria to facilitate post-attack and post-decontamination consequence management activities. Decision criteria analysis presented here provides first-time, open-literature documentation of multi-pathway, health-based remediation exposure guidelines for selected toxic industrial compounds, chemical warfare agents, and agent degradation products for pre-planning application in anticipation of a chemical terrorist attack. Guideline values are provided for inhalation and direct ocular vapor exposure routes as well as percutaneous vapor, surface contact, and ingestion. Target populations include various employees as well as transit passengers. This work has been performed as a national case study conducted in partnership with the Los Angeles International Airport and The Bradley International Terminal. All recommended guidelines have been selected for consistency with airport scenario release parameters of a one-time, short-duration, finite airborne release from a single source followed by compound-specific decontamination.

  13. Developing health-based pre-planning clearance goals for airport remediation following chemical terrorist attack: Introduction and key assessment considerations

    SciTech Connect (OSTI)

    Watson, Annetta Paule; Raber, Ellen; Dolislager, Frederick; Hauschild, Veronique; Hall, Dr. Linda; Love, Dr. Adam

    2011-01-01

    In the event of a chemical terrorist attack on a transportation hub, post-event remediation and restoration activities necessary to attain unrestricted facility re-use and re-entry could require hours to multiple days. While restoration timeframes are dependent on numerous variables, a primary controlling factor is the level of pre-planning and decision-making completed prior to chemical terrorist release. What follows is the first of a two-part analysis identifying key considerations, critical information, and decision criteria to facilitate post-attack and post-decontamination consequence management activities. A conceptual site model and human health-based exposure guidelines are developed and reported as an aid to site-specific pre-planning in the current absence of U.S. state or Federal values designated as compound-specific remediation or re-entry concentrations, and to safely expedite facility recovery to full operational status. Chemicals of concern include chemical warfare nerve and vesicant agents and the toxic industrial compounds phosgene, hydrogen cyanide, and cyanogen chloride. This work has been performed as a national case study conducted in partnership with the Los Angeles International Airport and The Bradley International Terminal. All recommended guidelines have been selected for consistency with airport scenario release parameters of a one-time, short-duration, finite airborne release from a single source followed by compound-specific decontamination.

  14. Webinar October 21: Opportunities for Wide Bandgap Semiconductor...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    from the development of next-generation power electronics based on wide bandgap (WBG) semiconductor materials such as SiC and GaN. Examples include the development of reliable,...

  15. Soraa Is Optimizing the Use of Non-Polar and Semi-Polar Substrates...

    Energy Savers [EERE]

    on low defect density native GaN substrate instead of the conventional approach of growing heteroepitaxially (i.e., on substrates such as sapphire, silicon carbide, or silicon). ...

  16. A High Temperature-Tolerant and Radiation-Resistant In-Core Neutron Sensor for Advanced Reactors. Final report

    SciTech Connect (OSTI)

    Cao, Lei; Miller, Don

    2015-01-23

    The objectives of this project are to develop a small and reliable gallium nitride (GaN) neutron sensor that is capable of withstanding high neutron fluence and high temperature, isolating gamma background, and operating in a wide dynamic range. The first objective will be the understanding of the fundamental materials properties and electronic response of a GaN semiconductor materials and device in an environment of high temperature and intense neutron field. To achieve such goal, an in-situ study of electronic properties of GaN device such as I-V, leakage current, and charge collection efficiency (CCE) in high temperature using an external neutron beam will be designed and implemented. We will also perform in-core irradiation of GaN up to the highest yet fast neutron fluence and an off-line performance evaluation.

  17. High Quality, Low Cost Bulk Gallium Nitride Substrates Grown...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    of crystalline GaN growth in ESG Results and Accomplishments HRXRD vs reference SEM surface view 0 20 40 60 80 100 120 140 160 180 200 0 10 20 30 40 50 Deposition rate ...

  18. Atomic Resolution in Situ Imaging of a Double-Bilayer Multistep Growth Mode in Gallium Nitride Nanowires

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Gamalski, A. D.; Tersoff, J.; Stach, E. A.

    2016-04-13

    We study the growth of GaN nanowires from liquid Au–Ga catalysts using environmental transmission electron microscopy. GaN wires grow in either (11¯20) or (11¯00) directions, by the addition of {11¯00} double bilayers via step flow with multiple steps. Step-train growth is not typically seen with liquid catalysts, and we suggest that it results from low step mobility related to the unusual double-height step structure. Finally, the results here illustrate the surprising dynamics of catalytic GaN wire growth at the nanoscale and highlight striking differences between the growth of GaN and other III–V semiconductor nanowires.

  19. NREL: Measurements and Characterization - Dual-Beam Sample Preparation

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    The FIB is equipped with a gas injection system (GIS) platinum metal deposition capability ... dual beam FIB showing nano deposition with GIS of Pt contacts to a single GaN nanowire. ...

  20. Search for: All records | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    ... Filter Results Filter by Subject materials science (5) crystal growth (3) indium arsenides ... Corresponding full PIN structures have been realized by growing a p-type GaN layer on the ...

  1. Supercomputer Helps Model 3D Map of Adolescent Universe

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    The new study, led by Khee-Gan Lee and his team at the Max Planck Institute for Astronomy ... Read the news release from Max Planck Institute for Astronomy here. About NERSC and ...

  2. Opportunities for Wide Bandgap Semiconductor Power Electronics...

    Broader source: Energy.gov (indexed) [DOE]

    Semiconductor Power Electronics for Hydrogen and Fuel Cell Applications" held on October 21, 2014. ... Vehicle Technologies Office Merit Review 2016: Advanced Low-Cost SiC and GaN Wide ...

  3. OE Report_rev0420.indd

    Broader source: Energy.gov (indexed) [DOE]

    ... Air Force Research Laboratories (AFRL) Various Projects Develop new GaN modules for unmanned aerial vehicles with 20 W and 50 W amplifi ers. A challenging aspect of the program ...

  4. Wide Bandgap Power Electronics

    Office of Environmental Management (EM)

    ... coal power plant. 463 In addition to power savings, an important benefit of using high frequency GaN electronics is that the 464 adapter size can be reduced by 10x. Consumers ...

  5. Publications, 2014 | MIT-Harvard Center for Excitonics

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    ... Shiue, Ren-Jye; Gan, Xuetao; and Englund, Dirk, "On-chip graphene optoelectronic devices for high-speed modulation and photodetection," Proc. SPIE OPTO, 89940P (2014, DOI:10.1117...

  6. fgr3372.tmp

    Office of Scientific and Technical Information (OSTI)

    ... of Science, Office of Basic Energy Science, Division of Materials Sciences of the ... GaN, a wide direct bandgap semiconductor, and its alloys with AIN and InN, have realized, ...

  7. Search for: All records | SciTech Connect

    Office of Scientific and Technical Information (OSTI)

    ... Damage evaluation processes in patterned GaN implanted by 3 MeV Au2+ ions were investigated as function of ion fluences and annealing temperatures. Surface swelling was observed ...

  8. Jackson Megiatto | Center for Bio-Inspired Solar Fuel Production

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Barun Das Bhupesh Goyal Jackson Megiatto Lu Gan Matthieu Koepf Matthieu Walther Sandip Shinde Sudhanshu Sharma Jackson Megiatto Postdoctoral Fellow Subtask 4 project: "Design and Synthesis of Artificial Reaction Centers for Artificial Photoelectrochemical Devices"

  9. HIGH-QUALITY, LOW-COST BULK GALLIUM NITRIDE SUBSTRATES GROWN...

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Efficient manufacturing of gallium nitride (GaN) could reduce the cost of and improve the output for light-emitting diodes, solid-state lighting, laser displays, and other power ...

  10. Search for: All records | DOE PAGES

    Office of Scientific and Technical Information (OSTI)

    Gan, Chee Lip (1) Schuh, Christopher A. (1) Tamura, Nobumichi (1) Zeng, Xiao Mei (1) Save Results Excel (limit 2000) CSV (limit 5000) XML (limit 5000) Have feedback or suggestions ...

  11. Arizona Geological Society Digest 22

    National Nuclear Security Administration (NNSA)

    ... on active northeast-striking faults (e.g., Meremonte et al., 1995; Smith et al., 2001). ... 05-9, scale 1:24,000. Faulds, J.E., Smith, E.I., and Gans, P., 1999, Spatial and ...

  12. Microstructure changes and thermal conductivity reduction in...

    Office of Scientific and Technical Information (OSTI)

    Authors: Janne Pakrinen ; Marat Khafizov ; Lingfeng He ; Chris Wetland ; Jian Gan ; Andrew T. Nelson ; David H Hurley ; Anter El-Azab ; Todd R Allen Publication Date: 2014-11-01 ...

  13. Center for Energy Nanoscience at USC

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    LEDs. image Hz field profile for a photonic crystal micro-cavity. Large polarization and piezoelectric fields present in InGaN GaN material structures present in typical...

  14. ARM - Data Announcements Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    October 8, 2014 Data Announcements Large-Scale Forcing Data for AMIE-GAN Updated Bookmark and Share Analysis domain for Revelle, with diameters of 300 km. The red star denotes ...

  15. ARM - Data Announcements Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    August 19, 2013 Data Announcements Large-Scale Forcing Data for AMIE-Gan Available for Evaluation Bookmark and Share Large-scale forcing data from the SMART-R precipitation radar ...

  16. Applied Materials Develops an Advanced Epitaxial Growth System to Bring Down LED Costs

    Broader source: Energy.gov [DOE]

    With the help of DOE funding, Applied Materials has developed an advanced epitaxial growth system for gallium nitride (GaN) LED devices that decreases operating costs, increases internal quantum efficiency, and improves binning yields.

  17. Microsoft Word - GIGA Summary Document_Dec 17 2015

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Controlling the Flow: Next-Generation Power Electronics Systems for Tomorrow's Electric Grid GaN Initiative for Grid Applications (GIGA) Project Summary Prepared for the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability by Energetics Incorporated in collaboration with Kerry Cheung. December 2015 GaN INITIATIVE FOR GRID APPLICATIONS (GIGA) PROJECT SUMMARY 2 Executive Summary Introduction The development of next-generation power electronics (PE) systems is critical

  18. Slide 1

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    High Temperature-tolerant and Radiation-resistant In- core Neutron Sensor for Advanced Reactors Lei R. Cao The Ohio State University Cao.152@osu.edu September 18, 2014 2 Project Overview  Goal and Objectives To develop a small and reliable gallium nitride (GaN) neutron sensor capable of withstanding high neutron fluences and high temperatures, while isolating gamma background. This project will provide an understanding of the fundamental material properties and electronic response of a GaN

  19. ARM - Data Announcements Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    4, 2013 [Data Announcements] Additional Data Added to Aerosol Optical Depth Product Bookmark and Share AOD at five wavelengths (top) and Angstrom exponent (bottom) at the Gan Island site on November 5, 2011. AOD at five wavelengths (top) and Angstrom exponent (bottom) at the Gan Island site on November 5, 2011. Aerosol optical depth (AOD) measures total aerosol burden in the atmosphere. The spectral dependence of AOD, typically described by the Angstrom exponent, is also an indicator of particle

  20. Microsoft Word - SEPA Final congressional justification 1-22-10.doc

    Energy Savers [EERE]

    Controlling the Flow: Next-Generation Power Electronics Systems for Tomorrow's Electric Grid GaN Initiative for Grid Applications (GIGA) Project Summary Prepared for the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability by Energetics Incorporated in collaboration with Kerry Cheung. December 2015 GaN INITIATIVE FOR GRID APPLICATIONS (GIGA) PROJECT SUMMARY 2 Executive Summary Introduction The development of next-generation power electronics (PE) systems is critical

  1. Summer 2010 Intern Project- John Haberstroh | Center for Energy Efficient

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Materials John Haberstroh THERMOELECTRIC PROPERTIES OF GaN AND InGaN BASED MATERIALS John Haberstroh CCS Physics UC Santa Barbara Mentor: Alex Sztein Faculty Advisor: Shuji Nakamura Department: Materials Science Recent advances in Metal Organic Chemical Vapor Deposition have made GaN and it's alloys a leading family of semiconductor materials. Despite this increased interest, however, the thermoelectric properties of this material system remain mostly unexplored, although a few basic studies

  2. Document

    Office of Environmental Management (EM)

    720 Federal Register / Vol. 75, No. 117 / Friday, June 18, 2010 / Notices We reference the regulations outlining the terms and conditions of an award in the Applicable Regulations section of this notice and include these and other specific conditions in the GAN. The GAN also incorporates your approved application as part of your binding commitments under the grant. 3. Grant Administration: Projects funded under this competition are encouraged to budget for a two-day meeting for project directors

  3. Abbreviated epitaxial growth mode (AGM) method for reducing cost and improving quality of LEDs and lasers

    DOE Patents [OSTI]

    Tansu, Nelson; Chan, Helen M; Vinci, Richard P; Ee, Yik-Khoon; Biser, Jeffrey

    2013-09-24

    The use of an abbreviated GaN growth mode on nano-patterned AGOG sapphire substrates, which utilizes a process of using 15 nm low temperature GaN buffer and bypassing etch-back and recovery processes during epitaxy, enables the growth of high-quality GaN template on nano-patterned AGOG sapphire. The GaN template grown on nano-patterned AGOG sapphire by employing abbreviated growth mode has two orders of magnitude lower threading dislocation density than that of conventional GaN template grown on planar sapphire. The use of abbreviated growth mode also leads to significant reduction in cost of the epitaxy. The growths and characteristics of InGaN quantum wells (QWs) light emitting diodes (LEDs) on both templates were compared. The InGaN QWs LEDs grown on the nano-patterned AGOG sapphire demonstrated at least a 24% enhancement of output power enhancement over that of LEDs grown on conventional GaN templates.

  4. Integrating AlGaN/GaN high electron mobility transistor with Si: A comparative study of integration schemes

    SciTech Connect (OSTI)

    Mohan, Nagaboopathy; Raghavan, Srinivasan; Manikant,; Soman, Rohith

    2015-10-07

    AlGaN/GaN high electron mobility transistor stacks deposited on a single growth platform are used to compare the most common transition, AlN to GaN, schemes used for integrating GaN with Si. The efficiency of these transitions based on linearly graded, step graded, interlayer, and superlattice schemes on dislocation density reduction, stress management, surface roughness, and eventually mobility of the 2D-gas are evaluated. In a 500 nm GaN probe layer deposited, all of these transitions result in total transmission electron microscopy measured dislocations densities of 1 to 3 × 10{sup 9}/cm{sup 2} and <1 nm surface roughness. The 2-D electron gas channels formed at an AlGaN-1 nm AlN/GaN interface deposited on this GaN probe layer all have mobilities of 1600–1900 cm{sup 2}/V s at a carrier concentration of 0.7–0.9 × 10{sup 13}/cm{sup 2}. Compressive stress and changes in composition in GaN rich regions of the AlN-GaN transition are the most effective at reducing dislocation density. Amongst all the transitions studied the step graded transition is the one that helps to implement this feature of GaN integration in the simplest and most consistent manner.

  5. Annual Review of BPA-Funded Projects in Natural and Artificial Propagation of Salmonids, March 27-29, 1985, Holiday Inn Airport, Portland, Oregon.

    SciTech Connect (OSTI)

    United States. Bonneville Power Administration.

    1985-04-01

    The Fish and Wildlife Division of Bonneville Power Administration (BPA) hosted a meeting for contractors to present the results of fiscal year 1984 research conducted to implement the Northwest Power Planning Council's Fish and Wildlife Program. The meeting focused on those projects specifically related to natural and artificial propagation of salmonids. The presentations were held at the Holiday Inn Airport in Portland, Oregon, on March 27-29, 1985. This document contains abstracts of the presentations from that meeting. Section 1 contains abstracts on artificial propagation, fish health, and downstream migration, and Section 2 contains abstracts on natural propagation and habitat improvement. The abstracts are indexed by BPA Project Number and by Fish and Wildlife Program Measure. The registered attendees at the meeting are listed alphabetically in Appendix A and by affiliation in Appendix B.

  6. Improving p-type doping efficiency in Al{sub 0.83}Ga{sub 0.17}N alloy substituted by nanoscale (AlN){sub 5}/(GaN){sub 1} superlattice with Mg{sub Ga}-O{sub N} δ-codoping: Role of O-atom in GaN monolayer

    SciTech Connect (OSTI)

    Zhong, Hong-xia; Shi, Jun-jie Jiang, Xin-he; Huang, Pu; Ding, Yi-min; Zhang, Min

    2015-01-15

    We calculate Mg-acceptor activation energy E{sub A} and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on E{sub A} in nanoscale (AlN){sub 5}/(GaN){sub 1} superlattice (SL), a substitution for Al{sub 0.83}Ga{sub 0.17}N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMg{sub Ga}-O{sub N} (n = 1-3) complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing E{sub A}. The shorter the Mg-O bond is, the smaller the E{sub A} is. The Mg-acceptor activation energy can be reduced significantly by nMg{sub Ga}-O{sub N} δ-codoping. Our calculated E{sub A} for 2Mg{sub Ga}-O{sub N} is 0.21 eV, and can be further reduced to 0.13 eV for 3Mg{sub Ga}-O{sub N}, which results in a high hole concentration in the order of 10{sup 20} cm{sup −3} at room temperature in (AlN){sub 5}/(GaN){sub 1} SL. Our results prove that nMg{sub Ga}-O{sub N} (n = 2,3) δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.

  7. Enhanced internal quantum efficiency and light extraction efficiency from textured GaN/AlGaN quantum wells grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Cabalu, J.S.; Thomidis, C.; Moustakas, T.D.; Riyopoulos, S.; Zhou Lin; Smith, David J.

    2006-03-15

    GaN/Al{sub 0.2}Ga{sub 0.8}N multiple quantum wells (MQWs) were grown by molecular beam epitaxy on randomly textured and atomically smooth (0001) GaN templates. Smooth and textured GaN templates were deposited on (0001) sapphire substrates by varying the III/V ratio and the substrate temperature during growth by the hydride vapor-phase epitaxy method. We find that the MQWs replicate the texture of the GaN template, which was found to have a Gaussian distribution. The peak photoluminescence intensity from the textured MQWs is always higher than from the smooth MQWs and for GaN (7 nm)/Al{sub 0.2}Ga{sub 0.8}N (8 nm) MQWs, it is 700 times higher than that from similarly produced MQWs on smooth GaN templates. This result is attributed partly to the enhancement in light extraction efficiency and partly to the enhancement in internal quantum efficiency. The origin of the increase in internal quantum efficiency is partly due to the reduction of the quantum-confined Stark effect, since the polarization vector intersects the quantum well (QW) planes at angles smaller than 90 deg. , and partly due to the charge redistribution in the QWs caused by the polarization component parallel to the planes of the QWs.

  8. Compact, Interactive Electric Vehicle Charger: Gallium-Nitride Switch Technology for Bi-directional Battery-to-Grid Charger Applications

    SciTech Connect (OSTI)

    2010-10-01

    ADEPT Project: HRL Laboratories is using gallium nitride (GaN) semiconductors to create battery chargers for electric vehicles (EVs) that are more compact and efficient than traditional EV chargers. Reducing the size and weight of the battery charger is important because it would help improve the overall performance of the EV. GaN semiconductors process electricity faster than the silicon semiconductors used in most conventional EV battery chargers. These high-speed semiconductors can be paired with lighter-weight electrical circuit components, which helps decrease the overall weight of the EV battery charger. HRL Laboratories is combining the performance advantages of GaN semiconductors with an innovative, interactive battery-to-grid energy distribution design. This design would support 2-way power flow, enabling EV battery chargers to not only draw energy from the power grid, but also store and feed energy back into it.

  9. Self-annihilation of inversion domains by high energy defects in III-Nitrides

    SciTech Connect (OSTI)

    Koukoula, T.; Kioseoglou, J. Kehagias, Th.; Komninou, Ph.; Ajagunna, A. O.; Georgakilas, A.

    2014-04-07

    Low-defect density InN films were grown on Si(111) by molecular beam epitaxy over an ?1??m thick GaN/AlN buffer/nucleation layer. Electron microscopy observations revealed the presence of inverse polarity domains propagating across the GaN layer and terminating at the sharp GaN/InN (0001{sup }) interface, whereas no inversion domains were detected in InN. The systematic annihilation of GaN inversion domains at the GaN/InN interface is explained in terms of indium incorporation on the Ga-terminated inversion domains forming a metal bonded In-Ga bilayer, a structural instability known as the basal inversion domain boundary, during the initial stages of InN growth on GaN.

  10. Growth of gallium nitride films via the innovative technique of atomic-layer epitaxy. Annual progress report, 1 June 1987-31 May 1988

    SciTech Connect (OSTI)

    Davis, R.F.; Paisley, M.J.; Sitar, Z.

    1988-06-01

    Gallium nitride (GaN) is a wide-bandgap (3.45 eV at 300K) III-V compound semiconductor. The large direct bandgap and high electron-drift velocity of GaN are important properties in the performance of short-wavelength optical devices and high-power microwave devices. Immediate applications that would be greatly enhanced by the availability of GaN and/or Al/sub x/Ga/sub 1-x/N devices include threat warning systems (based on the ultraviolet (UV) emission from the exhaust plumes of missiles) and radar systems (which require high-power microwave generation). Important future applications for devices produced from these materials include blue and ultraviolet semiconductor lasers, blue-light-emitting diodes (LEDs) and high temperature electronic devices. This report discusses this material.

  11. Investigation of the GaN-on-GaAs interface for vertical power device applications

    SciTech Connect (OSTI)

    Mreke, Janina Uren, Michael J.; Kuball, Martin; Novikov, Sergei V.; Foxon, C. Thomas; Hosseini Vajargah, Shahrzad; Wallis, David J.; Humphreys, Colin J.; Haigh, Sarah J.; Al-Khalidi, Abdullah; Wasige, Edward; Thayne, Iain

    2014-07-07

    GaN layers were grown onto (111) GaAs by molecular beam epitaxy. Minimal band offset between the conduction bands for GaN and GaAs materials has been suggested in the literature raising the possibility of using GaN-on-GaAs for vertical power device applications. I-V and C-V measurements of the GaN/GaAs heterostructures however yielded a rectifying junction, even when both sides of the junction were heavily doped with an n-type dopant. Transmission electron microscopy analysis further confirmed the challenge in creating a GaN/GaAs Ohmic interface by showing a large density of dislocations in the GaN layer and suggesting roughening of the GaN/GaAs interface due to etching of the GaAs by the nitrogen plasma, diffusion of nitrogen or melting of Ga into the GaAs substrate.

  12. Multi-phonon-assisted absorption and emission in semiconductors and its potential for laser refrigeration

    SciTech Connect (OSTI)

    Khurgin, Jacob B.

    2014-06-02

    Laser cooling of semiconductors has been an elusive goal for many years, and while attempts to cool the narrow gap semiconductors such as GaAs are yet to succeed, recently, net cooling has been attained in a wider gap CdS. This raises the question of whether wider gap semiconductors with higher phonon energies and stronger electron-phonon coupling are better suitable for laser cooling. In this work, we develop a straightforward theory of phonon-assisted absorption and photoluminescence of semiconductors that involves more than one phonon and use to examine wide gap materials, such as GaN and CdS and compare them with GaAs. The results indicate that while strong electron-phonon coupling in both GaN and CdS definitely improves the prospects of laser cooling, large phonon energy in GaN may be a limitation, which makes CdS a better prospect for laser cooling.

  13. Solid-State Lighting | Center for Energy Efficient Materials

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Solid-State Lighting Our goal is to advance the fundamental science and technology to both understand factors that limit efficiencies for light emitting diode-based lighting and to provide innovative and viable solutions to current roadblocks. We intend to achieve these goals by: (1) control and elucidation of the carrier loss mechanisms on nonpolar/semipolar GaN LEDs; (2) growth of defect-free bulk GaN crystals; and (3) full-spectrum lighting using an all semiconductor-based emission region;

  14. ARM - Meetings and Presentations

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Meetings and Presentations Related Links amie.png 34h AMIE Home cindy.png 50h CINDY2011 dynamo.png 34h DYNAMO ARM Data Discovery Browse Data Outreach News & Press Blog Backgrounder (PDF, 1.2MB) Education Flyer (PDF, 2.0MB) Images ARM flickr site Official AMIE Logo AMIE Gear Experiment Planning Steering Committee AMIE-MANUS Proposal Abstract AMIE-GAN Proposal Abstract Meetings Cloud Life Cycle Working Group Deployment Operations Science Plan - TWP Manus Site (PDF, 2.1 MB) Science Plan - Gan

  15. ARM - Steering Committee

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Steering Committee Related Links amie.png 34h AMIE Home cindy.png 50h CINDY2011 dynamo.png 34h DYNAMO ARM Data Discovery Browse Data Outreach News & Press Blog Backgrounder (PDF, 1.2MB) Education Flyer (PDF, 2.0MB) Images ARM flickr site Official AMIE Logo AMIE Gear Experiment Planning Steering Committee AMIE-MANUS Proposal Abstract AMIE-GAN Proposal Abstract Meetings Cloud Life Cycle Working Group Deployment Operations Science Plan - TWP Manus Site (PDF, 2.1 MB) Science Plan - Gan Island

  16. Screening of the quantum-confined Stark effect in AlN/GaN nanowire superlattices by germanium doping

    SciTech Connect (OSTI)

    Hille, P. Mener, J.; Becker, P.; Teubert, J.; Schrmann, J.; Eickhoff, M.; Mata, M. de la; Rosemann, N.; Chatterjee, S.; Magn, C.; Arbiol, J.; Institucio Catalana de Recerca i Estudis Avanats , 08010 Barcelona, CAT

    2014-03-10

    We report on electrostatic screening of polarization-induced internal electric fields in AlN/GaN nanowire heterostructures with germanium-doped GaN nanodiscs embedded between AlN barriers. The incorporation of germanium at concentrations above 10{sup 20}?cm{sup 3} shifts the photoluminescence emission energy of GaN nanodiscs to higher energies accompanied by a decrease of the photoluminescence decay time. At the same time, the thickness-dependent shift in emission energy is significantly reduced. In spite of the high donor concentration, a degradation of the photoluminescence properties is not observed.

  17. Printed assemblies of ultrathin, microscale inorganic light emitting diodes for deformable and semitransparent displays

    DOE Patents [OSTI]

    Rogers, John A; Nuzzo, Ralph; Kim, Hoon-sik; Brueckner, Eric; Park, Sang Il; Kim, Rak Hwan

    2014-10-21

    Described herein are printable structures and methods for making, assembling and arranging electronic devices. A number of the methods described herein are useful for assembling electronic devices where one or more device components are embedded in a polymer which is patterned during the embedding process with trenches for electrical interconnects between device components. Some methods described herein are useful for assembling electronic devices by printing methods, such as by dry transfer contact printing methods. Also described herein are GaN light emitting diodes and methods for making and arranging GaN light emitting diodes, for example for display or lighting systems.

  18. ARM - AMIE Manus - Data Plots

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Manus Related Links amie.png 34h AMIE Home cindy.png 50h CINDY2011 dynamo.png 34h DYNAMO ARM Data Discovery Browse Data Outreach News & Press Blog Backgrounder (PDF, 1.2MB) Education Flyer (PDF, 2.0MB) Images ARM flickr site Official AMIE Logo AMIE Gear Experiment Planning Steering Committee AMIE-MANUS Proposal Abstract AMIE-GAN Proposal Abstract Meetings Cloud Life Cycle Working Group Deployment Operations Science Plan - TWP Manus Site (PDF, 2.1 MB) Science Plan - Gan Island Site (PDF, 2.0

  19. Influence of strain induced by AlN nucleation layer on the electrical properties of AlGaN/GaN heterostructures on Si(111) substrate

    SciTech Connect (OSTI)

    Christy, Dennis; Watanabe, Arata; Egawa, Takashi

    2014-10-15

    The crack-free metal-organic chemical vapor deposition (MOCVD) grown AlGaN/GaN heterostructures on Si substrate with modified growth conditions of AlN nucleation layer (NL) and its influence on the electrical and structural properties of conductive GaN layer are presented. From the Hall electrical measurements, a gradual decrease of two-dimensional electron gas (2DEG) concentration near heterointerface as the function of NL thickness is observed possibly due to the reduction in difference of piezoelectric polarization charge densities between AlGaN and GaN layers. It also indicates that the minimum tensile stress and a relatively less total dislocation density for high pressure grown NL can ensure a 20 % increment in mobility at room temperature irrespective of the interface roughness. The thickness and pressure variations in NL and the subsequent changes in growth mode of AlN contributing to the post growth residual tensile stress are investigated using X-ray diffraction and Raman scattering experiments, respectively. The post growth intrinsic residual stress in top layers of heterostructures arises from lattice mismatches, NL parameters and defect densities in GaN. Hence, efforts to reduce the intrinsic residual stress in current conducting GaN layer give an opportunity to further improve the electrical characteristics of AlGaN/GaN device structures on Si.

  20. CX-010974: Categorical Exclusion Determination

    Broader source: Energy.gov [DOE]

    Advanced Low-Cost Silicon Carbide (SiC) and Gallium Nitride (GaN) Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction... CX(s) Applied: B3.6 Date: 09/16/2013 Location(s): Arkansas Offices(s): National Energy Technology Laboratory

  1. CX-010973: Categorical Exclusion Determination

    Broader source: Energy.gov [DOE]

    Advanced Low-Cost Silicon Carbide (SiC) and Gallium Nitride (GaN) Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction... CX(s) Applied: B3.6 Date: 09/16/2013 Location(s): Arkansas Offices(s): National Energy Technology Laboratory

  2. CX-000845: Categorical Exclusion Determination

    Broader source: Energy.gov [DOE]

    25A2445 - Ammonothermal Bulk Gallium Nitride (GaN) Crystal Growth for Energy Efficient LightingCX(s) Applied: B3.6Date: 01/15/2010Location(s): New YorkOffice(s): Advanced Research Projects Agency - Energy

  3. CX-009889: Categorical Exclusion Determination

    Broader source: Energy.gov [DOE]

    25A2445 - Ammonothermal Bulk GaN Crystal Growth for Energy Efficient Lighting CX(s) Applied: B3.6 Date: 01/15/2010 Location(s): New York Offices(s): Advanced Research Projects Agency-Energy

  4. CX-011468: Categorical Exclusion Determination

    Broader source: Energy.gov [DOE]

    Advanced Low-Cost Silicon-Carbide (SiC) and Gallium-Nitride (GaN) Wide Bandgap Inverters for Under-the-Hood Electric Vehicle Traction... CX(s) Applied: B3.6 Date: 10/29/2013 Location(s): Michigan Offices(s): National Energy Technology Laboratory

  5. Gallium nitride junction field-effect transistor

    DOE Patents [OSTI]

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  6. Gallium nitride junction field-effect transistor

    DOE Patents [OSTI]

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  7. CX-009000: Categorical Exclusion Determination

    Broader source: Energy.gov [DOE]

    "High Quality, Low Cost Bulk Gallium Nitride (GaN) Substrates Grown by the Electrochemical Solution Growth Method CX(s) Applied: A9, B3.6 Date: 08/20/2012 Location(s): Missouri Offices(s): Golden Field Office"

  8. Method to grow group III-nitrides on copper using passivation layers

    DOE Patents [OSTI]

    Li, Qiming; Wang, George T; Figiel, Jeffrey T

    2014-06-03

    Group III-nitride epilayers can be grown directly on copper substrates using intermediate passivation layers. For example, single crystalline c-plane GaN can be grown on Cu (110) substrates with MOCVD. The growth relies on a low temperature AlN passivation layer to isolate any alloying reaction between Ga and Cu.

  9. Multicolor, High Efficiency, Nanotextured LEDs

    SciTech Connect (OSTI)

    Jung Han; Arto Nurmikko

    2011-09-30

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and green for Solid State Lighting applications. Accomplishments in the duration of the contract period include (i) heteroepitaxy of nitrogen-polar LEDs on sapphire, (ii) heteroepitaxy of semipolar (11{bar 2}2) green LEDs on sapphire, (iii) synthesis of quantum-dot loaded nanoporous GaN that emits white light without phosphor conversion, (iv) demonstration of the highest quality semipolar (11{bar 2}2) GaN on sapphire using orientation-controlled epitaxy, (v) synthesis of nanoscale GaN and InGaN medium, and (vi) development of a novel liftoff process for manufacturing GaN thin-film vertical LEDs. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  10. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T.; Martinez, Julio A.

    2015-11-25

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN coremore » of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.« less

  11. Sandip Shinde | Center for Bio-Inspired Solar Fuel Production

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Principal Investigators Postdoctoral Fellows Center researchers Graduate Students Undergraduate Students All Bisfuel Center Personnel Barun Das Bhupesh Goyal Jackson Megiatto Lu Gan Matthieu Koepf Matthieu Walther Sandip Shinde Sudhanshu Sharma Sandip Shinde Postdoctoral Fellow (2010-2011) Subtask 1 * Subtask 2 * Subtask 3 * Subtask 4 * Subtask 5

  12. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

    SciTech Connect (OSTI)

    Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T.; Martinez, Julio A.

    2015-11-25

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

  13. Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May

    2015-05-04

    We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme.

  14. Optical characteristics of nanocrystalline Al{sub x}Ga{sub 1?x}N thin films deposited by hollow cathode plasma-assisted atomic layer deposition

    SciTech Connect (OSTI)

    Goldenberg, Eda; Ozgit-Akgun, Cagla; Biyikli, Necmi; Kemal Okyay, Ali

    2014-05-15

    Gallium nitride (GaN), aluminum nitride (AlN), and Al{sub x}Ga{sub 1?x}N films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200?C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al{sub x}Ga{sub 1?x}N films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2?nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4?nm when the annealing duration increased from 30?min to 2?h (800?C). For all films, the average optical transmission was ?85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and Al{sub x}Ga{sub 1?x}N were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (??=?550?nm) with the increased Al content x (0???x???1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400?nm). Postdeposition annealing at 900?C for 2?h considerably lowered the refractive index value of GaN films (2.331.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95?eV, and it decreased to 3.90?eV for films annealed at 800?C for 30?min and 2?h. On the other hand, this value increased to 4.1?eV for GaN films annealed at 900?C for 2?h. This might be caused by Ga{sub 2}O{sub 3} formation and following phase change. The optical bandgap value of as-deposited Al{sub x}Ga{sub 1?x}N films decreased from 5.75 to 5.25?eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not affect the bandgap of Al-rich films.

  15. Structural and optical properties of InGaN--GaN nanowire heterostructures grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Hofling, S.; Worschech, L.; Grutzmacher, D.

    2011-01-01

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaN to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, μ-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.

  16. Pittsburgh Airport Marriott Hotel Floor Plan

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    of LG Fuel Cell System Projects - Performance, Durability, Cost Shung Ik Lee and Adam Babcock, LG Fuel Cell Systems, Inc. 12:15 - 1:30 pm LUNCH in Coraopolis, Findlay, Moon Rooms 3 ...

  17. Microsoft Word - Airport_EA_Final.doc

    National Nuclear Security Administration (NNSA)

    ......... 26 3.6 Water Resources (Surface and Ground) ... sludge from a waste treatment plant, water supply treatment plant, or air pollution ...

  18. Advanced Epi Tools for Gallium Nitride Light Emitting Diode Devices

    SciTech Connect (OSTI)

    Patibandla, Nag; Agrawal, Vivek

    2012-12-01

    Over the course of this program, Applied Materials, Inc., with generous support from the United States Department of Energy, developed a world-class three chamber III-Nitride epi cluster tool for low-cost, high volume GaN growth for the solid state lighting industry. One of the major achievements of the program was to design, build, and demonstrate the world’s largest wafer capacity HVPE chamber suitable for repeatable high volume III-Nitride template and device manufacturing. Applied Materials’ experience in developing deposition chambers for the silicon chip industry over many decades resulted in many orders of magnitude reductions in the price of transistors. That experience and understanding was used in developing this GaN epi deposition tool. The multi-chamber approach, which continues to be unique in the ability of the each chamber to deposit a section of the full device structure, unlike other cluster tools, allows for extreme flexibility in the manufacturing process. This robust architecture is suitable for not just the LED industry, but GaN power devices as well, both horizontal and vertical designs. The new HVPE technology developed allows GaN to be grown at a rate unheard of with MOCVD, up to 20x the typical MOCVD rates of 3{micro}m per hour, with bulk crystal quality better than the highest-quality commercial GaN films grown by MOCVD at a much cheaper overall cost. This is a unique development as the HVPE process has been known for decades, but never successfully commercially developed for high volume manufacturing. This research shows the potential of the first commercial-grade HVPE chamber, an elusive goal for III-V researchers and those wanting to capitalize on the promise of HVPE. Additionally, in the course of this program, Applied Materials built two MOCVD chambers, in addition to the HVPE chamber, and a robot that moves wafers between them. The MOCVD chambers demonstrated industry-leading wavelength yield for GaN based LED wafers and industry

  19. Growth of GaN@InGaN Core-Shell and Au-GaN Hybrid Nanostructures for Energy Applications

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kuykendall, Tevye; Aloni, Shaul; Jen-La Plante, Ilan; Mokari, Taleb

    2009-01-01

    We demonstrated a method to control the bandgap energy of GaN nanowires by forming GaN@InGaN core-shell hybrid structures using metal organic chemical vapor deposition (MOCVD). Furthermore, we show the growth of Au nanoparticles on the surface of GaN nanowires in solution at room temperature. The work shown here is a first step toward engineering properties that are crucial for the rational design and synthesis of a new class of photocatalytic materials. The hybrid structures were characterized by various techniques, including photoluminescence (PL), energy dispersive x-ray spectroscopy (EDS), transmission and scanning electron microscopy (TEM and SEM), and x-ray diffraction (XRD).

  20. Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

    SciTech Connect (OSTI)

    Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth

    2015-12-28

    Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

  1. Capacitance-voltage characteristics of (Al/Ti)/Al{sub 2}O{sub 3}/n-GaN MIS structures

    SciTech Connect (OSTI)

    Ivanov, P. A. Potapov, A. S.; Nikolaev, A. E.; Lundin, V. V.; Sakharov, A. V.; Tsatsulnikov, A. F.; Afanas’ev, A. V.; Romanov, A. A.; Osachev, E. V.

    2015-08-15

    The capacitance-voltage characteristics of (Al/Ti)/Al{sub 2}O{sub 3}/n-GaN metal—insulator-semiconductor (MIS) structures are measured and analyzed. n-Type GaN films are grown on sapphire (0001) substrates by the metal-organic chemical vapor deposition method. An aluminum-oxide layer with a thickness of 60 nm is deposited onto the surface of GaN by the method of atomic-layer deposition from the gas phase. Metallic contacts are deposited by the electron-beam evaporation of titanium and aluminum in vacuum. According to the measurement results, the breakdown-field strength of the oxide, its dielectric constant, and the integrated electron density of states at the oxide-semiconductor interface are 5 × 10{sup 6} V/cm, 7.5, and 3 × 10{sup 12} cm{sup −2}, respectively.

  2. AlGaN/GaN heterostructure prepared on a Si (110) substrate via pulsed sputtering

    SciTech Connect (OSTI)

    Watanabe, T.; Ohta, J.; Kondo, T.; Ohashi, M.; Ueno, K.; Kobayashi, A.; Fujioka, H.

    2014-05-05

    GaN films were grown on Si (110) substrates using a low-temperature growth technique based on pulsed sputtering. Reduction of the growth temperature suppressed the strain in the GaN films, leading to an increase in the critical thickness for crack formation. In addition, an AlGaN/GaN heterostructure with a flat heterointerface was prepared using this technique. Furthermore, the existence of a two dimensional electron gas at the heterointerface with a mobility of 1360 cm{sup 2}/Vs and a sheet carrier density of 1.3??10{sup 13}?cm{sup ?2} was confirmed. Finally, the use of the AlGaN/GaN heterostructure in a high electron mobility transistor was demonstrated. These results indicate that low-temperature growth via pulsed sputtering is quite promising for the fabrication of GaN-based electronic devices.

  3. Low-Cost Substrates for High-Performance Nanorod Array LEDs

    SciTech Connect (OSTI)

    Sands, Timothy; Stach, Eric; Garcia, Edwin

    2009-04-30

    The completed project, entitled Low-Cost Substrates for High-Performance Nanorod LEDs, targeted the goal of a phosphor-free nanorod-based white LED with IQE > 50% across the spectrum from 450 nm to 600 nm on metallized silicon substrates. The principal achievements of this project included: Demonstration of (In,Ga)N nanopyramid heterostructures by a conventional OMVPE process. Verification of complete filtering of threading dislocations to yield dislocation-free pyramidal heterostructures. Demonstration of electroluminescence with a peak wavelength of ~600 nm from an (In,Ga)N nanopyramid array LED. Development of a reflective ZrN/AlN buffer layer for epitaxial growth of GaN films and GaN nanopyramid arrays on (111)Si.

  4. Measurement of temperature-dependent defect diffusion in proton-irradiated GaN(Mg, H).

    SciTech Connect (OSTI)

    Myers, Samuel Maxwell, Jr.; Fleming, Robert M.

    2005-06-01

    Deuterated p-type GaN(Mg,{sup 2}H) films were irradiated at room temperature with 1 MeV protons to create native point defects with a concentration approximately equal to the Mg doping (5 x 10{sup 19} cm{sup -3}). The samples were then annealed isothermally at a succession of temperatures while monitoring the infrared absorption due to the H local mode of the MgH defect. As the samples were annealed, the MgH absorption signal decreased and a new mode at slightly higher frequency appeared, which has been associated with the approach of a mobile nitrogen interstitial. We used the time dependence of the MgH absorption to obtain a diffusion barrier of the nitrogen interstitial in p-type GaN of 1.99 eV. This is in good agreement with theoretical calculations of nitrogen interstitial motion in GaN.

  5. Inversion by metalorganic chemical vapor deposition from N- to Ga-polar gallium nitride and its application to multiple quantum well light-emitting diodes

    SciTech Connect (OSTI)

    Hosalli, A. M.; Van Den Broeck, D. M.; Bedair, S. M. [Department of Electrical and Computer Engineering, NCSU, Raleigh, North Carolina 27695 (United States)] [Department of Electrical and Computer Engineering, NCSU, Raleigh, North Carolina 27695 (United States); Bharrat, D.; El-Masry, N. A. [Department of Material Science and Engineering, NCSU, Raleigh, North Carolina 27695 (United States)] [Department of Material Science and Engineering, NCSU, Raleigh, North Carolina 27695 (United States)

    2013-12-02

    We demonstrate a metalorganic chemical vapor deposition growth approach for inverting N-polar to Ga-polar GaN by using a thin inversion layer grown with high Mg flux. The introduction of this inversion layer allowed us to grow p-GaN films on N-polar GaN thin film. We have studied the dependence of hole concentration, surface morphology, and degree of polarity inversion for the inverted Ga-polar surface on the thickness of the inversion layer. We then use this approach to grow a light emitting diode structure which has the MQW active region grown on the advantageous N-polar surface and the p-layer grown on the inverted Ga-polar surface.

  6. Epitaxial Growth of GaN-based LEDs on Simple Sacrificial Substrates

    SciTech Connect (OSTI)

    Ian Ferguson; Chris Summers

    2009-12-31

    The objective of this project is to produce alternative substrate technologies for GaN-based LEDs by developing an ALD interlayer of Al{sub 2}O{sub 3} on sacrificial substrates such as ZnO and Si. A sacrificial substrate is used for device growth that can easily be removed using a wet chemical etchant leaving only the thin GaN epi-layer. After substrate removal, the GaN LED chip can then be mounted in several different ways to a metal heat sink/reflector and light extraction techniques can then be applied to the chip and compared for performance. Success in this work will lead to high efficiency LED devices with a simple low cost fabrication method and high product yield as stated by DOE goals for its solid state lighting portfolio.

  7. Room temperature photoluminescence from In{sub x}Al{sub (1?x)}N films deposited by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kong, W. Jiao, W. Y.; Kim, T. H.; Brown, A. S.; Mohanta, A.; Roberts, A. T.; Fournelle, J.; Losurdo, M.; Everitt, H. O.

    2014-09-29

    InAlN films deposited by plasma-assisted molecular beam epitaxy exhibited a lateral composition modulation characterized by 1012?nm diameter, honeycomb-shaped, columnar domains with Al-rich cores and In-rich boundaries. To ascertain the effect of this microstructure on its optical properties, room temperature absorption and photoluminescence characteristics of In{sub x}Al{sub (1?x)}N were comparatively investigated for indium compositions ranging from x?=?0.092 to 0.235, including x?=?0.166 lattice matched to GaN. The Stokes shift of the emission was significantly greater than reported for films grown by metalorganic chemical vapor deposition, possibly due to the phase separation in these nanocolumnar domains. The room temperature photoluminescence also provided evidence of carrier transfer from the InAlN film to the GaN template.

  8. Synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy of n-ZnO:Al/p-GaN:Mg heterojunction

    SciTech Connect (OSTI)

    Lee, Kai-Hsuan; Chen, Chia-Hao; Chang, Ping-Chuan; Chen, Tse-Pu; Chang, Sheng-Po; Chang, Shoou-Jinn; Department of Physics, National Tsing Hua University, Kuang-Fu Rd. 101, 30013 Hsinchu, Taiwan

    2013-02-18

    Al-doped ZnO (AZO) deposited by radio frequency co-sputtering is formed on epitaxial Mg-doped GaN template at room temperature to achieve n-AZO/p-GaN heterojunction. Alignment of AZO and GaN bands is investigated using synchrotron radiation based cross-sectional scanning photoelectron microscopy and spectroscopy on the nonpolar side-facet of a vertically c-axis aligned heterostructure. It shows type-II band configuration with valence band offset of 1.63 {+-} 0.1 eV and conduction band offset of 1.61 {+-} 0.1 eV, respectively. Rectification behavior is clearly observed, with a ratio of forward-to-reverse current up to six orders of magnitude when the bias is applied across the p-n junction.

  9. Ultraviolet band-pass Schottky barrier photodetectors formed by Al-doped ZnO contacts to n-GaN

    SciTech Connect (OSTI)

    Sheu, J.K.; Lee, M.L.; Tun, C.J.; Lin, S.W.

    2006-01-23

    This work prepared Al-doped ZnO(AZO) films using dc sputtering to form Schottky contacts onto GaN films with low-temperature-grown GaN cap layer. Application of ultraviolet photodetector showed that spectral responsivity exhibits a narrow bandpass characteristic ranging from 345 to 375 nm. Moreover, unbiased peak responsivity was estimated to be around 0.12 A/W at 365 nm, which corresponds to a quantum efficiency of around 40%. In our study, relatively low responsivity can be explained by the marked absorption of the AZO contact layer. When the reverse biases were below 5 V, the study revealed that dark currents were well below 5x10{sup -12} A even though the samples were annealed at increased temperatures.

  10. Sandia National Laboratories: Power Electronics

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Power Electronics Sensors Power electronics is the application of solid-state electronics for routing, control, and conversion of electrical power. Custom Solutions Wide-Bandgap Wide-bandgap semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) have the potential to revolutionize the field of power electronics. Sandia National Laboratories is well-suited to understand both performance and reliability in wide-bandgap power electronics. Understanding Material Properties

  11. Mobile Facility

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    govSitesMobile Facility AMF Information Science Architecture Baseline Instruments AMF1 AMF2 AMF3 MAOS AMF Fact Sheet Images Contacts AMF Deployments McMurdo Station, Antarctica, 2015-2016 Pearl Harbor, Hawaii, to San Francisco, California, 2015 Hyytiälä, Finland, 2014 Manacapuru, Brazil, 2014 Oliktok Point, Alaska, 2013 Los Angeles, California, to Honolulu, Hawaii, 2012 Cape Cod, Massachusetts, 2012 Gan Island, Maldives, 2011 Ganges Valley, India, 2011 Steamboat Springs, Colorado, 2010

  12. Notices

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    519 Federal Register / Vol. 77, No. 118 / Tuesday, June 19, 2012 / Notices send you a Grant Award Notification (GAN). We may notify you informally, also. If your application is not evaluated or not selected for funding, we notify you. 2. Administrative and National Policy Requirements: We identify administrative and national policy requirements in the application package and reference these and other requirements in the Applicable Regulations section of this notice. We reference the regulations

  13. ARM - Site Instruments

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    FacilitiesInstruments AMF Information Science Architecture Baseline Instruments AMF1 AMF2 AMF3 MAOS AMF Fact Sheet Images Contacts AMF Deployments McMurdo Station, Antarctica, 2015-2016 Pearl Harbor, Hawaii, to San Francisco, California, 2015 Hyytiälä, Finland, 2014 Manacapuru, Brazil, 2014 Oliktok Point, Alaska, 2013 Los Angeles, California, to Honolulu, Hawaii, 2012 Cape Cod, Massachusetts, 2012 Gan Island, Maldives, 2011 Ganges Valley, India, 2011 Steamboat Springs, Colorado, 2010 Graciosa

  14. ARM - Site Instruments

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    FacilitiesInstruments AMF Information Science Architecture Baseline Instruments AMF1 AMF2 AMF3 MAOS AMF Fact Sheet Images Contacts AMF Deployments McMurdo Station, Antarctica, 2015-2016 Pearl Harbor, Hawaii, to San Francisco, California, 2015 Hyytiälä, Finland, 2014 Manacapuru, Brazil, 2014 Oliktok Point, Alaska, 2013 Los Angeles, California, to Honolulu, Hawaii, 2012 Cape Cod, Massachusetts, 2012 Gan Island, Maldives, 2011 Ganges Valley, India, 2011 Steamboat Springs, Colorado, 2010 Graciosa

  15. ARM - Surface Aerosol Observing System

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    FacilitiesSurface Aerosol Observing System AMF Information Science Architecture Baseline Instruments AMF1 AMF2 AMF3 MAOS AMF Fact Sheet Images Contacts AMF Deployments McMurdo Station, Antarctica, 2015-2016 Pearl Harbor, Hawaii, to San Francisco, California, 2015 Hyytiälä, Finland, 2014 Manacapuru, Brazil, 2014 Oliktok Point, Alaska, 2013 Los Angeles, California, to Honolulu, Hawaii, 2012 Cape Cod, Massachusetts, 2012 Gan Island, Maldives, 2011 Ganges Valley, India, 2011 Steamboat Springs,

  16. Structural and optical properties of InGaN--GaN nanowire heterostructures grown by molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Hofling, S.; et al

    2011-01-01

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaNmore » to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, μ-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.« less

  17. Notices B. State Advisory Committees

    Office of Environmental Management (EM)

    519 Federal Register / Vol. 77, No. 118 / Tuesday, June 19, 2012 / Notices send you a Grant Award Notification (GAN). We may notify you informally, also. If your application is not evaluated or not selected for funding, we notify you. 2. Administrative and National Policy Requirements: We identify administrative and national policy requirements in the application package and reference these and other requirements in the Applicable Regulations section of this notice. We reference the regulations

  18. Pyramidal inversion domain boundaries revisited

    SciTech Connect (OSTI)

    Remmele, T.; Albrecht, M.; Irmscher, K.; Fornari, R.; Strassburg, M.

    2011-10-03

    The structure of pyramidal inversion domain boundaries in GaN:Mg was investigated by aberration corrected transmission electron microscopy. The analysis shows the upper (0001) boundary to consist of a single Mg layer inserted between polarity inverted GaN layers in an abcab stacking. The Mg bound in these defects is at least one order of magnitude lower than the chemical Mg concentration. Temperature dependent Hall effect measurements show that up to 27% of the Mg acceptors is electrically compensated.

  19. Amber light-emitting diode comprising a group III-nitride nanowire active region

    DOE Patents [OSTI]

    Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

    2014-07-22

    A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

  20. ARM - Facility News Article

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    December 21, 2010 [Education, Facility News] NSF Student Travel Fellowship for DYNAMO Field Campaign Bookmark and Share As part of the DYNAMO (Dynamics of the MJO) field campaign, which includes the AMIE-Gan campaign, several student travel fellowships funded by the National Science Foundation are available for advanced graduate students and recently graduated postdoctoral associates, especially those from under-represented groups. DYNAMO is the US contribution to the international field program

  1. InGaN/GaN multi-quantum well and LED growth on wafer-bonded sapphire-on-polycrystalline AlN substrates by metalorganic chemical vapor deposition.

    SciTech Connect (OSTI)

    Crawford, Mary Hagerott; Olson, S. M.; Banas, M.; Park, Y. -B.; Ladous, C.; Russell, Michael J.; Thaler, Gerald; Zahler, J. M.; Pinnington, T.; Koleske, Daniel David; Atwater, Harry A.

    2008-06-01

    We report growth of InGaN/GaN multi-quantum well (MQW) and LED structures on a novel composite substrate designed to eliminate the coefficient of thermal expansion (CTE) mismatch problems which impact GaN growth on bulk sapphire. To form the composite substrate, a thin sapphire layer is wafer-bonded to a polycrystalline aluminum nitride (P-AlN) support substrate. The sapphire layer provides the epitaxial template for the growth; however, the thermo-mechanical properties of the composite substrate are determined by the P-AlN. Using these substrates, thermal stresses associated with temperature changes during growth should be reduced an order of magnitude compared to films grown on bulk sapphire, based on published CTE data. In order to test the suitability of the substrates for GaN LED growth, test structures were grown by metalorganic chemical vapor deposition (MOCVD) using standard process conditions for GaN growth on sapphire. Bulk sapphire substrates were included as control samples in all growth runs. In situ reflectance monitoring was used to compare the growth dynamics for the different substrates. The material quality of the films as judged by X-ray diffraction (XRD), photoluminescence and transmission electron microscopy (TEM) was similar for the composite substrate and the sapphire control samples. Electroluminescence was obtained from the LED structure grown on a P-AlN composite substrate, with a similar peak wavelength and peak width to the control samples. XRD and Raman spectroscopy results confirm that the residual strain in GaN films grown on the composite substrates is dramatically reduced compared to growth on bulk sapphire substrates.

  2. Structural and optical properties of InGaNGaN nanowire heterostructures grown by molecular beam epitaxy

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Ho?fling, S.; et al

    2011-01-01

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaNmoreto higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-PL spectra measured on single NWs reveal a reduced broadening of the visible luminescence. The analysis of the longitudinal optical phonon Raman peak position and its shape reveal a variation in the In content between 20% and 30%, in agreement with the values estimated by PL and HRTEM investigations. The reported studies are important for understanding of the growth and properties of NW heterostructures suitable for applications in optoelectronics and photovoltaics.less

  3. Survey of Emissions Models for Distributed Combined Heat and Power Systems

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Survey of Emissions Models for Distributed Combined Heat and Power Systems Will Gans, Anna Monis Shipley, and R. Neal Elliott January 2007 Report Number IE071 ©American Council for an Energy-Efficient Economy 1001 Connecticut Avenue, N.W., Suite 801, Washington, D.C. 20036 (202) 429-8873 phone, (202) 429-2248 fax, http://aceee.org Web site Survey of Emissions Models for CHP, ACEEE CONTENTS

  4. Microstructure, crystallization and shape memory behavior of titania and

    Office of Scientific and Technical Information (OSTI)

    yttria co-doped zirconia (Journal Article) | SciTech Connect Microstructure, crystallization and shape memory behavior of titania and yttria co-doped zirconia Citation Details In-Document Search This content will become publicly available on March 16, 2018 Title: Microstructure, crystallization and shape memory behavior of titania and yttria co-doped zirconia Authors: Zeng, Xiao Mei ; Du, Zehui ; Schuh, Christopher A. ; Tamura, Nobumichi ; Gan, Chee Lip Search SciTech Connect for author

  5. Slide 1

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    New Structure found at Ionic Liquid Surfaces Markus Mezger, Benjamin M. Ocko, Harald Reichert, and Moshe Deutsch, Proc. Natl. Acad. Sci. USA 110, 3733 (2013). Work was performed at Lawrence Berkeley Natl. Lab. and Brookhaven Natl. Lab. in collaboration with MPI Polymer Research Mainz, European Synchrotron Radiation Facility, and Bar-Ilan University Ramat-Gan. Scientific Achievement Resonant soft x-ray reflectivity was used to study the near surface structure of an ionic liquid and its intriguing

  6. Group-III nitride based high electron mobility transistor (HEMT) with barrier/spacer layer

    DOE Patents [OSTI]

    Chavarkar, Prashant; Smorchkova, Ioulia P.; Keller, Stacia; Mishra, Umesh; Walukiewicz, Wladyslaw; Wu, Yifeng

    2005-02-01

    A Group III nitride based high electron mobility transistors (HEMT) is disclosed that provides improved high frequency performance. One embodiment of the HEMT comprises a GaN buffer layer, with an Al.sub.y Ga.sub.1-y N (y=1 or y 1) layer on the GaN buffer layer. An Al.sub.x Ga.sub.1-x N (0.ltoreq.x.ltoreq.0.5) barrier layer on to the Al.sub.y Ga.sub.1-y N layer, opposite the GaN buffer layer, Al.sub.y Ga.sub.1-y N layer having a higher Al concentration than that of the Al.sub.x Ga.sub.1-x N barrier layer. A preferred Al.sub.y Ga.sub.1-y N layer has y=1 or y.about.1 and a preferred Al.sub.x Ga.sub.1-x N barrier layer has 0.ltoreq.x.ltoreq.0.5. A 2DEG forms at the interface between the GaN buffer layer and the Al.sub.y Ga.sub.1-y N layer. Respective source, drain and gate contacts are formed on the Al.sub.x Ga.sub.1-x N barrier layer. The HEMT can also comprising a substrate adjacent to the buffer layer, opposite the Al.sub.y Ga.sub.1-y N layer and a nucleation layer between the Al.sub.x Ga.sub.1-x N buffer layer and the substrate.

  7. GaN-on-diamond electronic device reliability: Mechanical and thermo-mechanical integrity

    SciTech Connect (OSTI)

    Liu, Dong; Sun, Huarui; Pomeroy, James W.; Kuball, Martin; Francis, Daniel; Faili, Firooz; Twitchen, Daniel J.

    2015-12-21

    The mechanical and thermo-mechanical integrity of GaN-on-diamond wafers used for ultra-high power microwave electronic devices was studied using a micro-pillar based in situ mechanical testing approach combined with an optical investigation of the stress and heat transfer across interfaces. We find the GaN/diamond interface to be thermo-mechanically stable, illustrating the potential for this material for reliable GaN electronic devices.

  8. Lateral and Vertical Transistors Using the AlGaN/GaN Heterostructure

    SciTech Connect (OSTI)

    Chowdhury, S; Mishra, UK

    2013-10-01

    Power conversion losses are endemic in all areas of electricity consumption, including motion control, lighting, air conditioning, and information technology. Si, the workhorse of the industry, has reached its material limits. Increasingly, the lateral AlGaN/GaN HEMT based on gallium nitride (GaN-on-Si) is becoming the device of choice for medium power electronics as it enables high-power conversion efficiency and reduced form factor at attractive pricing for wide market penetration. The reduced form factor enabled by high-efficiency operation at high frequency further enables significant system price reduction because of savings in bulky extensive passive elements and heat sink costs. The high-power market, however, still remains unaddressed by lateral GaN devices. The current and voltage demand for high power conversion application makes the chip area in a lateral topology so large that it becomes more difficult to manufacture. Vertical GaN devices would play a big role alongside of silicon carbide (SiC) to address the high power conversion needs. In this paper, the development, performance, and status of lateral and vertical GaN devices are discussed.

  9. Smooth cubic commensurate oxides on gallium nitride

    SciTech Connect (OSTI)

    Paisley, Elizabeth A.; Gaddy, Benjamin E.; LeBeau, James M.; Shelton, Christopher T.; Losego, Mark D.; Mita, Seiji; Collazo, Ramn; Sitar, Zlatko; Irving, Douglas L.; Maria, Jon-Paul; Biegalski, Michael D.; Christen, Hans M.

    2014-02-14

    Smooth, commensurate alloys of ?111?-oriented Mg{sub 0.52}Ca{sub 0.48}O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100 reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

  10. Enthalpy of formation of gallium nitride

    SciTech Connect (OSTI)

    Ranade, M.R.; Tessier, F.; Navrotsky, A.; Leppert, V.J.; Risbud, S.H.; DiSalvo, F.J.; Balkas, C.M.

    2000-05-04

    A major discrepancy in the literature concerning the enthalpy of formation of GaN has been resolved using oxidative oxide melt solution calorimetry. Four samples of differing nitrogen contents were measured by dropping them into molten 3Na{sub 2}O{center_dot}4MoO{sub 3} in a calorimeter at 975 K with oxygen gas bubbling through the solvent. The samples were characterized by X-ray diffraction, chemical analysis, transmission electron microscopy, particle size analysis, and BET measurements. The enthalpy of drop solution (kJ/g) varied approximately linearly with nitrogen content. Extrapolated to stoichiometric GaN, the data yield a value of {minus}156.8 {+-} 16.0 kJ/mol for the standard enthalpy of formation from the elements at 298 K. The relatively large error reflects the deviation of individual points from the straight line rather than uncertainties in each set of data for a given sample. This new directly measured enthalpy of formation is in excellent agreement with that obtained from the temperature dependence of the equilibrium pressure of nitrogen over GaN, {minus}157.7 kJ/mol, measured by Madar et al. and Karpinski and Porowski. This value of {minus}156.8 kJ/mol should replace the commonly tabulated value of {minus}110 kJ/mol determined by Hahn and Juza using combustion calorimetry on an uncharacterized sample over 50 years ago.

  11. Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect (OSTI)

    Kotsar, Y.; Bellet-Amalric, E.; Das, A.; Monroy, E.; Sarigiannidou, E.

    2011-08-01

    We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

  12. Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Zhang, Xueqiang; Ptasinska, Sylwia

    2016-04-25

    We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto themore » GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. In conclusion, our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/ electrode interface in a photoelectrochemical solar cell.« less

  13. Monitoring of the Airport Calibration Pads at Walker Field, Grand...

    Broader source: Energy.gov (indexed) [DOE]

    More Documents & Publications Field Calibration Facilities for Environmental Measurement of Radium, Thorium, and Potassium (October 2013) UMTRCA Sites Fact Sheet Long-Term ...

  14. FAA - Obstruction Evaluation/Airport Airspace Analysis (OE-AAA...

    Open Energy Info (EERE)

    are required to inform the FAA of construction operations. Author Federal Aviation Administration Published Federal Aviation Administration, Date Not Provided DOI Not Provided...

  15. New airport liquid analysis system undergoes testing at Albuquerque...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    And sensors in the MRI machine detect these slightly different frequencies, which are in ... The fainter signals that MagViz teases out with a weaker magnet challenged the Los Alamos ...

  16. AVTA: Airport Ground Support Equipment Specifications and Test...

    Broader source: Energy.gov (indexed) [DOE]

    of Documentation (76.84 KB) ETA-GAC002 Control of Test Conduct (124.65 KB) ETA-GAC003 Preparation and Issuance of Test Reports (55.86 KB) ETA-GAC004 Review of Test Results ...

  17. 01-04519B_OR_Knox_AirportMap.ai

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Chattanooga (I-75) To Nashville (I-40W) Pellissippi State OAK RIDGE KNOXVILLE IN T E R S T A T E -4 0 I N T E R S T A T E - 7 5 I - 4 0 7 5 I - 4 0 7 5 I - 4 0 I- 6 4 0 I - 2 7...

  18. Alternative Fuels Data Center: Atlanta Airport Converts Shuttles...

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    ... Regional Heavy-Duty LNG Fueling Station March 21, 2015 Photo of a street sweeper New Hampshire Fleet Revs up With Natural Gas March 7, 2015 Photo of a truck pulling into a CNG ...

  19. Alternative Fuels Data Center: Dallas Airport Operates With Alternativ...

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    ... Regional Heavy-Duty LNG Fueling Station March 21, 2015 Photo of a street sweeper New Hampshire Fleet Revs up With Natural Gas March 7, 2015 Photo of a truck pulling into a CNG ...

  20. Alternative Fuels Data Center: Colorado Airport Relies on Natural...

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    ... Regional Heavy-Duty LNG Fueling Station March 21, 2015 Photo of a street sweeper New Hampshire Fleet Revs up With Natural Gas March 7, 2015 Photo of a truck pulling into a CNG ...

  1. New San Antonio Airport Terminal Generating Clean Power | Department...

    Office of Environmental Management (EM)

    Moreover, the project team integrated electric vehicle charging stations with the PV system and the garage's electrical system to increase the uses for the electricity generated ...

  2. Alternative Fuels Data Center: Propane Powers Airport Shuttles...

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    ... Electric Ice Resurfacers Improve Air Quality in Minnesota Sept. 14, 2013 Photo ... Fuels Dec. 25, 2010 Tennessee Reduces Pollution With Propane Hybrid Trolleys Dec. 11, ...

  3. Electron density and currents of AlN/GaN high electron mobility transistors with thin GaN/AlN buffer layer

    SciTech Connect (OSTI)

    Bairamis, A.; Zervos, Ch.; Georgakilas, A.; Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G.

    2014-09-15

    AlN/GaN high electron mobility transistor (HEMT) structures with thin GaN/AlN buffer layer have been analyzed theoretically and experimentally, and the effects of the AlN barrier and GaN buffer layer thicknesses on two-dimensional electron gas (2DEG) density and transport properties have been evaluated. HEMT structures consisting of [300?nm GaN/ 200?nm AlN] buffer layer on sapphire were grown by plasma-assisted molecular beam epitaxy and exhibited a remarkable agreement with the theoretical calculations, suggesting a negligible influence of the crystalline defects that increase near the heteroepitaxial interface. The 2DEG density varied from 6.8??10{sup 12} to 2.1 10{sup 13} cm{sup ?2} as the AlN barrier thickness increased from 2.2 to 4.5?nm, while a 4.5?nm AlN barrier would result to 3.1??10{sup 13} cm{sup ?2} on a GaN buffer layer. The 3.0?nm AlN barrier structure exhibited the highest 2DEG mobility of 900?cm{sup 2}/Vs for a density of 1.3??10{sup 13} cm{sup ?2}. The results were also confirmed by the performance of 1??m gate-length transistors. The scaling of AlN barrier thickness from 1.5?nm to 4.5?nm could modify the drain-source saturation current, for zero gate-source voltage, from zero (normally off condition) to 0.63?A/mm. The maximum drain-source current was 1.1?A/mm for AlN barrier thickness of 3.0?nm and 3.7?nm, and the maximum extrinsic transconductance was 320 mS/mm for 3.0?nm AlN barrier.

  4. Simulation study of HEMT structures with HfO{sub 2} cap layer for mitigating inverse piezoelectric effect related device failures

    SciTech Connect (OSTI)

    Nagulapally, Deepthi; Joshi, Ravi P.; Pradhan, Aswini

    2015-01-15

    The Inverse Piezoelectric Effect (IPE) is thought to contribute to possible device failure of GaN High Electron Mobility Transistors (HEMTs). Here we focus on a simulation study to probe the possible mitigation of the IPE by reducing the internal electric fields and related elastic energy through the use of high-k materials. Inclusion of a HfO{sub 2} “cap layer” above the AlGaN barrier particularly with a partial mesa structure is shown to have potential advantages. Simulations reveal even greater reductions in the internal electric fields by using “field plates” in concert with high-k oxides.

  5. Dual optical marker Raman characterization of strained GaN-channels on AlN using AlN/GaN/AlN quantum wells and {sup 15}N isotopes

    SciTech Connect (OSTI)

    Qi, Meng; Li, Guowang; Protasenko, Vladimir; Zhao, Pei; Verma, Jai; Song, Bo; Ganguly, Satyaki; Zhu, Mingda; Hu, Zongyang; Yan, Xiaodong; Xing, Huili Grace; Jena, Debdeep; Mintairov, Alexander

    2015-01-26

    This work shows that the combination of ultrathin highly strained GaN quantum wells embedded in an AlN matrix, with controlled isotopic concentrations of Nitrogen enables a dual marker method for Raman spectroscopy. By combining these techniques, we demonstrate the effectiveness in studying strain in the vertical direction. This technique will enable the precise probing of properties of buried active layers in heterostructures, and can be extended in the future to vertical devices such as those used for optical emitters and for power electronics.

  6. Cubic nitride templates

    DOE Patents [OSTI]

    Burrell, Anthony K; McCleskey, Thomas Mark; Jia, Quanxi; Mueller, Alexander H; Luo, Hongmei

    2013-04-30

    A polymer-assisted deposition process for deposition of epitaxial cubic metal nitride films and the like is presented. The process includes solutions of one or more metal precursor and soluble polymers having binding properties for the one or more metal precursor. After a coating operation, the resultant coating is heated at high temperatures under a suitable atmosphere to yield metal nitride films and the like. Such films can be used as templates for the development of high quality cubic GaN based electronic devices.

  7. Development of White-Light Emitting Active Layers in Nitride Based Heterostructures for Phosphorless Solid State Lighting

    SciTech Connect (OSTI)

    Jan Talbot; Kailash Mishra

    2007-12-31

    This report provides a summary of research activities carried out at the University of California, San Diego and Central Research of OSRAM SYLVANIA in Beverly, MA partially supported by a research contract from US Department of Energy, DE-FC26-04NT422274. The main objective of this project was to develop III-V nitrides activated by rare earth ions, RE{sup 3+}, which could eliminate the need for phosphors in nitride-based solid state light sources. The main idea was to convert electron-hole pairs injected into the active layer in a LED die to white light directly through transitions within the energy levels of the 4f{sup n}-manifold of RE{sup 3+}. We focused on the following materials: Eu{sup 3+}(red), Tb{sup 3+}(green), Er{sup 3+}(green), Dy{sup 3+}(yellow) and Tm{sup 3+}(blue) in AlN, GaN and alloys of AlN and GaN. Our strategy was to explore candidate materials in powder form first, and then study their behavior in thin films. Thin films of these materials were to be deposited on sapphire substrates using pulsed laser deposition (PLD) and metal organic vapor phase epitaxy (MOVPE). The photo- and cathode-luminescence measurements of these materials were used to investigate their suitability for white light generation. The project proceeded along this route with minor modifications needed to produce better materials and to expedite our progress towards the final goal. The project made the following accomplishments: (1) red emission from Eu{sup 3+}, green from Tb{sup 3+}, yellow from Dy{sup 3+} and blue from Tm{sup 3+} in AlN powders; (2) red emission from Eu{sup 3+} and green emission from Tb{sup 3+} in GaN powder; (3) red emission from Eu{sup 3+} in alloys of GaN and AlN; (4) green emission from Tb{sup 3+} in GaN thin films by PLD; (5) red emission from Eu{sup 3+} and Tb{sup 3+} in GaN thin films deposited by MOVPE; (6) energy transfer from host to RE{sup 3+}; (7) energy transfer from Tb{sup 3+} to Eu{sup 3+} in AlN powders; (8) emission from AlN powder samples

  8. Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

    SciTech Connect (OSTI)

    Guo, Lei; Yang, Xuelin Cheng, Jianpeng; Sang, Ling; Xu, Fujun; Tang, Ning; Feng, Zhihong; Lv, Yuanjie; Wang, Xinqiang; Shen, B.; Ge, Weikun

    2014-12-15

    We have investigated the variation of electron velocity in AlGaN/GaN heterostructures depending on illuminating light intensity and wavelength. It is shown that the electron velocity at high electric field increases under above-band light illumination. This electron velocity enhancement is found to be related to the photo-generated cold holes which interact with hot electrons and thus accelerate the energy relaxation at high electric field. The results suggest an alternative way to improve the electron energy relaxation rate and hence the electron velocity in GaN based heterostructures.

  9. Low Cost Production of InGaN for Next-Generation Photovoltaic Devices

    SciTech Connect (OSTI)

    Nick M. Sbrockey, Shangzhu Sun, Gary S. Tompa,

    2012-07-09

    The goal of this project is to develop a low-cost and low-energy technology for production of photovoltaic devices based on InGaN materials. This project builds on the ongoing development by Structured Materials Industries (SMI), of novel thin film deposition technology for Group III-Nitride materials, which is capable of depositing Group-III nitride materials at significantly lower costs and significantly lower energy usage compared to conventional deposition techniques. During this project, SMI demonstrated deposition of GaN and InGaN films using metalorganic sources, and demonstrated compatibility of the process with standard substrate materials and hardware components.

  10. Graphene/GaN diodes for ultraviolet and visible photodetectors

    SciTech Connect (OSTI)

    Lin, Fang; Chen, Shao-Wen; Meng, Jie; Tse, Geoffrey; Fu, Xue-Wen; Xu, Fu-Jun [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Shen, Bo; Liao, Zhi-Min, E-mail: liaozm@pku.edu.cn, E-mail: yudp@pku.edu.cn; Yu, Da-Peng, E-mail: liaozm@pku.edu.cn, E-mail: yudp@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2014-08-18

    The Schottky diodes based on graphene/GaN interface are fabricated and demonstrated for the dual-wavelength photodetection of ultraviolet (UV) and green lights. The physical mechanisms of the photoelectric response of the diodes with different light wavelengths are different. For UV illumination, the photo-generated carriers lower the Schottky barrier and increase the photocurrent. For green light illumination, as the photon energy is smaller than the bandgap of GaN, the hot electrons excited in graphene via internal photoemission are responsible for the photoelectric response. Using graphene as a transparent electrode, the diodes show a ?mS photoresponse, providing an alternative route toward multi-wavelength photodetectors.

  11. Gallium nitride nanotube lasers

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Li, Changyi; Liu, Sheng; Hurtado, Antonio; Wright, Jeremy Benjamin; Xu, Huiwen; Luk, Ting Shan; Figiel, Jeffrey J.; Brener, Igal; Brueck, Steven R. J.; Wang, George T.

    2015-01-01

    Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

  12. Structural and Optical Investigations of GaN-Si Interface for a Heterojunction Solar Cell

    SciTech Connect (OSTI)

    Williams, Joshua J.; Jeffries, April M.; Bertoni, Mariana I.; Williamson, Todd L.; Bowden, Stuart G.; Honsberg, Christiana B.

    2014-06-08

    In recent years the development of heterojunction silicon based solar cells has gained much attention, lea largely by the efforts of Panasonic’s HIT cell. The success of the HIT cell prompts the scientific exploration of other thin film layers, besides the industrially accepted amorphous silicon. In this paper we report upon the use of gallium nitride, grown by MBE at “low temperatures” (~200°C), on silicon wafers as one possible candidate for making a heterojunction solar cell; the first approximation of band alignments between GaN and Si; and the material quality as determined by X-ray diffraction.

  13. Semiconductor Science and Technology

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    lighting ReSeaRch & development at Sandia national laboRatoRieS The bridge to a new way of lighting the world ssls.sandia.gov Initiates decades-long investment into compound semiconductor science and technology, eventually establishing its Center for Compound Semiconductor Science and Technology 1 9 7 7 Begins investing in gallium nitride (GaN) materials, physics, and device capabilities 1 9 9 5 Launches its Grand Challenge Laboratory Directed Research and Development Project, "A

  14. Process for growing epitaxial gallium nitride and composite wafers

    DOE Patents [OSTI]

    Weber, Eicke R.; Subramanya, Sudhir G.; Kim, Yihwan; Kruger, Joachim

    2003-05-13

    A novel growth procedure to grow epitaxial Group III metal nitride thin films on lattice-mismatched substrates is proposed. Demonstrated are the quality improvement of epitaxial GaN layers using a pure metallic Ga buffer layer on c-plane sapphire substrate. X-ray rocking curve results indicate that the layers had excellent structural properties. The electron Hall mobility increases to an outstandingly high value of .mu.>400 cm.sup.2 /Vs for an electron background concentration of 4.times.10.sup.17 cm.sup.-3.

  15. Two-dimensional electron gas in monolayer InN quantum wells

    SciTech Connect (OSTI)

    Pan, Wei; Dimakis, Emmanouil; Wang, George T.; Moustakas, Theodore D.; Tsui, Daniel C.

    2014-11-24

    We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in monolayer InN quantum wells embedded in GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 5×1015 cm-2 and 420 cm2 /Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES.

  16. Two-dimensional electron gas in monolayer InN quantum wells

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Pan, Wei; Dimakis, Emmanouil; Wang, George T.; Moustakas, Theodore D.; Tsui, Daniel C.

    2014-11-24

    We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in monolayer InN quantum wells embedded in GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 5×1015 cm-2 and 420 cm2 /Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES.

  17. Epitaxial growth of aligned AlGalnN nanowires by metal-organic chemical vapor deposition

    DOE Patents [OSTI]

    Han, Jung; Su, Jie

    2008-08-05

    Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. <1010> M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.

  18. How much better are InGaN/GaN nanodisks than quantum wellsOscillator strength enhancement and changes in optical properties

    SciTech Connect (OSTI)

    Zhang, Lei; Hill, Tyler A.; Deng, Hui E-mail: peicheng@umich.edu; Lee, Leung-Kway; Teng, Chu-Hsiang; Ku, Pei-Cheng E-mail: peicheng@umich.edu

    2014-02-03

    We show over 100-fold enhancement of the exciton oscillator strength as the diameter of an InGaN nanodisk in a GaN nanopillar is reduced from a few micrometers to less than 40?nm, corresponding to the quantum dot limit. The enhancement results from significant strain relaxation in nanodisks less than 100?nm in diameter. Meanwhile, the radiative decay rate is only improved by 10 folds due to strong reduction of the local density of photon states in small nanodisks. Further increase in the radiative decay rate can be achieved by engineering the local density of photon states, such as adding a dielectric coating.

  19. Structural and morphological evolution of gallium nitride nanorods grown by chemical beam epitaxy

    SciTech Connect (OSTI)

    Kuo, Shou-Yi; Lai, Fang-I; Chen, Wei-Chun; Hsiao, Chien-Nan; Lin, Woei-Tyng

    2009-07-15

    The morphological and structural evolution is presented for GaN nanorods grown by chemical beam epitaxy on (0001) Al{sub 2}O{sub 3} substrates. Their structural and optical properties are investigated by x-ray diffraction, scanning and transmission electron microscopy, and temperature-dependent photoluminescence measurements. While increasing the growth temperature and the flow rate of radio-frequency nitrogen radical, the three-dimensional growth mode will be enhanced to form one-dimensional nanostructures. The high density of well-aligned nanorods with a diameter of 30-50 nm formed uniformly over the entire sapphire substrate. The x-ray diffraction patterns and transmission electron microscopic images indicate that the self-assembled GaN nanorods are a pure single crystal and preferentially oriented in the c-axis direction. Particularly, the ''S-shape'' behavior with localization of {approx}10 meV observed in the temperature-dependent photoluminescence might be ascribed to the fluctuation in crystallographic defects and composition.

  20. Fracture and buckling of piezoelectric nanowires subject to an electric field

    SciTech Connect (OSTI)

    Zhang, Jin; Wang, Chengyuan Adhikari, Sondipon

    2013-11-07

    Fracture and buckling are major failure modes of thin and long nanowires (NWs), which could be affected significantly by an electric field when piezoelectricity is involved in the NWs. This paper aims to examine the issue based on the molecular dynamics simulations, where the gallium nitride (GaN) NWs are taken as an example. The results show that the influence of the electric field is strong for the fracture and the critical buckling strains, detectable for the fracture strength but almost negligible for the critical buckling stress. In addition, the reversed effects are achieved for the fracture and the critical buckling strains. Subsequently, the Timoshenko beam model is utilized to account for the effect of the electric field on the axial buckling of the GaN NWs, where nonlocal effect is observed and characterized by the nonlocal coefficient e{sub 0}a=1.1 nm. The results show that the fracture and buckling of piezoelectric NWs can be controlled by applying an electric field.

  1. Depth-resolved confocal micro-Raman spectroscopy for characterizing GaN-based light emitting diode structures

    SciTech Connect (OSTI)

    Chen, Wei-Liang; Lee, Yu-Yang; Chang, Yu-Ming; Chang, Chiao-Yun; Huang, Huei-Min; Lu, Tien-Chang

    2013-11-15

    In this work, we demonstrate that depth-resolved confocal micro-Raman spectroscopy can be used to characterize the active layer of GaN-based LEDs. By taking the depth compression effect due to refraction index mismatch into account, the axial profiles of Raman peak intensities from the GaN capping layer toward the sapphire substrate can correctly match the LED structural dimension and allow the identification of unique Raman feature originated from the 0.3 μm thick active layer of the studied LED. The strain variation in different sample depths can also be quantified by measuring the Raman shift of GaN A{sub 1}(LO) and E{sub 2}(high) phonon peaks. The capability of identifying the phonon structure of buried LED active layer and depth-resolving the strain distribution of LED structure makes this technique a potential optical and remote tool for in operando investigation of the electronic and structural properties of nitride-based LEDs.

  2. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111)

    SciTech Connect (OSTI)

    Hennig, J. Dadgar, A.; Witte, H.; Bläsing, J.; Lesnik, A.; Strittmatter, A.; Krost, A.

    2015-07-15

    We report on GaN based field-effect transistor (FET) structures exhibiting sheet carrier densities of n = 2.9 10{sup 13} cm{sup −2} for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally x{sub In} = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the In{sub x}Ga{sub 1−x}N/GaN/AlN/Al{sub 0.87}In{sub 0.13}N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of I{sub SD} = 1300 mA/mm (560 mA/mm). In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents.

  3. Tunnel-injection quantum dot deep-ultraviolet light-emitting diodes with polarization-induced doping in III-nitride heterostructures

    SciTech Connect (OSTI)

    Verma, Jai Islam, S. M.; Protasenko, Vladimir; Kumar Kandaswamy, Prem; Xing, Huili; Jena, Debdeep

    2014-01-13

    Efficient semiconductor optical emitters in the deep-ultraviolet spectral window are encountering some of the most deep rooted problems of semiconductor physics. In III-Nitride heterostructures, obtaining short-wavelength photon emission requires the use of wide bandgap high Al composition AlGaN active regions. High conductivity electron (n-) and hole (p-) injection layers of even higher bandgaps are necessary for electrical carrier injection. This approach requires the activation of very deep dopants in very wide bandgap semiconductors, which is a difficult task. In this work, an approach is proposed and experimentally demonstrated to counter the challenges. The active region of the heterostructure light emitting diode uses ultrasmall epitaxially grown GaN quantum dots. Remarkably, the optical emission energy from GaN is pushed from 365?nm (3.4?eV, the bulk bandgap) to below 240?nm (>5.2?eV) because of extreme quantum confinement in the dots. This is possible because of the peculiar bandstructure and band alignments in the GaN/AlN system. This active region design crucially enables two further innovations for efficient carrier injection: Tunnel injection of carriers and polarization-induced p-type doping. The combination of these three advances results in major boosts in electroluminescence in deep-ultraviolet light emitting diodes and lays the groundwork for electrically pumped short-wavelength lasers.

  4. Mechanisms of the micro-crack generation in an ultra-thin AlN/GaN superlattice structure grown on Si(110) substrates by metalorganic chemical vapor deposition

    SciTech Connect (OSTI)

    Shen, X. Q. Takahashi, T.; Ide, T.; Shimizu, M.

    2015-09-28

    We investigate the generation mechanisms of micro-cracks (MCs) in an ultra-thin AlN/GaN superlattice (SL) structure grown on Si(110) substrates by metalorganic chemical vapor deposition. The SL is intended to be used as an interlayer (IL) for relaxing tensile stress and obtaining high-quality crack-free GaN grown on Si substrates. It is found that the MCs can be generated by two different mechanisms, where large mismatches of the lattice constant (LC) and the coefficient of thermal expansion (CTE) play key roles in the issue. Different MC configurations (low-density and high-density MCs) are observed, which are considered to be formed during the different growth stages (SL growth and cooling down processes) due to the LC and the CTE effects. In-situ and ex-situ experimental results support the mechanism interpretations of the MCs generation. The mechanism understanding makes it possible to optimize the SL IL structure for growing high-quality crack-free GaN films on Si substrates for optical and electronic device applications.

  5. X-ray diffraction study of short-period AlN/GaN superlattices

    SciTech Connect (OSTI)

    Kyutt, R. N. Shcheglov, M. P.; Ratnikov, V. V.; Yagovkina, M. A.; Davydov, V. Yu.; Smirnov, A. N.; Rozhavskaya, M. M.; Zavarin, E. E.; Lundin, V. V.

    2013-12-15

    The structure of short-period hexagonal GaN/AlN superlattices (SLs) has been investigated by X-ray diffraction. The samples have been grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal reactor at a temperature of 1050°C on (0001)Al{sub 2}O{sub 3} substrates using GaN and AlN buffer layers. The SL period changes from 2 to 6 nm, and the thickness of the structure varies in a range from 0.3 to 1 μm. The complex of X-ray diffraction techniques includes a measurement of θ-2θ rocking curves of symmetric Bragg reflection, the construction of intensity maps for asymmetric reflections, a measurement and analysis of peak broadenings in different diffraction geometries, a precise measurement of lattice parameters, and the determination of radii of curvature. The thickness and strain of separate SL layers are determined by measuring the θ-2θ rocking curves subsequent simulation. It is shown that most SL samples are completely relaxed as a whole. At the same time, relaxation is absent between sublayers, which is why strains in the AlN and GaN sublayers (on the order of 1.2 × 10{sup −2}) have different signs. An analysis of diffraction peak half-widths allows us to determine the densities of individual sets of dislocations and observe their change from buffer layers to SLs.

  6. P-type gallium nitride

    DOE Patents [OSTI]

    Rubin, Michael; Newman, Nathan; Fu, Tracy; Ross, Jennifer; Chan, James

    1997-01-01

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5.times.10.sup.11 /cm.sup.3 and hole mobilities of about 500 cm.sup.2 /V-sec, measured at 250.degree. K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al.

  7. P-type gallium nitride

    DOE Patents [OSTI]

    Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

    1997-08-12

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

  8. Comparative study of polar and semipolar (112?2) InGaN layers grown by metalorganic vapour phase epitaxy

    SciTech Connect (OSTI)

    Dinh, Duc V. E-mail: peter.parbrook@tyndall.ie; Zubialevich, V. Z.; Oehler, F.; Kappers, M. J.; Humphreys, C. J.; Alam, S. N.; Parbrook, P. J. E-mail: peter.parbrook@tyndall.ie; Caliebe, M.; Scholtz, F.

    2014-10-21

    InGaN layers were grown simultaneously on (112?2) GaN and (0001) GaN templates by metalorganic vapour phase epitaxy. At higher growth temperature (?750C), the indium content (<15%) of the (112?2) and (0001) InGaN layers was similar. However, for temperatures less than 750C, the indium content of the (112?2) InGaN layers (15%26%) were generally lower than those with (0001) orientation (15%32%). The compositional deviation was attributed to the different strain relaxations between the (112?2) and (0001) InGaN layers. Room temperature photoluminescence measurements of the (112?2) InGaN layers showed an emission wavelength that shifts gradually from 380 nm to 580 nm with decreasing growth temperature (or increasing indium composition). The peak emission wavelength of the (112?2) InGaN layers with an indium content of more than 10% blue-shifted a constant value of ?(5060) nm when using higher excitation power densities. This blue-shift was attributed to band filling effects in the layers.

  9. Hybrid Pd/Fe{sub 3}O{sub 4} nanowires: Fabrication, characterization, optical properties and application as magnetically reusable catalyst for the synthesis of N-monosubstituted ureas under ligand-free conditions

    SciTech Connect (OSTI)

    Nasrollahzadeh, Mahmoud; Azarian, Abbas; Ehsani, Ali; Sajadi, S.Mohammad; Babaei, Ferydon

    2014-07-01

    Highlights: • Preparation of Pd/Fe{sub 3}O{sub 4} nanowires as magnetically reusable catalysts. • The optical properties of the catalyst were studied using Gans theory. • N-arylation of benzylurea and in situ hydrogenolysis of 1-benzyl-3-arylureas. - Abstract: This paper reports the synthesis and use of Pd/Fe{sub 3}O{sub 4} nanowires, as magnetically separable catalysts for ligand-free amidation coupling reactions of aryl halides with benzylurea under microwave irradiation. Then, the in situ hydrogenolysis of the products was performed to afford the N-monosubstituted ureas from good to excellent yields. This method has the advantages of high yields, simple methodology and easy work up. The catalyst can be recovered by using a magnet and reused several times without significant loss of its catalytic activity. The catalyst was characterized using the powder XRD, SEM, EDS and UV–vis spectroscopy. Experimental absorbance spectra was compared with results from the Gans theory.

  10. Sacrificial template method of fabricating a nanotube

    DOE Patents [OSTI]

    Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yi-Ying; Li, Deyu; Majumdar, Arun

    2007-05-01

    Methods of fabricating uniform nanotubes are described in which nanotubes were synthesized as sheaths over nanowire templates, such as using a chemical vapor deposition process. For example, single-crystalline zinc oxide (ZnO) nanowires are utilized as templates over which gallium nitride (GaN) is epitaxially grown. The ZnO templates are then removed, such as by thermal reduction and evaporation. The completed single-crystalline GaN nanotubes preferably have inner diameters ranging from 30 nm to 200 nm, and wall thicknesses between 5 and 50 nm. Transmission electron microscopy studies show that the resultant nanotubes are single-crystalline with a wurtzite structure, and are oriented along the <001> direction. The present invention exemplifies single-crystalline nanotubes of materials with a non-layered crystal structure. Similar "epitaxial-casting" approaches could be used to produce arrays and single-crystalline nanotubes of other solid materials and semiconductors. Furthermore, the fabrication of multi-sheath nanotubes are described as well as nanotubes having multiple longitudinal segments.

  11. Combined TPRx, in situ GISAXS and GIXAS studies of model semiconductor-supported platinum catalysts in the hydrogenation of ethane.

    SciTech Connect (OSTI)

    Wyrzgol, S. A.; Schafer, S.; Lee, S.; Lee, B.; Di Vece, M.; Li, X.; Seifert, S.; Winans, R. E.; Stutzmann, M.; Lercher, J. A.; Vajda, S.; Technische Univ. Munchen; Yale Univ.

    2010-01-01

    The preparation, characterization and catalytic reactivity of a GaN supported Pt catalyst in the hydrogenation of ethene are presented in this feature article, highlighting the use of in situ characterization of the material properties during sample handling and catalysis by combining temperature programmed reaction with in situ grazing incidence small-angle X-ray scattering and X-ray absorption spectroscopy. The catalysts are found to be sintering resistant at elevated temperatures as well as during reduction and hydrogenation reactions. In contrast to Pt particles of approximately 7 nm diameter, smaller particles of 1.8 nm in size are found to dynamically adapt their shape and oxidation state to the changes in the reaction environment. These smaller Pt particles also showed an initial deactivation in ethene hydrogenation, which is paralleled by the change in the particle shape. The subtle temperature-dependent X-ray absorbance of the 1.8 nm sized Pt particles indicates that subtle variations in the electronic structure induced by the state of reduction by electron tunnelling over the Schottky barrier between the Pt particles and the GaN support can be monitored.

  12. Demonstration of isotype GaN/AlN/GaN heterobarrier diodes by NH{sub 3}-molecular beam epitaxy

    SciTech Connect (OSTI)

    Fireman, Micha N.; Browne, David A.; Mazumder, Baishakhi; Speck, James S.; Mishra, Umesh K.

    2015-05-18

    The results of vertical transport through nitride heterobarrier structures grown by ammonia molecular beam epitaxy are presented. Structures are designed with binary layers to avoid the effects of random alloy fluctuations in ternary nitride barriers. The unintentional incorporation of Ga in the AlN growth is investigated by atom probe tomography and is shown to be strongly dependent on both the NH{sub 3} flowrate and substrate temperature growth parameters. Once nominally pure AlN layer growth conditions are achieved, structures consisting of unintentionally doped (UID) GaN spacer layers adjacent to a nominally pure AlN are grown between two layers of n+ GaN, from which isotype diodes are fabricated. Varying the design parameters of AlN layer thickness, UID spacer layer thickness, and threading dislocation density show marked effects on the vertical transport characteristics of these structures. The lack of significant temperature dependence, coupled with Fowler-Nordheim and/or Milliken-Lauritsen analysis, point to a prevalently tunneling field emission mechanism through the AlN barrier. Once flatband conditions in the UID layer are achieved, electrons leave the barrier with significant energy. This transport mechanism is of great interest for applications in hot electron structures.

  13. Hysteresis phenomena of the two dimensional electron gas density in lattice-matched InAlN/GaN heterostructures

    SciTech Connect (OSTI)

    Sang, Ling; Yang, Xuelin Cheng, Jianpeng; Guo, Lei; Hu, Anqi; Xiang, Yong; Yu, Tongjun; Xu, Fujun; Tang, Ning; Jia, Lifang; He, Zhi; Wang, Maojun; Wang, Xinqiang; Shen, Bo; Ge, Weikun

    2015-08-03

    High-temperature transport properties in high-mobility lattice-matched InAlN/GaN heterostructures have been investigated. An interesting hysteresis phenomenon of the two dimensional electron gas (2DEG) density is observed in the temperature-dependent Hall measurements. After high-temperature thermal cycles treatment, the reduction of the 2DEG density is observed, which is more serious in thinner InAlN barrier samples. This reduction can then be recovered by light illumination. We attribute these behaviors to the shallow trap states with energy level above the Fermi level in the GaN buffer layer. The electrons in the 2DEG are thermal-excited when temperature is increased and then trapped by these shallow trap states in the buffer layer, resulting in the reduction and hysteresis phenomenon of their density. Three trap states are observed in the GaN buffer layer and C{sub Ga} may be one of the candidates responsible for the observed behaviors. Our results provide an alternative approach to assess the quality of InAlN/GaN heterostructures for applications in high-temperature electronic devices.

  14. Effects of high-temperature AIN buffer on the microstructure of AlGaN/GaN HEMTs

    SciTech Connect (OSTI)

    Coerekci, S.; Oeztuerk, M. K.; Yu, Hongbo; Cakmak, M.; Oezcelik, S.; Oezbay, E.

    2013-06-15

    Effects on AlGaN/GaN high-electron-mobility transistor structure of a high-temperature AlN buffer on sapphire substrate have been studied by high-resolution x-ray diffraction and atomic force microscopy techniques. The buffer improves the microstructural quality of GaN epilayer and reduces approximately one order of magnitude the edge-type threading dislocation density. As expected, the buffer also leads an atomically flat surface with a low root-mean-square of 0.25 nm and a step termination density in the range of 10{sup 8} cm{sup -2}. Due to the high-temperature buffer layer, no change on the strain character of the GaN and AlGaN epitaxial layers has been observed. Both epilayers exhibit compressive strain in parallel to the growth direction and tensile strain in perpendicular to the growth direction. However, an high-temperature AlN buffer layer on sapphire substrate in the HEMT structure reduces the tensile stress in the AlGaN layer.

  15. Wide-Bandgap Compound Semiconductors to Enable Novel Semiconductor Devices

    SciTech Connect (OSTI)

    Crawford, M.H.; Chow, W.W.; Wright, A.F.; Lee, S.R.; Jones, E.D.; Han, J.; Shul, R.J.

    1999-04-01

    This report represents the completion of a three-year Laboratory-Directed Research and Development (LDRD) program that focused on research and development of GaN-based wide bandgap semiconductor materials (referred to as III-N materials). Our theoretical investigations include the determination of fundamental materials parameters from first-principles calculations, the study of gain properties of III-N heterostructures using a microscopic laser theory and density-functional-theory, charge-state calculations to determine the core structure and energy levels of dislocations in III-N materials. Our experimental investigations include time-resolved photoluminescence and magneto-luminescence studies of GaN epilayers and multiquantum well samples as well as x-ray diffraction studies of AlGaN ternary alloys. In addition, we performed a number of experiments to determine how various materials processing steps affect both the optical and electrical properties of GaN-based materials. These studies include photoluminescence studies of GaN epilayers after post-growth rapid thermal annealing, ion implantation to produce n- and p-type material and electrical and optical studies of plasma-etched structures.

  16. High-Efficiency Non-Polar GaN-Based LEDs

    SciTech Connect (OSTI)

    Paul Fini

    2010-11-30

    Inlustra Technologies with subcontractor U.C. Santa Barbara conducted a project with the principle goal of demonstrating high internal quantum efficiency blue (430 nm) and green (540nm) light emitting diodes (LEDs) on low-defect density non-polar GaN wafers. Inlustra pursued the fabrication of smooth thick a-plane and m-plane GaN films, as well as defect reduction techniques such as lateral epitaxial overgrowth (LEO) to uniformly lower dislocation density in these films. Limited free-standing wafers were produced as well. By the end of the reporting period, Inlustra had met its milestone of dislocation reduction to < 5 x 10{sup 6} cm{sup -2}. Stacking faults were still present in appreciable density ({approx} 1 x 10{sup 5} cm{sup -1}), but were not the primary focus of defect reduction since there have been no published studies establishing their detrimental effects on LED performance. Inlustra's LEO progress built a solid foundation upon which further commercial development of GaN substrates will occur. UCSB encountered multiple delays in its LED growth and fabrication efforts due to unavoidable facilities outages imposed by ongoing construction in an area adjacent to the metalorganic chemical vapor deposition (MOCVD) laboratory. This, combined with the large amount of ab initio optimization required for the MOCVD system used during the project, resulted in unsatisfactory LED progress. Although numerous blue-green photoluminescence results were obtained, only a few LED structures exhibited electroluminescence at appreciable levels. UCSB also conducting extensive modeling (led by Prof. Van de Walle) on the problem of non-radiative Auger recombination in GaN-based LED structures, which has been posited to contribute to LED efficiency 'droop' at elevated current density. Unlike previous modeling efforts, UCSB's approach was truly a first-principles ab initio methodology. Building on solid numerical foundations, the Auger recombination rates of In{sub x}Ga{sub 1-x

  17. Comparative study of field-dependent carrier dynamics and emission kinetics of InGaN/GaN light-emitting diodes grown on (112{sup }2) semipolar versus (0001) polar planes

    SciTech Connect (OSTI)

    Ji, Yun; Liu, Wei; Chen, Rui; Tiam Tan, Swee; Zhang, Zi-Hui; Ju, Zhengang; Zhang, Xueliang; Sun, Handong; Wei Sun, Xiao; Erdem, Talha; Zhao, Yuji; DenBaars, Steven P. E-mail: volkan@stanfordalumni.org; Nakamura, Shuji; Volkan Demir, Hilmi E-mail: volkan@stanfordalumni.org

    2014-04-07

    The characteristics of electroluminescence (EL) and photoluminescence (PL) emission from GaN light-emitting diodes (LEDs) grown on (112{sup }2) semipolar plane and (0001) polar plane have been comparatively investigated. Through different bias-dependent shifting trends observed from the PL and time-resolved PL spectra (TRPL) for the two types of LEDs, the carrier dynamics within the multiple quantum wells (MQWs) region is systematically analyzed and the distinct field-dependent emission kinetics are revealed. Moreover, the polarization induced internal electric field has been deduced for each of the LEDs. The relatively stable emission behavior observed in the semipolar LED is attributed to the smaller polarization induced internal electric field. The study provides meaningful insight for the design of quantum well (QW) structures with high radiative recombination rates.

  18. High Efficacy Green LEDs by Polarization Controlled MOVPE

    SciTech Connect (OSTI)

    Wetzel, Christian

    2013-03-31

    Amazing performance in GaInN/GaN based LEDs has become possible by advanced epitaxial growth on a wide variety of substrates over the last decade. An immediate push towards product development and worldwide competition for market share have effectively reduced production cost and generated substantial primary energy savings on a worldwide scale. At all times of the development, this economic pressure forced very fundamental decisions that would shape huge industrial investment. One of those major aspects is the choice of epitaxial growth substrate. The natural questions are to what extend a decision for a certain substrate will limit the ultimate performance and to what extent, the choice of a currently more expensive substrate such as native GaN could overcome any of the remaining performance limitations. Therefore, this project has set out to explore what performance characteristic could be achieved under the utilization of bulk GaN substrate. Our work was guided by the hypotheses that line defects such as threading dislocations in the active region should be avoided and the huge piezoelectric polarization needs to be attenuated if not turned off for higher performing LEDs, particularly in the longer wavelength green and deep green portions of the visible spectrum. At their relatively lower performance level, deep green LEDs are a stronger indicator of relative performance improvements and seem particular sensitive to the challenges at hand. The project therefore made use of recently developed non-polar and semipolar bulk GaN substrates that were made available at Kyma Technologies by crystallographic cuts from thick polar growth of GaN. This approach naturally leads to rather small pieces of substrates, cm along the long side while mm along the short one. Small size and limited volume of sample material therefore set the limits of the ensuing development work. During the course of the project we achieved green and deep green LEDs in all those crystal growth

  19. A polarity-driven nanometric luminescence asymmetry in AlN/GaN heterostructures

    SciTech Connect (OSTI)

    Tizei, L. H. G. Meuret, S.; March, K.; Kociak, M.; Hestroffer, K.; Auzelle, T.; Daudin, B.

    2014-10-06

    Group III Nitrides nanowires are well suited materials for the design of light emitting devices. The internal electric field created by spontaneaous and piezoelectric polarizations in these materials poses some difficulties, but also possible solutions, towards this goal. Here, we report on the high spatial asymmetry of the cathodoluminescence intensity across a GaN quantum well embedded in an AlN nanowire, when a 60 keV, 1 nm wide electron beam is scanned over this heterostructure. This asymmetry is remarkable between positions at different sides of the quantum well. We interpret this asymmetry as originating from the different drift directions of carriers due to the internal electric field. This interpretation is corroborated by the direct determination of the polarity with convergent beam electron diffraction. A precise knowledge of hole mobility and diffusion coefficients would allow an estimate of the electric field in the AlN segment of the nanowire.

  20. Aberration corrected 1.2-MV cold field-emission transmission electron microscope with a sub-50-pm resolution

    SciTech Connect (OSTI)

    Akashi, Tetsuya; Takahashi, Yoshio; Tanigaki, Toshiaki Shimakura, Tomokazu; Kawasaki, Takeshi; Furutsu, Tadao; Shinada, Hiroyuki; Osakabe, Nobuyuki; Mller, Heiko; Haider, Maximilian; Tonomura, Akira

    2015-02-16

    Atomic-resolution electromagnetic field observation is critical to the development of advanced materials and to the unveiling of their fundamental physics. For this purpose, a spherical-aberration corrected 1.2-MV cold field-emission transmission electron microscope has been developed. The microscope has the following superior properties: stabilized accelerating voltage, minimized electrical and mechanical fluctuation, and coherent electron emission. These properties have enabled to obtain 43-pm information transfer. On the bases of these performances, a 43-pm resolution has been obtained by correcting lens aberrations up to the third order. Observations of GaN [411] thin crystal showed a projected atomic locations with a separation of 44?pm.

  1. High external quantum efficiency and fill-factor InGaN/GaN heterojunction solar cells grown by NH3-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Lang, J. R.; Neufeld, C. J.; Hurni, C. A.; Cruz, S. C.; Matioli, E.; Mishra, U. K.; Speck, J. S.

    2011-04-01

    High external quantum efficiency (EQE) p-i-n heterojunction solar cellsgrown by NH3 -based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorptionmeasurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By adjusting the thickness of the top p-type GaN window contact layer, it is shown that the short-wavelength (<365 nm) quantum efficiency is limited by the minority carrier diffusion length in highly Mg-doped p-GaN.

  2. Raman scattering as a tool for the evaluation of strain in GaN/AlN quantum dots: The effect of capping

    SciTech Connect (OSTI)

    Cros, A.; Cantarero, A.; Garro, N.; Coraux, J.; Daudin, B.

    2007-10-15

    The strain state of GaN/AlN quantum dots grown on 6H-SiC has been investigated as a function of AlN capping thickness by three different techniques. On the one hand, resonant Raman scattering allowed the detection of the A{sub 1}(LO) quasiconfined mode. It was found that its frequency increases with AlN deposition, while its linewidth did not evolve significantly. Available experiments of multiwavelength anomalous diffraction and diffraction anomalous fine structure on the same samples provided the determination of the wurtzite lattice parameters a and c of the quantum dots. A very good agreement is found between resonant Raman scattering and x-ray measurements, especially concerning the in-plane strain state. The results demonstrate the adequacy of Raman scattering, in combination with the deformation potential and biaxial approximations, to determine quantitatively values of strain in GaN quantum dot layers.

  3. Cantilever epitaxial process

    DOE Patents [OSTI]

    Ashby, Carol I.; Follstaedt, David M.; Mitchell, Christine C.; Han, Jung

    2003-07-29

    A process of growing a material on a substrate, particularly growing a Group II-VI or Group III-V material, by a vapor-phase growth technique where the growth process eliminates the need for utilization of a mask or removal of the substrate from the reactor at any time during the processing. A nucleation layer is first grown upon which a middle layer is grown to provide surfaces for subsequent lateral cantilever growth. The lateral growth rate is controlled by altering the reactor temperature, pressure, reactant concentrations or reactant flow rates. Semiconductor materials, such as GaN, can be produced with dislocation densities less than 10.sup.7 /cm.sup.2.

  4. Semiconductor light-emitting devices having concave microstructures providing improved light extraction efficiency and method for producing same

    DOE Patents [OSTI]

    Tansu, Nelson; Gilchrist, James F; Ee, Yik-Khoon; Kumnorkaew, Pisist

    2013-11-19

    A conventional semiconductor LED is modified to include a microlens layer over its light-emitting surface. The LED may have an active layer including at least one quantum well layer of InGaN and GaN. The microlens layer includes a plurality of concave microstructures that cause light rays emanating from the LED to diffuse outwardly, leading to an increase in the light extraction efficiency of the LED. The concave microstructures may be arranged in a substantially uniform array, such as a close-packed hexagonal array. The microlens layer is preferably constructed of curable material, such as polydimethylsiloxane (PDMS), and is formed by soft-lithography imprinting by contacting fluid material of the microlens layer with a template bearing a monolayer of homogeneous microsphere crystals, to cause concave impressions, and then curing the material to fix the concave microstructures in the microlens layer and provide relatively uniform surface roughness.

  5. Propagation of misfit dislocations from buffer/Si interface into Si

    DOE Patents [OSTI]

    Liliental-Weber, Zuzanna; Maltez, Rogerio Luis; Morkoc, Hadis; Xie, Jinqiao

    2011-08-30

    Misfit dislocations are redirected from the buffer/Si interface and propagated to the Si substrate due to the formation of bubbles in the substrate. The buffer layer growth process is generally a thermal process that also accomplishes annealing of the Si substrate so that bubbles of the implanted ion species are formed in the Si at an appropriate distance from the buffer/Si interface so that the bubbles will not migrate to the Si surface during annealing, but are close enough to the interface so that a strain field around the bubbles will be sensed by dislocations at the buffer/Si interface and dislocations are attracted by the strain field caused by the bubbles and move into the Si substrate instead of into the buffer epi-layer. Fabrication of improved integrated devices based on GaN and Si, such as continuous wave (CW) lasers and light emitting diodes, at reduced cost is thereby enabled.

  6. Looking for Auger signatures in III-nitride light emitters: A full-band Monte Carlo perspective

    SciTech Connect (OSTI)

    Bertazzi, Francesco Goano, Michele; Zhou, Xiangyu; Calciati, Marco; Ghione, Giovanni; Matsubara, Masahiko; Bellotti, Enrico

    2015-02-09

    Recent experiments of electron emission spectroscopy (EES) on III-nitride light-emitting diodes (LEDs) have shown a correlation between droop onset and hot electron emission at the cesiated surface of the LED p-cap. The observed hot electrons have been interpreted as a direct signature of Auger recombination in the LED active region, as highly energetic Auger-excited electrons would be collected in long-lived satellite valleys of the conduction band so that they would not decay on their journey to the surface across the highly doped p-contact layer. We discuss this interpretation by using a full-band Monte Carlo model based on first-principles electronic structure and lattice dynamics calculations. The results of our analysis suggest that Auger-excited electrons cannot be unambiguously detected in the LED structures used in the EES experiments. Additional experimental and simulative work are necessary to unravel the complex physics of GaN cesiated surfaces.

  7. Selective area epitaxy of monolithic white-light InGaN/GaN quantum well microstripes with dual color emission

    SciTech Connect (OSTI)

    Li, Yuejing; Tong, Yuying; Yang, Guofeng Yao, Chujun; Sun, Rui; Cai, Lesheng; Xu, Guiting; Wang, Jin; Zhang, Qing; Ye, Xuanchao; Wu, Mengting; Wen, Zhiqin

    2015-09-15

    Monolithic color synthesis is demonstrated using InGaN/GaN multiple quantum wells (QWs) grown on GaN microstripes formed by selective area epitaxy on SiO{sub 2} mask patterns. The striped microfacet structure is composed of (0001) and (11-22) planes, attributed to favorable surface polarity and surface energy. InGaN/GaN QWs on different microfacets contain spatially inhomogeneous compositions owing to the diffusion of adatoms among the facets. This unique property allows the microfacet QWs to emit blue light from the (11-22) plane and yellow light from the top (0001) plane, the mixing of which leads to the perception of white light emission.

  8. OMVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics (title change from A)

    SciTech Connect (OSTI)

    HAN,JUNG; FIGIEL,JEFFREY J.; PETERSEN,GARY A.; MYERS JR.,SAMUEL M.; CRAWFORD,MARY H.; BANAS,MICHAEL ANTHONY; HEARNE,SEAN JOSEPH

    2000-01-18

    We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GrdnN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

  9. Structural controlled magnetic anisotropy in Heusler L1{sub 0}-MnGa epitaxial thin films

    SciTech Connect (OSTI)

    Wang Kangkang; Lu Erdong; Smith, Arthur R.; Knepper, Jacob W.; Yang Fengyuan

    2011-04-18

    Ferromagnetic L1{sub 0}-MnGa thin films have been epitaxially grown on GaN, sapphire, and MgO substrates using molecular beam epitaxy. Using diffraction techniques, the epitaxial relationships are determined. It is found that the crystalline orientation of the films differ due to the influence of the substrate. By comparing the magnetic anisotropy to the structural properties, a clear correlation could be established indicating that the in-plane and out-of-plane anisotropy is directly determined by the crystal orientation of the film and could be controlled via selection of the substrates. This result could be helpful in tailoring magnetic anisotropy in thin films for spintronic applications.

  10. Development and Attestation of Gamma-Ray Measurement Methodologies for use by Rostekhnadzor Inspectors in the Russian Federation

    SciTech Connect (OSTI)

    Jeff Sanders

    2006-09-01

    Development and attestation of gamma-ray non-destructive assay measurement methodologies for use by inspectors of the Russian Federal Service for Environmental, Technological, and Nuclear Oversight (Rostekhnadzor, formerly Gosatomnadzor or GAN), as well as for use by Russian nuclear facilities, has been completed. Specifically, a methodology utilizing the gamma-ray multi group analysis (MGA) method for determining plutonium isotopic composition has been developed, while existing methodologies to determining uranium enrichment and isotopic composition have been revised to make them more appropriate to the material types and conditions present in nuclear facilities in the Russian Federation. This paper will discuss the development and revision of these methodologies, the metrological characteristics of the final methodologies, as well as the limitations and concerns specific to the utilization of these analysis methods in the Russian Federation.

  11. First-principles approach to calculating energy level alignment at aqueous semiconductor interfaces

    SciTech Connect (OSTI)

    Kharche, Neerav; Muckerman, James T.; Hybertsen, Mark S.

    2014-10-21

    A first-principles approach is demonstrated for calculating the relationship between an aqueous semiconductor interface structure and energy level alignment. The physical interface structure is sampled using density functional theory based molecular dynamics, yielding the interface electrostatic dipole. The GW approach from many-body perturbation theory is used to place the electronic band edge energies of the semiconductor relative to the occupied 1b? energy level in water. The application to the specific cases of nonpolar (1010 ) facets of GaN and ZnO reveals a significant role for the structural motifs at the interface, including the degree of interface water dissociation and the dynamical fluctuations in the interface Zn-O and O-H bond orientations. As a result, these effects contribute up to 0.5 eV.

  12. Interaction of defects and H in proton-irradiated GaN(Mg, H)

    SciTech Connect (OSTI)

    Myers, S.M.; Seager, C.H.

    2005-05-01

    Magnesium-doped, p-type GaN containing H was irradiated with MeV protons at room temperature and then annealed at a succession of increasing temperatures, with the behavior of defects and H in the material being followed through infrared absorption spectroscopy, nuclear-reaction analysis of the H, and photoluminescence. The results support the annihilation of Ga Frenkel pairs near room temperature, leaving the N interstitial and N vacancy to influence the elevated-temperature behavior. Multiple changes are observed with increasing temperature, ending with thermal release of the H above 700 deg. C. These effects are interpreted in terms of a succession of complexes involving Mg, the point defects, and H.

  13. Graphene in ohmic contact for both n-GaN and p-GaN

    SciTech Connect (OSTI)

    Zhong, Haijian; Liu, Zhenghui; Shi, Lin; Xu, Gengzhao; Fan, Yingmin; Huang, Zengli; Wang, Jianfeng; Ren, Guoqiang; Xu, Ke

    2014-05-26

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local IV results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.

  14. Metalorganic chemical vapor deposition and characterization of (Al,Si)O dielectrics for GaN–based devices

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Chan, Silvia; Mishra, Umesh K.; Tahhan, Maher; Liu, Xiang; Bisi, David; Gupta, Chirag; Koksaldi, Onur; Li, Haoran; Mates, Tom; DenBaars, Steven P.; et al

    2016-01-20

    In this study, we report on the growth and electrical characterization of (Al,Si)O dielectrics grown by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, oxygen, and silane as precursors. The growth rates, refractive indices, and composition of (Al,Si)O films grown on Si(001) were determined from ellipsometry and XPS measurements. Crystallinity and electrical properties of (Al,Si)O films grown in situ on c-plane GaN were characterized using grazing incidence X-ray diffraction and capacitance–voltage with current–voltage measurements, respectively. Si concentration in the films was found to be tunable by varying the trimethylaluminum and/or oxygen precursor flows. The Si incorporation suppressed the formation of crystallinemore » domains, leading to amorphous films that resulted in reduced interfacial trap density, low gate leakage and ultra-low hysteresis in (Al,Si)O/n-GaN MOS-capacitors.« less

  15. First-principles approach to calculating energy level alignment at aqueous semiconductor interfaces

    SciTech Connect (OSTI)

    Kharche, Neerav; Muckerman, James T.; Hybertsen, Mark S.

    2014-10-21

    A first-principles approach is demonstrated for calculating the relationship between an aqueous semiconductor interface structure and energy level alignment. The physical interface structure is sampled using density functional theory based molecular dynamics, yielding the interface electrostatic dipole. The GW approach from many-body perturbation theory is used to place the electronic band edge energies of the semiconductor relative to the occupied 1b? energy level in water. The application to the specific cases of nonpolar (1010 ) facets of GaN and ZnO reveals a significant role for the structural motifs at the interface, including the degree of interface water dissociation and the dynamical fluctuations in the interface Zn-O and O-H bond orientations. These effects contribute up to 0.5 eV.

  16. GaInN light-emitting diodes using separate epitaxial growth for the p-type region to attain polarization-inverted electron-blocking layer, reduced electron leakage, and improved hole injection

    SciTech Connect (OSTI)

    Meyaard, David S., E-mail: meyaad@rpi.edu; Lin, Guan-Bo; Ma, Ming; Fred Schubert, E. [Future Chips Constellation, Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)] [Future Chips Constellation, Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Cho, Jaehee [Future Chips Constellation, Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States) [Future Chips Constellation, Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Semiconductor Physics Research Center, School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Han, Sang-Heon; Kim, Min-Ho; Shim, HyunWook; Sun Kim, Young [LED Business, Samsung Electronics, Yongin 446-920 (Korea, Republic of)] [LED Business, Samsung Electronics, Yongin 446-920 (Korea, Republic of)

    2013-11-11

    A GaInN light-emitting diode (LED) structure is analyzed that employs a separate epitaxial growth for the p-type region, i.e., the AlGaN electron-blocking layer (EBL) and p-type GaN cladding layer, followed by wafer or chip bonding. Such LED structure has a polarization-inverted EBL and allows for uncompromised epitaxial-growth optimization of the p-type region, i.e., without the need to consider degradation of the quantum-well active region during p-type region growth. Simulations show that such an LED structure reduces electron leakage, reduces the efficiency droop, improves hole injection, and has the potential to extend high efficiencies into the green spectral region.

  17. Green cubic GaInN/GaN light-emitting diode on microstructured silicon (100)

    SciTech Connect (OSTI)

    Stark, Christoph J. M.; Detchprohm, Theeradetch; Wetzel, Christian, E-mail: wetzel@ieee.org [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States) [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Future Chips Constellation, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Lee, S. C.; Brueck, S. R. J. [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States)] [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States); Jiang, Y.-B. [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2013-12-02

    GaInN/GaN light-emitting diodes free of piezoelectric polarization were prepared on standard electronic-grade Si(100) substrates. Micro-stripes of GaN and GaInN/GaN quantum wells in the cubic crystal structure were grown on intersecting (111) planes of microscale V-grooved Si in metal-organic vapor phase epitaxy, covering over 50% of the wafer surface area. Crystal phases were identified in electron back-scattering diffraction. A cross-sectional analysis reveals a cubic structure virtually free of line defects. Electroluminescence over 20 to 100??A is found fixed at 487?nm (peak), 516?nm (dominant). Such structures therefore should allow higher efficiency, wavelength-stable light emitters throughout the visible spectrum.

  18. Mid-infrared electro-luminescence and absorption from AlGaN/GaN-based multi-quantum well inter-subband structures

    SciTech Connect (OSTI)

    Hofstetter, Daniel; Bour, David P.; Kirste, Lutz

    2014-06-16

    We present electro-modulated absorption and electro-luminescence measurements on chirped AlGaN/GaN-based multi-quantum well inter-subband structures grown by metal-organic vapour phase epitaxy. The absorption signal is a TM-polarized, 70?meV wide feature centred at 230?meV. At medium injection current, a 58?meV wide luminescence peak corresponding to an inter-subband transition at 1450?cm{sup ?1} (180?meV) is observed. Under high injection current, we measured a 4?meV wide structure peaking at 92.5?meV in the luminescence spectrum. The energy location of this peak is exactly at the longitudinal optical phonon of GaN.

  19. MI C H I GA N M E M O R I A L P H O E N I X PROJECT

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    M M P P - N P C - I - 4 MI C H I GA N M E M O R I A L P H O E N I X PROJECT THE U N I V E R S I T Y OF MI CHI GAN Facsimile Price $ Ij) Microfilm Price $ y / Avoiloble from the O ffic e of Technical Services Department o f Commerce Washington 25, D. C. LATTICE W A VES, SPIN W AVES A N D NEUTRON SCATTERING By B. N . BROCKHOUSE CHALK RIVER PROJECT A T O M IC ENERGY O F C A N A D A LIMITED A PAPER BASED O N LECTURES PRESENTED AT THE NEUTRON PHYSICS CONFERENCE M A C K IN A C ISLAND, M IC H IG A N JU

  20. Identification of microscopic hole-trapping mechanisms in nitride semiconductors

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    John L. Lyons; Krishnaswamy, Karthik; Luke Gordon; Van de Walle, Chris G.; Anderson, Janotti

    2015-12-17

    Hole trapping has been observed in nitride heterostructure devices, where the Fermi level is in the vicinity of the valence-band maximum. Using hybrid density functional calculations, we examine microscopic mechanisms for hole trapping in GaN and AlN. In a defect-free material, hole trapping does not spontaneously occur, but trapping can occur in the vicinity of impurities, such as C-a common unintentional impurity in nitrides. As a result, using Schrödinger-Poisson simulations, we assess the effects of C-derived hole traps on N-face high-electron mobility transistors, which we find to be more detrimental than the previously proposed interface traps.

  1. Molecular beam epitaxial growth and optical properties of red-emitting ({lambda} = 650 nm) InGaN/GaN disks-in-nanowires on silicon

    SciTech Connect (OSTI)

    Jahangir, S.; Bhattacharya, P.; Mandl, M.; Strassburg, M.

    2013-02-18

    We have investigated the radiative properties of InGaN disks in GaN nanowires grown by plasma enhanced molecular beam epitaxy on (001) silicon substrates. The growth of the nanowire heterostructures has been optimized to maximize the radiative efficiency, or internal quantum efficiency (IQE), for photoluminescence emission at {lambda} = 650 nm. It is found that the IQE increases significantly (by {approx}10%) to 52%, when post-growth passivation of nanowire surface with silicon nitride or parylene is applied. The increase in efficiency is supported by radiative- and nonradiative lifetimes derived from data obtained from temperature dependent- and time-resolved photoluminescence measurements. Light emitting diodes with p-i-n disk-in-nanowire heterostructures passivated with parylene have been fabricated and characterized.

  2. Barrier height of Pt-In{sub x}Ga{sub 1-x}N (0{<=}x{<=}0.5) nanowire Schottky diodes

    SciTech Connect (OSTI)

    Guo Wei; Banerjee, Animesh; Zhang Meng; Bhattacharya, Pallab

    2011-05-02

    The barrier height of Schottky diodes made on In{sub x}Ga{sub 1-x}N nanowires have been determined from capacitance-voltage measurements. The nanowires were grown undoped on n-type (001) silicon substrates by plasma-assisted molecular beam epitaxy. The length, diameter and density of the nanowires are {approx}1 {mu}m, 20 nm, and 1x10{sup 11} cm{sup -2}. The Schottky contact was made on the top surface of the nanowires with Pt after planarizing with parylene. The measured barrier height {Phi}{sub B} varies from 1.4 eV (GaN) to 0.44 eV (In{sub 0.5}Ga{sub 0.5}N) and agrees well with the ideal barrier heights in the Schottky limit.

  3. Comparison of Wide-Bandgap Semiconductors for Power Electronics Applications

    SciTech Connect (OSTI)

    Ozpineci, B.

    2004-01-02

    Recent developmental advances have allowed silicon (Si) semiconductor technology to approach the theoretical limits of the Si material; however, power device requirements for many applications are at a point that the present Si-based power devices cannot handle. The requirements include higher blocking voltages, switching frequencies, efficiency, and reliability. To overcome these limitations, new semiconductor materials for power device applications are needed. For high power requirements, wide-bandgap semiconductors like silicon carbide (SiC), gallium nitride (GaN), and diamond, with their superior electrical properties, are likely candidates to replace Si in the near future. This report compares wide-bandgap semiconductors with respect to their promise and applicability for power applications and predicts the future of power device semiconductor materials.

  4. First-principles approach to calculating energy level alignment at aqueous semiconductor interfaces

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Kharche, Neerav; Muckerman, James T.; Hybertsen, Mark S.

    2014-10-21

    A first-principles approach is demonstrated for calculating the relationship between an aqueous semiconductor interface structure and energy level alignment. The physical interface structure is sampled using density functional theory based molecular dynamics, yielding the interface electrostatic dipole. The GW approach from many-body perturbation theory is used to place the electronic band edge energies of the semiconductor relative to the occupied 1b₁ energy level in water. The application to the specific cases of nonpolar (101¯0 ) facets of GaN and ZnO reveals a significant role for the structural motifs at the interface, including the degree of interface water dissociation and themore » dynamical fluctuations in the interface Zn-O and O-H bond orientations. As a result, these effects contribute up to 0.5 eV.« less

  5. Temporally and spatially resolved photoluminescence investigation of (112{sup }2) semi-polar InGaN/GaN multiple quantum wells grown on nanorod templates

    SciTech Connect (OSTI)

    Liu, B.; Smith, R.; Athanasiou, M.; Yu, X.; Bai, J.; Wang, T.

    2014-12-29

    By means of time-resolved photoluminescence (PL) and confocal PL measurements, temporally and spatially resolved optical properties have been investigated on a number of In{sub x}Ga{sub 1?x}N/GaN multiple-quantum-well (MQW) structures with a wide range of indium content alloys from 13% to 35% on (112{sup }2) semi-polar GaN with high crystal quality, obtained through overgrowth on nanorod templates. With increasing indium content, the radiative recombination lifetime initially increases as expected, but decreases if the indium content further increases to 35%, corresponding to emission in the green spectral region. The reduced radiative recombination lifetime leads to enhanced optical performance for the high indium content MQWs as a result of strong exciton localization, which is different from the behaviour of c-plane InGaN/GaN MQWs, where quantum confined Stark effect plays a dominating role in emission process.

  6. Degradation of InGaN/GaN laser diodes investigated by micro-cathodoluminescence and micro-photoluminescence

    SciTech Connect (OSTI)

    Meneghini, M. Carraro, S.; Meneghesso, G.; Trivellin, N.; Zanoni, E.; Rossi, F.; Salviati, G.; Schade, L.; Karunakaran, M. A.; Schwarz, U. T.

    2013-12-02

    We present an investigation of the degradation of InGaN/GaN laser diodes grown on a GaN substrate. The results indicate that: (i) Ageing induces a significant increase in the threshold current (Ith) of the lasers, which is attributed to an increase in non-radiative recombination; (ii) Ith increase is correlated to a decrease in the micro-cathodoluminescence signal measured (after the removal of the top metallization) in the region under the ridge; (iii) micro-photoluminescence measurements indicate that constant current stress increases non-radiative recombination within the quantum wells (and not only within the barriers), and induces an increase in the emission wavelength of the degraded region.

  7. Intersubband transitions in In{sub x}Ga{sub 1?x}N/In{sub y}Ga{sub 1?y}N/GaN staggered quantum wells

    SciTech Connect (OSTI)

    Y?ld?r?m, Hasan; Aslan, Bulent

    2014-04-28

    Intersubband transition energies and absorption lineshape in staggered InGaN/GaN quantum wells surrounded by GaN barriers are computed as functions of structural parameters such as well width, In concentrations, and the doping level in the well. Schrdinger and Poisson equations are solved self-consistently by taking the free and bound surface charge concentrations into account. Many-body effects, namely, depolarization and excitonic shifts are also included in the calculations. Results for transition energies, oscillator strength, and the absorption lineshape up to nonlinear regime are represented as functions of the parameters mentioned. The well width (total and constituent layers separately) and In concentration dependence of the built-in electric field are exploited to tune the intersubband transition energies.

  8. A InGaN/GaN quantum dot green ({lambda}=524 nm) laser

    SciTech Connect (OSTI)

    Zhang Meng; Banerjee, Animesh; Lee, Chi-Sen; Hinckley, John M.; Bhattacharya, Pallab

    2011-05-30

    The characteristics of self-organized InGaN/GaN quantum dot lasers are reported. The laser heterostructures were grown on c-plane GaN substrates by plasma-assisted molecular beam epitaxy and the laser facets were formed by focused ion beam etching with gallium. Emission above threshold is characterized by a peak at 524 nm (green) and linewidth of 0.7 nm. The lowest measured threshold current density is 1.2 kA/cm{sup 2} at 278 K. The slope and wall plug efficiencies are 0.74 W/A and {approx}1.1%, respectively, at 1.3 kA/cm{sup 2}. The value of T{sub 0}=233 K in the temperature range of 260-300 K.

  9. Green, red and infrared Er-related emission in implanted GaN:Er and GaN:Er,O samples

    SciTech Connect (OSTI)

    Monteiro, T.; Soares, J.; Correia, M. R.; Alves, E.

    2001-06-01

    Er-related luminescence near 1.54 {mu}m ({similar_to}805 meV) is observed under below band gap excitation at 4.2 K in GaN:Er and GaN:Er,O implanted samples. The spectrum of the recovered damage samples is a multiline structure. So far, these lines are the sharpest ones reported for GaN. Well-resolved green and red luminescences are observed in implanted samples. The dependence of luminescence on the excitation energy as well as the influence of different nominal fluence and annealing conditions is discussed. Combining the results obtained from photoluminescence and Rutherford backscattering spectrometry, different lattice sites for the optical active Er-related centers are identified. {copyright} 2001 American Institute of Physics.

  10. High-field quasi-ballistic transport in AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Danilchenko, B. A.; Tripachko, N. A.; Belyaev, A. E.; Vitusevich, S. A. Hardtdegen, H.; Lth, H.

    2014-02-17

    Mechanisms of electron transport formation in 2D conducting channels of AlGaN/GaN heterostructures in extremely high electric fields at 4.2?K have been studied. Devices with a narrow constriction for the current flow demonstrate high-speed electron transport with an electron velocity of 6.8??10{sup 7}?cm/s. Such a velocity is more than two times higher than values reported for conventional semiconductors and about 15% smaller than the limit value predicted for GaN. Superior velocity is attained in the channel with considerable carrier reduction. The effect is related to a carrier runaway phenomenon. The results are in good agreement with theoretical predictions for GaN-based materials.

  11. Measuring the depth profiles of strain/composition in AlGaN-graded layer by high-resolution x-ray diffraction

    SciTech Connect (OSTI)

    Kuchuk, A. V.; Stanchu, H. V.; Kladko, V. P.; Belyaev, A. E.; Li, Chen; Ware, M. E.; Mazur, Yu. I.; Salamo, G. J.

    2014-12-14

    Here, we demonstrate X-ray fitting through kinematical simulations of the intensity profiles of symmetric reflections for epitaxial compositionally graded layers of AlGaN grown by molecular beam epitaxy pseudomorphically on [0001]-oriented GaN substrates. These detailed simulations depict obvious differences between changes in thickness, maximum concentration, and concentration profile of the graded layers. Through comparison of these simulations with as-grown samples, we can reliably determine these parameters, most important of which are the profiles of the concentration and strain which determine much of the electrical properties of the film. In addition to learning about these parameters for the characterization of thin film properties, these fitting techniques create opportunities to calibrate growth rates and control composition profiles of AlGaN layers with a single growth rather than multiple growths as has been done traditionally.

  12. Simulation Analysis of Inspections of International Travelers at Los Angeles International Airport for US-VISIT

    SciTech Connect (OSTI)

    Edmunds, T; Sholl, P; Yao, Y; Gansemer, J; Cantwell, E; Prosnitz, D; Rosenberg, P; Norton, G

    2004-02-11

    The United States Visitor and Immigrant Status Indicator Technology Program (US-VISIT) will deploy biometric and other systems to identify and track foreign nationals entering and exiting the U.S. Evaluation of the large number of possible policy options and technical configurations for implementation of US-VISIT requires validated system analyses with appropriate tools that can address the requirements of this new program and its processes. Early identification of performance issues and capability gaps will prove critical to the success of the program.

  13. U.S. Helps Equip Ukrainian Airport with Cutting-Edge Radiation...

    National Nuclear Security Administration (NNSA)

    ... NNSA maintains and enhances the safety, security, reliability, and performance of the U.S. nuclear weapons stockpile without nuclear testing; reduces the global danger from weapons ...

  14. Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

    SciTech Connect (OSTI)

    Novikov, S. V.; Staddon, C. R.; Foxon, C. T.; Yu, K. M.; Broesler, R.; Hawkridge, M.; Liliental-Weber, Z.; Walukiewicz, W.; Denlinger, J.; Demchenko, I.

    2009-10-06

    The authors have succeeded in growing GaN1?xAsx alloys over a large composition range (0 < x < 0.8) by plasma-assisted molecular beam epitaxy. The enhanced incorporation of As was achieved by growing the films with high As{sub 2} flux at low (as low as 100 C) growth temperatures, which is much below the normal GaN growth temperature range. Using x-ray and transmission electron microscopy, they found that the GaNAs alloys with high As content x > 0.17 are amorphous. Optical absorption measurements together with x-ray absorption and emission spectroscopy results reveal a continuous gradual decrease in band gap from -3.4 to < 1 eV with increasing As content. The energy gap reaches its minimum of -0.8 eV at x - 0.8. The composition dependence of the band gap of the crystalline GaN{sub 1?x}As{sub x} alloys follows the prediction of the band anticrossing model (BAC). However, our measured band gap of amorphous GaN{sub 1?x}As{sub x} with 0.3 < x < 0.8 are larger than that predicted by BAC. The results seem to indicate that for this composition range the amorphous GaN{sub 1?x}As{sub x} alloys have short-range ordering that resembles random crystalline GaN{sub 1?x}As{sub x} alloys. They have demonstrated the possibility of the growth of amorphous GaN{sub 1?x}As{sub x} layers with variable As content on glass substrates

  15. Review of Excess Weapons Plutonium Disposition LLNL Contract Work in Russia-(English)

    SciTech Connect (OSTI)

    Jardine, L; Borisov, G B

    2002-07-11

    This third meeting of the recently completed and ongoing Russian plutonium immobilization contract work was held at the State Education Center (SEC) in St. Petersburg on January 14-18, 2002. The meeting agenda is reprinted here as Appendix A and the attendance list as Appendix B. The meeting had 58 Russian participants from 21 Russian organizations, including the industrial sites (Mayak, Krasonayarsk-26, Tomsk), scientific institutes (VNIINM, KRI, VNIPIPT, RIAR), design organizations (VNIPIET and GSPI), universities (Nyzhny Novgorod, Urals Technical), Russian Academy of Sciences (Institute of Physical Chemistry or IPhCh, Institute of Ore-Deposit Geology, Petrography, Mineralogy, and Geochemistry or IGEM), Radon-Moscow, S&TC Podol'osk, Kharkov-Ukraine, GAN-SEC-NRS and SNIIChM, the RF Ministry of Atomic Energy (Minatom) and Gosatomnadzor (GAN). This volume, published by LLNL, documents this third annual meeting. Forty-nine technical papers were presented by the Russian participants, and nearly all of these have been collected in this Proceedings. The two objectives for the meeting were to: (1) Bring together the Russian organizations, experts, and managers performing this contract work into one place for four days to review and discuss their work amongst each other. (2) Publish a meeting summary and proceedings of all the excellent Russian plutonium immobilization and other plutonium disposition contract work in one document so that the wide extent of the Russian immobilization activities are documented, referencable and available for others to use, as were the Proceedings of the two previous meetings. Attendees gave talks describing their LLNL contract work and submitted written papers documenting their contract work (in English and Russian), in both hard copy and on computer disks. Simultaneous translation into Russian and English was used for presentations made at the State Region Educational Center (SEC).

  16. Slide 1

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    the Pittsburgh International Airport 1. Exit airport and head SOUTH toward AIRPORT BLVD. 2. Continue straight onto AIRPORT BLVD. 3. Keep LEFT at fork in road - (about 2 minutes)....

  17. Rosborne318's blog

    Open Energy Info (EERE)

    Shreveport Airport Authority - Response Deadline 2 January 2014 http:en.openei.orgcommunityblogrequest-information-renewable-energy-generationproduction-shreveport-airport-aut...

  18. Special Issue for the 9th International Conference on Carbonaceous Particles in the Atmosphere

    SciTech Connect (OSTI)

    Strawa, A.W.; Kirchstetter, T.W.; Puxbaum, H.

    2009-12-11

    adversely affect human health (Lighty et al., 2000; Pope and Dockery, 2006). Gan et al. (Gan et al., accepted) examined the indoor air quality aboard submarines and found that the diesel particulate matter concentrations exceeded the EPA 24 hour standard. Claeys et al. (Claeys et al., accepted) studied the importance and sources of secondary organic aerosol (SOA) in remote marine environment during a period of high biological activity. Methanesulphonate was the major SOA compound detected and there was no evidence for SOA from isoprene. The optical properties of gasoline and diesel vehicle particulate emissions and their relative contribution to radiative forcing was studied by Strawa et al. (Strawa et al., accepted).

  19. In vitro bio-functionality of gallium nitride sensors for radiation biophysics

    SciTech Connect (OSTI)

    Hofstetter, Markus; Howgate, John; Schmid, Martin; Schoell, Sebastian; Sachsenhauser, Matthias; Adiguezel, Denis; Stutzmann, Martin; Sharp, Ian D.; Thalhammer, Stefan

    2012-07-27

    Highlights: Black-Right-Pointing-Pointer Gallium nitride based sensors show promising characteristics to monitor cellular parameters. Black-Right-Pointing-Pointer Cell growth experiments reveal excellent biocompatibiltiy of the host GaN material. Black-Right-Pointing-Pointer We present a biofunctionality assay using ionizing radiation. Black-Right-Pointing-Pointer DNA repair is utilized to evaluate material induced alterations in the cellular behavior. Black-Right-Pointing-Pointer GaN shows no bio-functional influence on the cellular environment. -- Abstract: There is an increasing interest in the integration of hybrid bio-semiconductor systems for the non-invasive evaluation of physiological parameters. High quality gallium nitride and its alloys show promising characteristics to monitor cellular parameters. Nevertheless, such applications not only request appropriate sensing capabilities but also the biocompatibility and especially the biofunctionality of materials. Here we show extensive biocompatibility studies of gallium nitride and, for the first time, a biofunctionality assay using ionizing radiation. Analytical sensor devices are used in medical settings, as well as for cell- and tissue engineering. Within these fields, semiconductor devices have increasingly been applied for online biosensing on a cellular and tissue level. Integration of advanced materials such as gallium nitride into these systems has the potential to increase the range of applicability for a multitude of test devices and greatly enhance sensitivity and functionality. However, for such applications it is necessary to optimize cell-surface interactions and to verify the biocompatibility of the semiconductor. In this work, we present studies of mouse fibroblast cell activity grown on gallium nitride surfaces after applying external noxa. Cell-semiconductor hybrids were irradiated with X-rays at air kerma doses up to 250 mGy and the DNA repair dynamics, cell proliferation, and cell growth

  20. Stress-induced piezoelectric field in GaN-based 450-nm light-emitting diodes

    SciTech Connect (OSTI)

    Tawfik, Wael Z.; Hyeon, Gil Yong; Lee, June Key

    2014-10-28

    We investigated the influence of the built-in piezoelectric field induced by compressive stress on the characteristics of GaN-based 450-nm light-emitting diodes (LEDs) prepared on sapphire substrates of different thicknesses. As the sapphire substrate thickness was reduced, the compressive stress in the GaN layer was released, resulting in wafer bowing. The wafer bowing-induced mechanical stress altered the piezoelectric field, which in turn reduced the quantum confined Stark effect in the InGaN/GaN active region of the LED. The flat-band voltage was estimated by measuring the applied bias voltage that induced a 180° phase shift in the electro-reflectance (ER) spectrum. The piezoelectric field estimated by the ER spectra changed by ∼110 kV/cm. The electroluminescence spectral peak wavelength was blue-shifted, and the internal quantum efficiency was improved by about 22% at a high injection current of 100 mA. The LED on the 60-μm-thick sapphire substrate exhibited the highest light output power of ∼59 mW at an injection current of 100 mA, with the operating voltage unchanged.

  1. Hydrogen and fluorine co-decorated silicene: A first principles study of piezoelectric properties

    SciTech Connect (OSTI)

    Noor-A-Alam, Mohammad; Kim, Hye Jung; Shin, Young-Han

    2015-06-14

    A low-buckled silicene monolayer being centrosymmetric like graphene, in contrast to a piezoelectric hexagonal boron nitride (h-BN), is not intrinsically piezoelectric. However, based on first principles calculations, we show that chemical co-decoration of hydrogen (H) and fluorine (F) on opposite sides of silicene (i.e., one side is decorated with H, while the other one is with F) breaks the centrosymmetry. Redistributing the charge density due to the electronegativity difference between the atoms, non-centrosymmetric co-decoration induces an out-of-plane dipolar polarization and concomitant piezoelectricity into non-piezoelectric silicene monolayer. Our piezoelectric coefficients are comparable with other known two-dimensional piezoelectric materials (e.g., hydrofluorinated graphene/h-BN) and some bulk semiconductors, such as wurtzite GaN and wurtzite BN. Moreover, because of silicene's lower elastic constants compared to graphene or h-BN, piezoelectric strain constants are found significantly larger than those of hydrofluorinated graphene/h-BN. We also predict that a wide range of band gaps with an average of 2.52 eV can be opened in a low-buckled gapless semi-metallic silicene monolayer by co-decoration of H and F atoms on the surface.

  2. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect (OSTI)

    Russell D. Dupuis

    2004-09-30

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the first year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The first year activities were focused on the installation, set-up, and use of advanced equipment for the metalorganic chemical vapor deposition growth of III-nitride films and the characterization of these materials (Task 1) and the design, fabrication, testing of nitride LEDs (Task 4). As a progress highlight, we obtained improved quality of {approx} 2 {micro}m-thick GaN layers (as measured by the full width at half maximum of the asymmetric (102) X-ray diffraction peak of less than 350 arc-s) and higher p-GaN:Mg doping level (free hole carrier higher than 1E18 cm{sup -3}). Also in this year, we have developed the growth of InGaN/GaN active layers for long-wavelength green light emitting diodes, specifically, for emission at {lambda} {approx} 540nm. The effect of the Column III precursor (for Ga) and the post-growth thermal annealing effect were also studied. Our LED device fabrication process was developed and initially optimized, especially for low-resistance ohmic contacts for p-GaN:Mg layers, and blue-green light emitting diode structures were processed and characterized.

  3. NANOSTRUCTURED HIGH PERFORMANCE ULTRAVIOLET AND BLUE LIGHT EMITTING DIODES FOR SOLID STATE LIGHTING

    SciTech Connect (OSTI)

    Arto V. Nurmikko; Jung Han

    2004-10-01

    We report on research results in this project which synergize advanced material science approaches with fundamental optical physics concepts pertaining to light-matter interaction, with the goal of solving seminal problems for the development of very high performance light emitting diodes (LEDs) in the blue and near ultraviolet for Solid State Lighting applications. Accomplishments in the first 12 month contract period include (1) new means of synthesizing zero- and one-dimensional GaN nanostructures, (2) establishment of the building blocks for making GaN-based microcavity devices, and (3) demonstration of top-down approach to nano-scale photonic devices for enhanced spontaneous emission and light extraction. These include a demonstration of eight-fold enhancement of the external emission efficiency in new InGaN QW photonic crystal structures. The body of results is presented in this report shows how a solid foundation has been laid, with several noticeable accomplishments, for innovative research, consistent with the stated milestones.

  4. Synthesis, optical properties, and microstructure of semiconductor nanocrystals formed by ion implantation

    SciTech Connect (OSTI)

    Budai, J.D.; White, C.W.; Withrow, S.P.; Zuhr, R.A.; Zhu, J.G.

    1996-12-01

    High-dose ion implantation, followed by annealing, has been shown to provide a versatile technique for creating semiconductor nanocrystals encapsulated in the surface region of a substrate material. The authors have successfully formed nanocrystalline precipitates from groups IV (Si, Ge, SiGe), III-V (GaAs, InAs, GaP, InP, GaN), and II-VI (CdS, CdSe, CdS{sub x}Se{sub 1{minus}x}, CdTe, ZnS, ZnSe) in fused silica, Al{sub 2}O{sub 3} and Si substrates. Representative examples will be presented in order to illustrate the synthesis, microstructure, and optical properties of the nanostructured composite systems. The optical spectra reveal blue-shifts in good agreement with theoretical estimates of size-dependent quantum-confinement energies of electrons and holes. When formed in crystalline substrates, the nanocrystal lattice structure and orientation can be reproducibly controlled by adjusting the implantation conditions.

  5. Nitride based quantum well light-emitting devices having improved current injection efficiency

    DOE Patents [OSTI]

    Tansu, Nelson; Zhao, Hongping; Liu, Guangyu; Arif, Ronald

    2014-12-09

    A III-nitride based device provides improved current injection efficiency by reducing thermionic carrier escape at high current density. The device includes a quantum well active layer and a pair of multi-layer barrier layers arranged symmetrically about the active layer. Each multi-layer barrier layer includes an inner layer abutting the active layer; and an outer layer abutting the inner layer. The inner barrier layer has a bandgap greater than that of the outer barrier layer. Both the inner and the outer barrier layer have bandgaps greater than that of the active layer. InGaN may be employed in the active layer, AlInN, AlInGaN or AlGaN may be employed in the inner barrier layer, and GaN may be employed in the outer barrier layer. Preferably, the inner layer is thin relative to the other layers. In one embodiment the inner barrier and active layers are 15 .ANG. and 24 .ANG. thick, respectively.

  6. Group III-nitride thin films grown using MBE and bismuth

    DOE Patents [OSTI]

    Kisielowski, Christian K.; Rubin, Michael

    2002-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  7. Group III-nitride thin films grown using MBE and bismuth

    DOE Patents [OSTI]

    Kisielowski, Christian K.; Rubin, Michael

    2000-01-01

    The present invention comprises growing gallium nitride films in the presence of bismuth using MBE at temperatures of about 1000 K or less. The present invention further comprises the gallium nitride films fabricated using the inventive fabrication method. The inventive films may be doped with magnesium or other dopants. The gallium nitride films were grown on sapphire substrates using a hollow anode Constricted Glow Discharge nitrogen plasma source. When bismuth was used as a surfactant, two-dimensional gallium nitride crystal sizes ranging between 10 .mu.m and 20 .mu.m were observed. This is 20 to 40 times larger than crystal sizes observed when GaN films were grown under similar circumstances but without bismuth. It is thought that the observed increase in crystal size is due bismuth inducing an increased surface diffusion coefficient for gallium. The calculated value of 4.7.times.10.sup.-7 cm.sup.2 /sec. reveals a virtual substrate temperature of 1258 K which is 260 degrees higher than the actual one.

  8. Suppression of metastable-phase inclusion in N-polar (0001{sup }) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    SciTech Connect (OSTI)

    Shojiki, Kanako Iwabuchi, Takuya; Kuboya, Shigeyuki; Choi, Jung-Hun; Tanikawa, Tomoyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi; Usami, Noritaka

    2015-06-01

    The metastable zincblende (ZB) phase in N-polar (0001{sup }) (?c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the ?c-plane and Ga-polar (0001) (+c-plane), the ?c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the ?c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated.

  9. Ferromagnetic and paramagnetic magnetization of implanted GaN:Ho,Tb,Sm,Tm films

    SciTech Connect (OSTI)

    Maryško, M. Hejtmánek, J.; Laguta, V.; Sofer, Z.; Sedmidubský, D.; Šimek, P.; Veselý, M.; Mikulics, M.; Buchal, C.; Macková, A.; Malínský, P.; Wilhelm, R. A.

    2015-05-07

    The SQUID magnetic measurements were performed on the GaN films prepared by metal-organic vapour phase epitaxy and implanted by Tb{sup 3+}, Tm{sup 3+}, Sm{sup 3+}, and Ho{sup 3+} ions. The sapphire substrate was checked by the electron paramagnetic resonance method which showed a content of Cr{sup 3+} and Fe{sup 3+} impurities. The samples 5 × 5 mm{sup 2} were positioned in the classical straws and within an estimated accuracy of 10{sup −6 }emu, no ferromagnetic moment was detected in the temperature region of 2–300 K. The paramagnetic magnetization was studied for parallel and perpendicular orientation. In the case of GaN:Tb sample, at T = 2 K, a pronounced anisotropy with the easy axis perpendicular to the film was observed which can be explained by the lowest quasi-doublet state of the non-Kramers Tb{sup 3+} ion. The Weiss temperature deduced from the susceptibility data using the Curie-Weiss (C-W) law was found to depend substantially on the magnetic field.

  10. Impact of proton irradiation on deep level states in n-GaN

    SciTech Connect (OSTI)

    Zhang, Z.; Arehart, A. R.; Cinkilic, E.; Ringel, S. A.; Chen, J.; Zhang, E. X.; Fleetwood, D. M.; Schrimpf, R. D.; McSkimming, B.; Speck, J. S.

    2013-07-22

    Deep levels in 1.8 MeV proton irradiated n-type GaN were systematically characterized using deep level transient spectroscopies and deep level optical spectroscopies. The impacts of proton irradiation on the introduction and evolution of those deep states were revealed as a function of proton fluences up to 1.1 10{sup 13} cm{sup ?2}. The proton irradiation introduced two traps with activation energies of E{sub C} - 0.13 eV and 0.16 eV, and a monotonic increase in the concentration for most of the pre-existing traps, though the increase rates were different for each trap, suggesting different physical sources and/or configurations for these states. Through lighted capacitance voltage measurements, the deep levels at E{sub C} - 1.25 eV, 2.50 eV, and 3.25 eV were identified as being the source of systematic carrier removal in proton-damaged n-GaN as a function of proton fluence.

  11. Dislocation-related trap levels in nitride-based light emitting diodes

    SciTech Connect (OSTI)

    Venturi, Giulia; Castaldini, Antonio; Cavallini, Anna

    2014-05-26

    Deep level transient spectroscopy was performed on InGaN/GaN multiple quantum well light emitting diodes (LEDs) in order to determine the effect of the dislocation density on the deep intragap electronic levels. The LEDs were grown by metalorganic vapor phase epitaxy on GaN templates with a high dislocation density of 8 10{sup 9} cm{sup ?2} and a low dislocation density of 3 10{sup 8} cm{sup ?2}. Three trapping levels for electrons were revealed, named A, A1, and B, with energies E{sub A}???0.04?eV, E{sub A1}???0.13?eV, and E{sub B}???0.54?eV, respectively. The trapping level A has a much higher concentration in the LEDs grown on the template with a high density of dislocations. The logarithmic dependence of the peak amplitude on the bias pulse width for traps A and A1 identifies the defects responsible for these traps as associated with linearly arranged defects. We conclude that traps A and A1 are dislocation-related intragap energy levels.

  12. Nanoscale determinant to brighten up GaN:Eu red light-emitting diode: Local potential of Eu-defect complexes

    SciTech Connect (OSTI)

    Ishii, Masashi; Koizumi, Atsushi; Fujiwara, Yasufumi

    2015-04-21

    Emission sites in GaN:Eu red light-emitting diodes (LEDs) were investigated using a new spectroscopy technique, namely, site-selective pulse-driven emission spectroscopy (PDES). The PDES, in which the emission intensity of a pulse-driven LED is recorded with respect to the pulse frequency, revealed the charge-trapping dynamics of the Eu emission sites. We found that a determinant of the emission intensity of the sites was not their relative abundance, but rather the spatial extent of the local potential, which determines the effectiveness of the capture of injection charges. Minor sites with wider potentials enhanced the emission intensity of the LED, resulting in emission spectra that differ from those obtained using the photoluminescence of a GaN:Eu thin film. The potential curve is determined by the atomic structure of the complexes, which consist of a Eu dopant and nearby defects in the GaN host. The extent was characterized by a parameter, namely, cutoff frequency, and the emission sites with the wider and narrower potentials in the GaN:Eu LED were found to have cutoff frequencies of 400 kHz and 3 MHz, respectively. The cutoff frequency of 3 MHz was found to be the upper limit for emission sites in the LED. The emission site with the wider potential is useful for slower devices such as light fixtures, while the site with the narrower potential is useful for faster devices such as opto-isolators.

  13. MOCVD synthesis of group III-nitride heterostructure nanowires for solid-state lighting.

    SciTech Connect (OSTI)

    Wang, George T.; Creighton, James Randall; Talin, Albert Alec

    2006-11-01

    Solid-state lighting (SSL) technologies, based on semiconductor light emitting devices, have the potential to reduce worldwide electricity consumption by more than 10%, which could significantly reduce U.S. dependence on imported energy and improve energy security. The III-nitride (AlGaInN) materials system forms the foundation for white SSL and could cover a wide spectral range from the deep UV to the infrared. For this LDRD program, we have investigated the synthesis of single-crystalline III-nitride nanowires and heterostructure nanowires, which may possess unique optoelectronic properties. These novel structures could ultimately lead to the development of novel and highly efficient SSL nanodevice applications. GaN and III-nitride core-shell heterostructure nanowires were successfully synthesized by metal organic chemical vapor deposition (MOCVD) on two-inch wafer substrates. The effect of process conditions on nanowire growth was investigated, and characterization of the structural, optical, and electrical properties of the nanowires was also performed.

  14. Degradation mechanisms of 2 MeV proton irradiated AlGaN/GaN HEMTs

    SciTech Connect (OSTI)

    Greenlee, Jordan D. Anderson, Travis J.; Koehler, Andrew D.; Weaver, Bradley D.; Kub, Francis J.; Hobart, Karl D.; Specht, Petra; Dubon, Oscar D.; Luysberg, Martina; Weatherford, Todd R.

    2015-08-24

    Proton-induced damage in AlGaN/GaN HEMTs was investigated using energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM), and simulated using a Monte Carlo technique. The results were correlated to electrical degradation using Hall measurements. It was determined by EDS that the interface between GaN and AlGaN in the irradiated HEMT was broadened by 2.2 nm, as estimated by the width of the Al EDS signal compared to the as-grown interface. The simulation results show a similar Al broadening effect. The extent of interfacial roughening was examined using high resolution TEM. At a 2 MeV proton fluence of 6 × 10{sup 14} H{sup +}/cm{sup 2}, the electrical effects associated with the Al broadening and surface roughening include a degradation of the ON-resistance and a decrease in the electron mobility and 2DEG sheet carrier density by 28.9% and 12.1%, respectively.

  15. Quaternary AlInGaN/InGaN quantum well on vicinal c-plane substrate for high emission intensity of green wavelengths

    SciTech Connect (OSTI)

    Park, Seoung-Hwan; Pak, Y. Eugene; Park, Chang Young; Mishra, Dhaneshwar; Yoo, Seung-Hyun; Cho, Yong-Hee Shim, Mun-Bo; Kim, Sungjin

    2015-05-14

    Electronic and optical properties of non-trivial semipolar AlInGaN/InGaN quantum well (QW) structures are investigated by using the multiband effective-mass theory and non-Markovian optical model. On vicinal c-plane GaN substrate miscut by a small angle (??

  16. White light generation from Dy{sup 3+}-doped ZnO-B{sub 2}O{sub 3}-P{sub 2}O{sub 5} glasses

    SciTech Connect (OSTI)

    Jayasimhadri, M.; Jang, Kiwan; Lee, Ho Sueb; Chen, Baojiu; Yi, Soung-Soo; Jeong, Jung-Hyun

    2009-07-01

    Dysprosium doped ZnO-B{sub 2}O{sub 3}-P{sub 2}O{sub 5} (ZBP) glasses were prepared by a conventional melt quenching technique in order to study the luminescent properties and their utility for white light emitting diodes (LEDs). X-ray diffraction spectra revealed the amorphous nature of the glass sample. The present glasses were characterized by infrared and Raman spectra to evaluate the vibrational features of the samples. The emission and excitation spectra were reported for the ZBP glasses. Strong blue (484 nm) and yellow (574 nm) emission bands were observed upon various excitations. These two emissions correspond to the {sup 4}F{sub 9/2}->{sup 6}H{sub 15/2} and {sup 4}F{sub 9/2}->{sup 6}H{sub 13/2} transitions of Dy{sup 3+} ions, respectively. Combination of these blue and yellow bands gives white light to the naked eye. First time, it was found that ZnO-B{sub 2}O{sub 3}-P{sub 2}O{sub 5} glasses efficiently emit white light under 400 and 454 nm excitations, which are nearly match with the emissions of commercial GaN blue LEDs and InGaN LED, respectively. CIE chromaticity coordinates also calculated for Dy{sup 3+}: ZBP glasses to evaluate the white light emission.

  17. ZnCuInS/ZnSe/ZnS Quantum Dot-Based Downconversion Light-Emitting Diodes and Their Thermal Effect

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Liu, Wenyan; Zhang, Yu; Ruan, Cheng; Wang, Dan; Zhang, Tieqiang; Feng, Yi; Gao, Wenzhu; Yin, Jingzhi; Wang, Yiding; Riley, Alexis P.; et al

    2015-01-01

    The quantum dot-based light-emitting diodes (QD-LEDs) were fabricated using blue GaN chips and red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. The power efficiencies were measured as 14.0 lm/W for red, 47.1 lm/W for yellow, and 62.4 lm/W for green LEDs at 2.6 V. The temperature effect of ZnCuInS/ZnSe/ZnS QDs on these LEDs was investigated using CIE chromaticity coordinates, spectral wavelength, full width at half maximum (FWHM), and power efficiency (PE). The thermal quenching induced by the increased surface temperature of the device was confirmed to be one of the important factors to decrease power efficiencies while the CIE chromaticity coordinates changed little due to themore » low emission temperature coefficients of 0.022, 0.050, and 0.068 nm/°C for red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. These indicate that ZnCuInS/ZnSe/ZnS QDs are more suitable for downconversion LEDs compared to CdSe QDs.« less

  18. Plasma assisted molecular beam epitaxy growth and effect of varying buffer thickness on the formation of ultra-thin In{sub 0.17}Al{sub 0.83}N/GaN heterostructure on Si(111)

    SciTech Connect (OSTI)

    Chowdhury, Subhra; Biswas, Dhrubes

    2015-02-23

    This work reports on the detailed plasma-assisted molecular beam epitaxy (PAMBE) growth of ultra-thin In{sub 0.17}Al{sub 0.83}N/GaN heterostructures on Si(111) substrate with three different buffer thickness (600?nm, 400?nm, and 200?nm). Growth through critical optimization of growth conditions is followed by the investigation of impact of varying buffer thickness on the formation of ultra-thin 1.5?nm, In{sub 0.17}Al{sub 0.83}N1.25?nm, GaN1.5?nm, In{sub 0.17}Al{sub 0.83}N heterostructure, in terms of threading dislocation (TD) density. Analysis reveals a drastic reduction of TD density from the order 10{sup 10?}cm{sup ?2} to 10{sup 8?}cm{sup ?2} with increasing buffer thickness resulting smooth ultra-thin active region for thick buffer structure. Increasing strain with decreasing buffer thickness is studied through reciprocal space mapping analysis. Surface morphology through atomic force microscopy analysis also supports our study by observing an increase of pits and root mean square value (0.89?nm, 1.2?nm, and 1.45?nm) with decreasing buffer thickness which are resulted due to the internal strain and TDs.

  19. Enhanced optical power of GaN-based light-emitting diode with compound photonic crystals by multiple-exposure nanosphere-lens lithography

    SciTech Connect (OSTI)

    Zhang, Yonghui; Wei, Tongbo, E-mail: tbwei@semi.ac.cn; Xiong, Zhuo; Shang, Liang; Tian, Yingdong; Zhao, Yun; Zhou, Pengyu; Wang, Junxi; Li, Jinmin [Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2014-07-07

    The light-emitting diodes (LEDs) with single, twin, triple, and quadruple photonic crystals (PCs) on p-GaN are fabricated by multiple-exposure nanosphere-lens lithography (MENLL) process utilizing the focusing behavior of polystyrene spheres. Such a technique is easy and economical for use in fabricating compound nano-patterns. The optimized tilted angle is decided to be 26.6 through mathematic calculation to try to avoid the overlay of patterns. The results of scanning electron microscopy and simulations reveal that the pattern produced by MENLL is a combination of multiple ovals. Compared to planar-LED, the light output power of LEDs with single, twin, triple, and quadruple PCs is increased by 14.78%, 36.03%, 53.68%, and 44.85% under a drive current 350?mA, respectively. Furthermore, all PC-structures result in no degradation of the electrical properties. The stimulated results indicate that the highest light extraction efficiency of LED with the clover-shape triple PC is due to the largest scattering effect on propagation of light from GaN into air.

  20. Spectral softening in the X-RAY afterglow of GRB 130925A as predicted by the dust scattering model

    SciTech Connect (OSTI)

    Zhao, Yi-Nan; Shao, Lang, E-mail: lshao@hebtu.edu.cn [Department of Space Science and Astronomy, Hebei Normal University, Shijiazhuang 050024 (China)

    2014-07-01

    Gamma-ray bursts (GRBs) usually occur in a dense star-forming region with a massive circumburst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences and sometimes can dominate the X-ray afterglow. In most of the previous studies, only the Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius of a ? 0.1 ?m) in the diffuse interstellar medium. When the size of the grains may significantly increase, as in a more dense region where GRBs would occur, the RG approximation may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculations to understand the puzzling X-ray afterglow of recently observed GRB 130925A that showed a significant spectral softening. We find that the X-ray scattering scenarios with either AD or RG approximation adopted could well reproduce both the temporal and spectral profile simultaneously. Given the plateau present in the early X-ray light curve, a typical distribution of smaller grains as in the interstellar medium would be suggested for GRB 130925A.

  1. P-doping-free III-nitride high electron mobility light-emitting diodes and transistors

    SciTech Connect (OSTI)

    Li, Baikui; Tang, Xi; Chen, Kevin J.; Wang, Jiannong

    2014-07-21

    We report that a simple metal-AlGaN/GaN Schottky diode is capable of producing GaN band-edge ultraviolet emission at 3.4?eV at a small forward bias larger than ?2?V at room temperature. Based on the surface states distribution of AlGaN, a mature impact-ionization-induced Fermi-level de-pinning model is proposed to explain the underlying mechanism of the electroluminescence (EL) process. By experimenting with different Schottky metals, Ni/Au and Pt/Au, we demonstrated that this EL phenomenon is a universal property of metal-AlGaN/GaN Schottky diodes. Since this light-emitting Schottky diode shares the same active structure and fabrication processes as the AlGaN/GaN high electron mobility transistors, straight-forward and seamless integration of photonic and electronic functional devices has been demonstrated on doping-free III-nitride heterostructures. Using a semitransparent Schottky drain electrode, an AlGaN/GaN high electron mobility light-emitting transistor is demonstrated.

  2. Phonon densities of states and related thermodynamic properties of high temperature ceramics.

    SciTech Connect (OSTI)

    Loong, C.-K.

    1998-08-28

    Structural components and semiconductor devices based on silicon nitride, aluminum nitride and gallium nitride are expected to function more reliably at elevated temperatures and at higher levels of performance because of the strong atomic bonding in these materials. The degree of covalency, lattice specific heat, and thermal conductivity are important design factors for the realization of advanced applications. We have determined the phonon densities of states of these ceramics by the method of neutron scattering. The results provide a microscopic interpretation of the mechanical and thermal properties. Moreover, experimental data of the static, structures, and dynamic excitations of atoms are essential to the validation of interparticle potentials employed for molecular-dynamics simulations of high-temperature properties of multi-component ceramic systems. We present an overview of neutron-scattering investigations of the atomic organization, phonon excitations, as well as calculations of related thermodynamic properties of Si{sub 3}N{sub 4}, {beta}-sialon, AlN and GaN. The results are compared with those of the oxide analogs such as SiO{sub 2} and Al{sub 2}O{sub 3}.

  3. C-H surface diamond field effect transistors for high temperature (400 °C) and high voltage (500 V) operation

    SciTech Connect (OSTI)

    Kawarada, H.; Tsuboi, H.; Naruo, T.; Yamada, T.; Xu, D.; Daicho, A.; Saito, T.; Hiraiwa, A.

    2014-07-07

    By forming a highly stable Al{sub 2}O{sub 3} gate oxide on a C-H bonded channel of diamond, high-temperature, and high-voltage metal-oxide-semiconductor field-effect transistor (MOSFET) has been realized. From room temperature to 400 °C (673 K), the variation of maximum drain-current is within 30% at a given gate bias. The maximum breakdown voltage (V{sub B}) of the MOSFET without a field plate is 600 V at a gate-drain distance (L{sub GD}) of 7 μm. We fabricated some MOSFETs for which V{sub B}/L{sub GD} > 100 V/μm. These values are comparable to those of lateral SiC or GaN FETs. The Al{sub 2}O{sub 3} was deposited on the C-H surface by atomic layer deposition (ALD) at 450 °C using H{sub 2}O as an oxidant. The ALD at relatively high temperature results in stable p-type conduction and FET operation at 400 °C in vacuum. The drain current density and transconductance normalized by the gate width are almost constant from room temperature to 400 °C in vacuum and are about 10 times higher than those of boron-doped diamond FETs.

  4. Electron effective mass in Al{sub 0.72}Ga{sub 0.28}N alloys determined by mid-infrared optical Hall effect

    SciTech Connect (OSTI)

    Schöche, S. Kühne, P.; Hofmann, T.; Schubert, M.; Nilsson, D.; Kakanakova-Georgieva, A.; Janzén, E.; Darakchieva, V.

    2013-11-18

    The effective electron mass parameter in Si-doped Al{sub 0.72}Ga{sub 0.28}N is determined to be m{sup ∗}=(0.336±0.020) m{sub 0} from mid-infrared optical Hall effect measurements. No significant anisotropy of the effective electron mass parameter is found supporting theoretical predictions. Assuming a linear change of the effective electron mass with the Al content in AlGaN alloys and m{sup ∗}=0.232 m{sub 0} for GaN, an average effective electron mass of m{sup ∗}=0.376 m{sub 0} can be extrapolated for AlN. The analysis of mid-infrared spectroscopic ellipsometry measurements further confirms the two phonon mode behavior of the E{sub 1}(TO) and one phonon mode behavior of the A{sub 1}(LO) phonon mode in high-Al-content AlGaN alloys as seen in previous Raman scattering studies.

  5. Methods for improved growth of group III nitride buffer layers

    DOE Patents [OSTI]

    Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

    2014-07-15

    Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).

  6. Microwave to millimeter-wave electrodynamic response and applications of semiconductor nanostructures: LDRD project 67025 final report.

    SciTech Connect (OSTI)

    Shaner, Eric Arthur; Lee, Mark; Averitt, R. D. (Los Alamos National Laboratory); Highstrete, Clark; Taylor, A. J.; Padilla, W. J. (Los Alamos National Laboratory); Reno, John Louis; Wanke, Michael Clement; Allen, S. James (University of California Santa Barbara)

    2006-11-01

    Solid-state lighting (SSL) technologies, based on semiconductor light emitting devices, have the potential to reduce worldwide electricity consumption by more than 10%, which could significantly reduce U.S. dependence on imported energy and improve energy security. The III-nitride (AlGaInN) materials system forms the foundation for white SSL and could cover a wide spectral range from the deep UV to the infrared. For this LDRD program, we have investigated the synthesis of single-crystalline III-nitride nanowires and heterostructure nanowires, which may possess unique optoelectronic properties. These novel structures could ultimately lead to the development of novel and highly efficient SSL nanodevice applications. GaN and III-nitride core-shell heterostructure nanowires were successfully synthesized by metal organic chemical vapor deposition (MOCVD) on two-inch wafer substrates. The effect of process conditions on nanowire growth was investigated, and characterization of the structural, optical, and electrical properties of the nanowires was also performed.

  7. Microsoft PowerPoint - To NETL Albany Site from Eugene, Oregon...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Eugene, Oregon Airport 1. From the EUGENE AIRPORT take HWY 99 (the airport is located off Hwy 99). 2. Follow HWY 99 NORTH from EUGENE to ALBANY. 3. Outside of EUGENE, HWY 99 splits...

  8. Directions to Berkeley Lab

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Joint Genome Institute (JGI) San Francisco Bay Area Transit Information San Francisco Airport to the Lab by car San Francisco Airport to the Lab by BART San Francisco Airport to...

  9. Alternative Fuels Data Center

    Alternative Fuels and Advanced Vehicles Data Center [Office of Energy Efficiency and Renewable Energy (EERE)]

    Airport Zero Emission Vehicle (ZEV) and Infrastructure Incentives The Zero Emissions Airport Vehicle and Infrastructure Pilot Program provides funding to airports for up to 50% of the cost to acquire ZEVs and install or modify supporting infrastructure for acquired vehicles. Grant funding must be used for airport-owned, on-road vehicles used exclusively for airport purposes. Vehicles and infrastructure must meet the Federal Aviation Administration's Airport Improvement Program requirements,

  10. Visiting NETL Albany, Morgantown or Pittsburgh | netl.doe.gov

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Albany GPS Coordinates: 44.623157,-123.120658 Hotel Locations Restaurant Locations Eugene Airport to NETL Albany Site Portland International Airport to NETL Albany Site Morgantown...

  11. Transportation Resources | Advanced Photon Source

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Transportation Resources The following means of transportation are available for getting to Argonne. Airports Argonne is located within 25 miles of two major Chicago airports:...

  12. Microsoft Word - MARK YOUR CALENDARS_REV3.doc

    Office of Environmental Management (EM)

    (Group Code: tecteca) SuperShuttle Minneapolis - St. Paul (MSP) offers airport shuttle service to and from MSP International Airport. Approximate fares to the...

  13. SRI2007 Conference - Travel Tips

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Getting to the Hilton Baton Rouge Capitol Center: From the Baton Rouge Metropolitan Airport (BTR) From the New Orleans International Airport (MSY) Shuttles to and from the Baton...

  14. Superfund record of decision (EPA Region 7): St. Louis Airport/HHS/Futura Coatings Co. , St. Louis County, MO, August 27, 1998

    SciTech Connect (OSTI)

    Not Available

    1999-03-01

    This document presents the selected remedial action for the cleanup of wastes related to Manhattan Engineering District/Atomic Energy Commission (MED/AEC) operations in accessible soils and ground water at the St. Louis Downtown Site (SLDS). The main components of the selected remedial action include: Excavation and off-site disposal of approximately 65,000 cubic meters (85,000 cubic yards) (in-situ) contaminated soil; and No remedial action is required for ground water beneath the site. Perimeter monitoring of the ground water in the Mississippi River alluvial aquifer, designated as the hydrostratigraphic B Unit, will be performed and the need for ground water remediation will be evaluated as part of the periodic reviews performed for the site.

  15. Preliminary assessment report for Grubbs/Kyle Training Center, Smyrna/Rutherford County Regional Airport, Installation 47340, Smyrna, Tennessee. Installation Restoration Program

    SciTech Connect (OSTI)

    Dennis, C.; Stefano, J.

    1993-07-01

    This report presents the results of the preliminary assessment (PA) conducted by Argonne National Laboratory at the Tennessee Army National Guard (TNARNG) property near Smyrna, Tennessee. Preliminary assessments of federal facilities are being conducted to compile the information necessary for completing preremedial activities and to provide a basis for establishing corrective actions in response to releases of hazardous substances. The principal objective of the PA is to characterize the site accurately and determine the need for further action by examining site activities, quantities of hazardous substances present, and potential pathways by which contamination could affect public health and the environment. This PA satisfies, for the Grubbs/Kyle Training Center property, the requirement of the Department of Defense Installation Restoration Program.

  16. GaN-Ready Aluminum Nitride Substrates for Cost-Effective, Very Low Dislocation Density III-Nitride LED's

    SciTech Connect (OSTI)

    Sandra Schujman; Leo Schowalter

    2010-10-15

    The objective of this project was to develop and then demonstrate the efficacy of a costeffective approach for a low defect density substrate on which AlInGaN LEDs can be fabricated. The efficacy of this GaN-ready substrate would then be tested by growing high efficiency, long lifetime InxGa1-xN blue LEDs. The approach used to meet the project objectives was to start with low dislocation density AlN single-crystal substrates and grow graded AlxGa1-xN layers on top. Pseudomorphic AlxGa1-xN epitaxial layers grown on bulk AlN substrates were used to fabricate light emitting diodes and demonstrate better device performance as a result of the low defect density in these layers when benched marked against state-of-the-art LEDs fabricated on sapphire substrates. The pseudomorphic LEDs showed excellent output powers compared to similar wavelength devices grown on sapphire substrates, with lifetimes exceeding 10,000 hours (which was the longest time that could reliably be estimated). In addition, high internal quantum efficiencies were demonstrated at high driving current densities even though the external quantum efficiencies were low due to poor photon extraction. Unfortunately, these pseudomorphic LEDs require high Al content so they emit in the ultraviolet. Sapphire based LEDs typically have threading dislocation densities (TDD) > 108 cm-2 while the pseudomorphic LEDs have TDD ? 105 cm-2. The resulting TDD, when grading the AlxGa1-xN layer all the way to pure GaN to produce a GaN-ready substrate, has varied between the mid 108 down to the 106 cm-2. These inconsistencies are not well understood. Finally, an approach to improve the LED structures on AlN substrates for light extraction efficiency was developed by thinning and roughening the substrate.

  17. High efficiency, radiation-hard solar cells

    SciTech Connect (OSTI)

    Ager III, J.W.; Walukiewicz, W.

    2004-10-22

    The direct gap of the In{sub 1-x}Ga{sub x}N alloy system extends continuously from InN (0.7 eV, in the near IR) to GaN (3.4 eV, in the mid-ultraviolet). This opens the intriguing possibility of using this single ternary alloy system in single or multi-junction (MJ) solar cells of the type used for space-based surveillance satellites. To evaluate the suitability of In{sub 1-x}Ga{sub x}N as a material for space applications, high quality thin films were grown with molecular beam epitaxy and extensive damage testing with electron, proton, and alpha particle radiation was performed. Using the room temperature photoluminescence intensity as a indirect measure of minority carrier lifetime, it is shown that In{sub 1-x}Ga{sub x}N retains its optoelectronic properties at radiation damage doses at least 2 orders of magnitude higher than the damage thresholds of the materials (GaAs and GaInP) currently used in high efficiency MJ cells. This indicates that the In{sub 1-x}Ga{sub x}N is well-suited for the future development of ultra radiation-hard optoelectronics. Critical issues affecting development of solar cells using this material system were addressed. The presence of an electron-rich surface layer in InN and In{sub 1-x}Ga{sub x}N (0 < x < 0.63) was investigated; it was shown that this is a less significant effect at large x. Evidence of p-type activity below the surface in Mg-doped InN was obtained; this is a significant step toward achieving photovoltaic action and, ultimately, a solar cell using this material.

  18. Optical characterization of free electron concentration in heteroepitaxial InN layers using Fourier transform infrared spectroscopy and a 2 Multiplication-Sign 2 transfer-matrix algebra

    SciTech Connect (OSTI)

    Katsidis, C. C.; Ajagunna, A. O.; Georgakilas, A.

    2013-02-21

    Fourier Transform Infrared (FTIR) reflectance spectroscopy has been implemented as a non-destructive, non-invasive, tool for the optical characterization of a set of c-plane InN single heteroepitaxial layers spanning a wide range of thicknesses (30-2000 nm). The c-plane (0001) InN epilayers were grown by plasma-assisted molecular beam epitaxy (PAMBE) on GaN(0001) buffer layers which had been grown on Al{sub 2}O{sub 3}(0001) substrates. It is shown that for arbitrary multilayers with homogeneous anisotropic layers having their principal axes coincident with the laboratory coordinates, a 2 Multiplication-Sign 2 matrix algebra based on a general transfer-matrix method (GTMM) is adequate to interpret their optical response. Analysis of optical reflectance in the far and mid infrared spectral range has been found capable to discriminate between the bulk, the surface and interface contributions of free carriers in the InN epilayers revealing the existence of electron accumulation layers with carrier concentrations in mid 10{sup 19} cm{sup -3} at both the InN surface and the InN/GaN interface. The spectra could be fitted with a three-layer model, determining the different electron concentration and mobility values of the bulk and of the surface and the interface electron accumulation layers in the InN films. The variation of these values with increasing InN thickness could be also sensitively detected by the optical measurements. The comparison between the optically determined drift mobility and the Hall mobility of the thickest sample reveals a value of r{sub H} = 1.49 for the Hall factor of InN at a carrier concentration of 1.11 Multiplication-Sign 10{sup 19} cm{sup -3} at 300 Degree-Sign {Kappa}.

  19. State selective dynamics of molecules, clusters, and nanostructures

    SciTech Connect (OSTI)

    Keto, John W.

    2005-06-01

    Early objectives of this grant were: (1) Measure two-photon excitation of even parity excitons in liquid an solid xenon, (2) Study state-to-state energy transver between two-photon laser excited states or rare-gas atoms to other rare has atoms, (3) study reactive half-collisions between xenon and chlorine leading to the XeCl* B state, (4) measure the spectra of ro-vibrational states of cluster ions and radicals formed in high-pressure discharges and to study their dynamics, (5) measure the surface and bulk electronic states of nanoparticles produced by a unique method of synthesis--laser ablation of microspheres (LAM). Using near-field and microluminescence techniques, we obtained spectra of single nanocrystals to compare with spectra obtained in a supersonic jet apparatus using resonance excitation followed by photoionization (REMPI) with time-of-flight mass analysis. These materials combine the functional advantages obtained from the size-tunable properties of nanocomposite materials with the fabrication and direct-write advantages of NPs manufactured by LAM. We demostrated that CdSe nanoparticles produced by LAM were efficiient fluorescers, even when deposited dry on sapphire substrates. Si nanoparticles were fluorescent when captured in ethylene glycol. We also obtiained efficient fluorescence from Er doped phosphate glass nanopartiicles which have application to gain wafeguides in integrated optics or to nanoslush lasers. We used a femptosecond laser to study the nonlinear spectra of NC composites. We are currently measuring fluorescence and second and third-order susceptibilities of composites of Ag, Si, and GaN nanoparticles encapsulated within thin films of sapphire or SiO 2.

  20. Modulating dual-wavelength multiple quantum wells in white light emitting diodes to suppress efficiency droop and improve color rendering index

    SciTech Connect (OSTI)

    Zhao, Yukun; Wang, Shuai; Zheng, Min; Ding, Wen; Yun, Feng; Su, Xilin; Yang, Xiangrong; Liu, Shuo; Guo, Maofeng; Zhang, Ye

    2015-10-14

    In this paper, gallium nitride (GaN) based white light-emitting diodes (WLEDs) with modulated quantities of blue (In{sub 0.15}Ga{sub 0.85}N) quantum wells (QWs) and cyan QWs (In{sub 0.18}Ga{sub 0.82}N) in multiple QW (MQW) structures have been investigated numerically and experimentally. It is demonstrated that the optical performance of LEDs is sensitive to the quantities of cyan QWs in dual-wavelength MQW structures. Compared to the LEDs with respective 0, 4, and 8 cyan QWs (12 QWs in total), the optical performance of the sample with 6 cyan QWs is the best. The deterioration of the optical performance in the sample with less (4 pairs) cyan QWs or more (8 pairs) cyan QWs than 6 cyan QWs may be ascribed to weakened reservoir effect or more defects induced. Compared to conventional blue LEDs (12 blue QWs), the sample with 6 cyan QWs could effectively suppress the efficiency droop (the experimental droop ratio decreases from 50.3% to 39.5% at 80 A/cm{sup 2}) and significantly improve the color rendering index (CRI, increases from 66.4 to 77.0) simultaneously. We attribute the droop suppression to the strengthened reservoir effect and carrier confinement of deeper QWs (higher indium composition) incorporated in the dual-wavelength MQW structures, which lead to the better hole spreading and enhanced radiative recombination. Meanwhile, the remarkable experimental CRI improvement may result from the wider full-width at half-maximum of electroluminescence spectra and higher cyan intensity in WLED chips with dual-wavelength MQW structures.

  1. Controlling potential barrier height by changing V-shaped pit size and the effect on optical and electrical properties for InGaN/GaN based light-emitting diodes

    SciTech Connect (OSTI)

    Okada, Narihito Kashihara, Hiroyuki; Sugimoto, Kohei; Yamada, Yoichi; Tadatomo, Kazuyuki

    2015-01-14

    The internal quantum efficiency (IQE) of InGaN/GaN multiple quantum wells (MQWs) with blue light emission was improved by inserting an InGaN/GaN superlattice (SL) beneath the MQWs. While the SL technique is useful for improving the light-emitting diode (LED) performance, its effectiveness from a multilateral point of view requires investigation. V-shaped pits (V-pits), which generate a potential barrier and screen the effect of the threading dislocation, are one of the candidates for increasing the light emission efficiency of LEDs exceptionally. In this research, we investigated the relationship between the V-pit and SL and revealed that the V-pit diameter is strongly correlated with the IQE by changing the number of SL periods. Using scanning near-field optical microscopy and photoluminescence measurements, we demonstrated the distinct presence of the potential barrier formed by the V-pits around the dislocations. The relationship between the V-pit and the number of SL periods resulted in changing the potential barrier height, which is related to the V-pit diameter determined by the number of SL periods. In addition, we made an attempt to insert pit expansion layers (PELs) composed of combination of SL and middle temperature grown GaN layer instead of only SL structure. As a result of the evaluation of LEDs using SL or PEL, the EL intensity was strongly related to pit diameter regardless of the structures to form the V-pits. In addition, it was clear that larger V-pits reduce the efficiency droop, which is considered to be suppression of the carrier loss at high injection current.

  2. Analytical modeling of localized surface plasmon resonance in heterostructure copper sulfide nanocrystals

    SciTech Connect (OSTI)

    Caldwell, Andrew H.; Ha, Don-Hyung; Robinson, Richard D.; Ding, Xiaoyue

    2014-10-28

    Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals is a relatively new field of investigation that promises greater tunability of plasmonic properties compared to metal nanoparticles. A novel process by which the LSPR in semiconductor nanocrystals can be altered is through heterostructure formation arising from solution-based cation exchange. Herein, we describe the development of an analytical model of LSPR in heterostructure copper sulfide-zinc sulfide nanocrystals synthesized via a cation exchange reaction between copper sulfide (Cu{sub 1.81}S) nanocrystals and Zn ions. The cation exchange reaction produces dual-interface, heterostructure nanocrystals in which the geometry of the copper sulfide phase can be tuned from a sphere to a thin disk separating symmetrically-grown sulfide (ZnS) grains. Drude model electronic conduction and Mie-Gans theory are applied to describe how the LSPR wavelength changes during cation exchange, taking into account the morphology evolution and changes to the local permittivity. The results of the modeling indicate that the presence of the ZnS grains has a significant effect on the out-of-plane LSPR mode. By comparing the results of the model to previous studies on solid-solid phase transformations of copper sulfide in these nanocrystals during cation exchange, we show that the carrier concentration is independent of the copper vacancy concentration dictated by its atomic phase. The evolution of the effective carrier concentration calculated from the model suggests that the out-of-plane resonance mode is dominant. The classical model was compared to a simplified quantum mechanical model which suggested that quantum mechanical effects become significant when the characteristic size is less than ∼8 nm. Overall, we find that the analytical models are not accurate for these heterostructured semiconductor nanocrystals, indicating the need for new model development for this emerging field.

  3. Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

    SciTech Connect (OSTI)

    Hu, J. Groeseneken, G.; Stoffels, S.; Lenci, S.; Venegas, R.; Decoutere, S.; Bakeroot, B.

    2015-02-23

    This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5?V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ?{sub B} increase) together with R{sub ON} degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

  4. Atomic structure of defects in GaN:Mg grown with Ga polarity

    SciTech Connect (OSTI)

    Liliental-Weber, Z.; Tomaszewicz, T.; Zakharov, D.; Jasinski, J.; O'Keefe, M.A.; Hautakangas, S.; Laakso, A.; Saarinen, K.

    2003-11-25

    Electron microscope phase images, produced by direct reconstruction of the scattered electron wave from a focal series of high-resolution images, were used to determine the nature of defects formed in GaN:Mg crystals. We studied bulk crystals grown from dilute solutions of atomic nitrogen in liquid gallium at high pressure and thin films grown by the MOCVD method. All the crystals were grown with Ga-polarity. In both types of samples the majority of defects were three dimensional Mg-rich hexagonal pyramids with bases on the (0001) plane and six walls on {l_brace}11{und 2}3{r_brace} planes seen in cross-section as triangulars. Some other defects appear in cross-section as trapezoidal (rectangular) defects as a result of presence of truncated pyramids. Both type of defects have hollow centers. They are decorated by Mg on all six side walls and a base. The GaN which grows inside on the defect walls shows polarity inversion. It is shown that change of polarity starts from the defect tip and propagates to the base, and that the stacking sequence changes from ab in the matrix to bc inside the defect. Exchange of the Ga sublattice with the N sublattice within the defect leads to 0.6 {+-} 0.2{angstrom} displacement between Ga sublattices outside and inside the defects. It is proposed that lateral overgrowth of the cavities formed within the defect takes place to restore matrix polarity on the defect base.

  5. Impact of photonic crystals on LED light extraction efficiency: approaches and limits to vertical structure designs

    SciTech Connect (OSTI)

    Matioli, Elison; Weisbuch, Claude

    2010-08-19

    The enhancement of the extraction efficiency in light emitting diodes (LEDs) through the use of photonic crystals (PhCs) requires a structure design that optimizes the interaction of the guided modes with the PhCs. The main optimization parameters are related to the vertical structure of the LED, such as the thickness of layers, depth of the PhCs, position of the quantum wells as well as the PhC period and fill factor. We review the impact of the vertical design of different approaches of PhC LEDs through a theoretical and experimental standpoint, assessing quantitatively the competing mechanisms that act over each guided mode. Three approaches are described to overcome the main limitation of LEDs with surface PhCs, i.e. the insufficient interaction of low order guided modes with the PhCs. The introduction of an AlGaN confining layer in such structure is shown to be effective in extracting a fraction of the optical energy of low order modes; however, this approach is limited by the growth of the lattice mismatched AlGaN layer on GaN. The second approach, based on thin-film LEDs with PhCs, is limited by the presence of an absorbing reflective metal layer close to the guided modes that plays a major role in the competition between PhC extraction and metal dissipation. Finally, we demonstrate both experimentally and theoretically the superior extraction of the guided light in embedded PhC LEDs due to the higher interaction between all optical modes and the PhCs, which resulted in a close to unity extraction efficiency for this device. The use of high-resolution angle-resolved measurements to experimentally determine the PhC extraction parameters was an essential tool for corroborating the theoretical models and quantifying the competing absorption and extraction mechanisms in LEDs.

  6. Sandia National Laboratories: MTEM 2014: Malware Technical Exchange

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Meeting: Registration Hotels in Albuquerque ABQ Marriott ABQ Marriott Pyramid North Andaluz Hotel (downtown ABQ) Candlewood Suites ABQ Courtyard Albuquerque Airport Embassy Suites ABQ Hilton Garden Inn Uptown Hyatt Place Uptown Residence Inn Airport

  7. EERE Blog | Department of Energy

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    10, 2015 World's First Fuel Cell Cargo Trucks Deployed at U.S. Airport A ribbon-cutting ceremony held at Memphis International Airport on April 9, 2015 marked the start of a...

  8. Traveling to Princeton (NEW) - Combustion Energy Frontier Research...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    may take a van shuttle service http:olympic-limo.com or 1-800-822-9797. From Newark Airport, the fare is 40one way. From Philadelphia International Airport, the fare is 89...

  9. EA-1823: Draft Environmental Assessment | Department of Energy

    Broader source: Energy.gov (indexed) [DOE]

    Time: 4 p.m. to 7 p.m. Location: Auditorium at the Offices of the Greater Rockford Airport Authority, 60 Airport Drive, Rockford, Illinois, 61109 DOE's proposed action would...

  10. Microsoft PowerPoint - To NETL Albany Site from Portland, Oregon...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Portland, Oregon Airport (PDX) 1. Take the AIRPORT EXIT RD. until it intersects I-205. 2. Follow I-205 SOUTH for 25 MILES to the intersection with I-5 SOUTH (Salem exit). 3. Follow...

  11. Top 9 Things You Didn't Know about Alternative Fuel Vehicles...

    Energy Savers [EERE]

    Alternative Fuel Vehicles Top 9 Things You Didn't Know about Alternative Fuel Vehicles October 12, 2012 - 3:04pm Addthis Denver International Airport is one of many airports across ...

  12. City of Dallas- Green Energy Purchasing

    Office of Energy Efficiency and Renewable Energy (EERE)

    Furthermore, the Dallas/Fort Worth International Airport is the highest-ranked airport for renewable energy use, separately ranking 7th on the Green Power Partner listing of local government gree...

  13. Logistics | U.S. DOE Office of Science (SC)

    Office of Science (SC) Website

    Logistics Basic Energy Sciences Advisory Committee (BESAC) BESAC Home Meetings Meeting Presentations History Logistics BESAC 2016-2017 Membership Charges/Reports Charter .pdf file (128KB) BES Committees of Visitors Federal Advisory Committees BES Home Meetings Logistics Print Text Size: A A A FeedbackShare Page Transportation Airport Directions and Services Ronald Reagan (National) Airport External link Baltimore-Washington International Airport (BWI) External link Dulles International Airport

  14. EA-2000: Draft Environmental Assessment

    Office of Energy Efficiency and Renewable Energy (EERE)

    Proposed Land Transfer to Develop a General Aviation Airport at the East Tennessee Technology Park Heritage Center, Oak Ridge, Tennessee

  15. EA-1515: Finding of No Significant Impact

    Office of Energy Efficiency and Renewable Energy (EERE)

    Proposed Closure of the Airport Landfills Within Technical Area 73 at Los Alamos National Laboratory, Los Alamos, New Mexico

  16. Browse by Discipline -- E-print Network Subject Pathways: Mathematics...

    Office of Scientific and Technical Information (OSTI)

    Services Program Massachusetts Institute of Technology (MIT),Department of Civil and Environmental Engineering, Airport Systems Planning, Design, and Management ...

  17. EA-1515: Final Environmental Assessment

    Broader source: Energy.gov [DOE]

    Proposed Closure of the Airport Landfills Within Technical Area 73 at Los Alamos National Laboratory, Los Alamos, New Mexico

  18. EERE Success Story-World's First Fuel Cell Cargo Trucks Deployed at

    Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

    Memphis International Airport | Department of Energy Fuel Cell Cargo Trucks Deployed at Memphis International Airport EERE Success Story-World's First Fuel Cell Cargo Trucks Deployed at Memphis International Airport June 25, 2015 - 1:57pm Addthis EERE Success Story—World's First Fuel Cell Cargo Trucks Deployed at Memphis International Airport Thanks to R&D funding from the Energy Department's Fuel Cell Technologies Office (FCTO), the Federal Express Hub at the Memphis International

  19. EA-2000: Final Environmental Assessment

    Broader source: Energy.gov [DOE]

    Proposed Land Transfer to Develop a General Aviation Airport at the East Tennessee Technology Park Heritage Center, Oak Ridge, Tennessee

  20. DOE Recognizes EM Richland Operations Office Employees for Excellence in

    Energy Savers [EERE]

    International Airport | Department of Energy Mast Lighting at Philadelphia International Airport DOE Publishes GATEWAY Report on High-Mast Lighting at Philadelphia International Airport November 10, 2015 - 5:02pm Addthis The U.S. Department of Energy's GATEWAY program has released a report on a trial installation of LED apron lighting at Philadelphia International Airport (PHL). In addition to reducing energy, PHL also hoped to reduce required maintenance, reduce light pollution, and