Sample records for gan airport gan

  1. GaN nanowires show more 3D piezoelectricity than bulk GaN

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    Logo GaN nanowires show more 3D piezoelectricity than bulk GaN admin / January 11, 2012 individual gallium nitride (GaN) nanowires showing strong piezoelectric effect in 3D. This is in spite of the fact that each nanowire only measures 100nm in diameter. While GaN is ubiquitous in optoelectronic

  2. Invited Paper GaN HEMT reliability

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Invited Paper GaN HEMT reliability J.A. del Alamo *, J. Joh Microsystems Technology Laboratories mechanism recently identified in GaN high-electron mobility transistors subject to electrical stress. Under high voltage, it has been found that electrically active defects are generated in the AlGaN barrier

  3. Nanoair-bridged lateral overgrowth of GaN on ordered nanoporous GaN template

    SciTech Connect (OSTI)

    Wang, Y.D.; Zang, K.Y.; Chua, S.J.; Tripathy, S.; Chen, P.; Fonstad, C.G. [Singapore-MIT Alliance, E4-04-10, 4 Engineering Drive 3, Singapore 117576 (Singapore) and Centre for Optoelectronics, Department of Electrical and Computer Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore); Department of Electrical and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2005-12-19T23:59:59.000Z

    We report the growth of high-quality GaN epilayers on an ordered nanoporous GaN template by metalorganic chemical vapor deposition. The nanopores in GaN template were created by inductively coupled plasma etching using anodic aluminum oxide film as an etch mask. The average pore diameter and interpore distance is about 65 and 110 nm, respectively. Subsequent overgrowth of GaN first begins at the GaN crystallite surface between the pores, and then air-bridge-mediated lateral overgrowth leads to the formation of the continuous layer. Microphotoluminescence and micro-Raman measurements show improved optical properties and significant strain relaxation in the overgrown layer when compared to GaN layer of same thickness simultaneously grown on sapphire without any template. Similar to conventional epitaxial lateral overgrown GaN, such overgrown GaN on a nanopatterned surface would also serve as a template for the growth of ultraviolet-visible light-emitting III-nitride devices.

  4. Degradation mechanisms of GaN high electron mobility transistors

    E-Print Network [OSTI]

    Joh, Jungwoo

    2007-01-01T23:59:59.000Z

    In spite of their extraordinary performance, GaN high electron mobility transistors (HEMT) have still limited reliability. In RF power applications, GaN HEMTs operate at high voltage where good reliability is essential. ...

  5. GaN Nanopore Arrays: Fabrication and Characterization

    E-Print Network [OSTI]

    Wang, Yadong

    GaN nanopore arrays with pore diameters of approximately 75 nm were fabricated by inductively coupled plasma etching (ICP) using anodic aluminum oxide (AAO) films as etch masks. Nanoporous AAO films were formed on the GaN ...

  6. Rapid Communications Strong piezoelectricity in individual GaN nanowires

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    Rapid Communications Strong piezoelectricity in individual GaN nanowires Majid Minary@northwestern.edu (Received 12 July 2011; accepted 15 September 2011) Abstract GaN nanowires are promising building blocks piezoelectricity in individual single-crystal GaN nanowires revealed by direct measurement of the piezoelectric

  7. GaN Radiation Detectors for Particle Physics and

    E-Print Network [OSTI]

    Glasgow, University of

    GaN Radiation Detectors for Particle Physics and Synchrotron Applications James Paul Grant and monitoring applications. Gallium nitride (GaN) was investigated as a radiation hard particle detector diameter on three epitaxial GaN wafers grown on a sapphire sub- strate. Two of the wafers were obtained

  8. Growth of GaN on porous SiC and GaN substrates C. K. Inoki1

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Growth of GaN on porous SiC and GaN substrates C. K. Inoki1 , T. S. Kuan1 , Ashutosh Sagar2 , C, Albuquerque, NM 87185 4 Beckman Institute, University of Illinois, Urbana, IL 61801 GaN films were grown on porous SiC and GaN templates using both plasma-assisted molecular beam epitaxy (PAMBE) and metal

  9. GaN based nanorods for solid state lighting

    SciTech Connect (OSTI)

    Li Shunfeng; Waag, Andreas [Institute of Semiconductor Technology, Braunschweig University of Technology, 38106 Braunschweig (Germany)

    2012-04-01T23:59:59.000Z

    In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

  10. Amorphization Processes in Au Ion Irradiated GaN at 150 - 300...

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

    Processes in Au Ion Irradiated GaN at 150 - 300 K. Amorphization Processes in Au Ion Irradiated GaN at 150 - 300 K. Abstract: Epitaxial single-crystal gallium nitride (GaN) films...

  11. Damage Evolution in GaN Under MeV Heavy Ion Implantation. | EMSL

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

    Evolution in GaN Under MeV Heavy Ion Implantation. Damage Evolution in GaN Under MeV Heavy Ion Implantation. Abstract: Damage evaluation processes in patterned GaN implanted by 3...

  12. Mapping misorientation and crystallographic tilt in GaN layers via polychromatic microdiffraction

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    coefficients between GaN and the substrate. Understandingpenetrate both the GaN layer and the substrate. Two samplespattern from the GaN layer and the substrate on a charge-

  13. GROWTH OF GaN ON POROUS SiC AND GaN SUBSTRATES C. K. Inoki and T. S. Kuan

    E-Print Network [OSTI]

    Feenstra, Randall

    1 GROWTH OF GaN ON POROUS SiC AND GaN SUBSTRATES C. K. Inoki and T. S. Kuan Department of Physics Institute, University of Illinois, Urbana, IL 61801 ABSTRACT We have studied the growth of GaN on porous SiC and GaN substrates, employing both plasma-assisted molecular beam epitaxy (PAMBE) and metalorganic

  14. P-type doping of GaN

    SciTech Connect (OSTI)

    Wong, R.K.

    2000-04-10T23:59:59.000Z

    After implantation of As, As + Be, and As + Ga into GaN and annealing for short durations at temperatures as high as 1500 C, the GaN films remained highly resistive. It was apparent from c-RBS studies that although implantation damage did not create an amorphous layer in the GaN film, annealing at 1500 C did not provide enough energy to completely recover the radiation damage. Disorder recovered significantly after annealing at temperatures up to 1500 C, but not completely. From SIMS analysis, oxygen contamination in the AIN capping layer causes oxygen diffusion into the GaN film above 1400 C. The sapphire substrate (A1203) also decomposed and oxygen penetrated into the backside of the GaN layer above 1400 C. To prevent donor-like oxygen impurities from the capping layer and the substrate from contaminating the GaN film and compensating acceptors, post-implantation annealing should be done at temperatures below 1500 C. Oxygen in the cap could be reduced by growing the AIN cap on the GaN layer after the GaN growth run or by depositing the AIN layer in a ultra high vacuum (UHV) system post-growth to minimize residual oxygen and water contamination. With longer annealing times at 1400 C or at higher temperatures with a higher quality AIN, the implantation drainage may fully recover.

  15. Free excitons in wurtzite GaN A. V. Rodina*

    E-Print Network [OSTI]

    Nabben, Reinhard

    Free excitons in wurtzite GaN A. V. Rodina* I. Physics Institute, Justus Liebig University in wurtzite GaN. Using polarization-dependent measurements we were able to resolve the fine-structure energy these data a theory is developed for the exciton energy structure in hexagonal semiconductors with wurtzite

  16. New Faces of GaN: Growth, Doping and Devices

    E-Print Network [OSTI]

    California at Santa Barbara, University of

    New Faces of GaN: Growth, Doping and Devices James S. Speck Materials Department University of California Santa Barbara, CA LEO of a-GaN from circular opening Engineering Insights 2006 #12;#12;Personnel. Wraback (ARL) $$$ JST ­ ERATO UCSB SSLDC AFOSR ONR #12;Reversed direction of polarization Bulk GaN

  17. Ga NMR spectra and relaxation in wurtzite GaN M. Corti and A. Gabetta

    E-Print Network [OSTI]

    Svane, Axel Torstein

    69,71 Ga NMR spectra and relaxation in wurtzite GaN M. Corti and A. Gabetta Department of Physics properties of wurtzite GaN are studied by Ga nuclear magnetic resonance NMR in a GaN bulk crystal containing GaN is a wide band-gap semiconductor which crystallizes in the hexagonal wurtzite structure

  18. Structural and electronic properties of Fe3+ in GaN from optical and EPR experiments

    E-Print Network [OSTI]

    Nabben, Reinhard

    into GaN to compensate inherent n-type conductivity and to produce semi-insulating substrate materialStructural and electronic properties of Fe3+ and Fe2+ centers in GaN from optical and EPR, and electronic properties of Fe-doped GaN. A set of high-quality GaN crystals doped with Fe at concentrations

  19. GaN: Defect and Device Issues

    SciTech Connect (OSTI)

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

    1998-11-09T23:59:59.000Z

    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.

  20. ARM - AMIE Gan Island - Data Plots

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del(ANL-IN-03-032)8Li (59AJ76) (See theDoctoral20ALSNewstt^APPLIANCETracerOverviewGan

  1. Optical spectroscopy of cubic GaN in nanowires

    SciTech Connect (OSTI)

    Renard, J. [CEA-CNRS Group 'Nanophysique et semiconducteurs', CEA-Grenoble INAC-SP2M, Institut Neel, CNRS, Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada); Tourbot, G. [CEA-CNRS Group 'Nanophysique et semiconducteurs', CEA-Grenoble INAC-SP2M, Institut Neel, CNRS, Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France); CEA-LETI, MINATEC, 17 rue des Martyrs 38054 Grenoble Cedex 9 (France); Sam-Giao, D.; Bougerol, C.; Daudin, B.; Gayral, B. [CEA-CNRS Group 'Nanophysique et semiconducteurs', CEA-Grenoble INAC-SP2M, Institut Neel, CNRS, Universite Joseph Fourier, 17 rue des Martyrs, 38054 Grenoble (France)

    2010-08-23T23:59:59.000Z

    We show that highly homogeneous cubic GaN can be grown by plasma-assisted molecular beam epitaxy on wurtzite GaN nanowires. The line width of the donor bound exciton is below 3 meV and can reach 1.6 meV in the best parts of the studied sample. This allows to perform a detailed spectroscopy of cubic GaN, and, in particular, to determine the precise spectral positions of the donor bound exciton, the fundamental free exciton and the split-off exciton in a photoluminescence experiment.

  2. Design, characterization, and modeling of GaN based HFETs for millimeter wave and microwave power amplifier applications

    E-Print Network [OSTI]

    Conway, Adam M.

    2006-01-01T23:59:59.000Z

    power GaN electronics thermally resistive substrates,” IEEE400um SiC (Si, GaN, Sapphire, Diamond) substrate 5um Au 50umfree standing GaN or SiC substrates). At room temperature,

  3. TEM-Untersuchungen an GaN basierten Halbleiterheterostrukturen fur

    E-Print Network [OSTI]

    Schubart, Christoph

    TEM-Untersuchungen an GaN basierten Halbleiterheterostrukturen f¨ur optoelektronische Anwendungen . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.1.2 Versetzungen bei Homoapitaxie auf GaN-Substraten . . . . 79 5.2 Versetzungsreduktion durch

  4. Micro Raman Spectroscopy of Annealed Erbium Implanted GaN

    E-Print Network [OSTI]

    Vajpeyi, Agam P.

    Wurtzite GaN epilayers grown by metal organic chemical vapor deposition on sapphire substrates were subsequently ion implanted with Er to a dose of 5×10¹? cm?². The implanted samples were annealed in nitrogen atmosphere ...

  5. Ion-beam-induced chemical disorder in GaN

    SciTech Connect (OSTI)

    Ishimaru, Manabu; Zhang, Yanwen; Weber, William J.

    2009-09-08T23:59:59.000Z

    Atomistic structures of high-energy ion irradiated GaN have been examined using transmission electron microscopy (TEM). Single crystalline GaN substrates were irradiated at cryogenic temperature with 2 MeV Au2+ ions to a fluence of 7.35x1015 Au/cm2. Cross-sectional TEM observations revealed that damaged layers consisting of amorphous and nanocrystalline phases are formed at the surface and buried depth of the as-irradiated GaN substrate. Atomic radial distribution functions of the amorphous/poly-nanocrystalline regions showed that not only heteronuclear Ga-N bonds but also homonuclear Ga-Ga bonds exist within the first coordination shell. It was found that the ratio of heteronuclear-to-homonuclear bonds, i.e., the degree of chemical disorder is different between the surface and buried damaged layers. The alternation of chemical disorder was attributed to the difference in the defect formation processes between these layers.

  6. 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

    2011-04-11T23:59:59.000Z

    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 launches at a rate of eight per day for the duration of the deployment. The increased sonde launches for the entire period matches that of the AMIE-Manus campaign and makes possible a far more robust Variational Analysis forcing data set product for the entire campaign, and thus better capabilities for modeling studies and synergistic research using the data from both AMIE sites.

  7. Thermal evolution of microstructure in ion-irradiated GaN. |...

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

    evolution of microstructure in ion-irradiated GaN. Thermal evolution of microstructure in ion-irradiated GaN. Abstract: The thermal evolution of the microstructure created by...

  8. High Density Single Crystalline GaN Nanodot Arrays Fabricated Using Template-Assisted Selective Growth

    E-Print Network [OSTI]

    Wang, Yadong

    High density, uniform GaN nanodot arrays with controllable size have been synthesized by using template-assisted selective growth. The GaN nanodots with average diameter 40nm, 80nm and 120nm were selectively grown by ...

  9. Damage and Microstructure Evolution in GaN under Au Ion Irradiation...

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

    and Microstructure Evolution in GaN under Au Ion Irradiation. Damage and Microstructure Evolution in GaN under Au Ion Irradiation. Abstract: Damage and microstructure evolution in...

  10. Structural Defects in Laterally Overgrown GaN Layers Grown on Non-polar Substrates

    E-Print Network [OSTI]

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

    2007-01-01T23:59:59.000Z

    Overgrown GaN Layers Grown on Non-polar Substrates Z.in GaN layers grown on polar and non-polar substrates areGaN-based layers, since they are grown heteroepitaxially on foreign substrates (

  11. Raman scattering from defects in GaN: The question of vibrational or electronic scattering mechanism

    E-Print Network [OSTI]

    Nabben, Reinhard

    Raman scattering from defects in GaN: The question of vibrational or electronic scattering on defects in GaN, which appear in the Raman spectra as sharp and intense lines in the low-energy region from into the GaN material. S0163-1829 98 00344-0 I. INTRODUCTION Low-temperature Raman spectra of GaN films grown

  12. Zeeman spectroscopy of the Fe3 center in GaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    vapor deposition grown GaN Ronny Kirste, Ramón Collazo, Gordon Callsen, Markus R. Wagner, Thomas Kure et vapor deposition grown GaN Ronny Kirste,1,a) Ramo´n Collazo,2 Gordon Callsen,1 Markus R. Wagner,1 Thomas in GaN. GaN with Ga- to N-polar junctions was grown on sapphire using an AlN buffer layer. Results from

  13. Piezoelectric polarization associated with dislocations in wurtzite GaN Changchun Shi,a)

    E-Print Network [OSTI]

    Yu, Edward T.

    Piezoelectric polarization associated with dislocations in wurtzite GaN Changchun Shi,a) Peter M axis in wurtzite GaN. It is shown that the polarization field generated by screw components with the c-axis oriented dislocations in wurtzite GaN, and de- scribe the piezoelectric polarization

  14. Determination of wurtzite GaN lattice polarity based on surface reconstruction

    E-Print Network [OSTI]

    Determination of wurtzite GaN lattice polarity based on surface reconstruction A. R. Smith and R. M identify two categories of reconstructions occurring on wurtzite GaN surfaces, the first associated nitride-based devices, epi- taxial growth occurs on the c plane of wurtzite GaN. A key characteristic

  15. Wurtzite GaN Surface Structures Studied by Scanning Tunneling Microscopy and Reflection High Energy

    E-Print Network [OSTI]

    Feenstra, Randall

    Wurtzite GaN Surface Structures Studied by Scanning Tunneling Microscopy and Reflection High Energy studies of the surface reconstructions for both the Ga-face and the N-face of wurtzite GaN films grown a surface phenomenon. Although numerous surface studies of wurtzite GaN have been performed, progress

  16. Inversion of wurtzite GaN(0001) by exposure to V. Ramachandran and R. M. Feenstra

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Inversion of wurtzite GaN(0001) by exposure to magnesium V. Ramachandran and R. M. Feenstra 15213 Abstract Magnesium incorporation during the molecular beam epitaxy growth of wurtzite GaN is found important. Most devices are built on the polar basal plane of wurtzite GaN, and the characteristics

  17. Ab initio prediction of GaN ,,1010... and ,,110... anomalous surface relaxation John E. Jaffe

    E-Print Network [OSTI]

    Pandey, Ravi

    Ab initio prediction of GaN ,,101¯0... and ,,110... anomalous surface relaxation John E. Jaffe Received 22 September 1995 The results of a study of the surface relaxation of GaN in the framework is minimized the Ga-N surface bonds show a very small rotation angle of about 6° accompanied by a reduction

  18. Temperature and pressure dependence of Mg local modes in GaN G. Kaczmarczyk,a)

    E-Print Network [OSTI]

    Nabben, Reinhard

    Temperature and pressure dependence of Mg local modes in GaN G. Kaczmarczyk,a) A. Kaschner, A in the hexagonal modification of GaN was studied within a valence-force model. The contribution caused by thermal the shift of the GaN host modes. © 2001 American Institute of Physics. DOI: 10.1063/1.1339848 Doped III

  19. Stress analysis of selective epitaxial growth of GaN Q. K. K. Liua)

    E-Print Network [OSTI]

    Nabben, Reinhard

    Stress analysis of selective epitaxial growth of GaN Q. K. K. Liua) Bereich Theoretische Physik Stress distributions in selectively overgrown self-organized GaN hexagonal pyramids have been analyzed in the literature and an effective lattice mismatch between the GaN and the substrate that was determined from

  20. Band gap changes of GaN shocked to 13 GPa M. D. McCluskeya)

    E-Print Network [OSTI]

    McCluskey, Matthew

    Band gap changes of GaN shocked to 13 GPa M. D. McCluskeya) and Y. M. Gupta Institute for Shock, California 94304 Received 24 October 2001; accepted for publication 19 December 2001 The band gap of GaN in shock-wave experiments. Shock waves were generated by impacting the GaN samples with c-cut sapphire

  1. Indium-induced changes in GaN,,0001... surface morphology John E. Northrup

    E-Print Network [OSTI]

    Indium-induced changes in GaN,,0001... surface morphology John E. Northrup Xerox Palo Alto Research-principles calculations of the energetics of the In-terminated GaN 0001 , (0001), (1011), and (1011) surfaces indicate- retical studies to determine the behavior of In on GaN sur- faces. The term surfactant is used often

  2. Large atomic displacements associated with the nitrogen antisite in GaN T. Mattila*

    E-Print Network [OSTI]

    Large atomic displacements associated with the nitrogen antisite in GaN T. Mattila* Laboratory of an extensive theoretical study of the nitrogen antisite in GaN. The neutral antisite in c-GaN is reported the nitrogen antisite and the yellow luminescence commonly observed in GaN is discussed. S0163-1829 96 05824

  3. LA TECHNOLOGIE GAN ET SES APPLICATIONS POUR L'ELECTRONIQUE ROBUSTE, HAUTE FREQUENCE ET DE

    E-Print Network [OSTI]

    Boyer, Edmond

    technologies carbure de silicium (SiC) et nitrure de gallium (GaN) possèdent des qualités intrinsèques réalisation de dispositifs optiques (GaN et alliages InP, Al, P), ce qui autorise un spectre d'applications du visible aux ultraviolets, en émission et en détection : le matériau GaN est le seul qui puisse prétendre à

  4. Photoconduction studies on GaN nanowire transistors under UV and polarized UV illumination

    E-Print Network [OSTI]

    Zhou, Chongwu

    Photoconduction studies on GaN nanowire transistors under UV and polarized UV illumination Song Han carried out with single crystal GaN nanowires. The nanowire transistors exhibited a sub- stantial increase was demonstrated and studied for GaN nanowires working as polarized UV detectors. The nanowire conductance varied

  5. Porous GaN nanowires synthesized using thermal chemical vapor deposition

    E-Print Network [OSTI]

    Kim, Bongsoo

    Porous GaN nanowires synthesized using thermal chemical vapor deposition Seung Yong Bae a , Hee Won 2003 Abstract Porous structured GaN nanowires were synthesized with a large scale by chemical vapor to 1 mm. The porous GaN nanowires consist of the wurtzite single crystal grown with the [0 1 1

  6. Properties of GaN and ZnO Quantum Dots

    E-Print Network [OSTI]

    CHAPTER 3 Properties of GaN and ZnO Quantum Dots Vladimir A. Fonoberov, Alexander A. Balandin Nano. GaN Quantum Dots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 2.1. Electron and Hole States in Strained Wurtzite and Zincblende GaN Quantum Dots

  7. CO-IMPLANTATION AND DRY-ETCH DAMAGE RECOVERY BY PLASMA NITRIDATION IN GaN

    E-Print Network [OSTI]

    Pearton, Stephen J.

    CO-IMPLANTATION AND DRY-ETCH DAMAGE RECOVERY BY PLASMA NITRIDATION IN GaN BY DONALD G. KENT III ............................................................................ x CHAPTERS 1 INTRODUCTION ................................................................. 1 1.1 GaN Applications ........................................................ 1 1.2 GaN Material Issues

  8. Watching GaN Nanowires Grow Eric A. Stach,*, Peter J. Pauzauskie, Tevye Kuykendall,

    E-Print Network [OSTI]

    Yang, Peidong

    Watching GaN Nanowires Grow Eric A. Stach,*, Peter J. Pauzauskie, Tevye Kuykendall, Joshua of the growth of GaN nanowires via a self-catalytic vapor-liquid-solid (VLS) mechanism. High temperature thermal decomposition of GaN in a vacuum yields nanoscale Ga liquid droplets and gallium/nitrogen vapor species

  9. A conductivity-based selective etching for next generation GaN devices

    E-Print Network [OSTI]

    Cao, Hui

    A conductivity-based selective etching for next generation GaN devices Yu Zhang 1 , Sang-Wan Ryu 2 etching having large selectivity based on the conductivity of n-type GaN was investigated to demonstrate on the doping concentration and applied voltage. For photonic applications, GaN microdisks and distributed Bragg

  10. Growth of GaN Thin Films on Silicon Using Single Source Precursors

    E-Print Network [OSTI]

    Boo, Jin-Hyo

    Growth of GaN Thin Films on Silicon Using Single Source Precursors and Development of New We have grown the GaN thin films on silicon substrates using the newly developed single source precursors by thermal MOCVD method. Highly oriented GaN thin films in the [002] direction with hexagonal

  11. Control of growth orientation of GaN nanowires H.Y. Peng, N. Wang 1

    E-Print Network [OSTI]

    Zheng, Yufeng

    -dependent growth directions. At a substrate temperature of 900­950 °C, the growth direction of GaN nanowires, it has become possible to grow single crystal films of GaN on various substrates by metalControl of growth orientation of GaN nanowires H.Y. Peng, N. Wang 1 , X.T. Zhou, Y.F. Zheng, C

  12. Microstructures of GaN films deposited on (001) and (111) Si substrates using electron

    E-Print Network [OSTI]

    Basu, Soumendra N.

    Microstructures of GaN films deposited on (001) and (111) Si substrates using electron cyclotron 1993; accepted 26 April 1994) The microstructures of GaN films, grown on (001) and (111) Si substrates-blende structure. The GaN buffer layer, grown in the first deposition step, accommodated the 17% lattice mismatch

  13. In situ growth regime characterization of cubic GaN using reflection high energy electron diffraction

    E-Print Network [OSTI]

    As, Donat Josef

    from Knudsen cells. Cubic GaN layers were deposited at 720 °C directly on 3C-SiC substrates shutters the GaN surface was exposed to different Ga fluxes for a certain time. The substrate temperatureIn situ growth regime characterization of cubic GaN using reflection high energy electron

  14. Strain dependent facet stabilization in selective-area heteroepitaxial growth of GaN nanostructures

    E-Print Network [OSTI]

    Sharma, Pradeep

    of submicron GaN islands on GaN-sapphire, AlN-sapphire, and bare sapphire substrates. It is shown that strain due to the lattice mismatch between GaN and the underlying substrate has a significant influence- structures has received less attention. Heteroepitaxial growth of GaN is commonly carried out on substrates

  15. Vertical strain and doping gradients in thick GaN layers H. Siegle,a)

    E-Print Network [OSTI]

    Nabben, Reinhard

    between layer and common substrates, e.g., sapphire or GaAs.1 Consequently, most GaN layers and also from the surface of the GaN layer nearer to the substrate interface, as can be seen from the CLVertical strain and doping gradients in thick GaN layers H. Siegle,a) A. Hoffmann, L. Eckey, and C

  16. Growth of GaN on porous SiC by molecular beam epitaxy

    E-Print Network [OSTI]

    Feenstra, Randall

    growth of high quality GaN thin films is the unavailability suitable substrates. The lack of suitable matched between the GaN and the substrate are the lattice parameter and the coefficient of thermal to the absence of high quality, large area GaN substrates. Therefore one has to resort to the heteroepitaxial

  17. TEM studies of laterally overgrown GaN layers grown on non-polar substrates

    E-Print Network [OSTI]

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

    2006-01-01T23:59:59.000Z

    between these substrates and the GaN layers leads to a highpendeo-epitaxial GaN layer grown on (1120) 4H-SiC substrate.in GaN layers grown on polar and non-polar substrates are

  18. Anti-phase domains in cubic GaN

    SciTech Connect (OSTI)

    Maria Kemper, Ricarda; Schupp, Thorsten; Haeberlen, Maik; Lindner, Joerg; Josef As, Donat [University of Paderborn, Department of Physics, Warburger Str. 100, D-33098 Paderborn (Germany); Niendorf, Thomas; Maier, Hans-Juergen [University of Paderborn, Lehrstuhl fuer Werkstoffkunde, Pohlweg 47-49, D-33098 Paderborn (Germany); Dempewolf, Anja; Bertram, Frank; Christen, Juergen [University of Magdeburg, Institut fuer Festkoerperphysik, P.O. Box 4120, D-39016 Magdeburg (Germany); Kirste, Ronny; Hoffmann, Axel [Technische Universitaet Berlin, Institute of Solid State Physics, Hardenbergstr. 36, D-10623 Berlin (Germany)

    2011-12-15T23:59:59.000Z

    The existence of anti-phase domains in cubic GaN grown on 3C-SiC/Si (001) substrates by plasma-assisted molecular beam epitaxy is reported. The influence of the 3C-SiC/Si (001) substrate morphology is studied with emphasis on the anti-phase domains (APDs). The GaN nucleation is governed by the APDs of the substrate, resulting in equal plane orientation and the same anti-phase boundaries. The presence of the APDs is independent of the GaN layer thickness. Atomic force microscopy surface analysis indicates lateral growth anisotropy of GaN facets in dependence of the APD orientation. This anisotropy can be linked to Ga and N face types of the {l_brace}111{r_brace} planes, similar to observations of anisotropic growth in 3C-SiC. In contrast to 3C-SiC, however, a difference in GaN phase composition for the two types of APDs can be measured by electron backscatter diffraction, {mu}-Raman and cathodoluminescence spectroscopy.

  19. Abstract--A high performance GaN HFET WCDMA basestation power amplifier is presented, which uses an envelope

    E-Print Network [OSTI]

    Asbeck, Peter M.

    Abstract--A high performance GaN HFET WCDMA basestation power amplifier is presented, which uses, digital predistortion, WCDMA, GaN HFET. I. INTRODUCTION High power-added efficiency is an important] and FETs[3], and GaN HFETs[4][5] has been carried out. GaN HFETs are attractive options since they can

  20. Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    doped MOCVD grown GaN on sapphire substrate [2]. Park et al. performed the growth of Cr doped GaN singleScanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Orleans, New Orleans, LA 70148, USA Abstract: Cr doped GaN was grown by rf N-plasma molecular beam epitaxy

  1. Redistribution of Implanted Dopants in GaN

    SciTech Connect (OSTI)

    Fu, M.; Gao, X.A.; Han, J.; Pearton, S.J.; Rieger, D.J.; Scarvepalli, V. Sekhar, J.A.; Shul, R.J.; Singh, R.K.; Wilson, R.G.; Zavada, J.M.; Zolper, J.C.

    1998-11-20T23:59:59.000Z

    Donor (S, Se and Te) and acceptor (Mg, Be and C) dopants have been implanted into GaN at doses of 3-5x1014 cm-2 and annealed at temperatures up to 1450 *C. No redistribution of any of the elements is detectable by Secondary Ion Mass Spectrometry, except for Be, which displays an apparent damage-assisted diffusion at 900 "C. At higher temperatures there is no further movement of the Be, suggesting that the point defect flux that assists motion at lower temperatures has been annealed. Effective diffusivities are <2X 1013 cm2.sec-1 at 1450 `C for each of the dopants in GaN.

  2. Evidence of N substitution by Mn in GaN

    E-Print Network [OSTI]

    Pereira, LMC; Decoster, S; Correia, JG; da Silva, MR; Vantomme, A; Araújo, JP

    2012-01-01T23:59:59.000Z

    We report on the lattice location of Mn in wurtzite GaN using beta? emission channeling. In addition to the majority substituting for Ga, we locate up to 20% of the Mn atoms in N sites. We propose that the incorporation of Mn in N sites is enabled under sufficiently high concentrations of N vacancies, and stabilized by a highly charged state of the Mn cations. Since N substitution by Mn impurities in wurtzite GaN has never been observed experimentally or even considered theoretically before, it challenges the current paradigm of transition metal incorporation in wide-gap dilute magnetic semiconductors.

  3. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect (OSTI)

    Jeganathan, K., E-mail: kjeganathan@yahoo.com, E-mail: jagan@physics.bdu.ac.in; Purushothaman, V. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli - 620 024 (India)] [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli - 620 024 (India); Debnath, R. [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada)] [Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4 (Canada); Arumugam, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli – 620 024 (India)] [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli – 620 024 (India)

    2014-05-15T23:59:59.000Z

    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.

  4. GaN for x-ray detection

    SciTech Connect (OSTI)

    Duboz, Jean-Yves; Lauegt, Marguerite; Schenk, David [CRHEA, CNRS, rue Bernard Gregory, Sophia Antipolis, F-06560 Valbonne (France); Beaumont, Bernard [Lumilog, 2720 chemin de saint Bernard, F-06220 Vallauris (France); Reverchon, Jean-Luc [THALES R and T, route departementale 128, F-91767 Palaiseau Cedex (France); Wieck, Andreas D.; Zimmerling, Tino [Fakultaet fuer Physik und Astronomie, D-44780 Bochum (Germany)

    2008-06-30T23:59:59.000Z

    The potential of GaN based materials for x-ray detection is investigated. The absorption coefficient in GaN is measured as a function of photon energy between 6 and 40 keV. Metal-semiconductor-metal photodetectors are fabricated and characterized. The response dependence on bias, the temporal dynamics, and the response dependence on detector geometry all together point toward a mixing of photovoltaic and photoconductive effects. Thanks to a large photoconductive gain, the detector has a decent responsivity at the expense of a large response time.

  5. Properties of H, O and C in GaN

    SciTech Connect (OSTI)

    Pearton, S.J.; Abernathy, C.R.; Lee, J.W. [Univ. of Florida, Gainesville, FL (United States)] [and others

    1996-04-01T23:59:59.000Z

    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.

  6. Refractive index of erbium doped GaN thin films

    SciTech Connect (OSTI)

    Alajlouni, S.; Sun, Z. Y.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Zavada, J. M. [Department of Electrical and Computer Engineering, Polytechnic Institute of New York University, Brooklyn, New York 11201 (United States)

    2014-08-25T23:59:59.000Z

    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.

  7. Luminescence properties of defects in GaN

    SciTech Connect (OSTI)

    Reshchikov, Michael A.; Morkoc, Hadis [Department of Electrical Engineering and Physics Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)

    2005-03-15T23:59:59.000Z

    Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The point defects include native isolated defects (vacancies, interstitial, and antisites), intentional or unintentional impurities, as well as complexes involving different combinations of the isolated defects. Further improvements in device performance and longevity hinge on an in-depth understanding of point defects and their reduction. In this review a comprehensive and critical analysis of point defects in GaN, particularly their manifestation in luminescence, is presented. In addition to a comprehensive analysis of native point defects, the signatures of intentionally and unintentionally introduced impurities are addressed. The review discusses in detail the characteristics and the origin of the major luminescence bands including the ultraviolet, blue, green, yellow, and red bands in undoped GaN. The effects of important group-II impurities, such as Zn and Mg on the photoluminescence of GaN, are treated in detail. Similarly, but to a lesser extent, the effects of other impurities, such as C, Si, H, O, Be, Mn, Cd, etc., on the luminescence properties of GaN are also reviewed. Further, atypical luminescence lines which are tentatively attributed to the surface and structural defects are discussed. The effect of surfaces and surface preparation, particularly wet and dry etching, exposure to UV light in vacuum or controlled gas ambient, annealing, and ion implantation on the characteristics of the defect-related emissions is described.

  8. Ga adsorbate on (0001) GaN: In situ characterization with quadrupole mass spectrometry and reflection high-energy electron diffraction

    E-Print Network [OSTI]

    Brown, J S; Koblmuller, G; Wu, F; Averbeck, R; Riechert, H; Speck, J S

    2006-01-01T23:59:59.000Z

    PA-MBE GaN growth conditions, with substrate temperatures ofthe GaN surface roughness evolution, substrate vicinality,vapor and substrate temperature could form the basis for GaN

  9. In situ characterization of GaN quantum dot growth with reflection high-energy electron diffraction and line-of-sight mass spectrometry

    E-Print Network [OSTI]

    Brown, J S; Koblmuller, G; Averbeck, R; Riechert, H; Speck, J S

    2006-01-01T23:59:59.000Z

    PA-MBE GaN growth conditions, with substrate temperatures ofthe GaN surface roughness evolution, substrate vicinality,vapor and substrate temperature could form the basis for GaN

  10. Fabrication and Characterization of Nano-porous GaN Template for Strain Relaxed GaN Growth

    E-Print Network [OSTI]

    Hartono, Haryono

    A simple and cost-effective Si-doped porous GaN is fabricated by UV-enhanced electrochemical etching. An optimum current density of 20 mA/cm² applied for an hour in dilute NaOH solution produces a high density of uniform ...

  11. Growth and characterization of horizontal GaN wires on silicon

    SciTech Connect (OSTI)

    Zou, Xinbo; May Lau, Kei, E-mail: eekmlau@ust.hk [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Kowloon (Hong Kong); HKUST Jockey Club Institute for Advanced Study, The Hong Kong University of Science and Technology, Kowloon (Hong Kong); Lu, Xing [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Kowloon (Hong Kong); Lucas, Ryan [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Kuech, Thomas F. [HKUST Jockey Club Institute for Advanced Study, The Hong Kong University of Science and Technology, Kowloon (Hong Kong); Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Choi, Jonathan W.; Gopalan, Padma [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2014-06-30T23:59:59.000Z

    We report the growth of in-plane GaN wires on silicon by metalorganic chemical vapor deposition. Triangular-shaped GaN microwires with semi-polar sidewalls are observed to grow on top of a GaN/Si template patterned with nano-porous SiO{sub 2}. With a length-to-thickness ratio ?200, the GaN wires are well aligned along the three equivalent ? 112{sup ¯}0 ? directions. Micro-Raman measurements indicate negligible stress and a low defect density inside the wires. Stacking faults were found to be the only defect type in the GaN wire by cross-sectional transmission electron microscopy. The GaN wires exhibited high conductivity, and the resistivity was 20–30 m? cm, regardless of the wire thickness. With proper heterostructure and doping design, these highly aligned GaN wires are promising for photonic and electronic applications monolithically integrated on silicon.

  12. Computational synthesis of single-layer GaN on refractory materials

    SciTech Connect (OSTI)

    Singh, Arunima K.; Hennig, Richard G., E-mail: rhennig@cornell.edu [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States)

    2014-08-04T23:59:59.000Z

    The synthesis of single-layer materials relies on suitable substrates. In this paper, we identify suitable substrates for the stabilization and growth of single-layer GaN and characterize the effect of the substrate on the electronic structure of single-layer GaN. We identify two classes of epitaxial substrates, refractory metal diborides and transition-metal dichalcogenides. We find that the refractory diborides provide epitaxial stabilization for the growth and functionalization of single layer GaN. We show that chemical interactions of single layer GaN with the diboride substrates result in n-type doping of the single-layer GaN. Transition-metal dichalcogenides, on the other hand, although epitaxially matched, cannot provide sufficient thermodynamic stabilization for the growth of single layer GaN. Nonetheless, energy band alignments of GaN/metal chalcogenides show that they make good candidates for heterostructures.

  13. Determination of Wurtzite GaN Lattice Polarity Based on Surface Reconstruction

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Determination of Wurtzite GaN Lattice Polarity Based on Surface Reconstruction A. R. Smith,1 R. M of reconstructions occurring on wurtzite GaN surfaces, the first associated with the N-face, (000 ), and the secondN. In the fabrication of most nitride-based devices, epitaxial growth occurs on the c-plane of wurtzite GaN. A key

  14. Cubic GaN on Nanopatterned 3C-SiC/Si (001) Substrates

    E-Print Network [OSTI]

    As, Donat Josef

    Chapter 15 Cubic GaN on Nanopatterned 3C-SiC/Si (001) Substrates Ricarda Maria Kemper, Donat Josef relaxed cubic GaN by plasma-assisted molecular beam epitaxy on prepat- terned 3C-SiC/Si (001) substrates) process. We analyze the influence of the substrate on the GaN growth and show that it is possible to grow

  15. GaN Nanowire Arrays for High-Output Nanogenerators Chi-Te Huang,,

    E-Print Network [OSTI]

    Wang, Zhong L.

    epitaxially grown on GaN/sapphire substrates. The GaN NW possesses a triangular cross section enclosed by (0001j), (21j1j2), and (2j112) planes, and the angle between the GaN NW and the substrate surface is 62 process. For the epitaxial growth of GaN NW arrays, the substrates play an important role in determining

  16. Structural defects in GaN revealed by Transmission Electron Microscopy

    SciTech Connect (OSTI)

    Liliental-Weber, Zuzanna

    2014-04-18T23:59:59.000Z

    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.

  17. Ultra High Temperature Rapid Thermal Annealing of GaN

    SciTech Connect (OSTI)

    Cao, X.A.; Fu, M.; Han, J.; Pearton, S.J.; Rieger, D.J.; Sekhar, J.A.; Shul, R.J.; Singh, R.K.; Wilson, R.G.; Zolper, J.C.

    1998-11-20T23:59:59.000Z

    All of the major acceptor (Mg, C, Be) and donor (Si, S, Se and Te) dopants have been implanted into GaN films grown on A1203 substrates. Annealing was performed at 1100- 1500 C, using AIN encapsulation. Activation percentages of >90Y0 were obtained for Si+ implantation annealed at 1400 C, while higher temperatures led to a decrease in both carrier concentration and electron mobility. No measurable redistribution of any of the implanted dopants was observed at 1450 C.

  18. Submitted to J. Appl. Phys., revised October, 1999 1 A Rate Equation Model for the Growth of GaN on GaN(0001) by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Cohen, Philip I.

    Submitted to J. Appl. Phys., revised October, 1999 1 A Rate Equation Model for the Growth of GaN on GaN(000¯1) by Molecular Beam Epitaxy R.Held, B.E. Ishaug, A. Parkhomovsky, A.M. Dabiran, and P (October 7, 1999) GaN(000¯1)filmsweregrownbymolecularbeamepitaxyusingammoniaandelemental

  19. A3.2 Raman and IR studies of GaN C. Wetzel and I. Akasaki

    E-Print Network [OSTI]

    Wetzel, Christian M.

    energies in wurtzite and in zincblende GaN (Table 1.) [1-10]. Phonon and coupled modes have been employed of optical phonons modes in are very similar in wurtzite and cubic GaN. Selection rules in wurtzite allow to values in bulk GaN (Table 1): Table 1. Phonon modes in wurtzite GaN Symmetry active in Experiment (cm-1

  20. Intrinsic degradation mechanism of nearly lattice-matched InAlN layers grown on GaN substrates

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Intrinsic degradation mechanism of nearly lattice-matched InAlN layers grown on GaN substrates compared to GaN, In0.17Al0.83N layers lattice-matched to GaN are an attractive solution for applications-standing (0001) GaN substrates with a low density of threading dislocations, for In compositions of 13.5% (layers

  1. GaN1-xBix: Extremely mismatched semiconductor alloys A. X. Levander,1,2

    E-Print Network [OSTI]

    Wu, Junqiao

    GaN1-xBix: Extremely mismatched semiconductor alloys A. X. Levander,1,2 K. M. Yu,1,a S. V. Novikov epitaxy, we have grown GaN1-xBix alloys on sapphire substrates with x up to 0.11. The GaN1-xBix alloys are found to be amorphous with GaN crystals distributed throughout the film. A dramatic reduction

  2. Local vibrational modes of the MgH acceptor complex in GaN W. Gotz,a)

    E-Print Network [OSTI]

    McCluskey, Matthew

    Local vibrational modes of the Mg­H acceptor complex in GaN W. Go¨tz,a) N. M. Johnson,b) and D. P are reported for Mg-doped GaN grown by metalorganic chemical vapor deposition. Hetero-epitaxial layers of GaN complex. The new LVMs are assigned to the stretch modes of the Mg­H and Mg­D complexes in GaN

  3. Morphology and surface reconstructions of GaN(1 1 00) surfaces C. D. Lee and R. M. Feenstra

    E-Print Network [OSTI]

    Feenstra, Randall

    assisted molecular beam epitaxy on ZnO(1 1 00) substrates. Well-oriented (1 1 00) GaN surfaces are obtained, ZnO offers an attractive substrate for GaN heteroepitaxy. We obtain well oriented (1 1 00) GaN films this structure consists of 2 monolayers of Ga terminating the GaN surface. ZnO(1 1 00) substrates were obtained

  4. Red light emission by photoluminescence and electroluminescence from Pr-doped GaN on Si substrates

    E-Print Network [OSTI]

    Steckl, Andrew J.

    Red light emission by photoluminescence and electroluminescence from Pr-doped GaN on Si substrates to higher level Er3 transitions. In this letter, we report on Pr-doped GaN growth on Si 111 substrates from Pr-doped GaN thin films grown on Si 111 . The GaN was grown by molecular beam epitaxy using solid

  5. Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates

    E-Print Network [OSTI]

    Steckl, Andrew J.

    Green emission from Er-doped GaN grown by molecular beam epitaxy on Si substrates R. Birkhahn and A grown by MBE on sapphire substrates. In this letter, we report on Er-doped GaN growth experiments on Si Er-doped -GaN thin films grown on Si 111 . The GaN was grown by molecular beam epitaxy using solid

  6. GaN(0001) Surface Structures Studied Using Scanning Tunneling Microscopy and First-Principles Total Energy Calculations

    E-Print Network [OSTI]

    occurring on the (0001) surface of wurtzite GaN are studied using scanning tunneling microscopy, electron and electronic properties of wurtzite GaN surfaces. Several prior studies have reported that these surfaces do reconstructions were identified, corresponding to the two inequivalent polar fac- es of wurtzite GaN, the (0001

  7. Wurtzite GaN surface structures studied by scanning tunneling microscopy and reflection high energy electron diffraction

    E-Print Network [OSTI]

    Wurtzite GaN surface structures studied by scanning tunneling microscopy and reflection high energy-face of wurtzite GaN films grown using molecular beam epitaxy. N-face reconstructions are primarily adatom numerous surface studies of wurtzite GaN have been performed, progress in determining the true surface

  8. Phonon deformation potentials in wurtzite GaN and ZnO determined by uniaxial pressure dependent Raman measurements

    E-Print Network [OSTI]

    Nabben, Reinhard

    Phonon deformation potentials in wurtzite GaN and ZnO determined by uniaxial pressure dependent deformation potentials in wurtzite GaN and ZnO determined by uniaxial pressure dependent Raman measurements G online 9 February 2011 We report the phonon deformation potentials of wurtzite GaN and ZnO for all zone

  9. Mn-and Fe-doped GaN for spintronic applications Enno Malguth1,2

    E-Print Network [OSTI]

    Nabben, Reinhard

    Resonant Raman scattering on free and bound excitons in GaN A. Kaschner,* A. Hoffmann, and C Raman scattering effect in GaN at low temperatures applying a frequency-doubled titan-sapphire laser to detect inelastic scattered light from small sample volumes, for instance, in buried Al- GaN structures7

  10. Terahertz studies of carrier dynamics and dielectric response of n-type, freestanding epitaxial GaN

    E-Print Network [OSTI]

    Terahertz studies of carrier dynamics and dielectric response of n-type, freestanding epitaxial GaN conductivity and dielectric function of GaN by terahertz time-domain spectroscopy. Transmission measurements are performed on an n-type, 180- m-thick, freestanding GaN crystal. Frequency dependent electron dynamics, power

  11. Physica B 376377 (2006) 486490 Preferential substitution of Fe on physically equivalent Ga sites in GaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    2006-01-01T23:59:59.000Z

    in GaN W. GehlhoffÃ, D. Azamat1 , U. Haboeck, A. Hoffmann Institute for Solid State Physics, Technical freestanding hydride vapor phase grown GaN have been studied in the X- and Q-band. A complex resonance pattern with C3v symmetry in the wurtzite structure of GaN. Aside from the displacement of their magnetic axis

  12. Comment on ``Shallow donors in GaN studied by electronic Raman scattering in resonance with yellow luminescence transitions''

    E-Print Network [OSTI]

    Nabben, Reinhard

    Photoluminescence and Raman study of compensation effects in Mg-doped GaN epilayers L. Eckey, U for publication 17 July 1998 The compensation of Mg-doped GaN is systematically studied by low in semiconductor technology during the recent years was the realization of p conductivity in GaN, leading

  13. Selective growth of high quality GaN on Si,,111... substrates M. Seon, T. Prokofyeva, and M. Holtza)

    E-Print Network [OSTI]

    Holtz, Mark

    Selective growth of high quality GaN on Si,,111... substrates M. Seon, T. Prokofyeva, and M. Holtza September 1999; accepted for publication 4 February 2000 We demonstrate selective growth of high-quality GaN by gas-source molecular beam epitaxy on Si 111 wafers patterned with SiO2. GaN was grown on wafers having

  14. Temperature dependent photoluminescence of lateral polarity junctions of metal organic chemical vapor deposition grown GaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    implantation of Cu, Li and Ag into silicon doped GaN films grown by Metalorganic Chemical Vapor Deposition temperature (700-900°C) annealing. Low temperature (6K) photoluminescence (PL) for Cu-implanted GaN showed recovery of standard crystalline GaN features. Additional donor-acceptor pair features are observed below 3

  15. Cathodoluminescence of stacking fault bound excitons for local probing of the exciton diffusion length in single GaN nanowires

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    length in single GaN nanowires Gilles Nogues,1, 2, a) Thomas Auzelle,3 Martien Den Hertog,1, 2 Bruno correlated studies of individual GaN nanowires in scanning electron microscopy combined to low temperature that carrier diffusion length in InGaN and GaN bidimensional (2D) layers are rather small, in the range of 50

  16. Oxidized GaN(0001) Surfaces studied by Scanning Tunneling Microscopy and Spectroscopy and by First-Principles Theory

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Oxidized GaN(0001) Surfaces studied by Scanning Tunneling Microscopy and Spectroscopy Abstract Oxidized Ga-polar GaN surfaces have been studied both experimentally and theoretically. For in tunneling spectroscopy revealed a surface band gap with size close to that of GaN, indicating that any

  17. PHYSICAL REVIEW B 86, 104114 (2012) Molecular dynamics of irradiation-induced defect production in GaN nanowires

    E-Print Network [OSTI]

    Nordlund, Kai

    2012-01-01T23:59:59.000Z

    in GaN nanowires Wei Ren,* Antti Kuronen, and Kai Nordlund Department of Physics, University of Helsinki the defect production of small-cross-section GaN nanowires by Ar ion irradiation. We performed 200 random production in the nanowires was increased by a factor of 2 compared to bulk GaN. A simple model to estimate

  18. Strain relaxation in GaN grown on vicinal 4H-SiC(0001) J. Pernot and E. Bustarret

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Strain relaxation in GaN grown on vicinal 4H-SiC(0001) substrates J. Pernot and E. Bustarret, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands Abstract The strain of GaN layers grown by Metal Organic, the GaN layer grown on on-axis substrate has a slight and homogeneous tensile in-plane stress due

  19. Catalyst-Free GaN Nanowire Nucleation: Correlation of Temperature-Dependent Nanowire Orientation and Growth Matrix Changes

    E-Print Network [OSTI]

    Ayres, Virginia

    Catalyst-Free GaN Nanowire Nucleation: Correlation of Temperature-Dependent Nanowire Orientation nitride (GaN) nanowires have been under extensive investigation in recent years due to their unique that the GaN nanowires had internal structures that continued along the entire length of the nanowires

  20. Individual GaN Nanowires Exhibit Strong Piezoelectricity in 3D Majid Minary-Jolandan, Rodrigo A. Bernal, Irma Kuljanishvili,

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    Individual GaN Nanowires Exhibit Strong Piezoelectricity in 3D Majid Minary-Jolandan, Rodrigo A, Northwestern University, Evanston, Illinois 60208, United States ABSTRACT: Semiconductor GaN NWs are promising, the electromechanical coupling leads to a third rank tensor that for wurtzite crystals (GaN NWs) possesses three

  1. The adsorption of oxygen at GaN surfaces Tosja K. Zywietz, a) Jo rg Neugebauer, and Matthias Scheffler

    E-Print Network [OSTI]

    The adsorption of oxygen at GaN surfaces Tosja K. Zywietz, a) Jo Ë? rg Neugebauer, and Matthias based on GaN is the controlled doping and the incorporation of impurities like, e.g., oxygen. We have explored the adsorption of oxygen at the wurtzite ~0001! and (0001 â?¢ ) GaN surfaces employing density

  2. Radiative recombination and ultralong exciton photoluminescence lifetime in GaN freestanding film via two-photon excitation

    E-Print Network [OSTI]

    Radiative recombination and ultralong exciton photoluminescence lifetime in GaN freestanding film of a freestanding GaN film using one-photon and two-photon excitations to demonstrate the dramatic difference at 295 K is observed from a GaN freestanding film using two-photon excitation, whereas less than 100 ps

  3. Defect reduction in (112_O) a-plane GaN by two-stage epitaxial lateral overgrowth

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    c-axis (b) 50 ?m GaN c-axis (c) substrate window Ga wing NN wing (b) GaN c-axis 20 ?m (c) 10 ?m substrate Figure 3: (GaN films were grown on (1 102) r-plane sapphire substrates (

  4. GROWTH OF GaN ON POROUS SiC SUBSTRATES BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY

    E-Print Network [OSTI]

    Feenstra, Randall

    1 GROWTH OF GaN ON POROUS SiC SUBSTRATES BY PLASMA-ASSISTED MOLECULAR BEAM EPITAXY C. K. Inoki ABSTRACT We have explored the growth of GaN on porous SiC substrates by plasma-assisted molecular beam Ga droplets. Plan-view TEM observations indicate that the GaN layers grown on porous substrates

  5. Wafer-scale selective area growth of GaN hexagonal prismatic nanostructures on c-sapphire substrate

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ;2 ABSTRACT Selective area growth of GaN nanostructures has been performed on full 2" c-sapphire substrates on GaN layer template grown on c-sapphire substrate and usually result in pyramid-shaped nanostructures of homogeneity of the nucleation selectivity of SAG GaN nanostructures on c- sapphire substrate remains an issue

  6. Scanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Epitaxy

    E-Print Network [OSTI]

    on sapphire substrate [2]. Park et al. performed the growth of Cr doped GaN single crystal by sodium fluxScanning Tunneling Microscopy Study of Cr-doped GaN Surface Grown by RF Plasma Molecular Beam Orleans, New Orleans, LA 70148, USA Abstract: Cr doped GaN was grown by rf N-plasma molecular beam epitaxy

  7. Focused ion beam micromilling of GaN and related substrate materials ,,sapphire, SiC, and Si...

    E-Print Network [OSTI]

    Steckl, Andrew J.

    Focused ion beam micromilling of GaN and related substrate materials ,,sapphire, SiC, and Si... A. In addition, we report similar results for materials currently utilized as substrates for GaN growth. II-0030 Received 15 October 1998; accepted 18 December 1998 Micromilling of GaN films has been obtained using a Ga

  8. Growth of p-type and n-type m-plane GaN by molecular beam epitaxy

    E-Print Network [OSTI]

    McLaurin, M; Mates, T E; Wu, F; Speck, J S

    2006-01-01T23:59:59.000Z

    other more conventional substrates for GaN growth. As anbetween the GaN ?lm and the SiC substrate is considered. 19oriented GaN ?lms were grown on 6H m-plane SiC substrates

  9. A Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Myers, Tom

    as a function of substrate temperature and dopant flux for Ga-polarity and N-polarity GaN. Incorporation GaN templates on (0001) sapphire substrates. The doped layers were grown at a rate of 0.25 µmA Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam

  10. Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates with varying porosity

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates with varying porosity York, 12222 Abstract: We have grown GaN on porous SiC substrates and studied the effect of substrate show that the GaN film grown on porous substrates contains open tubes and a low dislocation density

  11. Hexagonal Growth Spirals on GaN Grown by Molecular Beam Epitaxy: Kinetics vs Thermodynamics

    E-Print Network [OSTI]

    Cohen, Philip I.

    prepared, Ga-polar GaN(0001) templates. The surface morphology was studied using reflection high-energy-edge energy of 0.26 eV/Ã?. They suggest that local conditions at step edges dominate the growth. 1 conducted ex situ using AFM. Desorption mass spectrometry (DMS) was used to measure the GaN growth rate. Our

  12. Unoccupied band structure of wurtzite GaN,,0001... T. Valla and P. D. Johnson

    E-Print Network [OSTI]

    Homes, Christopher C.

    Unoccupied band structure of wurtzite GaN,,0001... T. Valla and P. D. Johnson Department of Physics of the unoccupied states of thin-film n-type wurtzite GaN. For incident electron energies below 30 eV, free of electronic devices based on heteroepitaxially grown wurtzite films of these nitrides.1 Extensive investiga

  13. K.K. Gan Siena02 1 The Ohio State University

    E-Print Network [OSTI]

    Gan, K. K.

    .K. Gan Siena02 6 l Decode Bi-Phase Mark encoded (BPM) clock and command signals from PIN diode l Input Error Rate (BER): BPM #12;K.K. Gan Siena02 7 l Training period: ~25 ms of 20 MHz clock (BPM with no data) DORIC Logic ] Ready

  14. Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy

    E-Print Network [OSTI]

    Myers, Tom

    Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy A. J. Ptak, L. J-assisted molecular-beam epitaxy to study the dependence of oxygen incorporation on polarity and oxygen partial pressure. Oxygen incorporates at a rate ten times faster on nitrogen-polar GaN than on the Ga polarity

  15. Structural effects of field emission from GaN nanofilms on SiC substrates

    SciTech Connect (OSTI)

    Chen, Cheng-Cheng; Wang, Ru-Zhi, E-mail: wrz@bjut.edu.cn; Zhu, Man-Kang; Yan, Hui [College of Materials Science and Engineering, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100124 (China); Liu, Peng [Department of Physics Tsinghua University, Tsinghua-Foxconn Nanotechnology Research Center, Beijing 100084 (China); Wang, Bi-Ben [College of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400054 (China)

    2014-04-21T23:59:59.000Z

    GaN nanofilms (NFs) with different structures are grown on SiC substrates by pulsed laser deposition under different conditions. The synthesized GaN NFs are studied by X-ray diffraction, field-emission (FE) scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The GaN NFs are composed of diversified GaN nanoparticles with a diameter of 9–38?nm, thickness of 10–50?nm, and roughness of 0.22–13.03?nm. FE from the GaN NFs is structure dependent, which is explained by stress changing the band gap of the NFs. By structure modulation, the turn-on field of GaN NFs can be as low as 0.66?V/?m at a current density of 1??A/cm{sup 2}, with a current density of up to 1.1?mA/cm{sup 2} at a field of 4.18?V/?m. Fowler-Nordheim curves of some samples contain multiple straight lines, which originate from the structural change and diversification of GaN nanoparticles under an applied field. Overall, our results suggest that GaN NFs with excellent FE properties can be prepared on SiC substrates, which provides a new route to fabricate high-efficiency FE nanodevices.

  16. Preparation and characterization of one-dimensional GaN nanorods with Tb intermediate layer

    SciTech Connect (OSTI)

    Shi, Feng, E-mail: sf751106@sina.com.cn [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)] [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Xue, Chengshan [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)] [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)

    2012-12-15T23:59:59.000Z

    Graphical abstract: Display Omitted Highlights: ? GaN nanorods have been prepared on Si substrates by magnetron sputtering. ? GaN nanorods are single crystal with hexagonal wurtzite structure. ? GaN nanorods are high-quality crystalline after ammoniating at 950 °C for 15 min. ? Ammoniating temperatures and times affect the growth of GaN nanorods significantly. -- Abstract: GaN nanorods have been successfully prepared on Si(1 1 1) substrates by magnetron sputtering through ammoniating Ga{sub 2}O{sub 3}/Tb thin films. X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), FT-IR spectrophotometer, scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and photoluminescence (PL) spectroscopy were used to characterize the microstructures, morphologies compositions and optical properties of the GaN samples. The results demonstrate that the nanorods are single crystal GaN with hexagonal wurtzite structure and high-quality crystalline after ammoniating at 950 °C for 15 min, which have the size of 100–150 nm in diameter. Ammoniating temperatures and times affect the growth of GaN nanorods significantly. The growth procedure mainly follows the Tb catalyst-assisted VLS mechanism.

  17. GaN light-emitting diodes with Archimedean lattice photonic crystals Aurlien David,a

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    GaN light-emitting diodes with Archimedean lattice photonic crystals Aurélien David,a Tetsuo Fujii 2005; published online 16 February 2006 We study GaN-based light emitting diodes incorporating the semiconductor due to its index contrast with air.1­6 Recently, PhCs were used as out- coupling gratings in GaN

  18. Fermi Level Control of Point Defects During Growth of Mg-Doped GaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    Fermi Level Control of Point Defects During Growth of Mg-Doped GaN ZACHARY BRYAN,1,4 MARC HOFFMANN defects during metalorganic chem- ical vapor deposition (MOCVD) of Mg-doped GaN has been demonstrated of magnitude lower resistivity values compared with typical unan- nealed GaN:Mg samples. The PL spectra

  19. Anti-phase domains in cubic GaN Ricarda Maria Kemper,1,a)

    E-Print Network [OSTI]

    As, Donat Josef

    ) substrate morphology is studied with emphasis on the anti-phase domains (APDs). The GaN nucleation are the substrate of choice. There are three types of basic defects in epitaxial c-GaN thin films grown on 3CAnti-phase domains in cubic GaN Ricarda Maria Kemper,1,a) Thorsten Schupp,1 Maik Ha¨berlen,1 Thomas

  20. Polarization anisotropy in GaN films for different nonpolar orientations studied by polarized photoreflectance spectroscopy

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    lms grown on GaN substrates. 11–13 To determine ? cr and ?respective substrate. For optical spectra of GaN layers, theGaN ?lm ?sample III? also grown by PAMBE on ? -LiAlO 2 ?100? substrates.

  1. Zone-boundary phonons in hexagonal and cubic GaN H. Siegle, G. Kaczmarczyk, L. Filippidis, A. P. Litvinchuk, A. Hoffmann, and C. Thomsen

    E-Print Network [OSTI]

    Nabben, Reinhard

    Zone-boundary phonons in hexagonal and cubic GaN H. Siegle, G. Kaczmarczyk, L. Filippidis, A. P results of second-order Raman-scattering experiments on hexagonal and cubic GaN covering the acoustic- boundary phonons in hexagonal GaN. S0163-1829 97 01812-2 I. INTRODUCTION The wide-band-gap semiconductor GaN

  2. Hydrogen sensing characteristics of semipolar (112{sup ¯}2) GaN Schottky diodes

    SciTech Connect (OSTI)

    Hyeon Baik, Kwang [School of Materials Science and Engineering, Hongik University, Jochiwon, Sejong 339-701 (Korea, Republic of); Kim, Hyonwoong; Jang, Soohwan, E-mail: jangmountain@dankook.ac.kr [Department of Chemical Engineering, Dankook University, Yongin 448-701 (Korea, Republic of); Lee, Sung-Nam [Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung, Gyeonggi 429-793 (Korea, Republic of); Lim, Eunju [Department of Applied Physics, Institute of Nanosensor and Biotechnology, Dankook University, Yongin 448-701 (Korea, Republic of); Pearton, S. J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Ren, F. [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)

    2014-02-17T23:59:59.000Z

    The hydrogen detection characteristics of semipolar (112{sup ¯}2) plane GaN Schottky diodes were investigated and compared to c-plane Ga- and N-polar and nonpolar a-plane (112{sup ¯}0) GaN diodes. The semipolar GaN diodes showed large current response to 4% hydrogen in nitrogen gas with an accompanying Schottky barrier reduction of 0.53?eV at 25?°C, and the devices exhibited full recovery to the initial current level upon switching to a nitrogen ambient. The current-voltage characteristics of the semipolar devices remained rectifying after hydrogen exposure, in sharp contrast to the case of c-plane N-polar GaN. These results show that the surface atom configuration and polarity play a strong role in hydrogen sensing with GaN.

  3. Step-induced misorientation of GaN grown on r-plane sapphire

    SciTech Connect (OSTI)

    Smalc-Koziorowska, J.; Dimitrakopulos, G. P.; Sahonta, S.-L.; Komninou, Ph. [Physics Department, Aristotle University, GR 54124 Thessaloniki (Greece); Tsiakatouras, G.; Georgakilas, A. [Microelectronics Research Group, Department of Physics, University of Crete, P.O. Box 2208, GR 71003, and IESL, FORTH, P.O. Box 1527, GR 71110 Heraklion (Greece)

    2008-07-14T23:59:59.000Z

    In the growth of nonpolar (1120) a-plane GaN on r-plane (1102) sapphire by plasma-assisted molecular beam epitaxy, misoriented crystallites are observed close to the substrate. They have average diameter {approx}10 nm and are oriented with the (0001){sub GaN} plane approximately parallel to the (2113){sub sapph.} plane and [0110]{sub GaN} parallel [1101]{sub sapph.}. This semipolar orientation is promoted by a low misfit (2.4%) between (1011){sub GaN} and (1210){sub sapph.} planes. Its introduction, after nitridation treatment, is due to GaN nucleation on (2113){sub sapph.} step facets inclined at 26 deg. relative to the r-plane. Two variants are observed, leading to twinning when they abut inside the epilayer.

  4. Polarity of semipolar wurtzite crystals: X-ray photoelectron diffraction from GaN(101?1) and GaN(202?1) surfaces

    SciTech Connect (OSTI)

    Romanyuk, O., E-mail: romanyuk@fzu.cz; Ji?í?ek, P.; Bartoš, I. [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 53 Prague (Czech Republic); Paskova, T. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27606 (United States)

    2014-09-14T23:59:59.000Z

    Polarity of semipolar GaN(101?1) (101?1?) and GaN(202?1) (202?1?) surfaces was determined with X-ray photoelectron diffraction (XPD) using a standard MgK? source. The photoelectron emission from N 1s core level measured in the a-plane of the crystals shows significant differences for the two crystal orientations within the polar angle range of 80–100° from the (0001) normal. It was demonstrated that XPD polar plots recorded in the a-plane are similar for each polarity of the GaN(101?1) and GaN(202?1) crystals if referred to (0001) crystal axes. For polarity determinations of all important GaN(h0h?l) semipolar surfaces, the above given polar angle range is suitable.

  5. Surface morphology evolution of m-plane (1100) GaN during molecular beam epitaxy growth: Impact of Ga/N ratio, miscut direction, and growth temperature

    SciTech Connect (OSTI)

    Shao Jiayi; Tang Liang; Malis, Oana [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Edmunds, Colin [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Gardner, Geoff [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Manfra, Michael [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2013-07-14T23:59:59.000Z

    We present a systematic study of morphology evolution of [1100] m-plane GaN grown by plasma-assisted molecular beam epitaxy on free-standing m-plane substrates with small miscut angles towards the -c [0001] and +c [0001] directions under various gallium to nitrogen (Ga/N) ratios at substrate temperatures T = 720 Degree-Sign C and T = 740 Degree-Sign C. The miscut direction, Ga/N ratio, and growth temperature are all shown to have a dramatic impact on morphology. The observed dependence on miscut direction supports the notion of strong anisotropy in the gallium adatom diffusion barrier and growth kinetics. We demonstrate that precise control of Ga/N ratio and substrate temperature yields atomically smooth morphology on substrates oriented towards +c [0001] as well as the more commonly studied -c [0001] miscut substrates.

  6. GaN directional couplers for integrated quantum photonics

    E-Print Network [OSTI]

    Yanfeng Zhang; Loyd McKnight; Erman Engin; Ian M. Watson; Martin J. Cryan; Erdan Gu; Mark G. Thompson; Stephane Calvez; Jeremy L. O'Brien; Martin D. Dawson

    2012-02-20T23:59:59.000Z

    Large cross-section GaN waveguides are proposed as a suitable architecture to achieve integrated quantum photonic circuits. Directional couplers with this geometry have been designed with aid of the beam propagation method and fabricated using inductively coupled plasma etching. Scanning electron microscopy inspection shows high quality facets for end coupling and a well defined gap between rib pairs in the coupling region. Optical characterization at 800 nm shows single-mode operation and coupling-length-dependent splitting ratios. Two photon interference of degenerate photon pairs has been observed in the directional coupler by measurement of the Hong-Ou-Mandel dip with 96% visibility.

  7. Synthesis, structure, and optical properties of colloidal GaN quantum dots

    SciTech Connect (OSTI)

    Micic, O.I.; Ahrenkiel, S.P.; Bertram, D.; Nozik, A.J. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    1999-07-01T23:59:59.000Z

    Colloidal chemistry was used to synthesize GaN quantum dots. A GaN precursor, polymeric gallium imide, {l_brace}Ga(NH){sub 3/2}{r_brace}{sub n}, which was prepared by the reaction of dimeric amidogallium with ammonia at room temperature, was heated in trioctylamine at 360&hthinsp;{degree}C for one day to produce GaN nanocrystals. The GaN particles were separated, purified, and partially dispersed in a nonpolar solvent to yield transparent colloidal solutions that consisted of individual GaN particles. The GaN nanocrystals have a spherical shape and mean diameter of about 30{plus_minus}12&hthinsp;{Angstrom}. The spectroscopic behavior of colloidal transparent dispersion has been investigated and shows that the band gap of the GaN nanocrystals shifts to slightly higher energy due to quantum confinement. The photoluminescence spectrum at 10 K (excited at 310 nm) shows band edge emission with several emission peaks in the range between 3.2 and 3.8 eV, while the photoluminescence excitation spectrum shows two excited-state transitions at higher energies. {copyright} {ital 1999 American Institute of Physics.}

  8. Growth of GaN on Ge(111) by molecular beam epitaxy

    SciTech Connect (OSTI)

    Lieten, R. R.; Degroote, S.; Cheng, K.; Leys, M.; Kuijk, M.; Borghs, G. [MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium) and ETRO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels (Belgium); MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium); ETRO, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels (Belgium); MCP/ART, IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2006-12-18T23:59:59.000Z

    The epitaxial growth of GaN on Ge is reported. The authors found that direct growth of GaN performs exceptionally well on Ge(111) with plasma assisted molecular beam epitaxy. A streaky reflection high energy electron diffraction pattern is observed during growth. X-ray diffraction showed a rocking curve full width at half maximum of only 371 arc sec for a 38 nm GaN layer and indicates an abrupt interface between the GaN and Ge. Secondary ion mass spectrometry shows limited diffusion of Ga atoms into the Ge substrate and Ge atoms into the GaN layers. Current-voltage measurements show rectifying behavior for n-GaN on p-Ge. Their results indicate that GaN growth on Ge does not require intermediate layers, allowing the Ge substrate to be used as back contact in vertical devices. A p-n junction formed between GaN and Ge can be used in heterojunction devices.

  9. Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target

    SciTech Connect (OSTI)

    Kushvaha, S. S.; Kumar, M. Senthil; Maurya, K. K.; Dalai, M. K.; Sharma, Nita D. [CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi, India 110012 (India)] [CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi, India 110012 (India)

    2013-09-15T23:59:59.000Z

    Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

  10. X-Ray Studies of GaN Film Grown on Si Using Electrochemical Deposition Techniques

    SciTech Connect (OSTI)

    Al-Heuseen, K.; Hashim, M. R. [Nano-Optoelectronics Research and Technology Laboratory School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Penang (Malaysia)

    2011-03-30T23:59:59.000Z

    This paper reports on the X-ray studies of GaN thin films deposited on Si (111) substrate at different current density using electrochemical deposition technique. The structural properties of GaN films were studied by X-ray diffraction (XRD). XRD analysis showed that hexagonal wurtzite and cubic zinc blende GaN phases were both deposited on Si (111). The lattice constants, the average size of h-GaN crystals and the in-plane (along a-axis) and out of plane (along c-axis) strains were calculated from XRD analysis.

  11. Prospective emission efficiency and in-plane light polarization of nonpolar m-plane InxGa1-xN/GaN blue light emitting diodes fabricated on freestanding GaN substrates

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    fabricated on freestanding GaN substrates T. Koyama and T.on freestanding m-plane GaN substrates. Although the ? inton the freestanding GaN substrate. cause the current was

  12. Millimeter-wave GaN high electron mobility transistors and their integration with silicon electronics

    E-Print Network [OSTI]

    Chung, Jinwook W. (Jinwook Will)

    2011-01-01T23:59:59.000Z

    In spite of the great progress in performance achieved during the last few years, GaN high electron mobility transistors (HEMTs) still have several important issues to be solved for millimeter-wave (30 ~ 300 GHz) applications. ...

  13. Light extraction in individual GaN nanowires on Si for LEDs

    E-Print Network [OSTI]

    Zhou, Xiang

    GaN-based nanowires hold great promise for solid state lighting applications because of their waveguiding properties and the ability to grow nonpolar GaN nanowire-based heterostructures, which could lead to increased light ...

  14. Chromatin Ionic Atmosphere Analyzed by a Mesoscale Electrostatic Hin Hark Gan

    E-Print Network [OSTI]

    Schlick, Tamar

    Chromatin Ionic Atmosphere Analyzed by a Mesoscale Electrostatic Approach Hin Hark Gan and Tamar an electrostatic model to handle multivalent ions and compute the ionic distribution around a mesoscale chromatin

  15. Thermal Conductivity and Large Isotope Effect in GaN from First Principles

    SciTech Connect (OSTI)

    Lindsay, L. [Naval Research Lab. (NRL), Washington, DC (United States); Broido, D. A. [Boston College, Chestnut Hill, MA (United States); Reinecke, T. L. [Naval Research Lab. (NRL), Washington, DC (United States)

    2012-08-01T23:59:59.000Z

    We present atomistic first principles results for the lattice thermal conductivity of GaN and compare them to those for GaP, GaAs, and GaSb. In GaN we find a large increase to the thermal conductivity with isotopic enrichment, ~65% at room temperature. We show that both the high thermal conductivity and its enhancement with isotopic enrichment in GaN arise from the weak coupling of heat-carrying acoustic phonons with optic phonons. This weak scattering results from stiff atomic bonds and the large Ga to N mass ratio, which give phonons high frequencies and also a pronounced energy gap between acoustic and optic phonons compared to other materials. Rigorous understanding of these features in GaN gives important insights into the interplay between intrinsic phonon-phonon scattering and isotopic scattering in a range of materials.

  16. Atomic-Level Study of Melting Behavior of GaN Nanotubes. | EMSL

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

    Behavior of GaN Nanotubes. Abstract: Molecular dynamics simulations with a Stillinger-Weber potential have been used to investigate the melting behavior of wurtzite-type single...

  17. RF Power Degradation of GaN High Electron Mobility Transistors

    E-Print Network [OSTI]

    Joh, Jungwoo

    We have developed a versatile methodology to systematically investigate the RF reliability of GaN High-Electron Mobility Transistors. Our technique utilizes RF and DC figures of merit to diagnose the degradation of RF ...

  18. Correlation of doping, structure, and carrier dynamics in a single GaN nanorod

    E-Print Network [OSTI]

    Zhou, Xiang

    We report the nanoscale optical investigation of a single GaN p-n junction nanorod by cathodoluminescence (CL) in a scanning transmission electron microscope. CL emission characteristic of dopant-related transitions was ...

  19. Above room-temperature ferromagnetism of Mn delta-doped GaN nanorods

    SciTech Connect (OSTI)

    Lin, Y. T.; Wadekar, P. V.; Kao, H. S.; Chen, T. H.; Chen, Q. Y.; Tu, L. W., E-mail: lwtu@faculty.nsysu.edu.tw [Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Huang, H. C.; Ho, N. J. [Department of Materials and Optoelectronic Science and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China)

    2014-02-10T23:59:59.000Z

    One-dimensional nitride based diluted magnetic semiconductors were grown by plasma-assisted molecular beam epitaxy. Delta-doping technique was adopted to dope GaN nanorods with Mn. The structural and magnetic properties were investigated. The GaMnN nanorods with a single crystalline structure and with Ga sites substituted by Mn atoms were verified by high-resolution x-ray diffraction and Raman scattering, respectively. Secondary phases were not observed by high-resolution x-ray diffraction and high-resolution transmission electron microscopy. In addition, the magnetic hysteresis curves show that the Mn delta-doped GaN nanorods are ferromagnetic above room temperature. The magnetization with magnetic field perpendicular to GaN c-axis saturates easier than the one with field parallel to GaN c-axis.

  20. Reliability of GaN high electron mobility transistors on silicon substrates

    E-Print Network [OSTI]

    Demirtas, Sefa

    2009-01-01T23:59:59.000Z

    GaN High Electron Mobility Transistors are promising devices for high power and high frequency applications such as cellular base stations, radar and wireless network systems, due to the high bandgap and high breakdown ...

  1. Development of strain reduced GaN on Si (111) by substrate engineering

    SciTech Connect (OSTI)

    Jamil, M.; Grandusky, J.R.; Jindal, V.; Shahedipour-Sandvik, F.; Guha, S.; Arif, M. [College of Nanoscale Science and Engineering, University at Albany-State University of New York, 255 Fuller Rd, Albany, New York 12203 (United States); Department of Physics and Astronomy, University of Missouri-Columbia, Columbia, Missouri 65211 (United States)

    2005-08-22T23:59:59.000Z

    We report on a novel scheme of substrate engineering to obtain high-quality GaN layers on Si substrates. Ion implantation of an AlN/Si substrate is performed to create a defective layer that partially isolates the III-nitride layer and the Si substrate and helps to reduce the strain in the film. Raman spectroscopy shows a substantial decrease in in-plane strain in GaN films grown on nitrogen implanted substrates. This is confirmed by the enhancement of the E{sub 2} (TO) phonon frequency from 564 to 567 cm{sup -1} corresponding to 84% stress reduction and substantial decrease in crack density for a 2-{mu}m-thick GaN film. GaN films grown on implanted AlN/Si substrate have better optical properties and smoother surface morphology as compared to nonimplanted AlN/Si substrate.

  2. Radiative defects in GaN nanocolumns: Correlation with growth conditions and sample morphology

    SciTech Connect (OSTI)

    Lefebvre, P.; Fernandez-Garrido, S.; Grandal, J.; Ristic, J.; Sanchez-Garcia, M.-A.; Calleja, E. [Instituto de Sistemas Optoelectronicos y Microtecnologia, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2011-02-21T23:59:59.000Z

    Low-temperature photoluminescence is studied in detail in GaN nanocolumns (NCs) grown by plasma-assisted molecular beam epitaxy under various conditions (substrate temperature and impinging Ga/N flux ratio). The relative intensities of the different emission lines, in particular those related to structural defects, appear to be correlated with the growth conditions, and clearly linked to the NC sample morphology. We demonstrate, in particular, that all lines comprised between 3.10 and 3.42 eV rapidly lose intensity when the growth conditions are such that the NC coalescence is reduced. The well-known line around 3.45 eV, characteristic of GaN NC samples, shows, however, a behavior that is exactly the opposite of the other lines, namely, for growth conditions leading to reduced NC coalescence, this line tends to become more prominent, thus proving to be intrinsic to individual GaN NCs.

  3. Measurement of Channel Temperature in GaN High-Electron Mobility Transistors

    E-Print Network [OSTI]

    Joh, Jungwoo

    In this paper, a simple and reliable method to estimate the channel temperature of GaN high-electron mobility transistors (HEMTs) is proposed. The technique is based on electrical measurements of performance-related figures ...

  4. The study of in situ scanning tunnelling microscope characterization on GaN thin film grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Yang, R.; Krzyzewski, T.; Jones, T. [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)] [Department of Chemistry, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2013-03-18T23:59:59.000Z

    The epitaxial growth of GaN by Plasma Assisted Molecular Beam Epitaxy was investigated by Scanning Tunnelling Microscope (STM). The GaN film was grown on initial GaN (0001) and monitored by in situ Reflection High Energy Electron Diffraction and STM during the growth. The STM characterization was carried out on different sub-films with increased thickness. The growth of GaN was achieved in 3D mode, and the hexagonal edge of GaN layers and growth gradient were observed. The final GaN was of Ga polarity and kept as (0001) orientation, without excess Ga adlayers or droplets formed on the surface.

  5. Optical Properties of Mn-doped GaN O. Gelhausen1

    E-Print Network [OSTI]

    Nabben, Reinhard

    measurements. In the GaN:Mn, an intense absorption peak at 1.414 +/- 0.002 eV was observed. This peakOptical Properties of Mn-doped GaN O. Gelhausen1 , E. Malguth1,3 , M. R. Phillips1 , E. M. Goldys2, Germany ABSTRACT Molecular beam epitaxy-grown GaN with different Mn concentrations (5-23 x 1019 cm-3

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

    SciTech Connect (OSTI)

    Bolat, S., E-mail: bolat@ee.bilkent.edu.tr, E-mail: aokyay@ee.bilkent.edu.tr; Tekcan, B. [Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800 (Turkey); UNAM, National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Ozgit-Akgun, C.; Biyikli, N. [UNAM, National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Okyay, A. K., E-mail: bolat@ee.bilkent.edu.tr, E-mail: aokyay@ee.bilkent.edu.tr [Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800 (Turkey); UNAM, National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey)

    2014-06-16T23:59:59.000Z

    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.

  7. Behavior of aluminum adsorption and incorporation at GaN(0001) surface: First-principles study

    SciTech Connect (OSTI)

    Qin, Zhenzhen; Xiong, Zhihua, E-mail: xiong-zhihua@126.com; Wan, Qixin [Key Laboratory for Optoelectronics and Communication of Jiangxi Province, Jiangxi Science and Technology Normal University, Nanchang 330018 (China); Qin, Guangzhao [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, University of Chinese Academy of Sciences, Beijing 101408 (China)

    2013-11-21T23:59:59.000Z

    First-principles calculations are performed to study the energetics and atomic structures of aluminum adsorption and incorporation at clean and Ga-bilayer GaN(0001) surfaces. We find the favorable adsorption site changes from T4 to T1 as Al coverage increased to 1 monolayer on the clean GaN(0001) surface, and a two-dimensional hexagonal structure of Al overlayer appears. It is interesting the Al atoms both prefer to concentrate in one deeper Ga layer of clean and Ga-bilayer GaN(0001) surface, respectively, while different structures could be achieved in above surfaces. For the case of clean GaN(0001) surface, corresponding to N-rich and moderately Ga-rich conditions, a highly regular superlattice structure composed of wurtzite GaN and AlN becomes favorable. For the case of Ga-bilayer GaN(0001) surface, corresponding to extremely Ga-rich conditions, the Ga bilayer is found to be sustained stable in Al incorporating process, leading to an incommensurate structure directly. Furthermore, our calculations provide an explanation for the spontaneous formation of ordered structure and incommensurate structure observed in growing AlGaN films. The calculated results are attractive for further development of growth techniques and excellent AlGaN/GaN heterostructure electronic devices.

  8. Nondestructive characterization of GaN films grown at low and high temperatures

    SciTech Connect (OSTI)

    Yan, C.H.; Yao, H.W.; Hove, J.M. van; Wowchak, A.M.; Chow, P.P.; Han, J.; Zavada, J.M.

    2000-07-01T23:59:59.000Z

    GaN films grown on GaAs and sapphire substrates by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) at both low and high temperatures (LT and HT) were characterized by Raman scattering and variable angle spectroscopic ellipsometry (VASE). Optical phonon spectra of GaN films are obtained through back-scattering geometry. Crystal quality of these films was qualitatively examined using phonon line-width. Phonon spectra showed that the HT GaN has wurtzite crystal structure, while LT GaN and GaN/GaAs have cubic-like structures. Thickness nonuniformity and defect-related absorption can be characterized by pseudo dielectric functions directly. Surface roughness also can be determined by using an effective-medium approximation (EMA) over-layer in a VASE analysis. Anisotropic optical constants of GaN, both ordinary and extraordinary, were obtained in the spectral range of 0.75 to 6.5 eV with the consideration of surface roughness, through the small and large angles of incidence, respectively. The film thickness of the GaN was accurately determined via the analysis as well.

  9. Deposition of CVD diamond onto GaN P.W. May a,*, H.Y. Tsai b

    E-Print Network [OSTI]

    Bristol, University of

    of the polycrystalline diamond surface would prevent light from leaking out of the GaN layer and channel it to the endsDeposition of CVD diamond onto GaN P.W. May a,*, H.Y. Tsai b , W.N. Wang c , J.A. Smith a a School performed to deposit continuous layers of CVD diamond onto epitaxial GaN films. Such diamond coatings would

  10. Molecular Beam Epitaxial Growth of Zinc-Blende FeN(111) on Wurtzite GaN(0001)

    E-Print Network [OSTI]

    Molecular Beam Epitaxial Growth of Zinc-Blende FeN(111) on Wurtzite GaN(0001) Wenzhi Lin, Jeongihm], but not hexagonal (wurtzite) GaN, a fast-developing semiconductor material with important technological applicationsN on wurtzite GaN(0001), by employing e-beam evaporation in an ultra-high vacuum MBE cham- ber. The FeN films

  11. Calculated second-harmonic susceptibilities of BN, AlN, and GaN Jian Chen,a)

    E-Print Network [OSTI]

    Wilkins, John

    and the second-harmonic susceptibility d for BN, AlN, and GaN in both zincblende and wurtzite structures within the Kohn­Sham local-density approximation. For wurtzite AlN and GaN, the computed dxxz (w) and dzzz (w) closely agree with experiment. For zincblende AlN and GaN as well as zincblende and wurtzite BN, we

  12. Doping of GaN12xAsx with high As content A. X. Levander,1,2

    E-Print Network [OSTI]

    Wu, Junqiao

    Doping of GaN12xAsx with high As content A. X. Levander,1,2 S. V. Novikov,3 Z. Liliental-Weber,1 R; published online 2 November 2011) Recent work has shown that GaN1ÀxAsx can be grown across the entire report the bipolar doping of GaN1ÀxAsx with high As content to conductivities above 4 S=cm at room

  13. Role of nitrogen vacancies in the luminescence of Mg-doped GaN Qimin Yan,1

    E-Print Network [OSTI]

    Role of nitrogen vacancies in the luminescence of Mg-doped GaN Qimin Yan,1 Anderson Janotti,1 or act as recombination centers in Mg- doped GaN is essential for improving the performance of group-vacancy complexes (MgGa-VN) on the electrical and optical properties of GaN. We find that MgGa-VN are compensating

  14. The adsorption of oxygen at GaN surfaces Tosja K. Zywietz, Jrg Neugebauer, and Matthias Scheffler

    E-Print Network [OSTI]

    The adsorption of oxygen at GaN surfaces Tosja K. Zywietz, Jörg Neugebauer, and Matthias Scheffler://apl.aip.org/about/rights_and_permissions #12;The adsorption of oxygen at GaN surfaces Tosja K. Zywietz,a) Jo¨rg Neugebauer, and Matthias based on GaN is the controlled doping and the incorporation of impurities like, e.g., oxygen. We have

  15. Low gap amorphous GaN1-xAsx alloys grown on glass substrate K. M. Yu,1,a

    E-Print Network [OSTI]

    Wu, Junqiao

    Low gap amorphous GaN1-xAsx alloys grown on glass substrate K. M. Yu,1,a S. V. Novikov,2 R September 2010 Amorphous GaN1-xAsx layers with As content in the range of x=0.1 to 0.6 were grown defined optical absorption edges. The measured band gap values for the crystalline and amorphous GaN1-x

  16. Comparison of strong coupling regimes in bulk GaAs, GaN and ZnO semiconductor microcavities

    E-Print Network [OSTI]

    Boyer, Edmond

    , transmission and absorption spectra of bulk GaAs, GaN and ZnO microcavities, in order to compareComparison of strong coupling regimes in bulk GaAs, GaN and ZnO semiconductor microcavities SAs and GaN microcavities. PACS numbers: 78.67.-n, 71.36.+c, 78.20.Ci, 78.55.Cr, 78.55.Et Keywords: polariton

  17. Thermal Stability of MOCVD and HVPE GaN Layers in H2, HCl, NH3 and N2

    E-Print Network [OSTI]

    Anderson, Timothy J.

    GaN, and the black is the sapphire substrate. At 900 C nearly 1/4 of the film has sublimated leavingThermal Stability of MOCVD and HVPE GaN Layers in H2, HCl, NH3 and N2 M. A. Mastro1 ) (a), O. M.60.Dv; 81.15.Gh; S7.14 This work represents a complete study of GaN annealed in H2, HCl, NH3 and N2

  18. Transition between wurtzite and zinc-blende GaN: An effect of deposition condition of molecular-beam epitaxy

    SciTech Connect (OSTI)

    Shi, B. M.; Xie, M. H.; Wu, H. S.; Wang, N.; Tong, S. Y. [Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (China); Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tang, Hong Kong (China)

    2006-10-09T23:59:59.000Z

    GaN exists in both wurtzite and zinc-blende phases and the growths of the two on its (0001) or (111) surfaces are achieved by choosing proper deposition conditions of molecular-beam epitaxy (MBE). At low substrate temperatures but high gallium fluxes, metastable zinc-blende GaN films are obtained, whereas at high temperatures and/or using high nitrogen fluxes, equilibrium wurtzite phase GaN epilayers resulted. This dependence of crystal structure on substrate temperature and source flux is not affected by deposition rate. Rather, the initial stage nucleation kinetics plays a primary role in determining the crystallographic structures of epitaxial GaN by MBE.

  19. Impact of substrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN grown by molecular beam epitaxy

    E-Print Network [OSTI]

    Armstrong, A; Poblenz, C; Green, D S; Mishra, U K; Speck, J S; Ringel, S A

    2006-01-01T23:59:59.000Z

    GaN grown by molecular beam epitaxy and codoped with carbon and silicon were investigated for substratesubstrate temperature on the incorporation of carbon-related defects and mechanism for semi-insulating behavior in GaN

  20. 596 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 41, NO. 4, APRIL 2005 Nanoscale Spatial Phase Modulation of GaN on

    E-Print Network [OSTI]

    New Mexico, University of

    Modulation of GaN on a V-Grooved Si Substrate--Cubic Phase GaN on Si(001) for Monolithic Integration S. C Abstract--Nanoscale spatial phase modulation of GaN gorwn on a 355-nm period array of V-grooves fabricated in a Si(001) substrate is reported. Orientation-dependent selective nucleation of GaN in metal

  1. Energetics of H and NH2 on GaN,,1010... and implications for the origin of nanopipe defects John E. Northrup and R. Di Felice

    E-Print Network [OSTI]

    Energetics of H and NH2 on GaN,,101¯0... and implications for the origin of nanopipe defects John E-terminated GaN 101¯0 surfaces. The calculations indicate that H adsorption on GaN 101¯0 will proceed. The implications of these results for the origin of nanopipe defects in GaN are examined. S0163-1829 97 51832

  2. IPAP Conference Series 1: IWN2000, Nov., 2000 1 Morphology Dependent Growth Kinetics of Ga-polar GaN(0001)

    E-Print Network [OSTI]

    Cohen, Philip I.

    IPAP Conference Series 1: IWN2000, Nov., 2000 1 Morphology Dependent Growth Kinetics of Ga-polar GaN, cohen@ece.umn.edu GaN grown on Ga polar GaN templates prepared by metal-organic vapor deposition shows to equilibrium models of the growth. The results indicate that Ga-polar GaN(0001) has a step energy of the order

  3. Crystallographically tilted and partially strain relaxed GaN grown on inclined (111) facets etched on Si(100) substrate

    SciTech Connect (OSTI)

    Ansah Antwi, K. K. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, 3 Research Link, 117602 Singapore (Singapore); Soh, C. B. [Singapore Institute of Technology, 10 Dover Drive, Singapore 138683 (Singapore); Wee, Q. [Singapore-MIT Alliance, National University of Singapore, Singapore 117576 (Singapore); Tan, Rayson J. N.; Tan, H. R. [Institute of Materials Research and Engineering, 3 Research Link, 117602 Singapore (Singapore); Yang, P. [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, 117603 Singapore (Singapore); Sun, L. F.; Shen, Z. X. [School of Physical and Mathematical Sciences, Nanyang Technological University, SPMS-03-01, 21 Nanyang Link (Singapore); Chua, S. J., E-mail: elecsj@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, 3 Research Link, 117602 Singapore (Singapore); Singapore-MIT Alliance, National University of Singapore, Singapore 117576 (Singapore)

    2013-12-28T23:59:59.000Z

    High resolution X-ray diffractometry (HR-XRD), Photoluminescence, Raman spectroscopy, and Transmission electron microscope measurements are reported for GaN deposited on a conventional Si(111) substrate and on the (111) facets etched on a Si(100) substrate. HR-XRD reciprocal space mappings showed that the GaN(0002) plane is tilted by about 0.63°?±?0.02° away from the exposed Si(111) growth surface for GaN deposited on the patterned Si(100) substrate, while no observable tilt existed between the GaN(0002) and Si(111) planes for GaN deposited on the conventional Si(111) substrate. The ratio of integrated intensities of the yellow to near band edge (NBE) luminescence (I{sub YL}/I{sub NBE}) was determined to be about one order of magnitude lower in the case of GaN deposited on the patterned Si(100) substrate compared with GaN deposited on the conventional Si(111) substrate. The Raman E{sub 2}(high) optical phonon mode at 565.224?±?0.001?cm{sup ?1} with a narrow full width at half maximum of 1.526?±?0.002?cm{sup ?1} was measured, for GaN deposited on the patterned Si(100) indicating high material quality. GaN deposition within the trench etched on the Si(100) substrate occurred via diffusion and mass-transport limited mechanism. This resulted in a differential GaN layer thickness from the top (i.e., 1.8??m) of the trench to the bottom (i.e., 0.3??m) of the trench. Mixed-type dislocation constituted about 80% of the total dislocations in the GaN grown on the inclined Si(111) surface etched on Si(100)

  4. High-electron-mobility GaN grown on free-standing GaN templates by ammonia-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Kyle, Erin C. H., E-mail: erinkyle@umail.ucsb.edu; Kaun, Stephen W.; Burke, Peter G.; Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wu, Yuh-Renn [Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei City 10617, Taiwan (China)

    2014-05-21T23:59:59.000Z

    The dependence of electron mobility on growth conditions and threading dislocation density (TDD) was studied for n{sup ?}-GaN layers grown by ammonia-based molecular beam epitaxy. Electron mobility was found to strongly depend on TDD, growth temperature, and Si-doping concentration. Temperature-dependent Hall data were fit to established transport and charge-balance equations. Dislocation scattering was analyzed over a wide range of TDDs (?2?×?10{sup 6}?cm{sup ?2} to ?2?×?10{sup 10}?cm{sup ?2}) on GaN films grown under similar conditions. A correlation between TDD and fitted acceptor states was observed, corresponding to an acceptor state for almost every c lattice translation along each threading dislocation. Optimized GaN growth on free-standing GaN templates with a low TDD (?2?×?10{sup 6}?cm{sup ?2}) resulted in electron mobilities of 1265 cm{sup 2}/Vs at 296?K and 3327 cm{sup 2}/Vs at 113?K.

  5. Micro-Raman and cathodoluminescence studies of epitaxial laterally overgrown GaN with tungsten masks: A method to map the free-carrier

    E-Print Network [OSTI]

    Nabben, Reinhard

    Micro-Raman and cathodoluminescence studies of epitaxial laterally overgrown GaN with tungsten properties of two epitaxial-laterally overgrown GaN structures with tungsten masks in 1100 and 1120 direction by tungsten masks3 to prevent the in-diffusion of silicon and oxygen atoms in the overgrown GaN, which

  6. GaN nanowire lasers with low lasing thresholds Silvija Gradecak, Fang Qian, Yat Li, Hong-Gyu Park, and Charles M. Liebera

    E-Print Network [OSTI]

    Li, Yat

    GaN nanowire lasers with low lasing thresholds Silvija Gradecak, Fang Qian, Yat Li, Hong-Gyu Park September 2005; published online 18 October 2005 We report optically pumped room-temperature lasing in GaN of 22 kW/cm2 that are substantially lower than other previously reported GaN nanowires. Key

  7. PHYSICAL REVIEW B VOLUME 52, NUMBER 23 15 DECEMBER 1995-I Properties of the yellow luminescence in undoped GaN epitaxial layers

    E-Print Network [OSTI]

    Nabben, Reinhard

    Micro-Raman and cathodoluminescence studies of epitaxial laterally overgrown GaN with tungsten masks: A method to map the free-carrier concentration of thick GaN samples A. Kaschner,a) A. Hoffmann properties of two epitaxial-laterally overgrown GaN structures with tungsten masks in 1100 and 1120 direction

  8. Impact of high-power stress on dynamic ON-resistance of high-voltage GaN HEMTs Donghyun Jin

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Impact of high-power stress on dynamic ON-resistance of high-voltage GaN HEMTs Donghyun Jin-resistance (RON) in high- voltage GaN High-Electron-Mobility Transistors (HEMTs). We use a newly proposed dynamic. All rights reserved. 1. Introduction In the last decade, GaN Field-Effect Transistors have emerged

  9. GaN0.011P0.989–GaP Double-Heterostructure Red Light-Emitting Diodes Directly Grown on GaP Substrates

    E-Print Network [OSTI]

    Tu, Charles W

    2000-01-01T23:59:59.000Z

    and C. W. Tu, GaN diodes on GaP substrates, 2000. [7] J. W.on a GaN directly grown on a GaP substrate was successfullyDH) directly a GaN grown on a (100) GaP substrate. Fig. 1(a)

  10. The influence of substrate surface preparation on LP MOVPE GaN epitaxy on differently oriented 4H-SiC substrates

    E-Print Network [OSTI]

    Ozbay, Ekmel

    The influence of substrate surface preparation on LP MOVPE GaN epitaxy on differently oriented 4H preparation and off-cut of 4H-SiC substrates on morphological and structural properties of GaN grown by low-SiC is most suitable for GaN epitaxy and that substrate etching improves the surface morphology of epilayer

  11. Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M. FEENSTRA

    E-Print Network [OSTI]

    Feenstra, Randall

    years as a substrate for both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy of GaN of the substrate preparation and growth technique. Experimental GaN films of typically 1 mm thickness are deposited1 Growth of GaN on SiC(0001) by Molecular Beam Epitaxy C. D. LEE (a), ASHUTOSH SAGAR (a), R. M

  12. Effect of dislocation scattering on the transport properties of InN grown on GaN substrates by molecular beam epitaxy

    E-Print Network [OSTI]

    Effect of dislocation scattering on the transport properties of InN grown on GaN substrates on GaN substrates by plasma-assisted molecular beam epitaxy. They have found a strong correlation, optical, and transport properties of InN on GaN substrates. In this work, we have studied the MBE growth

  13. 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

    2009-07-01T23:59:59.000Z

    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 using optical reflectance and the nucleation density was determined using atomic force microscopy (AFM) and Nomarski microscopy. Dislocation density was measured using X-ray diffraction and AFM after coating the surface with silicon nitride to delineate all dislocation types. The program milestone of producing GaN films with dislocation densities of 1 x 10{sup 8} cm{sup -2} was met by silicon nitride treatment of annealed sapphire followed by the multiple deposition of a low density of GaN nuclei followed by high temperature GaN growth. Details of this growth process and the underlying science are presented in this final report along with problems encountered in this research and recommendations for future work.

  14. Optically active centers in Eu implanted, Eu in situ doped GaN, and Eu doped GaN quantum dots

    SciTech Connect (OSTI)

    Bodiou, L.; Braud, A.; Doualan, J.-L.; Moncorge, R. [Centre de Recherche sur les Ions, les Materiaux et la Photonique (CIMAP), CNRS-CEA-ENSICAEN, Universite de Caen, UMR 6252, 14050 Caen (France); Park, J. H.; Munasinghe, C.; Steckl, A. J. [University of Cincinnati, Cincinnati, Ohio 45221-0030 (United States); Lorenz, K.; Alves, E. [Instituto Tecnologico e Nuclear, Estrada Nacional 10, PT-2685-953 Sacavem (Portugal); Daudin, B. [INAC SP2M/PSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2009-02-15T23:59:59.000Z

    A comparison is presented between Eu implanted and Eu in situ doped GaN thin films showing that two predominant Eu sites are optically active around 620 nm in both types of samples with below and above bandgap excitation. One of these sites, identified as a Ga substitutional site, is common to both types of Eu doped GaN samples despite the difference in the GaN film growth method and in the doping technique. High-resolution photoluminescence (PL) spectra under resonant excitation reveal that in all samples these two host-sensitized sites are in small amount compared to the majority of Eu ions which occupy isolated Ga substitutional sites and thus cannot be excited through the GaN host. The relative concentrations of the two predominant host-sensitized Eu sites are strongly affected by the annealing temperature for Eu implanted samples and by the group III element time opening in the molecular beam epitaxy growth. Red luminescence decay characteristics for the two Eu sites reveal different excitation paths. PL dynamics under above bandgap excitation indicate that Eu ions occupying a Ga substitutional site are either excited directly into the {sup 5}D{sub 0} level or into higher excited levels such as {sup 5}D{sub 1}, while Eu ions sitting in the other site are only directly excited into the {sup 5}D{sub 0} level. These differences are discussed in terms of the spectral overlap between the emission band of a nearby bound exciton and the absorption bands of Eu ions. The study of Eu doped GaN quantum dots reveals the existence of only one type of Eu site under above bandgap excitation, with Eu PL dynamics features similar to Eu ions in Ga substitutional sites.

  15. Thermoelectric effects in wurtzite GaN and AlxGa1-xN alloys and Alexander A. Balandin

    E-Print Network [OSTI]

    with the active thermoelectric cooling implemented on the same material system can improve the device performance, for the pro- posed cooling system should also be based on GaN. To real- ize this, the high-efficiency Ga,6 Great progress has been achieved in GaN-based microwave technology. GaN transistors with very high

  16. First-principles studies of beryllium doping of GaN Chris G. Van de Walle* and Sukit Limpijumnong

    E-Print Network [OSTI]

    First-principles studies of beryllium doping of GaN Chris G. Van de Walle* and Sukit Limpijumnong Received 12 October 2000; published 8 June 2001 The structural and electronic properties of beryllium acceptors, and between hydrogen and substitutional beryllium. The results for wurtzite GaN are compared

  17. Reconstructions of GaN,,0001... and ,,0001... surfaces: Ga-rich metallic A. R. Smith and R. M. Feenstraa)

    E-Print Network [OSTI]

    wurtzite material.1­9 A common theme regarding the growth of these surfaces in the absence of hydrogen and elec- tronic properties of two reconstructions for wurtzite GaN: the 1 1 structure of the GaN 0001

  18. PHYSICAL REVIEW B 86, 075207 (2012) Optical signature of Mg-doped GaN: Transfer processes

    E-Print Network [OSTI]

    Nabben, Reinhard

    2012-01-01T23:59:59.000Z

    PHYSICAL REVIEW B 86, 075207 (2012) Optical signature of Mg-doped GaN: Transfer processes G; published 23 August 2012) Mg doping of high quality, metal organic chemical vapor deposition grown GaN films GaN:Mg grown on sapphire substrates and identify two Mg related acceptor states, one additional

  19. Belgirate, Italy, 28-30 September 2005 THERMAL MODELLING OF MULTI-FINGER ALGAN/GAN HEMT's

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    Belgium contact author: herman.oprins@imec.be ABSTRACT AlGaN/GaN high electron mobility transistors (HEMTs validation of the modelling, both structures are thermally optimized. 1. INTRODUCTION As GaN devices operate of delivering about 0.75W/mm. The rapid increase in power density since the beginning of the development of GaN

  20. Luminescence Efficiency of InGaN/GaN Quantum Wells on Bulk GaN Substrate M. Dworzak1

    E-Print Network [OSTI]

    Nabben, Reinhard

    Luminescence Efficiency of InGaN/GaN Quantum Wells on Bulk GaN Substrate M. Dworzak1 , T. Stempel1/37, 01-142 Warsaw, Poland ABSTRACT Time-integrated and time-resolved photoluminescence measurements on InGaN quantum wells grown by MOCVD on two different substrates (sapphire and GaN) show that the lumines- cence

  1. Effect of Trapping on the Critical Voltage for Degradation in GaN High Electron Mobility Transistors

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    power and high frequency applications. Si is an attractive substrate for GaN HEMTs because of its lower and thermal mismatch between GaN and Si as compared to the more commonly used substrate, SiC, results in more regardless of the characteristics of the substrate. II. EXPERIMENTAL We studied experimental AlxGa1­xN/GaN

  2. The Effect of Periodic Silane Burst on the Properties of GaN on Si (111) Substrates

    E-Print Network [OSTI]

    Zang, Keyan

    The periodic silane burst technique was employed during metalorganic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111). Periodic silicon delta doping during growth of both the AlN and GaN ...

  3. Tuning linear and nonlinear optical properties of wurtzite GaN by c-axial stress

    E-Print Network [OSTI]

    Cai, Duanjun; 10.1088/0022-3727/42/18/185107

    2009-01-01T23:59:59.000Z

    We study the linear and nonlinear optical properties of wurtzite GaN under c-axial stress field, using density functional theory calculations. The fully structural optimization at each c-axial strain was performed. The calculated dielectric functions show that tensile c-axial strain effectively improves the linear optical efficiency, especially for the band-edge transitions, and significantly increase the mobility of electrons in the conduction band. Second-order nonlinear optical susceptibilities show that the tensile c-axial strain will enhance the zero- and low-frequency nonlinear responses of GaN. The enhancement of the nonlinear optical property is explained by the reduction of the polarization of wurtzite GaN under tensile c-axial strains. Based on these findings, we propose a method for improving the electrical and optical properties of the crystal through imposing appropriate stress on the high symmetry crystalline directions.

  4. Electrical characterization of ensemble of GaN nanowires grown by the molecular beam epitaxy technique

    SciTech Connect (OSTI)

    Kolkovsky, Vl. [Technische Universität Dresden, 01062 Dresden (Germany)] [Technische Universität Dresden, 01062 Dresden (Germany); Zytkiewicz, Z. R.; Sobanska, M.; Klosek, K. [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32-46, 02-668 Warsaw (Poland)] [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32-46, 02-668 Warsaw (Poland)

    2013-08-26T23:59:59.000Z

    High quality Schottky contacts are formed on GaN nanowires (NWs) structures grown by the molecular beam epitaxy technique on Si(111) substrate. The current-voltage characteristics show the rectification ratio of about 10{sup 3} and the leakage current of about 10{sup ?4} A/cm{sup 2} at room temperature. From the capacitance-voltage measurements the free carrier concentration in GaN NWs is determined as about 10{sup 16} cm{sup ?3}. Two deep levels (H200 and E280) are found in the structures containing GaN NWs. H200 is attributed to an extended defect located at the interface between the substrate and SiN{sub x} or near the sidewalls at the bottom of the NWs whereas E280 is tentatively assigned to a gallium-vacancy- or nitrogen interstitials-related defect.

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

    SciTech Connect (OSTI)

    Kuppulingam, B., E-mail: drbaskar2009@gmail.com; Singh, Shubra, E-mail: drbaskar2009@gmail.com; Baskar, K., E-mail: drbaskar2009@gmail.com [Crystal Growth Centre, Anna University, Chennai-600025 (India)

    2014-04-24T23:59:59.000Z

    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.

  6. Interaction of hydrogen with gallium vacancies in wurtzite GaN

    SciTech Connect (OSTI)

    Wright, A. F.

    2001-08-01T23:59:59.000Z

    First-principles techniques are used to investigate the interaction of hydrogen with gallium vacancies in wurtzite GaN. The calculations reveal that hydrogen can either compensate a vacancy by donating an electron to a vacancy acceptor level, or passivate the vacancy by forming a hydrogen-vacancy complex. A gallium vacancy can bind up to four hydrogen atoms, and hydrogen removal energies are computed as a function of the number of hydrogen atoms. Removal energies are found to depend strongly on Fermi level and complexes containing more than two hydrogen atoms are predicted to be unstable in n-type GaN. Hydrogen vibration frequencies are computed and compared with previously reported infrared absorption measurements for hydrogen-implanted GaN.

  7. Long-Lived, Coherent Acoustic Phonon Oscillations in GaN Single Crystals

    SciTech Connect (OSTI)

    Wu, S.; Geiser, P.; Jun, J.; Karpinski, J.; Park, J.-R.; Sobolewski, R.

    2006-01-31T23:59:59.000Z

    We report on coherent acoustic phonon (CAP) oscillations studied in high-quality bulk GaN single crystals with a two-color femtosecond optical pump-probe technique. Using a far-above-the-band gap ultraviolet excitation (~270 nm wavelength) and a near-infrared probe beam (~810 nm wavelength), the long-lived, CAP transients were observed within a 10 ns time-delay window between the pump and probe pulses, with a dispersionless (proportional to the probe-beam wave vector) frequency of ~45 GHz. The measured CAP attenuation corresponded directly to the absorption of the probe light in bulk GaN, indicating that the actual (intrinsic) phonon-wave attenuation in our crystals was significantly smaller than the measured 65.8 cm^-1 value. The velocity of the phonon propagation was equal to the velocity of sound in GaN.

  8. Effect of buffer layer growth temperature on epitaxial GaN films deposited by magnetron sputtering

    SciTech Connect (OSTI)

    Mohanta, P.; Singh, D.; Kumar, R.; Ganguli, T.; Srinivasa, R. S.; Major, S. S. [Center For Research in Nano-Technology and Science (India); Semiconductor Laser Section, RRCAT, Indore-452013 (India); Department of Metallurgical Engineering and Materials Science (India); Department of Physics, Indian Institute of Technology Bombay, Mumbai - 400076 (India)

    2012-06-05T23:59:59.000Z

    Epitaxial GaN films were deposited by reactive sputtering of a GaAs target in 100 % nitrogen at 700 deg. C on ZnO buffer layers grown at different substrate temperatures over sapphire substrates. High resolution X-ray diffraction measurements and the corresponding analysis show that the growth temperature of buffer layers significantly affects the micro-structural parameters of GaN epilayer, such as lateral coherence length, tilt and twist, while the vertical coherence length remains unaffected. The optimum substrate temperature for buffer layer growth has been found to be 300 deg. C. High epitaxial quality GaN film grown on such a buffer layer exhibited micro strain of 1.8x10{sup -4} along with screw and edge type dislocation densities of 7.87x10{sup 9} and 1.16x10{sup 11}, respectively.

  9. Evidence of satellite valley position in GaN by photoexcited field emission spectroscopy

    SciTech Connect (OSTI)

    Yilmazoglu, O.; Pavlidis, D.; Hartnagel, H. L. [Department of High Frequency Electronics, Technische Universitaet Darmstadt, 64283 Darmstadt (Germany); Evtukh, A.; Litovchenko, V.; Semenenko, N. [Institute of Semiconductor Physics, NASU, 03028 Kiev (Ukraine)

    2008-06-01T23:59:59.000Z

    GaN field emitter rods with nanometer diameter were fabricated by photoelectrochemical etching on a n{sup +}-GaN substrate. Their electron field emission properties were investigated under ultraviolet (UV) illumination. The Fowler-Nordheim plots of the emission current show different slopes for nonilluminated and UV illuminated devices. A model based on the electron emission from valleys having different specific electron affinities is proposed to explain the experimental results. In the absence of illumination, the GaN rods are almost fully depleted and emission takes place only from the lower valley. Upon UV illumination and presence of a high electric field at the emitter tip, the upper valley of the conduction band appears to be occupied by electrons generated at the valence band. The energy difference between the lower and upper valleys was determined to be 1.15 eV and is in good agreement with formerly published theoretical and measured values.

  10. Design and Experimental Characterization of an Erbium Doped GaN Waveguide

    E-Print Network [OSTI]

    Wang, Qian

    2012-05-31T23:59:59.000Z

    temperatures as compared to other semiconductor host materials such as Si and GaAs. 1540nm optical emission in Er- doped waveguide has also been demonstrated using a 365nm light emitting diode as the optical pumping source. UV pumping above the GaN bandgap....9 eV In Table 2 - 1, GaN is the semiconductor material with the largest bandgap (SiO2 is not a semiconductor), which has proven to be an accomplished host of erbium, with reports of fabrication of light- emitting diodes operating in the visible...

  11. X-ray detectors based on GaN Schottky diodes

    SciTech Connect (OSTI)

    Duboz, Jean-Yves; Frayssinet, Eric; Chenot, Sebastien [CRHEA, CNRS, Rue Bernard Gregory, Sophia Antipolis, F-06560 Valbonne (France); Reverchon, Jean-Luc [THALES R and T, Campus Polytechnique, 1 avenue Augustin Fresnel, F-91767 Palaiseau Cedex (France); Idir, Mourad [Synchrotron SOLEIL L'Orme des Merisiers, Saint-Aubin-BP 48 91192, GIF-sur-Yvette Cedex (France)

    2010-10-18T23:59:59.000Z

    GaN Schottky diodes have been fabricated and tested as x-ray detectors in the range from 6 to 21 keV. The spectral response has been measured and is compared to its theoretical value. The study of the response and its temporal dynamics as a function of the bias allows to identify a photovoltaic behavior at low bias and a photoconductive one at larger reverse biases. The GaN diode turned out to be linear as a function of the incident power. The noise and detectivity are given and discussed.

  12. Characterization of GaN microstructures grown by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Lo, Ikai; Pang, Wen-Yuan; Hsu, Yu-Chi; Hsieh, Chia-Ho; Shih, Cheng-Hung; Chou, Mitch M. C. [Department of Physics and Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Chen, Wen-Yen; Hsu, Tzu-Min [Department of Physics, National Central University, Jhong-li, Taoyuan 32001, Taiwan (China); Hsu, Gary Z. L. [United Crystal Corporation, No.243-3, Wenshan, 36061, Miaoli, Taiwan (China)

    2013-06-15T23:59:59.000Z

    The characterization of GaN microstructures grown by plasma-assisted molecular beam epitaxy on LiAlO{sub 2} substrate was studied by cathodoluminescence and photoluminescence measurements. We demonstrated that the cathodoluminescence from oblique semi-polar surfaces of mushroom-shaped GaN was much brighter than that from top polar surface due to the reduction of polarization field on the oblique semi-polar surfaces. It implies that the oblique semi-polar surface is superior for the light-emitting surface of wurtzite nano-devices.

  13. Ge doped GaN with controllable high carrier concentration for plasmonic applications

    SciTech Connect (OSTI)

    Kirste, Ronny; Hoffmann, Marc P.; Sachet, Edward; Bobea, Milena; Bryan, Zachary; Bryan, Isaac; Maria, Jon-Paul; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States)] [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Nenstiel, Christian; Hoffmann, Axel [Institut f?r Festkörperphsyik, TU-Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)] [Institut f?r Festkörperphsyik, TU-Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

    2013-12-09T23:59:59.000Z

    Controllable Ge doping in GaN is demonstrated for carrier concentrations of up to 2.4?×?10{sup 20} cm{sup ?3}. Low temperature luminescence spectra from the highly doped samples reveal band gap renormalization and band filling (Burstein-Moss shift) in addition to a sharp transition. Infrared ellipsometry spectra demonstrate the existence of electron plasma with an energy around 3500?cm{sup ?1} and a surface plasma with an energy around 2000?cm{sup ?1}. These findings open possibilities for the application of highly doped GaN for plasmonic devices.

  14. Partially filled intermediate band of Cr-doped GaN films

    SciTech Connect (OSTI)

    Sonoda, S. [Department of Electronics, Kyoto Institute of Technology, Kyoto 606-8585 (Japan)

    2012-05-14T23:59:59.000Z

    We investigated the band structure of sputtered Cr-doped GaN (GaCrN) films using optical absorption, photoelectron yield spectroscopy, and charge transport measurements. It was found that an additional energy band is formed in the intrinsic band gap of GaN upon Cr doping, and that charge carriers in the material move in the inserted band. Prototype solar cells showed enhanced short circuit current and open circuit voltage in the n-GaN/GaCrN/p-GaN structure compared to the GaCrN/p-GaN structure, which validates the proposed concept of an intermediate-band solar cell.

  15. Extraction of absorption coefficients from GaN nanowires grown on opaque substrates

    E-Print Network [OSTI]

    Jayaprakash, Rahul; Germanis, Savvas; Androulidaki, Maria; Tsagaraki, Katerina; Georgakilas, Alexandros; Pelekanos, Nikos T

    2014-01-01T23:59:59.000Z

    We demonstrate a new method to measure absorption coefficients in any family of nanowires, provided they are grown on a substrate having considerable difference in permittivity with the nanowire-air matrix. In the case of high crystal quality, strain-free GaN nanowires, grown on Si (111) substrates with a density of ~1010 cm-2, the extracted absorption coefficients do not exhibit any enhancement compared to bulk GaN values, unlike relevant claims in the literature. This may be attributed to the relatively small diameters, short heights, and high densities of our nanowire arrays.

  16. Realization of compressively strained GaN films grown on Si(110) substrates by inserting a thin AlN/GaN superlattice interlayer

    SciTech Connect (OSTI)

    Shen, X. Q.; Takahashi, T.; Kawashima, H.; Ide, T.; Shimizu, M. [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan)

    2012-07-16T23:59:59.000Z

    We investigate the strain properties of GaN films grown by plasma-assisted molecular beam epitaxy on Si(110) substrates. It is found that the strain of the GaN film can be converted from a tensile to a compressive state simply by inserting a thin AlN/GaN superlattice structure (SLs) within the GaN film. The GaN layers seperated by the SLs can have different strain states, which indicates that the SLs plays a key role in the strain modulation during the growth and the cooling down processes. Using this simple technique, we grow a crack-free GaN film exceeding 2-{mu}m-thick. The realization of the compressively strained GaN film makes it possible to grow thick GaN films without crack generation on Si substrates for optic and electronic device applications.

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

    SciTech Connect (OSTI)

    Vidyasagar, R., E-mail: dr.vidyasagar1979@gmail.com [Department of Physics and Centre for Nanoscience and Nanotechnology, National Sun-Yat Sen University, Kaohsiung 80424, Taiwan, ROC (China); Lin, Y.-T.; Tu, L.-W. [Department of Physics and Centre for Nanoscience and Nanotechnology, National Sun-Yat Sen University, Kaohsiung 80424, Taiwan, ROC (China)] [Department of Physics and Centre for Nanoscience and Nanotechnology, National Sun-Yat Sen University, Kaohsiung 80424, Taiwan, ROC (China)

    2012-12-15T23:59:59.000Z

    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.

  18. 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 [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)] [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2013-01-28T23:59:59.000Z

    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.

  19. Low frequency noise in GaN metal semiconductor and metal oxide semiconductor field effect transistors

    E-Print Network [OSTI]

    Pala, Nezih

    , and Systems Engineering and Center for Integrated Electronics and Electronics Manufacturing, CII 9017, University of South Carolina, Columbia, South Carolina 29208 Received 22 January 2001; accepted American Institute of Physics. DOI: 10.1063/1.1372364 I. INTRODUCTION A recent report on GaN highly doped

  20. Performance degradation of GaN field-effect transistors due to thermal

    E-Print Network [OSTI]

    . We used the standard model for the band gap energy temperature dependence EG ¼ EG0 À aT2 =(b þ material specific models for carrier drift-diffusion and thermal conductivity the authors deter- mine in GaN transis- tors is also discussed. Obtained results can be used for structure optimisation of Ga

  1. Atomic-scale studies on the growth of palladium and titanium on GaN(0001)

    E-Print Network [OSTI]

    Castell, Martin

    Atomic-scale studies on the growth of palladium and titanium on GaN(0001) C. No¨renberg a,b,*, M nitride; Palladium; Titanium; Alloys; Epitaxy; Metal­semiconductor interfaces; Nanostructures; Scanning;Here, we have focused on atomic-scale studies of the ini- tial growth stages of palladium and titanium

  2. FOURIER COEFFICIENTS OF MODULAR FORMS ON G2 WEE TECK GAN, BENEDICT GROSS AND GORDAN SAVIN

    E-Print Network [OSTI]

    Gan, Wee Teck

    FOURIER COEFFICIENTS OF MODULAR FORMS ON G2 WEE TECK GAN, BENEDICT GROSS AND GORDAN SAVIN Abstract. We develop a theory of Fourier coefficients for modular forms on the split ex- ceptional group G2 on the group SL2(Z) is the wealth of information carried by the Fourier coefficients an(f), for n 0

  3. Lattice Protein Folding With Two and Four-Body Statistical Hin Hark Gan,1

    E-Print Network [OSTI]

    Schlick, Tamar

    Lattice Protein Folding With Two and Four-Body Statistical Potentials Hin Hark Gan,1 Alexander/sequence compatibility of proteins,5,6 homology modeling,7 and protein folding simulations.8 ­10 Currently, most structures. Multibody potentials may help improve our understanding of the cooperativity of protein folding

  4. High-Efficiency X-Band MMIC GaN Power Amplifiers Operating as Rectifiers

    E-Print Network [OSTI]

    Popovic, Zoya

    High-Efficiency X-Band MMIC GaN Power Amplifiers Operating as Rectifiers Michael Litchfield, Scott two 10 x 100j.Lm power combined devices. The MMICs exhibit 67% and 56% power added efficiency at VDD a RF-to-DC efficiency of 64%. The output powers of the two MMIC PAs are around 3.2W. In rectifier mode

  5. GaN Based Nanomaterials Fabrication with Anodic Aluminium Oxide by MOCVD

    E-Print Network [OSTI]

    Wang, Yadong

    A highly self-ordered hexagonal array of cylindrical pores has been fabricated by anodizing a thin film of Al on substrate and subsequent growth of GaN and InGaN in these nanoholes has been performed. This AAO template-based ...

  6. Lifetime estimation of intrinsic silicon nitride MIM capacitors in a gan MMIC process

    E-Print Network [OSTI]

    Demirtas, Sefa

    We have studied the reliability of intrinsic SiN MIM capacitors designed for 48 V and 125 [superscript 0]C operation and manufactured in a GaN process flow. It is shown that very small area capacitors (10um x 10um) with a ...

  7. Fine structure of the red luminescence band in undoped GaN

    SciTech Connect (OSTI)

    Reshchikov, M. A., E-mail: mreshchi@vcu.edu [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Usikov, A. [Nitride Crystals, Inc., 181E Industry Ct., Ste. B, Deer Park, New York 11729 (United States); Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics, 49 Kronverkskiy Ave., 197101 Saint Petersburg (Russian Federation); Helava, H.; Makarov, Yu. [Nitride Crystals, Inc., 181E Industry Ct., Ste. B, Deer Park, New York 11729 (United States)

    2014-01-20T23:59:59.000Z

    Many point defects in GaN responsible for broad photoluminescence (PL) bands remain unidentified. Their presence in thick GaN layers grown by hydride vapor phase epitaxy (HVPE) detrimentally affects the material quality and may hinder the use of GaN in high-power electronic devices. One of the main PL bands in HVPE-grown GaN is the red luminescence (RL) band with a maximum at 1.8?eV. We observed the fine structure of this band with a zero-phonon line (ZPL) at 2.36?eV, which may help to identify the related defect. The shift of the ZPL with excitation intensity and the temperature-related transformation of the RL band fine structure indicate that the RL band is caused by transitions from a shallow donor (at low temperature) or from the conduction band (above 50?K) to an unknown deep acceptor having an energy level 1.130?eV above the valence band.

  8. Electron Beam-induced Light Emission and Transport in GaN Nanowires

    SciTech Connect (OSTI)

    Tringe, J W; MoberlyChan, W J; Stevens, C G; Davydov, A V; Motayed, A

    2006-05-10T23:59:59.000Z

    We report observations of electron beam-induced light from GaN nanowires grown by chemical vapor deposition. GaN nanowires were modified in-situ with deposited opaque platinum coatings to estimate the extent to which light is channeled to the ends of nanowires. Some evidence of light channeling was found, but wire microstructure and defects play an important role in light scattering and transport, limiting the extent to which light is confined. Optical interconnects are powerful components presently applied for high bandwidth communications among high-performance processors. Future circuits based on nanometer-scale components could similarly benefit from optical information transfer among processing blocks. Strong light channeling (and even lasing) has been observed in GaN nanowires, suggesting that these structures could be useful building blocks in a future networked electro-optical processor. However, the extent to which defects and microstructure control optical performance in nanowire waveguides has not been measured. In this study, we use electron microscopy and in-situ modification of individual nanowires to begin to correlate wire structure with light transport efficiency through GaN nanowires tens of microns long.

  9. Anomalous photoresponse of GaN x-ray Schottky detectors

    SciTech Connect (OSTI)

    Duboz, Jean-Yves [CRHEA, CNRS, rue Bernard Gregory, Sophia Antipolis, F-06560 Valbonne (France); Beaumont, Bernard [Lumilog Groupe Saint GOBAIN Crystals, 2720 Chemin de Saint Bernard, F-06220 Vallauris (France); Reverchon, Jean-Luc [THALES R and T, Campus Polytechnique, 1 Avenue Augustin Fresnel, F-91767 Palaiseau Cedex (France); Wieck, Andreas D. [Fakultaet fuer Physik und Astronomie, Lehrstuhl fuer Angewandte Festkoerperphysik, D-44780 Bochum (Germany)

    2009-06-01T23:59:59.000Z

    GaN based materials are believed to be very stable materials, in particular, under irradiation by high energy photons such as x rays. We have studied x-ray detectors based on GaN Schottky diodes. Vertical Schottky diodes were fabricated based on a 20 mum thick undoped GaN layer grown on a conductive GaN substrate. Their photoresponse to near UV light and to x rays was measured. While the response to near UV light was fast and linear as expected, anomalous behaviors were observed under x-ray illumination. The photocurrent increases as the third power of the incident x-ray flux. The photocurrent transient when the x rays is turned on are long and nonexponential (S shape) and strongly differs from the off transient which is fast and exponential. Also, a very strong quenching of the x-ray photoresponse is observed when the detector is simultaneously illuminated with visible light. All of these anomalous behaviors are explained in the frame of a complete model involving traps and tunnel currents. A reasonable quantitative agreement between the model and the experimental data is obtained.

  10. Epitaxial GaN films by hyperthermal ion-beam nitridation of Ga droplets

    SciTech Connect (OSTI)

    Gerlach, J. W.; Ivanov, T.; Neumann, L.; Hoeche, Th.; Hirsch, D.; Rauschenbach, B. [Leibniz-Institut fuer Oberflaechenmodifizierung (IOM), D-04318 Leipzig (Germany)

    2012-06-01T23:59:59.000Z

    Epitaxial GaN film formation on bare 6H-SiC(0001) substrates via the process of transformation of Ga droplets into a thin GaN film by applying hyperthermal nitrogen ions is investigated. Pre-deposited Ga atoms in well defined amounts form large droplets on the substrate surface which are subsequently nitridated at a substrate temperature of 630 Degree-Sign C by a low-energy nitrogen ion beam from a constricted glow-discharge ion source. The Ga deposition and ion-beam nitridation process steps are monitored in situ by reflection high-energy electron diffraction. Ex situ characterization by x-ray diffraction and reflectivity techniques, Rutherford backscattering spectrometry, and electron microscopy shows that the thickness of the resulting GaN films depends on the various amounts of pre-deposited gallium. The films are epitaxial to the substrate, exhibit a mosaic like, smooth surface topography and consist of coalesced large domains of low defect density. Possible transport mechanisms of reactive nitrogen species during hyperthermal nitridation are discussed and the formation of GaN films by an ion-beam assisted process is explained.

  11. Critical Voltage for Electrical Reliability of GaN High Electron Mobility Transistors on Si Substrate

    E-Print Network [OSTI]

    Demirtas, Sefa

    We have evaluated the electrical reliability of GaN HEMTs on Si by carrying out V[subscript DS] = 0 V step-stress experiments. We have found that these devices show a degradation pattern that is very similar to that of ...

  12. The Growth of GaN on Si by the Beam Flux Modulation

    SciTech Connect (OSTI)

    Roh, C. H.; Ha, M. W.; Song, H. J.; Choi, H. G.; Lee, J. H.; Ra, Y. W.; Hahn, C. K. [Compound Semiconductor Devices Research Center, Energy-Display R and D Division, Korea Electronics Technology Institute, Seongnam (Korea, Republic of)

    2011-12-23T23:59:59.000Z

    AlGaN/GaN HEMT structure was grown on Si (111) substrate by plasma-assisted molecular beam epitaxy (PA-MBE) using a beam flux modulation methods. In this result, it was verified that the propagation of treading dislocation (TD) due to N-rich GaN layer was effectively suppressed.

  13. High Efficiency m-plane LEDs on Low Defect Density Bulk GaN Substrates

    SciTech Connect (OSTI)

    David, Aurelien

    2012-10-15T23:59:59.000Z

    Solid-state lighting is a key technology for reduction of energy consumption in the US and worldwide. In principle, by replacing standard incandescent bulbs and other light sources with sources based on light-emitting diodes (LEDs), ultimate energy efficiency can be achieved. The efficiency of LEDs has improved tremendously over the past two decades, however further progress is required for solid- state lighting to reach its full potential. The ability of an LED at converting electricity to light is quantified by its internal quantum efficiency (IQE). The material of choice for visible LEDs is Gallium Nitride (GaN), which is at the basis of blue-emitting LEDs. A key factor limiting the performance of GaN LEDs is the so-called efficiency droop, whereby the IQE of the LED decreases significantly at high current density. Despite decades of research, efficiency droop remains a major issue. Since high-current operation is necessary for practical lighting applications, reducing droop is a major challenge for the scientific community and the LED industry. Our approach to solving the droop issue is the use of newly available low-defect-density bulk GaN non-polar substrates. In contrast to the standard foreign substrates (sapphire, silicon carbide, silicon) used in the industry, we have employed native bulk GaN substrates with very low defect density, thus ensuring exquisite material quality and high IQE. Whereas all commercial LEDs are grown along the c-plane crystal direction of GaN, we have used m-plane non-polar substrates; these drastically modify the physical properties of the LED and enable a reduction of droop. With this approach, we have demonstrated very high IQE performance and low droop. Our results focused on violet and blue LEDs. For these, we have demonstrated very high peak IQEs and current droops of 6% and 10% respectively (up to a high current density of 200A.cm-2). All these results were obtained under electrical operation. These high IQE and low droop values are in line with the program’s milestones. They demonstrate that bulk non-polar GaN substrates represent a disruptive technology for LED performance. Application of this technology to real-world products is feasible, provided that the cost of GaN substrates is compatible with the market’s requirement.

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

    SciTech Connect (OSTI)

    Vladimir Dmitriev

    2007-06-30T23:59:59.000Z

    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 better understanding of p-type GaN formation for Solid State Lighting community. Grown p-type GaN layers were used as substrates for blue and green InGaN-based LEDs made by HVPE technology at TDI. These results proved proposed technical approach and facilitate fabrication of highly conductive p-GaN materials by low-cost HVPE technology for solid state lighting applications. TDI has started the commercialization of p-GaN epitaxial materials.

  15. Ab initio density functional theory study of non-polar (101{sup ¯}0),?(112{sup ¯}0) and semipolar (202{sup ¯}1) GaN surfaces

    SciTech Connect (OSTI)

    Mutombo, P.; Romanyuk, O., E-mail: romanyuk@fzu.cz [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 16200 Prague (Czech Republic)

    2014-05-28T23:59:59.000Z

    The atomic structures of non-polar GaN(101{sup ¯}0),?(112{sup ¯}0) and semipolar GaN(202{sup ¯}1),?(202{sup ¯}1{sup ¯}) surfaces were studied using ab initio calculations within density functional theory. The bulk-like truncated (1?×?1) structure with buckled Ga-N or Ga-Ga dimers was found stable on the non-polar GaN(101{sup ¯}0) surface in agreement with previous works. Ga-N heterodimers were found energetically stable on the GaN(112{sup ¯}0)-(1?×?1) surface. The formation of vacancies and substitution site defects was found unfavorable for non-polar GaN surfaces. Semipolar GaN(202{sup ¯}1)-(1?×?1) surface unit cells consist of non-polar (101{sup ¯}0) and semipolar (101{sup ¯}1) nano-facets. The (101{sup ¯}1) nano-facets consist of two-fold coordinated atoms, which form N-N dimers within a (2?×?1) surface unit cell on a GaN(202{sup ¯}1) surface. Dimers are not formed on the GaN(202{sup ¯}1{sup ¯}) surface. The stability of the surfaces with single (101{sup ¯}0) or (101{sup ¯}1) nano-facets was analyzed. A single non-polar (101{sup ¯}0)-(1?×?1) nano-facet was found stable on the GaN(202{sup ¯}1) surface, but unstable on the GaN(202{sup ¯}1{sup ¯}) surface. A single (101{sup ¯}1) nano-facet was found unstable. Semipolar GaN surfaces with (202{sup ¯}1) and (202{sup ¯}1{sup ¯}) polarity can be stabilized with a Ga overlayer at Ga-rich experimental conditions.

  16. Ultra-low resistance ohmic contacts to GaN with high Si doping concentrations grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Afroz Faria, Faiza; Guo Jia; Zhao Pei; Li Guowang; Kumar Kandaswamy, Prem; Wistey, Mark; Xing Huili; Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2012-07-16T23:59:59.000Z

    Ti/Al/Ni/Au ohmic contacts were formed on heavily doped n{sup +} metal-polar GaN samples with various Si doping concentrations grown by molecular beam epitaxy. The contact resistivity (R{sub C}) and sheet resistance (R{sub sh}) as a function of corresponding GaN free carrier concentration (n) were measured. Very low R{sub C} values (<0.09 {Omega} mm) were obtained, with a minimum R{sub C} of 0.035 {Omega} mm on a sample with a room temperature carrier concentration of {approx}5 Multiplication-Sign 10{sup 19} cm{sup -3}. Based on the systematic study, the role of R{sub C} and R{sub sh} is discussed in the context of regrown n{sup +} GaN ohmic contacts for GaN based high electron mobility transistors.

  17. Synchrotron radiation x-ray topography and defect selective etching analysis of threading dislocations in GaN

    SciTech Connect (OSTI)

    Sintonen, Sakari, E-mail: sakari.sintonen@aalto.fi; Suihkonen, Sami; Jussila, Henri; Tuomi, Turkka O.; Lipsanen, Harri [Department of Micro- and Nanosciences, Aalto University School of Electrical Engineering, 02150 Espoo (Finland); Rudzi?ski, Mariusz [Epitaxy Department, Institute of Electronic Materials Technology, 01-919 Warsaw (Poland); Knetzger, Michael; Meissner, Elke [Fraunhofer Institute for Integrated Systems and Device Technology, 91058 Erlangen (Germany); Danilewsky, Andreas [Kristallographie Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg (Germany)

    2014-08-28T23:59:59.000Z

    The crystal quality of bulk GaN crystals is continuously improving due to advances in GaN growth techniques. Defect characterization of the GaN substrates by conventional methods is impeded by the very low dislocation density and a large scale defect analysis method is needed. White beam synchrotron radiation x-ray topography (SR-XRT) is a rapid and non-destructive technique for dislocation analysis on a large scale. In this study, the defect structure of an ammonothermal c-plane GaN substrate was recorded using SR-XRT and the image contrast caused by the dislocation induced microstrain was simulated. The simulations and experimental observations agree excellently and the SR-XRT image contrasts of mixed and screw dislocations were determined. Apart from a few exceptions, defect selective etching measurements were shown to correspond one to one with the SR-XRT results.

  18. Step-flow growth mode instability of N-polar GaN under N-excess

    SciTech Connect (OSTI)

    Chèze, C. [TopGaN Ltd., Soko?owska 29/37, 01142 Warszawa (Poland)] [TopGaN Ltd., Soko?owska 29/37, 01142 Warszawa (Poland); Sawicka, M.; Siekacz, M.; ?ucznik, B.; Bo?kowski, M.; Skierbiszewski, C. [TopGaN Ltd., Soko?owska 29/37, 01142 Warszawa (Poland) [TopGaN Ltd., Soko?owska 29/37, 01142 Warszawa (Poland); Institute of High Pressure Physics, PAS, Soko?owska 29/37, 01142 Warszawa (Poland); Turski, H.; Cywi?ski, G.; Smalc-Koziorowska, J.; Weyher, J. L.; Kry?ko, M. [Institute of High Pressure Physics, PAS, Soko?owska 29/37, 01142 Warszawa (Poland)] [Institute of High Pressure Physics, PAS, Soko?owska 29/37, 01142 Warszawa (Poland)

    2013-08-12T23:59:59.000Z

    GaN layers were grown on N-polar GaN substrates by plasma-assisted molecular beam epitaxy under different III/V ratios. Ga-rich conditions assure step-flow growth with atomically flat surface covered by doubly-bunched steps, as for Ga-polar GaN. Growth under N-excess however leads to an unstable step-flow morphology. Particularly, for substrates slightly miscut towards <1010>, interlacing fingers are covered by atomic steps pinned on both sides by small hexagonal pits. In contrast, a three-dimensional island morphology is observed on the Ga-polar equivalent sample. We attribute this result to lower diffusion barriers on N-polar compared to Ga-polar GaN under N-rich conditions.

  19. Band alignment between GaN and ZrO{sub 2} formed by atomic layer deposition

    SciTech Connect (OSTI)

    Ye, Gang; Wang, Hong, E-mail: ewanghong@ntu.edu.sg; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong [Novitas, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Liu, Zhi Hong [Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602 (Singapore)

    2014-07-14T23:59:59.000Z

    The band alignment between Ga-face GaN and atomic-layer-deposited ZrO{sub 2} was investigated using X-ray photoelectron spectroscopy (XPS). The dependence of Ga 3d and Zr 3d core-level positions on the take-off angles indicated upward band bending at GaN surface and potential gradient in ZrO{sub 2} layer. Based on angle-resolved XPS measurements combined with numerical calculations, valence band discontinuity ?E{sub V} of 1?±?0.2?eV and conduction band discontinuity ?E{sub C} of 1.2?±?0.2?eV at ZrO{sub 2}/GaN interface were determined by taking GaN surface band bending and potential gradient in ZrO{sub 2} layer into account.

  20. Substrate-dependent wetting layer formation during GaN growth: Impact on the morphology of the films

    SciTech Connect (OSTI)

    Sidorenko, A.; Peisert, H.; Neumann, H.; Chasse, T. [Universitaet Tuebingen, Institut fuer Physikalische und Theoretische Chemie, Auf der Morgenstelle 8, D-72076 Tuebingen (Germany); Leibniz-Institut fuer Oberflaechenmodifizierung e.V. Permoserstrasse 15, D-04318 Leipzig (Germany); Universitaet Tuebingen, Institut fuer Physikalische und Theoretische Chemie, Auf der Morgenstelle 8, D-72076 Tuebingen (Germany)

    2007-08-15T23:59:59.000Z

    We have compared epitaxial growth of GaN films on 6H-SiC(0001)-({radical}(3)x{radical}(3))R30 deg. -Ga and on (0001)-sapphire. Predeposited Ga layers were nitrided by ion beam assisted molecular beam epitaxy. Whereas on SiC the initially deposited Ga covers the substrate surface completely, on sapphire only Ga droplets are present. The different distribution of the predeposited Ga affects the morphology of GaN significantly. Scanning electron microscopy and atomic force microscopy analysis of the grown films show that the complete wetting of the SiC substrate with Ga enhances finally the size and the flatness of GaN terraces and thus the quality of the film. X-ray photoelectron spectroscopy measurements reveal that metallic Ga resides also on top of the GaN films during the growth.

  1. Photoluminescence study of the 1.047 eV emission in GaN K. Pressela)

    E-Print Network [OSTI]

    Nabben, Reinhard

    GaN/ AlGaN blue green light emitting diode, which has a much higher quantum efficiency than the SiC blue light emitting diode, became possible.2 Presently the wide bandgap semi- conductor GaN is intensively. Especially the 1.19 eV is very intense. Thus one can think of developing a light emitting diode in the near

  2. Comparative Study of the Electronic Band Structure of Strained C-plane and M-plane GaN Films

    E-Print Network [OSTI]

    Ghosh, Sandip

    to the unique c axis of wurtzite GaN, and the spectral features do not change with polarization rotation emitters [1]. The surface normal to an M-plane film is perpen- dicular (?) to the unique c axis of wurtzite (1100)M-plane y C-plane (0001) xc z||c Fig. 1. a) Wurtzite GaN unit cell showing the choice

  3. Emission mechanisms of bulk GaN and InGaN quantum wells prepared by lateral epitaxial overgrowth

    E-Print Network [OSTI]

    Bowers, John

    Emission mechanisms of bulk GaN and InGaN quantum wells prepared by lateral epitaxial overgrowth S for publication 5 January 1999 The emission mechanisms of bulk GaN and InGaN quantum wells QWs were studied suggest that TDs simply reduce the net volume of light-emitting area. This effect is less pronounced in InGaN

  4. Growth and characterizations of GaN micro-rods on graphene films for flexible light emitting diodes

    SciTech Connect (OSTI)

    Chung, Kunook; Beak, Hyeonjun; Tchoe, Youngbin; Oh, Hongseok; Yi, Gyu-Chul, E-mail: gcyi@snu.ac.kr [Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 151-747 (Korea, Republic of); Yoo, Hyobin; Kim, Miyoung [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2014-09-01T23:59:59.000Z

    We report the growth of GaN micro-rods and coaxial quantum-well heterostructures on graphene films, together with structural and optical characterization, for applications in flexible optical devices. Graphene films were grown on Cu foil by means of chemical vapor deposition, and used as the substrates for the growth of the GaN micro-rods, which were subsequently transferred onto SiO{sub 2}/Si substrates. Highly Si-doped, n-type GaN micro-rods were grown on the graphene films using metal–organic chemical vapor deposition. The growth and vertical alignment of the GaN micro-rods, which is a critical factor for the fabrication of high-performance light-emitting diodes (LEDs), were characterized using electron microscopy and X-ray diffraction. The GaN micro-rods exhibited promising photoluminescence characteristics for optoelectronic device applications, including room-temperature stimulated emission. To fabricate flexible LEDs, In{sub x}Ga{sub 1–x}N/GaN multiple quantum wells and a p-type GaN layer were deposited coaxially on the GaN micro-rods, and transferred onto Ag-coated polymer substrates using lift-off. Ti/Au and Ni/Au metal layers were formed to provide electrical contacts to the n-type and p-type GaN regions, respectively. The micro-rod LEDs exhibited intense emission of visible light, even after transfer onto the flexible polymer substrate, and reliable operation was achieved following numerous cycles of mechanical deformation.

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

    SciTech Connect (OSTI)

    Armstrong, A. M., E-mail: aarmstr@sandia.gov [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Kelchner, K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)] [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Nakamura, S.; DenBaars, S. P. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States) [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)] [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2013-12-02T23:59:59.000Z

    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.

  6. Lateral color integration on rare-earth-doped GaN electroluminescent D. S. Lee and A. J. Steckla)

    E-Print Network [OSTI]

    Steckl, Andrew J.

    and thermal robust- ness. GaN films were grown on p-type 111 Si substrate by molecular beam epitaxy MBE growth from solid sources. GaN:RE layers were typically grown for 1 h at either 100 or 400 °C substrateLateral color integration on rare-earth-doped GaN electroluminescent thin films D. S. Lee and A. J

  7. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kushvaha, S. S., E-mail: kushvahas@nplindia.org; Pal, P.; Shukla, A. K.; Joshi, Amish G.; Gupta, Govind; Kumar, M.; Singh, S.; Gupta, Bipin K.; Haranath, D. [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)] [CSIR- National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India 110012 (India)

    2014-02-15T23:59:59.000Z

    We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 ?m thick GaN epi-layer on sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 10{sup 8} cm{sup ?2} at 750 °C) than that of the low temperature grown sample (1.1 × 10{sup 9} cm{sup ?2} at 730 °C). A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  8. Calculation of linear and second-order optical response in wurtzite GaN and AlN James L. P. Hughes, Y. Wang, and J. E. Sipe

    E-Print Network [OSTI]

    Sipe,J. E.

    Calculation of linear and second-order optical response in wurtzite GaN and AlN James L. P. Hughes and nonlinear optical response of GaN and AlN in the wurtzite structure. The dielectric function ( ), the second there to the wurtzite mate- rials GaN and AlN. Our evaluation of optical response is based on a first principles

  9. Nucleation and Stoichiometry Dependence of rutile-TiO2(001)/GaN(0001) Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Feenstra, Randall

    the initial nucleation and the stoichiometry of rutile- TiO2(001) grown on wurtzite GaN(0001) by radio explore the growth of rutile-TiO2(001) on wurtzite GaN(0001) by oxygen plasma-assisted molecular beam) was maintained constant at 400 W. The substrates were commercially available wurtzite Ga-polar GaN(0001) grown

  10. Nonparabolicity of the conduction band of wurtzite GaN S. Syed, J. B. Heroux, Y. J. Wang, M. J. Manfra, R. J. Molnar et al.

    E-Print Network [OSTI]

    Manfra, Michael J.

    Nonparabolicity of the conduction band of wurtzite GaN S. Syed, J. B. Heroux, Y. J. Wang, M. J://apl.aip.org/about/rights_and_permissions #12;Nonparabolicity of the conduction band of wurtzite GaN S. Syeda) Department of Applied Physics of the nonparabolicity NP of the con- duction band of wurtzite GaN currently remains controver- sial. NP of a band can

  11. MECHANISMS OF OPTICAL GAIN IN CUBIC GAN AND INGAN J. Holst, A. Hoffmann, I. Broser, T. Frey*, B. Schttker*, D.J. As*, D. Schikora*, K.

    E-Print Network [OSTI]

    Nabben, Reinhard

    -blende (cubic) GaN and InGaN on GaAs with a common cleavage plane and readily high-quality, low-cost wafers may detailed information about the potential of cubic GaN and InGaN for device applications we performed structure at 3.265 eV in cubic GaN [10]. For the highest pump intensities, the electron- hole

  12. Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact-exchange density-functional theory

    E-Print Network [OSTI]

    Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact; published online 20 October 2006 The authors have studied the electronic structure of InN and GaN employing. © 2006 American Institute of Physics. DOI: 10.1063/1.2364469 The group III-nitrides AlN, GaN, and In

  13. Shock-induced band-gap shift in GaN: Anisotropy of the deformation potentials H. Y. Peng, M. D. McCluskey,* and Y. M. Gupta

    E-Print Network [OSTI]

    McCluskey, Matthew

    Shock-induced band-gap shift in GaN: Anisotropy of the deformation potentials H. Y. Peng, M. D. Mc Alto, California 94304, USA Received 19 October 2004; published 24 March 2005 The band-gap shift of GaN=1.9 eV, and D4=-1.0 eV. These values indicate that the deformation potentials in wurtzite GaN

  14. Submitted to J. Vac. Sci. Technol., December 11, 1998 1 Growth of Hf and HfN on GaN by Molecular Beam Epitaxy

    E-Print Network [OSTI]

    Cohen, Philip I.

    Submitted to J. Vac. Sci. Technol., December 11, 1998 1 Growth of Hf and HfN on GaN by Molecular-type GaN(000¯1) by MBE using a custom built Hf electron beam source and an ammonia leak. The films were). It was found that epitaxial growth of Hf is possible even at room temperature. GaN films varying in thickness

  15. Room-temperature-grown rare-earth-doped GaN luminescent thin films D. S. Lee and A. J. Steckla)

    E-Print Network [OSTI]

    Steckl, Andrew J.

    efforts to achieve this goal with GaN growth on oxide films or on glass substrates3­6 being a main focus: 50­100 °C. GaN films were grown on p-type 111 Si substrate by MBE with a Ga elemental sourceRoom-temperature-grown rare-earth-doped GaN luminescent thin films D. S. Lee and A. J. Steckla

  16. Growth of cubic GaN on nano-patterned 3C-SiC/Si (0 0 1) substrates R.M. Kemper n

    E-Print Network [OSTI]

    As, Donat Josef

    Growth of cubic GaN on nano-patterned 3C-SiC/Si (0 0 1) substrates R.M. Kemper n , M. Weinl, C matched nano- patterned substrates. In hexagonal GaN inherent spontaneous and piezoelectric polarization conditions to achieve heteroepitaxial growth of cubic GaN [8]. The most ade- quate substrate is 3C-SiC (0 0 1

  17. Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.

    SciTech Connect (OSTI)

    Kurtz, Steven Ross; Follstaedt, David Martin; Wright, Alan Francis; Baca, Albert G.; Briggs, Ronald D.; Provencio, Paula Polyak; Missert, Nancy A.; Allerman, Andrew Alan; Marsh, Phil F.; Koleske, Daniel David; Lee, Stephen Roger; Shul, Randy John; Seager, Carleton Hoover; Tigges, Christopher P.

    2005-12-01T23:59:59.000Z

    GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaN on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted and techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.

  18. Probing temperature gradients within the GaN buffer layer of AlGaN/GaN high electron mobility transistors with Raman thermography

    SciTech Connect (OSTI)

    Hodges, C., E-mail: chris.hodges@bristol.ac.uk; Pomeroy, J.; Kuball, M. [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom)

    2014-02-14T23:59:59.000Z

    We demonstrate the ability of confocal Raman thermography using a spatial filter and azimuthal polarization to probe vertical temperature gradients within the GaN buffer layer of operating AlGaN/GaN high electron mobility transistors. Temperature gradients in the GaN layer are measured by using offset focal planes to minimize the contribution from different regions of the GaN buffer. The measured temperature gradient is in good agreement with a thermal simulation treating the GaN thermal conductivity as homogeneous throughout the layer and including a low thermal conductivity nucleation layer to model the heat flow between the buffer and substrate.

  19. Influence of vicinal sapphire substrate on the properties of N-polar GaN films grown by metal-organic chemical vapor deposition

    SciTech Connect (OSTI)

    Lin, Zhiyu; Zhang, Jincheng, E-mail: jchzhang@xidian.edu.cn; Xu, Shengrui; Chen, Zhibin; Yang, Shuangyong; Tian, Kun; Hao, Yue [Key Lab of Wide Band-Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an, Shaanxi 710071 (China); Su, Xujun [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123 (China); Shi, Xuefang [School of Advanced Materials and Nanotechnology, Xidian University, Xi'an, Shaanxi 710071 (China)

    2014-08-25T23:59:59.000Z

    The influence of vicinal sapphire substrates on the growth of N-polar GaN films by metal-organic chemical vapor deposition is investigated. Smooth GaN films without hexagonal surface feature are obtained on vicinal substrate. Transmission electron microscope results reveal that basal-plane stacking faults are formed in GaN on vicinal substrate, leading to a reduction in threading dislocation density. Furthermore, it has been found that there is a weaker yellow luminescence in GaN on vicinal substrate than that on (0001) substrate, which might be explained by the different trends of the carbon impurity incorporation.

  20. Spectroscopic study of semipolar (112{sup ¯}2)-HVPE GaN exhibiting high oxygen incorporation

    SciTech Connect (OSTI)

    Schustek, Philipp, E-mail: philipp.schustek@gmail.com [Institute of Quantum Matter, Ulm University, 89081 Ulm (Germany); Research Unit, Parc Sanitari Sant Joan de Déu and Foundation Sant Joan de Déu, Esplugues de Llobregat, 08950, Barcelona (Spain); Hocker, Matthias; Thonke, Klaus [Institute of Quantum Matter, Ulm University, 89081 Ulm (Germany); Klein, Martin; Scholz, Ferdinand [Institute of Optoelectronics, Ulm University, 89081 Ulm (Germany); Simon, Ulrich [Scientific Computing Centre Ulm, Ulm University, 89081 Ulm (Germany)

    2014-10-28T23:59:59.000Z

    Spatially resolved luminescence and Raman spectroscopy investigations are applied to a series of (112{sup ¯}2)-GaN samples grown by hydride vapor phase epitaxy (HVPE) grown over an initial layer deposited by metal organic vapor phase epitaxy on patterned sapphire substrates. Whereas these two differently grown GaN layers are crystallographically homogeneous, they differ largely in their doping level due to high unintentional oxygen uptake in the HVPE layer. This high doping shows up in luminescence spectra, which can be explained by a free-electron recombination band for which an analytical model considering the Burstein-Moss shift, conduction band tailing, and the bandgap renormalization is included. Secondary ion mass spectrometry, Raman spectroscopy, and Hall measurements concordantly determine the electron density to be above 10{sup 19?}cm{sup ?3}. In addition, the strain state is assessed by Raman spectroscopy and compared to a finite element analysis.

  1. Charge transfer in Fe-doped GaN: The role of the donor

    SciTech Connect (OSTI)

    Sunay, Ustun; Dashdorj, J.; Zvanut, M. E.; Harrison, J. G. [Department of Physics, University of Alabama at Birmingham, 1300 University Blvd., CH 310, Birmingham, Alabama 35294-1170 (United States); Leach, J. H.; Udwary, K. [Kyma Technologies, 8829 Midway West Rd., Raleigh, North Carolina 27617 (United States)

    2014-02-21T23:59:59.000Z

    Several nitride-based device structures would benefit from the availability of high quality, large-area, freestanding semi-insulating GaN substrates. Due to the intrinsic n-type nature of GaN, however, the incorporation of compensating centers such as Fe is necessary to achieve the high resistivity required. We are using electron paramagnetic resonance (EPR) to explore charge transfer in 450 um thick GaN:Fe plates to understand the basic mechanisms related to compensation so that the material may be optimized for device applications. The results suggest that the simple model based on one shallow donor and a single Fe level is insufficient to describe compensation. Rather, the observation of the neutral donor and Fe3+ indicates that either the two species are spatially segregated or additional compensating and donor defects must be present.

  2. Strong light-matter coupling in ultrathin double dielectric mirror GaN microcavities

    SciTech Connect (OSTI)

    Bejtka, K.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); CRHEA-CNRS, Rue Bernard Gregory, Parc Sophia Antipolis, 06560 Valbonne (France); Reveret, F.; Vasson, A.; Leymarie, J. [LASMEA, UMR 6602 UBP/CNRS, 24 Avenue des Landais, F-63177 Aubiere Cedex (France); Edwards, P. R. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Sellers, I. R.; Duboz, J. Y.; Leroux, M.; Semond, F. [CRHEA-CNRS, Rue Bernard Gregory, Parc Sophia Antipolis, 06560 Valbonne (France)

    2008-06-16T23:59:59.000Z

    Strong light-matter coupling is demonstrated at low temperature in an ultrathin GaN microcavity fabricated using two silica/zirconia Bragg mirrors, in addition to a three-period epitaxial (Al,Ga)N mirror serving as an etch stop and assuring good quality of the overgrown GaN. The {lambda}/2 cavity is grown by molecular beam epitaxy on a Si substrate. Analysis of angle-resolved data reveal key features of the strong coupling regime in both reflectivity and transmission spectra at 5 K: anticrossing with a normal mode splitting of 43{+-}2 meV and 56{+-}2 meV for reflectivity and transmission, respectively, and narrowing of the lower polariton linewidth near resonance.

  3. Europium doping of zincblende GaN by ion implantation K. Lorenz,1,2,a

    E-Print Network [OSTI]

    As, Donat Josef

    /channeling spectrometry. A low concentration 10% of wurtzite phase inclusions was observed by XRD analysis in as-lattice parameter of wurtzite GaN W-GaN . For ZB-GaN:Eu, a large fraction of Eu ions is found on a high symmetry-GaN:Eu. The implantation damage in ZB-GaN:Eu could partly be removed by thermal annealing, but an increase in the wurtzite

  4. K.K. Gan ATLAS Pixel Week 1 New Results on Opto-Electronics

    E-Print Network [OSTI]

    Gan, K. K.

    with lower thresholds with BPM/DRX ] opto-board design is compatible with BPM/DRX PIN Current Thresholds with BPM/DRX 0 5 10 15 20 25 30 35 link#1 link#2 link#3 link#4 link#5 link#6 link#7 Ipin(mA) Opto-Board on Test Board Opto-Board on Test Board with BPM/DRX #12;K.K. Gan ATLAS Pixel Week 8 l one irradiated VCSEL

  5. Structure and electronic properties of mixed (a?+?c) dislocation cores in GaN

    SciTech Connect (OSTI)

    Horton, M. K., E-mail: m.horton11@imperial.ac.uk [Department Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Rhode, S. L. [Department Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Moram, M. A. [Department Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Department Materials Science and Metallurgy, University of Cambridge, Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)

    2014-08-14T23:59:59.000Z

    Classical atomistic models and atomic-resolution scanning transmission electron microscopy studies of GaN films reveal that mixed (a?+?c)-type dislocations have multiple different core structures, including a dissociated structure consisting of a planar fault on one of the (12{sup ¯}10) planes terminated by two different partial dislocations. Density functional theory calculations show that all cores introduce localized states into the band gap, which affects device performance.

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

    DOE Patents [OSTI]

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16T23:59:59.000Z

    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.

  7. Cr Atom Alignment in Cr-Delta-Doped GaN

    SciTech Connect (OSTI)

    Kimura, S.; Emura, S.; Zhou, Y. K.; Choi, S. W.; Yamauchi, Y.; Hasegawa, S.; Asahi, H. [Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Osaka, 567-0047 (Japan); Ofuchi, H. [SPring-8 / Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo 679-5198 (Japan); Nakata, Y. [College of Science and Engineering, Iwaki Meisei University, Iwaki, Fukushima 970-8551 (Japan)

    2007-02-02T23:59:59.000Z

    Structural properties and Cr atom alignments in Cr-delta doped GaN grown by molecular beam epitaxy are studied with transmission electron microscopy and X-ray absorption fine structure (XAFS) measurements. It is found that the environment around Cr atoms in delta-doped samples is dramatically changed under various growth conditions. The XAFS analysis of these synthesized layers suggests that new Cr-related complexes are grown.

  8. Optimization of ion-atomic beam source for deposition of GaN ultrathin films

    SciTech Connect (OSTI)

    Mach, Jind?ich, E-mail: mach@fme.vutbr.cz; Kolíbal, Miroslav; Zlámal, Jakub; Voborny, Stanislav; Bartošík, Miroslav; Šikola, Tomáš [Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic); CEITEC BUT, Brno University of Technology, Technická 10, 61669 Brno (Czech Republic); Šamo?il, Tomáš [Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic)

    2014-08-15T23:59:59.000Z

    We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20–200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ?15 mm by one order of magnitude (j ? 1000 nA/cm{sup 2}). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300?°C) than in conventional metalorganic chemical vapor deposition technologies (?1000?°C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.

  9. Anisotropy of effective electron masses in highly doped nonpolar GaN

    SciTech Connect (OSTI)

    Feneberg, Martin, E-mail: martin.feneberg@ovgu.de; Lange, Karsten; Lidig, Christian; Wieneke, Matthias; Witte, Hartmut; Bläsing, Jürgen; Dadgar, Armin; Krost, Alois; Goldhahn, Rüdiger [Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg (Germany)] [Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg (Germany)

    2013-12-02T23:59:59.000Z

    The anisotropic effective electron masses in wurtzite GaN are determined by generalized infrared spectroscopic ellipsometry. Nonpolar (112{sup ¯}0) oriented thin films allow accessing both effective masses, m{sub ?}{sup *} and m{sub ?}{sup *}, by determining the screened plasma frequencies. A n-type doping range up to 1.7?×?10{sup 20}?cm{sup ?3} is investigated. The effective mass ratio m{sub ?}{sup *}/m{sub ?}{sup *} is obtained with highest accuracy and is found to be 1.11 independent on electron concentration up to 1.2?×?10{sup 20}?cm{sup ?3}. For higher electron concentrations, the conduction band non-parabolicity is mirrored in changes. Absolute values for effective electron masses depend on additional input of carrier concentrations determined by Hall effect measurements. We obtain m{sub ?}{sup *}=(0.239±0.004)m{sub 0} and m{sub ?}{sup *}=(0.216±0.003)m{sub 0} for the parabolic range of the GaN conduction band. Our data are indication of a parabolic GaN conduction band up to an energy of approximately 400?meV above the conduction band minimum.

  10. Valence band hybridization in N-rich GaN1-xAsx alloys

    SciTech Connect (OSTI)

    Wu, J.; Walukiewicz, W.; Yu, K.M.; Denlinger, J.D.; Shan, W.; Ager III, J.W.; Kimura, A.; Tang, H.F.; Kuech, T.F.

    2004-05-04T23:59:59.000Z

    We have used photo-modulated transmission and optical absorption spectroscopies to measure the composition dependence of interband optical transitions in N-rich GaN{sub 1-x}As{sub x} alloys with x up to 0.06. The direct bandgap gradually decreases as x increases. In the dilute x limit, the observed band gap approaches 2.8 eV; this limiting value is attributed to a transition between the As localized level, which has been previously observed in As-doped GaN at 0.6 eV above the valence band maximum in As-doped GaN, and the conduction band minimum. The structure of the valence band of GaN{sub 1-x}As{sub x} is explained by the hybridization of the localized As states with the extended valence band states of GaN matrix. The hybridization is directly confirmed by soft x-ray emission experiments. To describe the electronic structure of the GaN{sub 1-x}As{sub x} alloys in the entire composition range a linear interpolation is used to combine the effects of valence band hybridization in N-rich alloys with conduction band anticrossing in As-rich alloys.

  11. Heteroepitaxial VO{sub 2} thin films on GaN: Structure and metal-insulator transition characteristics

    SciTech Connect (OSTI)

    Zhou You; Ramanathan, Shriram [Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

    2012-10-01T23:59:59.000Z

    Monolithic integration of correlated oxide and nitride semiconductors may open up new opportunities in solid-state electronics and opto-electronics that combine desirable functional properties of both classes of materials. Here, we report on epitaxial growth and phase transition-related electrical properties of vanadium dioxide (VO{sub 2}) thin films on GaN epitaxial layers on c-sapphire. The epitaxial relation is determined to be (010){sub vo{sub 2}} parallel (0001){sub GaN} parallel (0001){sub A1{sub 2O{sub 3}}} and [100]{sub vo{sub 2}} parallel [1210]{sub GaN} parallel [0110]{sub A1{sub 2O{sub 3}}} from x-ray diffraction. VO{sub 2} heteroepitaxial growth and lattice mismatch are analyzed by comparing the GaN basal plane (0001) with the almost close packed corrugated oxygen plane in vanadium dioxide and an experimental stereographic projection describing the orientation relationship is established. X-ray photoelectron spectroscopy suggests a slightly oxygen rich composition at the surface, while Raman scattering measurements suggests that the quality of GaN layer is not significantly degraded by the high-temperature deposition of VO{sub 2}. Electrical characterization of VO{sub 2} films on GaN indicates that the resistance changes by about four orders of magnitude upon heating, similar to epitaxial VO{sub 2} films grown directly on c-sapphire. It is shown that the metal-insulator transition could also be voltage-triggered at room temperature and the transition threshold voltage scaling variation with temperature is analyzed in the framework of a current-driven Joule heating model. The ability to synthesize high quality correlated oxide films on GaN with sharp phase transition could enable new directions in semiconductor-photonic integrated devices.

  12. Investigation of MOVPE-grown GaN layers doped with As atoms A. F. Tsatsul'nikov, B. Ya. Ber, A. P. Kartashova, Yu. A. Kudryavtsev, N. N. Ledentsov,

    E-Print Network [OSTI]

    Nabben, Reinhard

    Investigation of MOVPE-grown GaN layers doped with As atoms A. F. Tsatsul'nikov, B. Ya. Ber, A. P vapor-phase epitaxy. It is shown that the deposition of GaAs on a GaN surface relieves stresses in the GaN layer. The high-temperature overgrowth of a thin GaAs layer by a GaN layer causes As atoms

  13. Growth of GaN films with controlled out-of-plane texture on Si wafers Jung-Il Hong , Yanling Chang, Yong Ding, Zhong Lin Wang , Robert L. Snyder

    E-Print Network [OSTI]

    Wang, Zhong L.

    Growth of GaN films with controlled out-of-plane texture on Si wafers Jung-Il Hong , Yanling Chang Interface structure GaN films were deposited on Si (400) wafers by a pulsed laser deposition technique, thereby achieving polar or nonpolar film surfaces as desired. The GaN film and Si substrate were found

  14. Total current collapse in High-Voltage GaN MIS-HEMTs induced by Zener trapping D. Jin, J. Joh*, S. Krishnan*, N. Tipirneni*, S. Pendharkar* and J. A. del Alamo

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Total current collapse in High-Voltage GaN MIS-HEMTs induced by Zener trapping D. Jin, J. Joh*, S collapse in GaN MIS-HEMTs for >600 V operation. Extreme trapping leading to total current collapse has been trapping ("Zener trapping") inside the AlGaN barrier or the GaN channel layers. The trapping takes place

  15. Vacancies in GaN bulk and nanowires: effect of self-interaction corrections This article has been downloaded from IOPscience. Please scroll down to see the full text article.

    E-Print Network [OSTI]

    Vacancies in GaN bulk and nanowires: effect of self-interaction corrections This article has been 24 (2012) 255801 (8pp) doi:10.1088/0953-8984/24/25/255801 Vacancies in GaN bulk and nanowires: effect vacancies in gallium nitride (GaN) bulk and nanowires using self-interaction corrected pseudopotentials (SIC

  16. Low dislocation GaN via defect-filtering, self-assembled SiO2-sphere layers.

    SciTech Connect (OSTI)

    Wang, George T.; Li, Qiming

    2009-09-01T23:59:59.000Z

    The III-nitride (AlGaInN) materials system forms the foundation for white solid-state lighting, the adoption of which could significantly reduce U.S. energy needs. While the growth of GaN-based devices relies on heteroepitaxy on foreign substrates, the heteroepitaxial layers possess a high density of dislocations due to poor lattice and thermal expansion match. These high dislocation densities have been correlated with reduced internal quantum efficiency and lifetimes for GaN-based LEDs. Here, we demonstrate an inexpensive method for dislocation reduction in GaN grown on sapphire and silicon substrates. This technique, which requires no lithographic patterning, GaN is selectively grown through self-assembled layers of silica microspheres which act to filter out dislocations. Using this method, the threading dislocation density for GaN on sapphire was reduced from 3.3 x 10{sup 9} cm{sup -2} to 4.0 x 10{sup 7} cm{sup -2}, and from the 10{sup 10} cm{sup -2} range to {approx}6.0 x 10{sup 7} cm{sup -2} for GaN on Si(111). This large reduction in dislocation density is attributed to a dislocation blocking and bending by the unique interface between GaN and silica microspheres.

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

    SciTech Connect (OSTI)

    Greenlee, Jordan D., E-mail: jordan.greenlee.ctr@nrl.navy.mil [National Research Council, 500 Fifth St. NW, Washington, DC 20001 (United States); Feigelson, Boris N.; Anderson, Travis J.; Hite, Jennifer K.; Mastro, Michael A.; Eddy, Charles R.; Hobart, Karl D.; Kub, Francis J. [Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Tadjer, Marko J. [American Society for Engineering Education, 1818 N St. NW, Washington, DC 20036 (United States)

    2014-08-14T23:59:59.000Z

    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.

  18. Ga induced superstructures as templates for lattice matched hetroepitaxial growth of GaN on Si(111) substrate

    SciTech Connect (OSTI)

    Kumar, Praveen; Kuyyalil, Jithesh; Shivaprasad, S. M. [Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, 560 064 Bangalore (India)

    2010-11-29T23:59:59.000Z

    High quality GaN is grown by plasma assisted molecular beam epitaxy on Ga induced superstructural phases of Si(111)7x7. Three stable surface phases induced by Ga adsorption, viz., (1x1), (6.3x6.3), and ({radical}3x{radical}3)R30 deg., are employed as templates to grow epitaxial (0001) GaN thin films. GaN grown on Si({radical}3x{radical}3)R30 deg. -Ga is found to be highly crystalline with intense (0002) x-ray diffraction and photoluminescence peaks with low full width at half maximum, low surface roughness, and stoichiometric surface composition. The high quality of these GaN films formed at a low temperature of 400 deg. C is explained by the integral (x2) lattice matching between the unit cell of GaN and the ({radical}3x{radical}3) phase. The experiments demonstrate a plausible approach of adsorbate induced surface modifications as templates for III-V hetroepitaxy on Si surfaces.

  19. The effect of substrate on high-temperature annealing of GaN epilayers: Si versus sapphire

    SciTech Connect (OSTI)

    Pastor, D.; Cusco, R.; Artus, L.; Gonzalez-Diaz, G.; Iborra, E.; Jimenez, J.; Peiro, F.; Calleja, E. [Institut Jaume Almera, Consell Superior d'Investigacions Cientifiques (CSIC), Lluis Sole i Sabaris s.n., 08028 Barcelona (Spain); Departamento Fisica Aplicada III, Universidad Complutense, 28040 Madrid (Spain); Departamento Tecnologia Electronica, ETSIT, Universidad Politecnica, 28040 Madrid (Spain); Departamento Fisica de la Materia Condensada, ETSII, Universidad de Valladolid, 47011 Valladolid (Spain); Departamento Electronica, Universidad de Barcelona, 08028 Barcelona (Spain); ISOM, Universidad Politecnica, Ciudad Universitaria, 28040 Madrid, Spain and Departamento Ingenieria Electronica, ETSIT, Universidad Politecnica, Ciudad Universitaria, 28040 Madrid (Spain)

    2006-08-15T23:59:59.000Z

    We have studied the effects of rapid thermal annealing at 1300 deg.C on GaN epilayers grown on AlN buffered Si(111) and on sapphire substrates. After annealing, the epilayers grown on Si display visible alterations with craterlike morphology scattered over the surface. The annealed GaN/Si layers were characterized by a range of experimental techniques: scanning electron microscopy, optical confocal imaging, energy dispersive x-ray microanalysis, Raman scattering, and cathodoluminescence. A substantial Si migration to the GaN epilayer was observed in the crater regions, where decomposition of GaN and formation of Si{sub 3}N{sub 4} crystallites as well as metallic Ga droplets and Si nanocrystals have occurred. The average diameter of the Si nanocrystals was estimated from Raman scattering to be around 3 nm. Such annealing effects, which are not observed in GaN grown on sapphire, are a significant issue for applications of GaN grown on Si(111) substrates when subsequent high-temperature processing is required.

  20. Formation of manganese -doped atomic layer in wurtzite GaN Meng Shi, Abhijit Chinchore, Kangkang Wang, Andrada-Oana Mandru, Yinghao Liu et al.

    E-Print Network [OSTI]

    Formation of manganese -doped atomic layer in wurtzite GaN Meng Shi, Abhijit Chinchore, Kangkang in wurtzite GaN Meng Shi, Abhijit Chinchore, Kangkang Wang, Andrada-Oana Mandru, Yinghao Liu, and Arthur R 2012) We describe the formation of a d-doped manganese layer embedded within c-plane wurtzite gallium

  1. Submitted to J. Appl. Phys. November 4, 1998; not for further distribution 1 Structure and Composition of GaN(0001) A and B Surfaces

    E-Print Network [OSTI]

    Cohen, Philip I.

    , Poland, 01-141 Both c-plane surfaces of bulk GaN crystals were examined using reflection high-energy, Sokololowska 29, Warsaw, Poland, 01-141 B.E. Ishaug, S.M. Seutter , A. Parkhomovsky , A.M. Dabiran, and P energy elec- tron diffraction (RHEED) observations of unipolar films grown on bulk GaN{0001} and compare

  2. High linearity GaN HEMT power amplifier with pre-linearization gate diode Shouxuan Xie, Vamsi Paidi, Sten Heikman, Alessandro Chini,

    E-Print Network [OSTI]

    Rodwell, Mark J. W.

    High linearity GaN HEMT power amplifier with pre-linearization gate diode Shouxuan Xie, Vamsi Paidi Santa Barbara, CA 93106, USA A high linearity MMIC RF power amplifier is reported in the AlGaN/GaN HEMT to compensate the non-linear effect caused by the nonlinear input capacitance Cgs of the GaN HEMT device

  3. High Power GaN Oscillators using Field-Plated HEMT Structure Hongtao Xu, Christopher Sanabria, Sten Heikman, Stacia Keller, Umesh K. Mishra, and Robert A.

    E-Print Network [OSTI]

    York, Robert A.

    High Power GaN Oscillators using Field-Plated HEMT Structure Hongtao Xu, Christopher Sanabria, Sten Engineering University of California, Santa Barbara, California 93106, USA Abstract -- 5 GHz MMIC GaN oscillators based on AlGaN/GaN HEMTs are presented. By using field-plated HEMT structures, both the output

  4. Intrafacet migration effects in InGaN/GaN structures grown on triangular GaN ridges studied by submicron beam x-ray diffraction

    E-Print Network [OSTI]

    Sirenko, Andrei

    Intrafacet migration effects in InGaN/GaN structures grown on triangular GaN ridges studied for x-ray diffraction and reciprocal space mapping of InGaN/GaN multiple-quantum-well MQW structures grown on the sidewalls of 10- m-wide triangular GaN ridges with 1-1.1 facets. Samples were produced

  5. Growth of single crystalline GaN thin films on Si,,111... substrates by high vacuum metalorganic chemical vapor deposition using a single

    E-Print Network [OSTI]

    Boo, Jin-Hyo

    Growth of single crystalline GaN thin films on Si,,111... substrates by high vacuum metalorganic; published 20 August 2004 Hexagonal GaN thin films were grown on Si 111 substrates using single molecular precursor of diethylazidogallium methylhydrazine adduct, (Et)2Ga N3)HzMe], with the objectives of reducing

  6. AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates

    E-Print Network [OSTI]

    Manfra, Michael J.

    PS-4 AlGaN/GaN HEMTs grown by Molecular Beam Epitaxy on sapphire, Sic, and HVPE GaN templates Nils ABSTRACT Molecular Beam Epitaxy of GaN and related alloys is becoming a rival to the more established, and HVPE SI-GaN templates on sapphire. While sapphire and SI-Sic are established substrates for the growth

  7. Growth of cubic GaN on 3CSiC/Si (001) nanostructures R.M. Kemper a,n

    E-Print Network [OSTI]

    As, Donat Josef

    ) substrate. These anti-phase domains strongly influence the optimum growth of GaN layers in these regions are due to the lattice mismatch with the substrate. For c-GaN, 3C­SiC is the preferred substrate of GaN on post shaped nanostructures and analyze the influence of substrate domains on the defect

  8. Phonons in sapphire Al2O3 substrate for ZnO and GaN H.W. Kunert a,, A.G.J. Machatine b

    E-Print Network [OSTI]

    Nabben, Reinhard

    Phonons in sapphire Al2O3 substrate for ZnO and GaN H.W. Kunert a,, A.G.J. Machatine b , A. Keywords: Phonons; Sapphire; Group theory; Time reversal; Zno; GaN 1. Introduction The lattice structure in semiconductor research enabled fabrication of GaN-based blued emitting diodes and laser devices[1,2]. Due

  9. 1282 IEEE ELECTRON DEVICE LETTERS, VOL. 33, NO. 9, SEPTEMBER 2012 Top-Gate GaN Thin-Film Transistors Based

    E-Print Network [OSTI]

    is to deposit high-quality GaN thin films using inexpensive substrate under low temper- ature. Recently1282 IEEE ELECTRON DEVICE LETTERS, VOL. 33, NO. 9, SEPTEMBER 2012 Top-Gate GaN Thin-Film Transistors Based on AlN/GaN Heterostructures Rongsheng Chen, Wei Zhou, Meng Zhang, and Hoi Sing Kwok Abstract

  10. Transmission Electron Microscopy Study of Nonpolar a-Plane GaN Grown by Pendeo-Epitaxy on (112_0) 4H-SiC

    E-Print Network [OSTI]

    Zakharov, D.N.; Liliental-Weber, Z.; Wagner, B.; Reitmeier, Z.J.; Preble, E.A.; Davis, R.F.

    2008-01-01T23:59:59.000Z

    pendeo-epitaxial GaN layer grown on (1120) 4H-SiC substrate.a-plane GaN layers grown on (1120) 4H-SiC substrate with AlNGaN layers grown by heteroepitaxial methods on different substrates

  11. ZrO2 gate dielectrics produced by ultraviolet ozone oxidation for GaN and AlGaN/GaN transistors

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    MOSCAP process ?ow: n-GaN substrate; Ohmic metallization andtion for a AlGaN/ GaN HEMT on a substrate which has a poorsapphire substrate, a well-passivated AlGaN/ GaN HEMT grown

  12. Selective area growth and characterization of GaN nanocolumns, with and without an InGaN insertion, on semi-polar (11–22) GaN templates

    SciTech Connect (OSTI)

    Bengoechea-Encabo, A.; Albert, S.; Barbagini, F.; Sanchez-Garcia, M. A.; Calleja, E. [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040 Madrid (Spain)] [ISOM and Departamento de Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040 Madrid (Spain); Zuñiga-Perez, J.; Mierry, P. de [CRHEA-CNRS, 06560 Valbonne (France)] [CRHEA-CNRS, 06560 Valbonne (France); Trampert, A. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)] [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2013-12-09T23:59:59.000Z

    The aim of this work is the selective area growth (SAG) of GaN nanocolumns, with and without an InGaN insertion, by molecular beam epitaxyon semi-polar (11–22) GaN templates. The high density of stacking faults present in the template is strongly reduced after SAG. A dominant sharp photoluminescence emission at 3.473 eV points to high quality strain-free material. When embedding an InGaN insertion into the ordered GaN nanostructures, very homogeneous optical properties are observed, with two emissions originating from different regions of each nanostructure, most likely related to different In contents on different crystallographic planes.

  13. AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

    SciTech Connect (OSTI)

    Hodges, C., E-mail: chris.hodges@bristol.ac.uk; Anaya Calvo, J.; Kuball, M. [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom)] [H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); Stoffels, S.; Marcon, D. [IMEC, Kapeldreef 75, B3001 Leuven (Belgium)] [IMEC, Kapeldreef 75, B3001 Leuven (Belgium)

    2013-11-11T23:59:59.000Z

    AlGaN/GaN heterostructure field effect transistors with a 150?nm thick GaN channel within stacked Al{sub x}Ga{sub 1?x}N layers were investigated using Raman thermography. By fitting a thermal simulation to the measured temperatures, the thermal conductivity of the GaN channel was determined to be 60?W m{sup ?1} K{sup ?1}, over 50% less than typical GaN epilayers, causing an increased peak channel temperature. This agrees with a nanoscale model. A low thermal conductivity AlGaN buffer means the GaN spreads heat; its properties are important for device thermal characteristics. When designing power devices with thin GaN layers, as well as electrical considerations, the reduced channel thermal conductivity must be considered.

  14. Structural and energy characteristics of native vacancy-type defects in the biaxially stressed GaN lattice

    SciTech Connect (OSTI)

    Bez'yazychnaya, T. V.; Zelenkovskii, V. M.; Gurskii, A. L.; Ryabtsev, G. I. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus)], E-mail: ryabtsev@dragon.bas-net.by

    2008-11-15T23:59:59.000Z

    For biaxially stressed GaN clusters, the structure, charges, and energies of the formation of intrinsic Ga and N vacancies are calculated by the quantum-chemical method in the SCF MO LCAO approximation taking into account relaxation of the crystalline surroundings. It is established that the use of substrates introducing compressive or tensile stresses into the epitaxial layer affects the concentrations of intrinsic vacancy-type point defects. This effect most clearly manifests itself in the nitrogen sublattice in the GaN crystal lattice, especially in the case of its tension, i.e., during the epitaxial grown of GaN on the Si substrate. Redistribution of the electron density in the defect region in the case of lattice compression or tension can be the cause of variation in the location of electronic levels of defects in the band gap of the crystal.

  15. 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 [Department of Electronic Engineering, Faculty of Engineering, Gunma University, Kiryu-shi, Gunma 376-8515 (Japan); Research and Development Division, Sanken Electric Co., Ltd., Niiza-shi, Saitama 352-8666 (Japan)

    2005-05-01T23:59:59.000Z

    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.

  16. US Department of Energy (DOE)/Gosatomnadzor (GAN) of Russia project at the Petersburg Nuclear Physics Institute (PNPI)

    SciTech Connect (OSTI)

    Baranov, I.A.; Konoplev, K.A. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Hauser, G.C. [Sandia National Lab., Albuquerque, NM (United States)] [and others

    1997-08-01T23:59:59.000Z

    This paper presents a summary of work accomplished within the scope of the DOE-Gosatomnadzor (GAN) Agreement to reduce vulnerability to theft of direct-use nuclear materials in Russia. The DOE-GAN agreement concerns the Russian Academy of Science B.P. Konstantinov Petersburg Nuclear Physics Institute (PNPI), located 45 kilometers from St. Petersburg. The PNPI operates facilities to research basic nuclear physics. Current world conditions require particular attention to the issue of Material Protection, Control, and Accounting (MPC&A) of nuclear materials. The long-term plan to increase security at the facility is outlined, including training, physical protection upgrades, and material control and accountability. 4 figs.

  17. High temperature electron spin dynamics in bulk cubic GaN: Nanosecond spin lifetimes far above room-temperature

    SciTech Connect (OSTI)

    Buß, J. H.; Schaefer, A.; Hägele, D.; Rudolph, J. [Arbeitsgruppe Spektroskopie der kondensierten Materie, Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum (Germany); Schupp, T.; As, D. J. [Department of Physics, University of Paderborn, Warburger Str. 100, D-33095 Paderborn (Germany)

    2014-11-03T23:59:59.000Z

    The electron spin dynamics in n-doped bulk cubic GaN is investigated for very high temperatures from 293?K up to 500?K by time-resolved Kerr-rotation spectroscopy. We find extraordinarily long spin lifetimes exceeding 1?ns at 500?K. The temperature dependence of the spin relaxation time is in qualitative agreement with predictions of Dyakonov-Perel theory, while the absolute experimental times are an order of magnitude shorter than predicted. Possible reasons for this discrepancy are discussed, including the role of phase mixtures of hexagonal and cubic GaN as well as the impact of localized carriers.

  18. Hydrogen effect on near-atmospheric nitrogen plasma assisted chemical vapor deposition of GaN film growth

    SciTech Connect (OSTI)

    Nagata, T.; Haemori, M.; Sakuma, Y.; Chikyow, T. [Advanced Electronic Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Anzai, J.; Uehara, T. [Sekisui Chemical Co., Ltd., Wadai, Tsukuba, Ibaraki 300-4292 (Japan)

    2009-03-15T23:59:59.000Z

    The effect of hydrogen on near-atmospheric nitrogen plasma and low temperature growth of GaN thin film was investigated. To investigate nitrogen plasma diluted with hydrogen, optical emission spectroscopy (OES) was employed. OES indicates that hydrogen enhances the generation of the nitrogen first positive system and first negative systems by providing an additional kinetic pathway. The plasma also decomposed triethylgallium and generated Ga ions even at room temperature. Using this plasma, GaN film grew on sapphire substrate epitaxially at growth temperatures of above 170 deg. C and crystallized at 55 deg. C.

  19. Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy

    SciTech Connect (OSTI)

    Chen, Yen-Ting [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China) [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China); Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden); Araki, Tsutomu [Department of Electrical and Electronic Engineering, Ritsumeikan University, 525-8577 Shiga (Japan)] [Department of Electrical and Electronic Engineering, Ritsumeikan University, 525-8577 Shiga (Japan); Palisaitis, Justinas; Persson, Per O. Å.; Olof Holtz, Per; Birch, Jens [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology (IFM), Linköping University, S-58183 Linköping (Sweden); Chen, Li-Chyong [Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China)] [Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China); Chen, Kuei-Hsien [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China) [Institute of Atomic and Molecular Sciences, Academia Sinica, 10617 Taipei, Taiwan (China); Center for Condensed Matter Sciences, National Taiwan University, 10617 Taipei, Taiwan (China); Nanishi, Yasushi [Global Innovation Research Organization, Ritsumeikan University, 525-8577 Shiga (Japan)] [Global Innovation Research Organization, Ritsumeikan University, 525-8577 Shiga (Japan)

    2013-11-11T23:59:59.000Z

    Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (<35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a “narrow-pass” approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.

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

    SciTech Connect (OSTI)

    Mamand, S.M., E-mail: soran.mamand@univsul.net [Department of Physics, College of Science, University of Sulaimani, Sulaimanyah, Iraqi Kurdistan (Iraq); Omar, M.S. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)] [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Muhammad, A.J. [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq)] [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq)

    2012-05-15T23:59:59.000Z

    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.

  1. Lattice location of implanted $^{147}$Nd and $^{147*}$Pm in GaN using emission channeling

    E-Print Network [OSTI]

    De Vries, B; Vantomme, A; Correia, J G

    2003-01-01T23:59:59.000Z

    The lattice location of $^{147}$Nd and $^{147^{*}}$Pm in thin-film, single-crystalline hexagonal GaN was studied by means of the emission channeling technique. The angular emission yields of $\\beta^{-}$-particles and conversion electrons emitted by the radioactive isotopes $^{147}$Nd and $^{147^{*}}$Pm were measured using a position-sensitive detector following 60 keV room temperature implantation at a dose of 1 $\\times 10^{13}$ cm$^{-2}$ and annealing at 900°C. The emission patterns around the [0001], [1102], [1101], and [2113] crystal axes give direct evidence that the majority (70%) of Nd and Pm atoms occupy substitutional Ga sites.

  2. Evaluation of GaN substrates grown in supercritical basic ammonia

    SciTech Connect (OSTI)

    Saito, Makoto; Yamada, Hisashi; Iso, Kenji; Sato, Hitoshi; Hirasawa, Hirohiko; Kamber, Derrick S.; Hashimoto, Tadao; Baars, Steven P. den; Speck, James S.; Nakamura, Shuji [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2009-02-02T23:59:59.000Z

    GaN crystals grown by the basic ammonothermal method were investigated for their use as substrates for device regrowth. X-ray diffraction analysis indicated that the substrates contained multiple grains while secondary ion mass spectroscopy (SIMS) revealed a high concentration of hydrogen, oxygen, and sodium. Despite these drawbacks, the emission from the light emitting diode structures grown by metal organic chemical vapor deposition on both the c-plane and m-plane epitaxial wafers was demonstrated. The SIMS depth profiles showed that the diffusion of the alkali metal from the substrate into the epitaxial film was small, especially in the m-direction.

  3. Metallicity of InN and GaN surfaces exposed to NH{sub 3}.

    SciTech Connect (OSTI)

    Walkosz, W.; Zapol, P.; Stephenson, G. B. (Materials Science Division)

    2012-01-01T23:59:59.000Z

    A systematic study of energies and structures of InN and GaN (0001) surfaces exposed to NH{sub 3} and its decomposition products was performed with first-principles methods. A phenomenological model including electron counting contributions is developed based on calculated DFT energies and is used to identify low-energy structures. These predictions are checked with additional DFT calculations. The equilibrium phase diagrams are found to contain structures that violate the electron counting rule. Densities of states for these structures indicate n-type conductivity, consistent with available experimental results.

  4. Time-resolved photoluminescence from defects in n-type GaN

    SciTech Connect (OSTI)

    Reshchikov, M. A., E-mail: mreshchi@vcu.edu [Physics Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)

    2014-03-14T23:59:59.000Z

    Point defects in GaN were studied with time-resolved photoluminescence (PL). The effects of temperature and excitation intensity on defect-related PL have been investigated theoretically and experimentally. A phenomenological model, based on rate equations, explains the dependence of the PL intensity on excitation intensity, as well as the PL lifetime and its temperature dependence. We demonstrate that time-resolved PL measurements can be used to find the concentrations of free electrons and acceptors contributing to PL in n-type semiconductors.

  5. Experimental evidence of Ga-vacancy induced room temperature ferromagnetic behavior in GaN films

    SciTech Connect (OSTI)

    Roul, Basanta; Kumar, Mahesh [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Rajpalke, Mohana K.; Bhat, Thirumaleshwara N.; Krupanidhi, S. B. [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Kalghatgi, A. T. [Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Kumar, Nitesh; Sundaresan, A. [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P. O., Bangalore 560064 (India)

    2011-10-17T23:59:59.000Z

    We have grown Ga deficient GaN epitaxial films on (0001) sapphire substrate by plasma-assisted molecular beam epitaxy and report the experimental evidence of room temperature ferromagnetic behavior. The observed yellow emission peak in room temperature photoluminescence spectra and the peak positioning at 300 cm{sup -1} in Raman spectra confirms the existence of Ga vacancies. The x-ray photoelectron spectroscopic measurements further confirmed the formation of Ga vacancies; since the N/Ga is found to be >1. The ferromagnetism is believed to originate from the polarization of the unpaired 2p electrons of N surrounding the Ga vacancy.

  6. Si (111) substrates as highly effective pseudomasks for selective growth of GaN material and devices by ammonia-molecular-beam epitaxy

    SciTech Connect (OSTI)

    Tang, H.; Haffouz, S.; Bardwell, J.A. [Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)

    2006-04-24T23:59:59.000Z

    The unique property of Si (111) as effective pseudomask substrate for selective growth of GaN by ammonia-molecular-beam epitaxy is reported. The critical nucleation temperature of GaN on Si (111) surface is found to be as low as 700 deg. C, much lower than that on sapphire or AlN surface. As a result, selective growth of GaN is possible by ammonia-molecular-beam epitaxy on Si (111) substrates using a patterned AlN buffer layer. The wide range of growth temperatures (700-900 deg. C) available for selective growth is a critical advantage for control and optimization of the facet characteristics of the selectively grown GaN patterns as required for potential fabrication of site-specific GaN or InGaN quantum dots. The demonstrated ease of selective growth of GaN on silicon has also implications in potential on-chip integration of GaN devices with silicon devices.

  7. Atomistic simulation of Er irradiation induced defects in GaN nanowires

    SciTech Connect (OSTI)

    Ullah, M. W., E-mail: mohammad.ullah@helsinki.fi; Kuronen, A.; Djurabekova, F.; Nordlund, K. [Department of Physics, University of Helsinki, P.O. Box 64, FIN-00014 (Finland); Stukowski, A. [Technische Universität Darmstadt, 64287 Darmstadt (Germany)

    2014-09-28T23:59:59.000Z

    Classical molecular dynamics simulation was used to irradiate a GaN nanowire with rear-earth erbium (Er). Ten cumulative irradiations were done using an ion energy of 37.5?keV on a 10?×?10?nm{sup 2} surface area which corresponds to a fluence of 1?×?10{sup 13?}cm{sup ?2}. We studied the location and types of defects produced in the irradiation. Er implantation leads to a net positive (expansion) strain in the nanowire and especially at the top region a clear expansion has been observed in the lateral and axial directions. The lattice expansion is due to the hydrostatic strain imposed by a large number of radiation induced defects at the top of the NW. Due to the large surface-to-volume ratio, most of the defects were concentrated at the surface region, which suggests that the experimentally observed yellow luminescence (YL) in ion implanted GaN NWs arises from surface defects. We observed big clusters of point defects and vacancy clusters which are correlated with stable lattice strain and the YL band, respectively.

  8. Influence of substrate material, orientation, and surface termination on GaN nanowire growth

    SciTech Connect (OSTI)

    Schuster, Fabian, E-mail: Fabian.Schuster@wsi.tum.de; Weiszer, Saskia; Hetzl, Martin; Winnerl, Andrea; Garrido, Jose A.; Stutzmann, Martin [Walter Schottky Institut and Physics Department, Technische Universität München, Am Coulombwall 4, 85748 Garching (Germany)

    2014-08-07T23:59:59.000Z

    In this work, we investigate the fundamental role of the substrate material, surface orientation, and termination on GaN nanowire (NW) nucleation and growth. First of all, the use of a patterned a-Si/diamond substrate confirms that NW shape and dimension are mainly determined by the applied growth conditions instead of the nature of the substrate. More important is the surface orientation as it defines growth direction and epitaxial relationship towards the GaN NWs, where both (111) and (100) surfaces yield NW growth for equivalent growth conditions. (110) substrates are found to be not suited for NW growth. Finally, the surface termination of diamond is demonstrated to survive the employed growth conditions and, therefore, to affect the nucleation of nanowires and the electronic properties of the heterointerface by its surface dipoles. This difference in nucleation is exploited as an alternative approach for selective area growth without deposition of a foreign mask material, which might also be transferable to other substrates.

  9. Non-degenerate pump-probe spectroscopy of single GaN nanowires

    SciTech Connect (OSTI)

    Upadhya, Prashanth C [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory; Prasankumar, Rohiy P [Los Alamos National Laboratory; Wang, George T [SNL; Martinez, Julio A [SNL; Li, Qiming [SNL; Swartzentruber, Brian S [SNL

    2010-01-01T23:59:59.000Z

    Spatially-resolved ultrafast transient absorption measurements on a single GaN nanowire give insight into carrier relaxation dynamics as a function of the probe polarization and position on the nanowire on a femtosecond timescale. The synthesis and optical characterization of semiconductor nanowires (NWs) has gained considerable attention in recent years owing to their unique electronic and optical properties that arise from their anisotropic geometry, large surface to volume ratio and two-dimensional quasiparticle confinement, Post-growth characterization of their properties is crucial in understanding the fundamental physical processes that can lead to enhanced functionality of NW-based devices, In particular, it is important to understand the carrier relaxation pathways in individual NWs, since the geometry of these nanostructures can significantly influence carrier recombination and/or trapping. In this respect, ultrafast optical techniques offer reliable and non-contact spectroscopic tools to study carrier dynamics in semiconductor nanostructures. In summary, time-resolved optical pump-probe spectroscopy was performed on single GaN NWs. These measurements give insight into the different processes that govern carrier capture, particularly at surface states, and relaxation in individual nanostructures. Our experiments thus demonstrate the value of single-particle ultrafast optical spectroscopy in understanding the physical processes that govern the properties of semiconductor NWs, while suggesting approaches to optimize NW-based devices for nanophotonic applications.

  10. Polarity inversion of N-face GaN by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Wong, M.H.; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Wu Feng; Mates, Thomas E.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2008-11-01T23:59:59.000Z

    The polarity of GaN grown by plasma-assisted molecular beam epitaxy was inverted from N-face to Ga-face by simultaneously exposing the surface to Mg and activated N fluxes during a growth interruption at a reduced substrate temperature. Growth studies suggested that a Mg{sub x}N{sub y} compound was responsible for inverting the crystal. The change in polarity was verified in situ by reflection high energy electron diffraction via GaN surface reconstructions, and ex situ by convergent beam electron diffraction and KOH etch studies. The surface of the inverted material showed smooth step flow features. Ga-face high electron mobility transistors with good dc and small signal performance were fabricated on the inverted epilayers. A drain-source current of 0.84 A/mm was measured at a gate-source voltage of +1 V. Current-gain cutoff and maximum oscillation frequencies of 22 and 53 GHz, respectively, were measured in these devices. The device performance is similar to that of Ga-face transistors with comparable dimensions.

  11. Buffer transport mechanisms in intentionally carbon doped GaN heterojunction field effect transistors

    SciTech Connect (OSTI)

    Uren, Michael J.; Cäsar, Markus; Kuball, Martin [Center for Device Thermography and Reliability, H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); Gajda, Mark A. [NXP Semiconductors, Bramhall Moor Lane, Hazel Grove, Stockport SK7 5BJ (United Kingdom)

    2014-06-30T23:59:59.000Z

    Temperature dependent pulsed and ramped substrate bias measurements are used to develop a detailed understanding of the vertical carrier transport in the buffer layers in a carbon doped GaN power heterojunction field effect transistor. Carbon doped GaN and multiple layers of AlGaN alloy are used in these devices to deliver an insulating and strain relieved buffer with high breakdown voltage capability. However, understanding of the detailed physical mechanism for its operation is still lacking. At the lowest electric fields (<10 MV/m), charge redistribution within the C doped layer is shown to occur by hole conduction in the valence band with activation energy 0.86?eV. At higher fields, leakage between the two-dimensional electron gas and the buffer dominates occurring by a Poole-Frenkel mechanism with activation energy ?0.65?eV, presumably along threading dislocations. At higher fields still, the strain relief buffer starts to conduct by a field dependent process. Balancing the onset of these leakage mechanisms is essential to allow the build-up of positive rather than negative space charge, and thus minimize bulk-related current-collapse in these devices.

  12. Grating-gate tunable plasmon absorption in InP and GaN based R. E. Peale*a

    E-Print Network [OSTI]

    Peale, Robert E.

    Grating-gate tunable plasmon absorption in InP and GaN based HEMTs R. E. Peale*a , H. Saxenaa , W, Inc., 1195 Atlas Road, Columbia SC, USA 29209 ABSTRACT Gate-voltage tunable plasmon resonances incident THz radiation into 2D plasmons. Narrow-band resonant absorption of THz radiation was observed

  13. Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers C. Wetzel, Nagoya, Japan Received 11 December 1995; accepted for publication 21 February 1996 Infrared reflection, their alloys and potential substrates need to be investigated as well. Here we present a study of the infrared

  14. Self-heating in a GaN based heterostructure field effect transistor: Ultraviolet and visible Raman measurements and simulations

    E-Print Network [OSTI]

    Holtz, Mark

    Self-heating in a GaN based heterostructure field effect transistor: Ultraviolet and visible Raman online 8 December 2006 We report direct self-heating measurements for AlGaN/GaN heterostructure field density can be commensurately high, collisional energy loss from electrons to the crystal leads to self-heating

  15. Thermoelectric and micro-Raman measurements of carrier density and mobility in heavily Si-doped GaN wires

    E-Print Network [OSTI]

    Boyer, Edmond

    Thermoelectric and micro-Raman measurements of carrier density and mobility in heavily Si-doped Ga (Received 19 July 2013; accepted 28 October 2013; published online 11 November 2013) Combined thermoelectric epitaxy (MOVPE). These highly conductive Si-doped GaN wires were studied by means of thermoelectrical

  16. Electronic band structure of wurtzite GaN under biaxial strain in the M plane investigated with photoreflectance spectroscopy

    E-Print Network [OSTI]

    Ghosh, Sandip

    Electronic band structure of wurtzite GaN under biaxial strain in the M plane investigated; published 7 January 2002 We investigate the modification of the electronic band structure in wurtzite Ga.40.Fy I. INTRODUCTION The wurtzite WZ structure of III-V nitrides leads to electrostatic fields due

  17. OPTIMIZATION OF GaN WINDOW LAYER FOR InGaN SOLAR CELLS USING POLARIZATION EFFECT

    E-Print Network [OSTI]

    Honsberg, Christiana

    on the design of wide-band gap GaN window layers for InGaN solar cells. Window layers serve to passivate the top into account during design of the solar cell to improve its collection efficiency. Previously, we have. The present work is a subset of the design optimization process for such solar cells, where we focus

  18. RF Power Degradation of GaN High Electron Mobility Transistors Jungwoo Joh and Jess A. del Alamo

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    RF Power Degradation of GaN High Electron Mobility Transistors Jungwoo Joh and Jesús A. del Alamo Transistors. Our technique utilizes RF and DC figures of merit to diagnose the degradation of RF stressed and to introduce new degradation modes. At high power level, RF stress induces a prominent trapping

  19. A Transient Stability Constrained Optimal Power Flow Deqiang Gan (M) Robert J. Thomas (F) Ray D. Zimmerman (M)

    E-Print Network [OSTI]

    Cornell University Ithaca, NY 14853 Abstract Stability is an important constraint in power system1 A Transient Stability Constrained Optimal Power Flow Deqiang Gan (M) Robert J. Thomas (F) Ray D. The methodology involves a stability constrained Optimal Power Flow (OPF). The theoretical development

  20. IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 56, NO. 12, DECEMBER 2009 2895 Measurement of Channel Temperature in GaN

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    -temperature estimation is particularly complicated in high-power-density devices such as GaN HEMTs because self-heating transistors (HEMTs) is proposed. The technique is based on electrical measurements of performance electrical measurement, no special design in device geometry is required, and packaged devices can

  1. Fe-Centers in GaN as Candidates for Spintronics Applications Enno Malguth, Axel Hoffmann1

    E-Print Network [OSTI]

    Nabben, Reinhard

    High quality factor nitride-based optical cavities: microdisks with embedded GaN/Al(Ga)N quantum We compare the quality factor values of the whispery gallery modes of microdisks incorporating GaN quantum dots (QDs) grown on AlN and AlGaN barriers by performing room temperature photoluminescence (PL

  2. Role of Embedded Clustering in Dilute Magnetic Semiconductors: Cr Doped GaN X. Y. Cui,1

    E-Print Network [OSTI]

    Medvedeva, Julia E.

    Role of Embedded Clustering in Dilute Magnetic Semiconductors: Cr Doped GaN X. Y. Cui,1 J. E provide direct evidence that Cr atoms in Cr:GaN have a strong tendency to form embedded clusters, to date, the ma- jority of first-principles investigations into DMS--and Cr:GaN, Mn:GaN, and Mn

  3. Semipolar (202{sup ¯}1) GaN and InGaN quantum wells on sapphire substrates

    SciTech Connect (OSTI)

    Leung, Benjamin; Wang, Dili; Kuo, Yu-Sheng; Xiong, Kanglin; Song, Jie; Chen, Danti; Park, Sung Hyun; Han, Jung [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States); Hong, Su Yeon; Choi, Joo Won [Seoul Viosys Co., Ltd., Ansan City, Kyunggi-do 425-851 (Korea, Republic of)

    2014-06-30T23:59:59.000Z

    Here, we demonstrate a process to produce planar semipolar (202{sup ¯}1) GaN templates on sapphire substrates. We obtain (202{sup ¯}1) oriented GaN by inclined c-plane sidewall growth from etched sapphire, resulting in single crystal material with on-axis x-ray diffraction linewidth below 200?arc sec. The surface, composed of (101{sup ¯}1) and (101{sup ¯}0) facets, is planarized by the chemical-mechanical polishing of full 2?in. wafers, with a final surface root mean square roughness of <0.5?nm. We then analyze facet formation and roughening mechanisms on the (202{sup ¯}1) surface and establish a growth condition in N{sub 2} carrier gas to maintain a planar surface for further device layer growth. Finally, the capability of these semipolar (202{sup ¯}1) GaN templates to produce high quality device structures is verified by the growth and characterization of InGaN/GaN multiple quantum well structures. It is expected that the methods shown here can enable the benefits of using semipolar orientations in a scalable and practical process and can be readily extended to achieve devices on surfaces using any orientation of semipolar GaN on sapphire.

  4. A comparative study on magnetism in Zn-doped AlN and GaN from first-principles

    SciTech Connect (OSTI)

    Xu, Liang; Wang, Lingling, E-mail: llwang@hnu.edu.cn, E-mail: xiaowenzhi@hnu.edu.cn; Huang, Weiqing [School of Physics and Microelectronics, Hunan University, Changsha 410082 (China); Xiao, Wenzhi, E-mail: llwang@hnu.edu.cn, E-mail: xiaowenzhi@hnu.edu.cn; Xiao, Gang [Department of Physics and Mathematics, Hunan Institute of Engineering, Xiangtan 411104 (China)

    2014-09-14T23:59:59.000Z

    First-principles calculations have been used to comparatively investigate electronic and magnetic properties of Zn-doped AlN and GaN. A total magnetic moment of 1.0 ?B{sub B} induced by Zn is found in AlN, but not in GaN. Analyses show that the origin of spontaneous polarization not only depend on the localized atomic orbitals of N and sufficient hole concentration, but also the relative intensity of the covalency of matrix. The relatively stronger covalent character of GaN with respect to AlN impedes forming local magnetic moment in GaN matrix. Our study offers a fresh sight of spontaneous spin polarization in d? magnetism. The much stronger ferromagnetic coupling in c-plane of AlN means that it is feasible to realize long-range ferromagnetic order via monolayer delta-doping. This can apply to other wide band-gap semiconductors in wurtzite structure.

  5. Low-temperature GaN growth on silicon substrates by single gas-source epitaxy and photo-excitation

    SciTech Connect (OSTI)

    Trivedi, R.A.; Tolle, J.; Chizmeshya, A.V.G.; Roucka, R.; Ritter, Cole; Kouvetakis, J.; Tsong, I.S.T. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2005-08-15T23:59:59.000Z

    We report a unique low-temperature growth method for epitaxial GaN on Si(111) substrates via a ZrB{sub 2}(0001) buffer layer. The method utilizes the decomposition of a single gas-source precursor (D{sub 2}GaN{sub 3}){sub 3} on the substrate surface to form GaN. The film growth process is further promoted by irradiation of ultraviolet light to enhance the growth rate and ordering of the film. The best epitaxial film quality is achieved at a growth temperature of 550 deg. C with a growth rate of 3 nm/min. The films exhibit intense photoluminescence emission at 10 K with a single peak at 3.48 eV, indicative of band-edge emission for a single-phase hexagonal GaN film. The growth process achieved in this study is compatible with low Si processing temperatures and also enables direct epitaxy of GaN on ZrB{sub 2} in contrast to conventional metalorganic chemical vapor deposition based approaches.

  6. Spectroscopic ellipsometry studies of GaN films deposited by reactive rf sputtering of GaAs target

    SciTech Connect (OSTI)

    Biswas, A.; Bhattacharyya, D.; Sahoo, N. K. [Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Yadav, Brajesh S.; Major, S. S. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India); Srinivasa, R. S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

    2008-04-15T23:59:59.000Z

    GaN films have been deposited by reactive rf sputtering of GaAs target in 100% nitrogen ambient on quartz substrates at different substrate temperatures ranging from room temperature to 700 deg. C. A series of films, from arsenic-rich amorphous to nearly arsenic-free polycrystalline hexagonal GaN, has been obtained. The films have been characterized by phase modulated spectroscopic ellipsometry to obtain the optical parameters, viz., fundamental band gap, refractive index, and extinction coefficient, and to understand their dependence on composition and microstructure. A generalized optical dispersion model has been used to carry out the ellipsometric analysis for amorphous and polycrystalline GaN films and the variation of the optical parameters of the films has been studied as a function of substrate temperature. The refractive index values of polycrystalline films with preferred orientation of crystallites are slightly higher (2.2) compared to those for amorphous and randomly oriented films. The dominantly amorphous GaN film shows a band gap of 3.47 eV, which decreases to 3.37 eV for the strongly c-axis oriented polycrystalline film due to the reduction in amorphous phase content with increase in substrate temperature.

  7. Band gap tuning in GaN through equibiaxial in-plane strains S. K. Yadav,2

    E-Print Network [OSTI]

    Alpay, S. Pamir

    in photovoltaics and light emission diodes LEDs . The InGaN system has been intensively studied during the past to the large atomic size mismatch between Ga and In.3 Thus, other methods to tune the band gap are needed for potential appli- cations of GaN and related materials systems. It is well-known that the structure

  8. 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

    2010-09-01T23:59:59.000Z

    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 concert with sophisticated molecular-dynamics calculations of surface and defect-mediated NW thermal transport. This proposal seeks to elucidate long standing material science questions for GaN while addressing issues critical to realizing reliable GaN NW devices.

  9. Evolution of AlN buffer layers on Silicon and the effect on the property of the expitaxial GaN film

    E-Print Network [OSTI]

    Zang, Keyan

    The morphology evolution of high-temperature grown AlN nucleation layers on (111) silicon has been studied using atomic force microscopy (AFM). The structure and morphology of subsequently grown GaN film were characterized ...

  10. Ammothermal Growth of Gan Substrates For Leds: High-Pressure Ammonothermal Process for Bulk Gallium Nitride Crystal Growth for Energy Efficient Commercially Competitive Lighting

    SciTech Connect (OSTI)

    None

    2011-01-01T23:59:59.000Z

    Broad Funding Opportunity Announcement Project: The new GaN crystal growth method is adapted from that used to grow quartz crystals, which are very inexpensive and represent the second-largest market for single crystals for electronic applications (after silicon). More extreme conditions are required to grow GaN crystals and therefore a new type of chemical growth chamber was invented that is suitable for large-scale manufacturing. A new process was developed that grows GaN crystals at a rate that is more than double that of current processes. The new technology will enable GaN substrates with best-in-world quality at lowest-in-world prices, which in turn will enable new generations of white LEDs, lasers for full-color displays, and high-performance power electronics.

  11. Energy relaxation of hot electrons in Si-doped GaN

    SciTech Connect (OSTI)

    Zhang, J.-Z., E-mail: tfyjzzhang@hotmail.com, E-mail: jian-zhong.zhang@hull.ac.uk [School of Systems Science, Beijing Normal University, Beijing 100875 (China)

    2014-05-28T23:59:59.000Z

    Energy relaxation of the hot electrons in Si-doped bulk GaN is studied theoretically, taking into account non-equilibrium polar optical phonons, electron degeneracy, and screening from the mobile electrons. The electron power dissipation and energy relaxation time are calculated as functions of the electron temperature T{sub e}, the hot-phonon effect (HPE) is examined by varying the optical phonon lifetime values, and the results are compared with previous calculations for typical GaN-based heterostructures. Particular attention is paid to the distinct temperature T{sub e} dependences of the power loss and the energy relaxation time ?{sub E} at the low and high electron temperatures. At low electron temperatures (T{sub e}<500?K), the exponential rise of phonon generation number, fast weakened screening and HPE result in a rapid increase of power loss and sharp drop of relaxation time with T{sub e}. At high electron temperatures (T{sub e}>1500?K), the power loss increases slowly with T{sub e} due to the decrease in phonon generation rate, and the temperature-dependence of the energy relaxation time depends on the polar optical phonon lifetime—saturation in energy relaxation occurs when the phonon lifetime increases or varies little with T{sub e}. Our calculated temperature dependences of the energy relaxation time are in good agreement with experimental findings [Liberis et al., Appl. Phys. Lett. 89, 202117 (2006); Matulionis et al., Phys. Status Solidi C 2, 2585 (2005)]. With no HPE, the electron energy relaxation is much faster in bulk GaN (?{sub E}? several tens femtoseconds) than in the GaN-based heterostructures. However, stronger hot-phonon re-absorption occurs in bulk GaN due to rapid polar-optical phonon emission compared to phonon decay. Therefore, including HPE yields very close power loss and energy relaxation times in bulk and heterostructures with similar densities of electrons (?{sub E}? several tenths of a picosecond). Transparent expressions for energy relaxation are obtained in the Boltzmann approximation, which are very useful for resolving the temperature dependences of the energy relaxation in the low- and high-T{sub e} regions.

  12. Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen

    E-Print Network [OSTI]

    York, Robert A.

    Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN P. J. Hansen Materials Department March 2005 Titanium dioxide TiO2, with the rutile structure was grown on 0001 oriented GaN and 0001 Al0.33Ga0.67N/GaN heterostructure field effect transistor HFET structures by molecular beam epitaxy. X

  13. Band Gap Shift of GaN under Uniaxial Strain Compression H. Y. Peng, M. D. McCluskey, Y. M. Gupta, M. Kneissl1

    E-Print Network [OSTI]

    McCluskey, Matthew

    Band Gap Shift of GaN under Uniaxial Strain Compression H. Y. Peng, M. D. McCluskey, Y. M. Gupta, M.S.A. ABSTRACT The band-gap shift of GaN:Mg epilayers on (0001)-oriented sapphire was studied as a function is approximately 0.026 eV/GPa. Combining this result with the known behavior of wurtzite GaN under hydrostatic

  14. Single-Wire Light-Emitting Diodes Based on GaN Wires Containing Both Polar and Nonpolar InGaN/GaN Quantum Wells

    E-Print Network [OSTI]

    Single-Wire Light-Emitting Diodes Based on GaN Wires Containing Both Polar and Nonpolar InGaN/GaN based on radial p­i­n multi quantum well (QW) junctions have been realized from GaN wires grown by catalyst- free metal organic vapor phase epitaxy. The Inx Ga1Àx N/GaN undoped QW system is coated over both

  15. Growth of M- and A-plane GaN on LiGaO{sub 2} by plasma-assisted MBE

    SciTech Connect (OSTI)

    Schuber, R.; Schaadt, D. M. [Institute for Applied Physics, Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); DFG-Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); Chou, M. M. C. [Department of Materials Science and Opto-electronic Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Vincze, P. [Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); Schimmel, Th. [Institute for Applied Physics, Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany)

    2011-12-23T23:59:59.000Z

    We have performed non-polar M- and A-plane GaN growth on LiGaO{sub 2}(LGO) by plasma-assisted molecular beam expitaxy (MBE). We demonstrate that non-polar GaN growth on LGO yields high phase purity and flat surfaces. We find that annealing of the substrates prior to growth is a suitable method for avoiding a peeling off of the film from the substrate after growth.

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

    SciTech Connect (OSTI)

    Nandi, R., E-mail: rajunandi@iitb.ac.in; Mohan, S., E-mail: rajunandi@iitb.ac.in; Major, S. S. [Department of Physics, Indian Institute of Technology Bombay, Mumbai - 400076 (India); Srinivasa, R. S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai - 400076 (India)

    2014-04-24T23:59:59.000Z

    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.

  17. Interfacial chemistry and valence band offset between GaN and Al{sub 2}O{sub 3} studied by X-ray photoelectron spectroscopy

    SciTech Connect (OSTI)

    Duan, T. L.; Ang, D. S. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore)] [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Pan, J. S. [Institute of Materials Research and Engineering, A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)] [Institute of Materials Research and Engineering, A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)

    2013-05-20T23:59:59.000Z

    The interface region between Ga-face n-type GaN and Al{sub 2}O{sub 3} dielectric (achieved via atomic-layer deposition or ALD) is investigated by X-ray photoelectron spectroscopy (XPS). An increase in the Ga-O to Ga-N bond intensity ratio following Al{sub 2}O{sub 3} deposition implies that the growth of an interfacial gallium sub-oxide (GaO{sub x}) layer occurred during the ALD process. This finding may be ascribed to GaN oxidation, which may still happen following the reduction of a thin native GaO{sub x} by trimethylaluminum (TMA) in the initial TMA-only cycles. The valence band offset between GaN and Al{sub 2}O{sub 3}, obtained using both core-level and valence band spectra, is found to vary with the thickness of the deposited Al{sub 2}O{sub 3}. This observation may be explained by an upward energy band bending at the GaN surface (due to the spontaneous polarization induced negative bound charge on the Ga-face GaN) and the intrinsic limitation of the XPS method for band offset determination.

  18. Transformation of c-oriented nanowall network to a flat morphology in GaN films on c-plane sapphire

    SciTech Connect (OSTI)

    Kesaria, Manoj; Shetty, Satish [International Centre for Material Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India)] [International Centre for Material Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Cohen, P.I. [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 (United States)] [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Shivaprasad, S.M., E-mail: smsprasad@jncasr.ac.in [International Centre for Material Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India)

    2011-11-15T23:59:59.000Z

    Highlights: {yields} High quality wurtzite structures GaN nanowall network formed on c-plane sapphire. {yields} Tapering of nanowalls at the apex cause electron confinement effects. {yields} Temperature dependent transformation of the six fold nanowall network to a flat morphology. {yields} Growth kinetics is influenced by adatom diffusion, interactions and bonding for GaN layer. -- Abstract: The work significantly optimizes growth parameters for nanostructured and flat GaN film in the 480-830 {sup o}C temperature range. The growth of ordered, high quality GaN nanowall hexagonal honeycomb like network on c-plane sapphire under nitrogen rich (N/Ga ratio of 100) conditions at temperatures below 700 {sup o}C is demonstrated. The walls are c-oriented wurtzite structures 200 nm wide at base and taper to 10 nm at apex, manifesting electron confinement effects to tune optoelectronic properties. For substrate temperatures above 700 {sup o}C the nanowalls thicken to a flat morphology with a dislocation density of 10{sup 10}/cm{sup 2}. The role of misfit dislocations in the GaN overlayer evolution is discussed in terms of growth kinetics being influenced by adatom diffusion, interactions and bonding at different temperatures. The GaN films are characterized by reflection high energy electron diffraction (RHEED), field emission scanning electron (FESEM), high resolution X-ray diffraction (HRXRD) and cathodoluminescence (CL).

  19. Structural and optical studies of GaN pn-junction with AlN buffer layer grown on Si (111) by RF plasma enhanced MBE

    SciTech Connect (OSTI)

    Yusoff, Mohd Zaki Mohd; Hassan, Zainuriah; Woei, Chin Che; Hassan, Haslan Abu; Abdullah, Mat Johar [Nano-Optoelectronics Research and Technology Laboratory School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia and Department of Applied Sciences Universiti Teknologi MARA (UiTM) 13500 Permatang Pauh, Penang (Malaysia); Department of Applied Sciences Universiti Teknologi MARA (UiTM) 13500 Permatang Pauh, Penang (Malaysia)

    2012-06-29T23:59:59.000Z

    GaN pn-junction grown on silicon substrates have been the focus in a number of recent reports and further effort is still necessary to improve its crystalline quality for practical applications. GaN has the high n-type background carrier concentration resulting from native defects commonly thought to be nitrogen vacancies. In this work, we present the growth of pn-junction of GaN on Si (111) substrate using RF plasma-enhanced molecular beam epitaxy (MBE). Both of the layers show uniformity with an average thickness of 0.709 {mu}m and 0.095 {mu}m for GaN and AlN layers, respectively. The XRD spectra indicate that no sign of cubic phase of GaN are found, so it is confirmed that the sample possessed hexagonal structure. It was found that all the allowed Raman optical phonon modes of GaN, i.e. the E2 (low), E1 (high) and A1 (LO) are clearly visible.

  20. Growth of AlGaN/GaN heterojunction field effect transistors on semi-insulating GaN using an AlGaN interlayer

    SciTech Connect (OSTI)

    Chen, Z.; Denbaars, S. P. [Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States); Pei, Y.; Newman, S.; Chu, R.; Brown, D.; Keller, S.; Mishra, U. K. [Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Chung, R.; Nakamura, S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2009-03-16T23:59:59.000Z

    Semi-insulating (SI) GaN layers were grown on 4H-SiC substrates by inserting an AlGaN layer between the AlN buffer and the GaN layer. Secondary ion mass spectroscopy measurements showed that the AlGaN layer prevented Si from diffusing from the substrate into the GaN layer. X-ray diffraction and atomic force microscopy analyses showed that an optimized AlGaN interlayer does not degrade the crystal quality or surface morphology of the SI GaN. The room temperature mobility of an AlGaN/GaN heterostructure using this SI GaN was 2200 cm{sup 2}/V s. High electron mobility transistors (HEMTs) with 0.65 {mu}m long gates were also fabricated on these SI GaN buffers. A power density of 19.0 W/mm with a power added efficiency of 48% was demonstrated at 10 GHz at a drain bias of 78 V. These HEMTs also exhibited sharp pinch off, low leakage, and negligible dispersion.

  1. Structural Properties of Eu-Doped GaN Investigated by Raman Spectroscopy

    SciTech Connect (OSTI)

    Senawiratne, J; Xia, Y; Detchprohm, T; Tringe, J W; Stevens, C G; Wetzel, C

    2006-06-20T23:59:59.000Z

    Rare-earth (RE) impurities doped GaN are highly promising candidates for light emitting device applications due to their efficient electroluminescence properties at room temperature. Among those, Eu doped GaN has been identified as an excellent material for the red spectral region due to its strong emission at 620 nm. As a transition internal to the Eu doping atom (4f-4f), light emission originates in a much smaller complex than the more flexibly controllable quantum structures of wells, wires, and dots. This is thought to make the center less susceptible to structural defects and in particular radiation damage in the lattice host. Nevertheless, the lattice host is crucial for providing the excitation in from of free electrons and holes. In this respect, the actual lattice site Eu occupies in the host lattice, i.e. in GaN, is important. A large fraction of Eu atoms are typically inactive which must be attributed to their lattice site and local environment. GaN films implanted with Eu to concentrations of {approx}10{sup 18} cm{sup -3} were subjected to a highly directed beam of 500 keV He{sup +} at a dose of 5 x 10{sup 14} cm{sup -2}. By means of a shadow mask, irradiated and unexposed regions lie very close to each other on the same sample. We used optical and structural analysis to identify the exerted radiation damage. At the full radiation dose, photoluminescence intensity has decayed to {approx}0.01 of its initial value. From the dose dependence of the radiation decay we previously concluded, that this decay is in part due to the destruction of radiative Eu sites [J.W. Tringe, unpublished (2006)]. Along the transition from virgin to irradiated material we analyze the accumulated damage in terms of surface morphology (atomic force microscopy), crystallinity (x-ray diffraction), and phonon dispersion using micro-Raman spectroscopy. In addition to the well-studied E{sub 2}(high) mode, two new vibrational modes at 659 cm{sup -1} and 201 cm{sup -1} were observed in the Eu implanted and annealed sample, prior to He{sup +} irradiation. These modes are either remnants of the implantation damage or related to the Eu impurity. As such they can be indicative of the actual lattice site the Eu atom resides on. After irradiation, broad Raman modes at 300 cm-1 are being observed. This band indicates disorder activated Raman scattering (DARS) due to the radiation damage. An additional narrow mode appears at 672 cm{sup -1}, which can possibly be due to a nitrogen vacancy related vibrational mode. The continuous transition from irradiated to un-irradiated sample allows the direct evolution of radiation damage and its coordinated effects in structural, optical and vibrational properties. By its systematic correlation we anticipate to be able to elucidate the Eu lattice interaction and the processes of radiation damage.

  2. Picosecond Z-scan measurements on bulk GaN crystals

    SciTech Connect (OSTI)

    Pacebutas, V.; Stalnionis, A.; Krotkus, A.; Suski, T.; Perlin, P.; Leszczynski, M.

    2001-06-25T23:59:59.000Z

    Bulk GaN crystals were characterized by using picosecond laser pulses at {lambda}=0.527{mu}m and Z-scan techniques. The role of the free-carrier absorption was evaluated by a dynamical, pump-and-probe-type transmitivity measurement. The values of two-photon absorption coefficient (17{endash}20 cm/GW) and refractive index changes at high optical irradiances due to bound (n{sub 2}={minus}4{times}10{sup {minus}12}esu) and free ({sigma}{sub r}={minus}1.0{times}10{sup {minus}20}cm{sup 3}) electrons in that material were determined. {copyright} 2001 American Institute of Physics.

  3. The influence of Mg doping on the nucleation of self-induced GaN nanowires

    SciTech Connect (OSTI)

    Limbach, F.; Gotschke, T.; Calarco, R.; Geelhaar, L.; Riechert, H. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Caterino, R.; Stoica, T. [Forschungszentrum Julich, Institute for Bio and Nanosystems IBN and JARA FIT Julich Aachen Research Alliance, 52425 Julich (Germany)

    2012-03-15T23:59:59.000Z

    GaN nanowires were grown without any catalyst by plasma-assisted molecular beam epitaxy. Under supply of Mg, nanowire nucleation is faster, the areal density of wires increases to a higher value, and nanowire coalescence is more pronounced than without Mg. During nanowire nucleation the Ga desorption was monitored in-situ by line-of-sight quadrupole mass spectrometry for various substrate temperatures. Nucleation energies of 4.0{+-}0.3 eV and 3.2{+-}0.3 eV without and with Mg supply were deduced, respectively. This effect has to be taken into account for the fabrication of nanowire devices and could be employed to tune the NW areal density.

  4. Cubic GaN formation in MnGaN multilayer films grown on 6H-SiC,,0001... Y. Cui, V. K. Lazorov, M. M. Goetz, H. Liu, D. P. Robertson, M. Gajdardziska-Josifovska,

    E-Print Network [OSTI]

    Li, Lian

    Cubic GaN formation in MnÕGaN multilayer films grown on 6H-SiC,,0001... Y. Cui, V. K. Lazorov, M. M; accepted 30 April 2003 Cubic GaN was grown on 6H-SiC 0001 by electron-cyclotron resonance plasma-assisted molecular-beam epitaxy. The growth process consisted of first depositing a 20-nm GaN buffer, followed by ten

  5. Combined MOCVD and MBE growth of GaN on porous SiC Ashutosh Sagar (a), R. M. Feenstra (a), C. K. Inoki (b), T. S. Kuan (b), D. D. Koleske (c)

    E-Print Network [OSTI]

    Feenstra, Randall

    homoepitaxially by MOCVD on MBE-grown GaN template layers, using both porous and nonporous SiC substrates. The effect of the porous SiC substrates on dislocations in the MBE and MOCVD GaN layers has been studied in the recent years as an attractive substrate for epitaxy of GaN and SiC [1-6]. Earlier studies have shown

  6. Engineering the (In, Al, Ga)N back-barrier to achieve high channel-conductivity for extremely scaled channel-thicknesses in N-polar GaN high-electron-mobility-transistors

    SciTech Connect (OSTI)

    Lu, Jing, E-mail: jing@ece.ucsb.edu; Zheng, Xun; Guidry, Matthew; Denninghoff, Dan; Ahmadi, Elahe; Lal, Shalini; Keller, Stacia; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); DenBaars, Steven P. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-03-03T23:59:59.000Z

    Scaling down the channel-thickness (t{sub ch}) in GaN/(In, Al, Ga)N high-electron-mobility-transistors (HEMTs) is essential to eliminating short-channel effects in sub 100?nm gate length HEMTs. However, this scaling can degrade both charge density (n{sub s}) and mobility (?), thereby reducing channel-conductivity. In this study, the back-barrier design in N-polar GaN/(In, Al, Ga)N was engineered to achieve highly conductive-channels with t{sub ch}?

  7. Optically active vacancies in GaN grown on Si substrates probed using a monoenergetic positron beam

    SciTech Connect (OSTI)

    Uedono, Akira, E-mail: uedono.akira.gb@u.tsukuba.ac.jp; Zhang, Yang; Yoshihara, Nakaaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Fujishima, Tatsuya; Palacios, Tomás [Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Cao, Yu; Laboutin, Oleg; Johnson, Wayne [IQE, 200 John Hancock Road, Taunton, Massachusetts 01581 (United States); Ishibashi, Shoji [Nanosystem Research Institute “RICS,” National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan); Sumiya, Masatomo [Wide Bandgap Material Group, National Institute for Materials Science, Tsukuba 305-0044 (Japan)

    2014-02-24T23:59:59.000Z

    Native defects in GaN layers grown on Si substrates by metal organic chemical vapor deposition have been studied using a monoenergetic positron beam. Measurements of Doppler broadening spectra of the annihilation radiation for GaN layers showed that optically active vacancy-type defects were formed in the layers. Charge transition of the defects due to electron capture was found to occur when the layers were irradiated by photons with energy above 2.71?eV. The concentration of such defects increased after 600–800?°C annealing, but the defects have not been annealed out even at 1000?°C. They were identified as Ga-vacancy-type defects, such as complexes between Ga vacancies and carbon impurities, and the relationship between their charge transition and optical properties were discussed.

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

    SciTech Connect (OSTI)

    None

    2012-02-13T23:59:59.000Z

    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.

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

    DOE Patents [OSTI]

    Bourret-Courchesne, Edith D. (Richmond, CA)

    2003-01-01T23:59:59.000Z

    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.

  10. Quantum efficiency affected by localized carrier distribution near the V-defect in GaN based quantum well

    SciTech Connect (OSTI)

    Cho, Yong-Hee, E-mail: yonghee2.cho@samsung.com; Shim, Mun-Bo; Hwang, Sangheum; Kim, Sungjin [Computational Science Group, CAS Center, SAIT, Samsung Electronics, Nongsuh-dong, Giheung-gu, Yongin-si, Kyeonggi-do 446-712 (Korea, Republic of)] [Computational Science Group, CAS Center, SAIT, Samsung Electronics, Nongsuh-dong, Giheung-gu, Yongin-si, Kyeonggi-do 446-712 (Korea, Republic of); Kim, Jun-Youn; Kim, Jaekyun; Park, Young-Soo [GaN Device Group, Advanced Device Lab, SAIT, Samsung Electronics, Nongsuh-dong, Giheung-gu, Yongin-si, Kyeonggi-do 446-712 (Korea, Republic of)] [GaN Device Group, Advanced Device Lab, SAIT, Samsung Electronics, Nongsuh-dong, Giheung-gu, Yongin-si, Kyeonggi-do 446-712 (Korea, Republic of); Park, Seoung-Hwan [Department of Physics and Semiconductor Science, Catholic University of Daegu, Hayang, Kyeongbuk (Korea, Republic of)] [Department of Physics and Semiconductor Science, Catholic University of Daegu, Hayang, Kyeongbuk (Korea, Republic of)

    2013-12-23T23:59:59.000Z

    It is known that due to the formation of in-plane local energy barrier, V-defects can screen the carriers which non-radiatively recombine in threading dislocations (TDs) and hence, enhance the internal quantum efficiency in GaN based light-emitting diodes. By a theoretical modeling capable of describing the inhomogeneous carrier distribution near the V-defect in GaN based quantum wells, we show that the efficient suppression of non-radiative (NR) recombination via TD requires the local energy barrier height of V-defect larger than ?80?meV. The NR process in TD combined with V-defect influences the quantum efficiency mainly in the low injection current density regime suitably described by the linear dependence of carrier density. We provide a simple phenomenological expression for the NR recombination rate based on the model result.

  11. Polarization ratio enhancement of a-plane GaN light emitting diodes by asymmetric two-dimensional photonic crystals

    SciTech Connect (OSTI)

    Chou, Yen; Li, Hsiang-Wei; Yin, Yu-Feng; Wang, Yu-Ting; Lin, Yen-Chen; Wu, Yuh-Renn; Huang, Jian Jang, E-mail: jjhuang@ntu.edu.tw [Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan (China); Lin, Da-Wei; Kuo, Hao-Chung [Department of Photonics and Electro-Optical Engineering, National Chiao-Tung University, Hsinchu, Taiwan (China)

    2014-05-21T23:59:59.000Z

    Fabricating photonic crystals (PhCs) on GaN based non-polar light emitting diodes (LEDs) is an effective way to increase light extraction and meanwhile to preserve or improve polarization ratio. In this work, a-plane GaN LEDs with two-dimensional PhCs were demonstrated. With the E // m polarized modes (which mean the optical polarization with the electric field parallel to m-axis) as the target of diffraction, we matched E//m modes to the photonic bands and aligned E//c modes to fall within the photonic band gap. The results show stronger E//m but weaker E//c mode diffractions on both c- and m-axes. At the vertical direction, the polarization ratio is enhanced from 45.8% for the planar device to 52.3% for the LEDs with PhCs.

  12. Properties of TiO{sub 2}-based transparent conducting oxide thin films on GaN(0001) surfaces

    SciTech Connect (OSTI)

    Kasai, J.; Nakao, S.; Yamada, N. [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hitosugi, T. [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577 (Japan); Moriyama, M.; Goshonoo, K. [Toyoda Gosei Co., Ltd., Nishikasugai, Aichi 452-8564 (Japan); Hoang, N. L. H. [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Hasegawa, T. [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan)

    2010-03-15T23:59:59.000Z

    Anatase Nb-doped TiO{sub 2} transparent conducting oxide has been formed on GaN(0001) surfaces using a sputtering method. Amorphous films deposited at room temperature were annealed at a substrate temperature of 500 deg. C in vacuum to form single-phase anatase films. Films with a thickness of 170 nm exhibited a resistivity of 8x10{sup -4} {Omega} cm with absorptance less than 5% at a wavelength of 460 nm. Furthermore, the refractive index of the Nb-doped TiO{sub 2} was well matched to that of GaN. These findings indicate that Nb-doped TiO{sub 2} is a promising material for use as transparent electrodes in GaN-based light emitting diodes (LEDs), particularly since reflection at the electrode/GaN boundary can be suppressed, enhancing the external quantum efficiency of blue LEDs.

  13. Optical Properties of Wurtzite GaN and ZnO Quantum Dots Vladimir A. Fonoberov and Alexander A. Balandin

    E-Print Network [OSTI]

    Fonoberov, Vladimir

    Optical Properties of Wurtzite GaN and ZnO Quantum Dots Vladimir A. Fonoberov and Alexander A-Riverside, Riverside, California 92521, U.S.A. ABSTRACT We have investigated exciton states in wurtzite GaN/AlN and ZnO quantum dots. A strong piezoelectric field in GaN/AlN quantum dots is found to tilt conduction and valence

  14. Structural, optical, and magnetic properties of highly-resistive Sm-implanted GaN thin films

    SciTech Connect (OSTI)

    Lo, Fang-Yuh, E-mail: fangyuhlo@ntnu.edu.tw; Huang, Cheng-De; Chou, Kai-Chieh; Guo, Jhong-Yu; Liu, Hsiang-Lin; Chia, Chi-Ta [Department of Physics, National Taiwan Normal University, 11677 Taipei City, Taiwan (China); Ney, Verena; Ney, Andreas [Experimentalphysik, Universität Duisburg-Essen, 47057 Duisburg (Germany); Shvarkov, Stepan; Reuter, Dirk; Wieck, Andreas D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum (Germany); Pezzagna, Sébastien [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum (Germany); Centre de Recherche sur l'Hétéroépitaxie et ses Application, 06560 Valbonne, UPR-CNRS (France); Chern, Ming-Yau [Department of Physics, National Taiwan University, 10617 Taipei City, Taiwan (China); Massies, Jean [Centre de Recherche sur l'Hétéroépitaxie et ses Application, 06560 Valbonne, UPR-CNRS (France)

    2014-07-28T23:59:59.000Z

    Samarium ions of 200?keV in energy were implanted into highly-resistive molecular-beam-epitaxy grown GaN thin films with a focused-ion-beam implanter at room temperature. The implantation doses range from 1?×?10{sup 14} to 1?×?10{sup 16?}cm{sup ?2}. Structural properties studied by x-ray diffraction and Raman-scattering spectroscopy revealed Sm incorporation into GaN matrix without secondary phase. The optical measurements showed that the band gap and optical constants changed very slightly by the implantation. Photoluminescence measurements showed emission spectra similar to p-type GaN for all samples. Magnetic investigations with a superconducting quantum interference device identified magnetic ordering for Sm dose of and above 1?×?10{sup 15?}cm{sup ?2} before thermal annealing, while ferromagnetism was only observed after thermal annealing from the sample with highest Sm dose. The long-range magnetic ordering can be attributed to interaction of Sm ions through the implantation-induced Ga vacancy.

  15. Study of gain and photoresponse characteristics for back-illuminated separate absorption and multiplication GaN avalanche photodiodes

    SciTech Connect (OSTI)

    Wang, Xiaodong; Pan, Ming; Hou, Liwei; Xie, Wei [No. 50 Research Institute of China Electronics Technology Group Corporation, 200331 Shanghai (China); Hu, Weida, E-mail: wdhu@mail.sitp.ac.cn; Xu, Jintong; Li, Xiangyang; Chen, Xiaoshuang, E-mail: xschen@mail.sitp.ac.cn; Lu, Wei [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 200083 Shanghai (China)

    2014-01-07T23:59:59.000Z

    The gain and photoresponse characteristics have been numerically studied for back-illuminated separate absorption and multiplication (SAM) GaN avalanche photodiodes (APDs). The parameters of fundamental models are calibrated by simultaneously comparing the simulated dark and light current characteristics with the experimental results. Effects of environmental temperatures and device dimensions on gain characteristics have been investigated, and a method to achieve the optimum thickness of charge layer is obtained. The dependence of gain characteristics and breakdown voltage on the doping concentration of the charge layer is also studied in detail to get the optimal charge layer. The bias-dependent spectral responsivity and quantum efficiency are then presented to study the photoresponse mechanisms inside SAM GaN APDs. It is found the responsivity peak red-shifts at first due to the Franz-Keldysh effect and then blue-shifts due to the reach-through effect of the absorption layer. Finally, a new SAM GaN/AlGaN heterojunction APD structure is proposed for optimizing SAM GaN APDs.

  16. VOLUME 88, NUMBER 6 P H Y S I C A L R E V I E W L E T T E R S 11 FEBRUARY 2002 First-Principles Surface Phase Diagram for Hydrogen on GaN Surfaces

    E-Print Network [OSTI]

    -Principles Surface Phase Diagram for Hydrogen on GaN Surfaces Chris G. Van de Walle1,2,3 and J. Neugebauer2 1 Xerox-functional calculations. Applying the approach to hydrogenated GaN surfaces, we find that the Gibbs free energies. In the case of GaN, where materials quality is still limiting device progress, the investigations until now

  17. Growth diagram of N-face GaN (0001{sup ¯}) grown at high rate by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Okumura, Hironori, E-mail: okumura@engineering.ucsb.edu; McSkimming, Brian M.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)] [Materials Department, University of California, Santa Barbara, California 93106 (United States); Huault, Thomas; Chaix, Catherine [RIBER S.A., 3a Rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France)] [RIBER S.A., 3a Rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France)

    2014-01-06T23:59:59.000Z

    N-face GaN was grown on free-standing GaN (0001{sup ¯}) substrates at a growth rate of 1.5??m/h using plasma-assisted molecular beam epitaxy. Difference in growth rate between (0001{sup ¯}) and (0001) oriented GaN depends on nitrogen plasma power, and the (0001{sup ¯}) oriented GaN had only 70% of the growth rate of the (0001) oriented GaN at 300?W. Unintentional impurity concentrations of silicon, carbon, and oxygen were 2?×?10{sup 15}, 2?×?10{sup 16}, and 7?×?10{sup 16}?cm{sup ?3}, respectively. A growth diagram was constructed that shows the dependence of the growth modes on the difference in the Ga and active nitrogen flux, ?{sub Ga}????{sub N*}, and the growth temperature. At high ?{sub Ga}????{sub N*} (?{sub Ga}????{sub N*}), two-dimensional (step-flow and layer-by-layer) growth modes were realized. High growth temperature (780?°C) expanded the growth window of the two-dimensional growth modes, achieving a surface with rms roughness of 0.48?nm without Ga droplets.

  18. Efficient reduction of defects in (1120) non-polar and (1122) semi-polar GaN grown on nanorod templates

    SciTech Connect (OSTI)

    Bai, J.; Gong, Y.; Xing, K.; Yu, X.; Wang, T. [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)] [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)

    2013-03-11T23:59:59.000Z

    (1120) non-polar and (1122) semi-polar GaNs with a low defect density have been achieved by means of an overgrowth on nanorod templates, where a quick coalescence with a thickness even below 1 {mu}m occurs. On-axis and off-axis X-ray rocking curve measurements have shown a massive reduction in the linewidth for our overgrown GaN in comparison with standard GaN films grown on sapphire substrates. Transmission electron microscope observation demonstrates that the overgrowth on the nanorod templates takes advantage of an omni-directional growth around the sidewalls of the nanostructures. The dislocations redirect in basal planes during the overgrowth, leading to their annihilation and termination at voids formed due to a large lateral growth rate. In the non-polar GaN, the priority <0001> lateral growth from vertical sidewalls of nanorods allows basal plane stacking faults (BSFs) to be blocked in the nanorod gaps; while for semi-polar GaN, the propagation of BSFs starts to be impeded when the growth front is changed to be along inclined <0001> direction above the nanorods.

  19. Zinc-blende (Cubic) GaN and AlGaN Layers, Structures and Bulk Crystals by Molecular Beam Epitaxy

    SciTech Connect (OSTI)

    Novikov, Sergei V.; Zainal, Norzaini; Akimov, Andrey V.; Staddon, Chris R.; Foxon, C. Thomas; Kent, Anthony J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2010-11-01T23:59:59.000Z

    We have studied the growth of zinc-blende GaN and AlGaN layers, structures and bulk crystals by molecular beam epitaxy (MBE). We have developed a process for growth by MBE of free-standing cubic GaN layers. Undoped thick cubic GaN films were grown on semi-insulating GaAs (001) substrates by a modified plasma-assisted molecular beam epitaxy (PA-MBE) method and were removed from the GaAs substrate after the growth. The resulting free-standing GaN wafers with thicknesses in the 30-100 {mu}m range may be used as substrates for further epitaxy of cubic GaN-based structures and devices. We have developed procedures to cleave the wafers into 10x10 mm{sup 2} square substrates and to polish them to produce epi-ready surfaces. The first GaN/InGaN LEDs on our zinc-blende GaN substrates have been demonstrated by our collaborators at Sharp Laboratories of Europe.

  20. Growth kinetics of AlN and GaN films grown by molecular beam epitaxy on R-plane sapphire substrates

    SciTech Connect (OSTI)

    Chandrasekaran, R.; Moustakas, T. D. [Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215 (United States); Ozcan, A. S.; Ludwig, K. F. [Physics Department, Boston University, Boston, Massachusetts 02215 (United States); Zhou, L.; Smith, David J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

    2010-08-15T23:59:59.000Z

    This paper reports the growth by molecular beam epitaxy of AlN and GaN thin films on R-plane sapphire substrates. Contrary to previous findings that GaN grows with its (1120) A-plane parallel to the (1102) R-plane of sapphire, our results indicate that the crystallographic orientation of the III-nitride films is strongly dependent on the kinetic conditions of growth for the GaN or AlN buffer layers. Thus, group III-rich conditions for growth of either GaN or AlN buffers result in nitride films having (1120) planes parallel to the sapphire surface, and basal-plane stacking faults parallel to the growth direction. The growth of these buffers under N-rich conditions instead leads to nitride films with (1126) planes parallel to the sapphire surface, with inclined c-plane stacking faults that often terminate threading dislocations. Moreover, electron microscope observations indicate that slight miscut ({approx}0.5 deg. ) of the R-plane sapphire substrate almost completely suppresses the formation of twinning defects in the (1126) GaN films.

  1. Improved growth of GaN layers on ultra thin silicon nitride/Si (1 1 1) by RF-MBE

    SciTech Connect (OSTI)

    Kumar, Mahesh; Roul, Basanta [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India) [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Bhat, Thirumaleshwara N.; Rajpalke, Mohana K. [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India)] [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Misra, P.; Kukreja, L.M. [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)] [Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Sinha, Neeraj [Office of Principal Scientific Advisor, Government of India, New Delhi 110011 (India)] [Office of Principal Scientific Advisor, Government of India, New Delhi 110011 (India); Kalghatgi, A.T. [Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India)] [Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Krupanidhi, S.B., E-mail: sbk@mrc.iisc.ernet.in [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India)

    2010-11-15T23:59:59.000Z

    High-quality GaN epilayers were grown on Si (1 1 1) substrates by molecular beam epitaxy using a new growth process sequence which involved a substrate nitridation at low temperatures, annealing at high temperatures, followed by nitridation at high temperatures, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. The material quality of the GaN films was also investigated as a function of nitridation time and temperature. Crystallinity and surface roughness of GaN was found to improve when the Si substrate was treated under the new growth process sequence. Micro-Raman and photoluminescence (PL) measurement results indicate that the GaN film grown by the new process sequence has less tensile stress and optically good. The surface and interface structures of an ultra thin silicon nitride film grown on the Si surface are investigated by core-level photoelectron spectroscopy and it clearly indicates that the quality of silicon nitride notably affects the properties of GaN growth.

  2. Modeling of electronic transport in GaN n-i-p junctions Laboratoire de Physique du Solide, Facults Universitaires Notre-Dame de la Paix, Rue de Bruxelles 61,

    E-Print Network [OSTI]

    Mayer, Alexandre

    Modeling of electronic transport in GaN n-i-p junctions A. Mayera) Laboratoire de Physique du) We propose a model and an algorithm for computing the transport properties of GaN n-i-p devices as cold cathodes2,3 or thermoelectric coolers.4­8 For applications as electronic emitters, the idea

  3. Lattice site location and annealing behaviour of Ca and Sr implanted GaN

    E-Print Network [OSTI]

    De Vries, Bart; Wahl, Ulrich; Correia, J G; Araújo, João Pedro; Lojkowski, W; Kolesnikov, D

    2006-01-01T23:59:59.000Z

    We report on the lattice location of ion-implanted Ca and Sr in thin films of single-crystalline wurtzite GaN. Using the emission channeling technique the angular distributions of $\\beta\\!^{-}$?particles emitted by the radioactive isotopes $^{45}$Ca(t$_{ 1/2}$=163.8 d) and $^{89}$Sr(t$_{ 1/2}$=50.53 d) were monitored with a position-sensitive detector following 60 keV room-temperature implantation. Our experiments give direct evidence that $\\sim$90% of Ca and > 60% of Sr atoms were occupying substitutional Ga sites with root mean square displacements of the order of 0.15–0.30 Å, i.e., larger than the expected thermal vibration amplitude of 0.074 Å. Annealing the Ca implanted samples at 1100–1350 °C in high-pressure N$_{2}$ atmosphere resulted in a better incorporation into the substitutional Ga site. The Sr implanted sample showed a small decrease in rms displacements for vacuum annealing up to 900 °C, while the substitutional fraction remained nearly constant. The annealing behavior of the rms disp...

  4. Surface oxidation of GaN(0001): Nitrogen plasma-assisted cleaning for ultrahigh vacuum applications

    SciTech Connect (OSTI)

    Gangopadhyay, Subhashis [Institute of Solid State Physics, University of Bremen, P.O. Box 330440, 28334 Bremen, Germany and Department of Physics, Birla Institute of Technology and Science, Pilani, 333031 Rajasthan (India); Schmidt, Thomas, E-mail: tschmidt@ifp.uni-bremen.de; Kruse, Carsten; Figge, Stephan; Hommel, Detlef; Falta, Jens [Institute of Solid State Physics, University of Bremen, P.O. Box 330440, 28334 Bremen (Germany)

    2014-09-01T23:59:59.000Z

    The cleaning of metal-organic vapor-phase epitaxial GaN(0001) template layers grown on sapphire has been investigated. Different procedures, performed under ultrahigh vacuum conditions, including degassing and exposure to active nitrogen from a radio frequency nitrogen plasma source have been compared. For this purpose, x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and scanning tunneling microscopy have been employed in order to assess chemical as well as structural and morphological surface properties. Initial degassing at 600?°C under ultrahigh vacuum conditions only partially eliminates the surface contaminants. In contrast to plasma assisted nitrogen cleaning at temperatures as low as 300?°C, active-nitrogen exposure at temperatures as high as 700?°C removes the majority of oxide species from the surface. However, extended high-temperature active-nitrogen cleaning leads to severe surface roughening. Optimum results regarding both the removal of surface oxides as well as the surface structural and morphological quality have been achieved for a combination of initial low-temperature plasma-assisted cleaning, followed by a rapid nitrogen plasma-assisted cleaning at high temperature.

  5. Atom probe tomography studies of Al?O? gate dielectrics on GaN

    SciTech Connect (OSTI)

    Mazumder, Baishakhi, E-mail: bmazumder@engineering.ucsb.edu; Wu, Feng; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Liu, Xiang; Yeluri, Ramya; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2014-10-07T23:59:59.000Z

    Atom probe tomography was used to achieve three-dimensional characterization of in situ Al?O?/GaN structures grown by metal organic chemical vapor deposition (MOCVD). Al?O? dielectrics grown at three different temperatures of 700, 900, and 1000 °C were analyzed and compared. A low temperature GaN cap layer grown atop Al?O? enabled a high success rate in the atom probe experiments. The Al?O?/GaN interfaces were found to be intermixed with Ga, N, and O over the distance of a few nm. Impurity measurements data showed that the 1000 °C sample contains higher amounts of C (4 × 10¹?/cm³) and lower amounts of H (7 × 10¹?/cm³), whereas the 700 °C sample exhibits lower C impurities (<10¹?/cm³) and higher H incorporation (2.2 × 10²?/cm³). On comparing with Al?O? grown by atomic layer deposition (ALD), it was found that the MOCVD Al?O?/GaN interface is comparatively abrupt. Scanning transmission electron microscopy data showed that the 900 °C and 1000 °C MOCVD films exhibit polycrystalline nature, while the ALD films were found to be amorphous.

  6. Nanostructured GaN Nucleation Layer for Light-Emitting Diodes

    SciTech Connect (OSTI)

    Narayan, Jagdish [North Carolina State University; Pant, Punam [North Carolina State University; Wei, Wei [North Carolina State University; Narayan, Roger [University of North Carolina, Chapel Hill; Budai, John D [ORNL

    2007-01-01T23:59:59.000Z

    This paper addresses the formation of nanostructured gallium nitride nucleation (NL) or initial layer (IL), which is necessary to obtain a smooth surface morphology and reduce defects in h-GaN layers for light-emitting diodes and lasers. From detailed X-ray and HR-TEM studies, researchers determined that this layer consists of nanostructured grains with average grain size of 25 nm, which are separated by small-angle grain boundaries (with misorientation 1 ), known as subgrain boundaries. Thus NL is considered to be single-crystal layer with mosaicity of about 1 . These nc grains are mostly faulted cubic GaN (c-GaN) and a small fraction of unfaulted c-GaN. This unfaulted Zinc-blende c-GaN, which is considered a nonequilibrium phase, often appears as embedded or occluded within the faulted c-GaN. The NL layer contained in-plane tensile strain, presumably arising from defects due to island coalescence during Volmer-Weber growth. The 10L X-ray scans showed c-GaN fraction to be over 63% and the rest h-GaN. The NL layer grows epitaxially with the (0001) sapphire substrate by domain matching epitaxy, and this epitaxial relationship is remarkably maintained when c-GaN converts into h-GaN during high-temperature growth.

  7. Correlative analysis of the in situ changes of carrier decay and proton induced photoluminescence characteristics in chemical vapor deposition grown GaN

    SciTech Connect (OSTI)

    Gaubas, E., E-mail: eugenijus.gaubas@ff.vu.lt; Ceponis, T.; Jasiunas, A.; Meskauskaite, D.; Pavlov, J.; Tekorius, A.; Vaitkus, J. [Vilnius University, Institute of Applied Research, Vilnius LT-10222 (Lithuania); Kovalevskij, V.; Remeikis, V. [Centre for Physical Sciences and Technology, Vilnius LT-02300 (Lithuania)

    2014-02-10T23:59:59.000Z

    In order to evaluate carrier densities created by 1.6?MeV protons and to trace radiation damage of the 2.5??m thick GaN epi-layers grown by metalorganic chemical vapor deposition technique, a correlation between the photoconductivity transients and the steady-state photoluminescence spectra have been examined. Comparison of luminescence spectra induced by proton beam and by laser pulse enabled us to evaluate the efficiency of a single proton generation being of 1?×?10{sup 7}?cm{sup ?3} per 1.6?MeV proton and 40 carrier pairs per micrometer of layer depth. This result indicates that GaN layers can be an efficient material for detection of particle flows. It has been demonstrated that GaN material can also be a rather efficient scintillating material within several wavelength ranges.

  8. Enhanced catalyst-free nucleation of GaN nanowires on amorphous Al{sub 2}O{sub 3} by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Sobanska, Marta, E-mail: sobanska@ifpan.edu.pl; Klosek, Kamil; Borysiuk, Jolanta; Kret, Slawomir; Tchutchulasvili, Giorgi; Gieraltowska, Sylwia; Zytkiewicz, Zbigniew R. [Institute of Physics Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-01-28T23:59:59.000Z

    We report on plasma-assisted molecular beam epitaxial growth of GaN nanowires (NWs) on Si(111) substrates with a thin amorphous Al{sub 2}O{sub 3} buffer layer deposited by atomic layer deposition. Comparison of nucleation kinetics shows that presence of amorphous Al{sub 2}O{sub 3} buffer significantly enhances spontaneous nucleation of GaN NWs. Slower nucleation was observed on partially amorphous silicon nitride films. No growth of NWs was found on sapphire substrate under the same growth conditions which we explain by a low density of defects on monocrystalline substrate surface where NWs may nucleate. Our finding shows that tuning of substrate microstructure is an efficient tool to control rate of self-induced nucleation of GaN NWs.

  9. Annealing behaviors of vacancy-type defects near interfaces between metal contacts and GaN probed using a monoenergetic positron beam

    SciTech Connect (OSTI)

    Uedono, Akira, E-mail: uedono.akira.gb@u.tsukuba.ac.jp; Yoshihara, Nakaaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Fujishima, Tatsuya; Piedra, Daniel; Palacios, Tomás [Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Ishibashi, Shoji [Nanosystem Research Institute “RICS,” National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan); Sumiya, Masatomo [Wide Bandgap Material Group, National Institute for Materials Science, Tsukuba 305-0044 (Japan); Laboutin, Oleg; Johnson, Wayne [IQE, 200 John Hancock Road, Taunton, Massachusetts 01581 (United States)

    2014-08-04T23:59:59.000Z

    Vacancy-type defects near interfaces between metal contacts and GaN grown on Si substrates by metal organic chemical vapor deposition have been studied using a monoenergetic positron beam. Measurements of Doppler broadening spectra of the annihilation radiation for Ti-deposited GaN showed that optically active vacancy-type defects were introduced below the Ti/GaN interface after annealing at 800?°C. Charge transition of those defects due to electron capture was observed and was found to correlate with a yellow band in the photoluminescence spectrum. The major defect species was identified as vacancy clusters such as three to five Ga-vacancies coupled with multiple nitrogen-vacancies. The annealing behaviors of vacancy-type defects in Ti-, Ni-, and Pt-deposited GaN were also examined.

  10. Substrate misorientation induced strong increase in the hole concentration in Mg doped GaN grown by metalorganic vapor phase epitaxy

    SciTech Connect (OSTI)

    Suski, T.; Litwin-Staszewska, E.; Piotrzkowski, R.; Krysko, M.; Nowak, G.; Franssen, G.; Dmowski, L. H.; Lucznik, B. [Institute of High Pressure Physics UNIPRESS, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); Czernecki, R.; Grzanka, S. [TopGaN Ltd., Sokolowska 29/37 01-142 Warszawa (Poland); Leszczynski, M.; Perlin, P.; Grzegory, I. [Institute of High Pressure Physics UNIPRESS, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland); TopGaN Ltd., Sokolowska 29/37 01-142 Warsaw (Poland); Jakiela, R. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32, 02-668 Warsaw (Poland)

    2008-10-27T23:59:59.000Z

    We demonstrate that relatively small GaN substrate misorientation can strongly change hole carrier concentration in Mg doped GaN layers grown by metalorganic vapor phase epitaxy. In this work intentionally misoriented GaN substrates (up to 2 deg. with respect to ideal <0001> plane) were employed. An increase in the hole carrier concentration to the level above 10{sup 18} cm{sup -3} and a decrease in GaN:Mg resistivity below 1 {omega} cm were achieved. Using secondary ion mass spectroscopy we found that Mg incorporation does not change with varying misorientation angle. This finding suggests that the compensation rate, i.e., a decrease in unintentional donor density, is responsible for the observed increase in the hole concentration. Analysis of the temperature dependence of electrical transport confirms this interpretation.

  11. Growth of GaN on Si(111): Surfaces and crystallinity of the epifilms and the transport behavior of GaN/Si heterojunctions

    SciTech Connect (OSTI)

    Xu Zhongjie; Xie Maohai [Physics Department, University of Hong Kong, Pokfulam Road (Hong Kong); Zhang Lixia; He Hongtao; Wang Jiannong [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2011-11-01T23:59:59.000Z

    Growths of GaN on Si(111) - (7 x 7) substrates by plasma-assisted molecular-beam epitaxy (PA-MBE) have been studied. Optimal conditions of MBE and the effect of a low-temperature (LT) buffer are followed. It is found that irrespective of the growth conditions and the growth strategies (direct versus two-step growth), a thin amorphous-like interface layer always forms. For smooth surfaces and better crystallinity of the epifilms, a LT-buffer preceding the high-temperature deposition is helpful, and the grown GaN films are of nitrogen-polar. Transport measurements of the heterojunctions of GaN on heavily p- and n-doped Si reveal ohmic behavior, whereas that of n-GaN on lightly doped n{sup -}-Si substrate shows rectifying characteristics.

  12. High optical and structural quality of GaN epilayers grown on (2{sup ¯}01) ?-Ga{sub 2}O{sub 3}

    SciTech Connect (OSTI)

    Muhammed, M. M.; Roqan, I. S., E-mail: iman.roqan@kaust.edu.sa [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); Peres, M.; Franco, N.; Lorenz, K. [IPFN, Instituto Superior Técnico (IST), Campus Tecnológico e Nuclear, Estrada Nacional 10, P-2695-066 Bobadela LRS (Portugal); Yamashita, Y.; Morishima, Y.; Sato, S.; Kuramata, A. [Tamura Corporation, Sayama, Saitama 350-1328 (Japan)

    2014-07-28T23:59:59.000Z

    Producing highly efficient GaN-based optoelectronic devices has been a challenge for a long time due to the large lattice mismatch between III-nitride materials and the most common substrates, which causes a high density of threading dislocations. Therefore, it is essential to obtain alternative substrates with small lattice mismatches, appropriate structural, thermal and electrical properties, and a competitive price. Our results show that (2{sup ¯}01) oriented ?-Ga{sub 2}O{sub 3} has the potential to be used as a transparent and conductive substrate for GaN-growth. Photoluminescence spectra of thick GaN layers grown on (2{sup ¯}01) oriented ?-Ga{sub 2}O{sub 3} are found to be dominated by intense bandedge emission. Atomic force microscopy studies show a modest threading dislocation density of ?10{sup 8?}cm{sup ?2}. X-ray diffraction studies show the high quality of the single-phase wurtzite GaN thin film on (2{sup ¯}01) ?-Ga{sub 2}O{sub 3} with in-plane epitaxial orientation relationships between the ?-Ga{sub 2}O{sub 3} and the GaN thin film defined by (010) ?-Ga{sub 2}O{sub 3} || (112{sup ¯}0) GaN and (2{sup ¯}01) ?-Ga{sub 2}O{sub 3} || (0001) GaN leading to a lattice mismatch of ?4.7%. Complementary Raman spectroscopy indicates that the quality of the GaN epilayer is high.

  13. Evaluation of growth methods for the heteroepitaxy of non-polar (11-20) GaN on sapphire by MOVPE

    E-Print Network [OSTI]

    Oehler, F.; Sutherland, D.; Zhu, T.; Emery, R.; Badcock, T. J.; Kappers, M. J.; Humphreys, C. J.; Dawson, P.; Oliver, R. A.

    2014-09-16T23:59:59.000Z

    double grating spectrometer equipped with a Peltier-cooled GaAs photomultiplier tube. The spectra were recorded with signal lock-in processing techniques. As the HeCd laser absorption length is ca. 350 nm for 99% absorption in GaN (ignoring any carrier... double grating spectrometer equipped with a Peltier-cooled GaAs photomultiplier tube. The spectra were recorded with signal lock-in processing techniques. As the HeCd laser absorption length is ca. 350 nm for 99% absorption in GaN (ignoring any carrier...

  14. Effects of material growth technique and Mg doping on Er{sup 3+} photoluminescence in Er-implanted GaN

    SciTech Connect (OSTI)

    Kim, S.; Henry, R. L.; Wickenden, A. E.; Koleske, D. D.; Rhee, S. J.; White, J. O.; Myoung, J. M.; Kim, K.; Li, X.; Coleman, J. J. (and others)

    2001-07-01T23:59:59.000Z

    Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies have been carried out at 6 K on the {similar_to}1540 nm {sup 4}I{sub 13/2}{endash}{sup 4}I{sub 15/2} emissions of Er{sup 3+} in Er-implanted and annealed GaN. These studies revealed the existence of multiple Er{sup 3+} centers and associated PL spectra in Er-implanted GaN films grown by metalorganic chemical vapor deposition, hydride vapor phase epitaxy, and molecular beam epitaxy. The results demonstrate that the multiple Er{sup 3+}PL centers and below-gap defect-related absorption bands by which they are selectively excited are universal features of Er-implanted GaN grown by different techniques. It is suggested that implantation-induced defects common to all the GaN samples are responsible for the Er site distortions that give rise to the distinctive, selectively excited Er{sup 3+}PL spectra. The investigations of selectively excited Er{sup 3+}PL and PLE spectra have also been extended to Er-implanted samples of Mg-doped GaN grown by various techniques. In each of these samples, the so-called violet-pumped Er{sup 3+}PL band and its associated broad violet PLE band are significantly enhanced relative to the PL and PLE of the other selectively excited Er{sup 3+}PL centers. More importantly, the violet-pumped Er{sup 3+}PL spectrum dominates the above-gap excited Er{sup 3+}PL spectrum of Er-implanted Mg-doped GaN, whereas it was unobservable under above-gap excitation in Er-implanted undoped GaN. These results confirm the hypothesis that appropriate codopants can increase the efficiency of trap-mediated above-gap excitation of Er{sup 3+} emission in Er-implanted GaN. {copyright} 2001 American Institute of Physics.

  15. 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.

    2009-08-29T23:59:59.000Z

    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.

  16. Effect of pressure and temperature on electronic structure of GaN in the zinc-blende structure

    SciTech Connect (OSTI)

    Degheidy, A. R., E-mail: ardegheidy@mans.edu.eg; Elkenany, E. B., E-mail: kena@mans.edu.eg [Mansoura University, Department of Physics, Faculty of Science (Egypt)

    2011-10-15T23:59:59.000Z

    The effect of the hydrostatic pressure and the temperature on the electronic structure in GaN semiconductor has been calculated using the local empirical pseudopotential method. The variation of the direct and indirect energy gaps with the pressure up to 120 kbar and with the temperature up to 500 K has been done. The calculated fundamental energy gap at different pressures and different temperatures are calculated and compared with the available experimental data which show excellent agreement. The effect of pressure and temperature on the refractive index of the considered materials has also been studied.

  17. Patterned silicon substrates: a common platform for room temperature GaN and ZnO polariton lasers

    E-Print Network [OSTI]

    Zuniga-Perez, J; Hahe, R; Rashid, M J; Bouchoule, S; Brimont, C; Disseix, P; Duboz, J Y; Gommé, G; Guillet, T; Jamadi, O; Lafosse, X; Leroux, M; Leymarie, J; Li, Feng; Réveret, F; Semond, F

    2014-01-01T23:59:59.000Z

    A new platform for fabricating polariton lasers operating at room temperature is introduced: nitride-based distributed Bragg reflectors epitaxially grown on patterned silicon substrates. The patterning allows for an enhanced strain relaxation thereby enabling to stack a large number of crack-free AlN/AlGaN pairs and achieve cavity quality factors of several thousands with a large spatial homogeneity. GaN and ZnO active regions are epitaxially grown thereon and the cavities are completed with top dielectric Bragg reflectors. The two structures display strong-coupling and polariton lasing at room temperature and constitute an intermediate step in the way towards integrated polariton devices.

  18. Vacancy-type defects in Er-doped GaN studied by a monoenergetic positron beam

    SciTech Connect (OSTI)

    Uedono, A.; Shaoqiang, C.; Jongwon, S.; Ito, K.; Nakamori, H.; Honda, N.; Tomita, S.; Akimoto, K.; Kudo, H. [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, 305-8573 (Japan); Ishibashi, S. [Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8568 (Japan)

    2008-05-15T23:59:59.000Z

    A relationship between intra-4f transitions of Er and vacancy-type defects in Er-doped GaN was studied by using a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured for Er-doped GaN grown by molecular beam epitaxy. A clear correlation between the defect concentration and the photoluminescence (PL) intensity was observed. The major defect species detected by positrons was identified as a Ga vacancy V{sub Ga}, and its concentration increased with increasing Er concentration [Er]. For the sample with [Er]=3.3 at. %, the maximum integrated intensity of PL was observed. The V{sub Ga} concentration was above 10{sup 18} cm{sup -3} and additional vacancies such as divacancies started to be introduced at this Er concentration. For the sample with higher [Er], the PL intensity decreased, and the mean size of vacancies decreased due to an introduction of precipitates and/or metastable phases.

  19. Plasma chemistries for dry etching GaN, AlN, InGaN and InAlN

    SciTech Connect (OSTI)

    Pearton, S.J.; Vartuli, C.B.; Lee, J.W.; Donovan, S.M.; MacKenzie, J.D.; Abernathy, C.R. [Univ. of Florida, Gainesville, FL (United States); Shul, R.J. [Sandia National Labs., Albuquerque, NM (United States); McLane, G.F. [Army Research Lab., Fort Monmouth, NJ (United States); Ren, F. [AT and T Bell Labs., Murray Hill, NJ (United States)

    1996-04-01T23:59:59.000Z

    Etch rates up to 7,000 {angstrom}/min. for GaN are obtained in Cl{sub 2}/H{sub 2}/Ar or BCl{sub 3}/Ar ECR discharges at 1--3mTorr and moderate dc biases. Typical rates with HI/H{sub 2} are about a factor of three lower under the same conditions, while CH{sub 4}/H{sub 2} produces maximum rates of only {approximately}2,000 {angstrom}/min. The role of additives such as SF{sub 6}, N{sub 2}, H{sub 2} or Ar to the basic chlorine, bromine, iodine or methane-hydrogen plasma chemistries are discussed. Their effect can be either chemical (in forming volatile products with N) or physical (in breaking bonds or enhancing desorption of the etch products). The nitrides differ from conventional III-V`s in that bond-breaking to allow formation of the etch products is a critical factor. Threshold ion energies for the onset of etching of GaN, InGaN and InAlN are {ge} 75 eV.

  20. Operation of ohmic Ti/Al/Pt/Au multilayer contacts to GaN at 600?°C in air

    SciTech Connect (OSTI)

    Hou, Minmin, E-mail: mmhou@stanford.edu [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Senesky, Debbie G. [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305 (United States)

    2014-08-25T23:59:59.000Z

    The high-temperature characteristics (at 600?°C) of Ti/Al/Pt/Au multilayer contacts to gallium nitride (GaN) in air are reported. Microfabricated circular-transfer-line-method test structures were subject to 10 h of thermal storage at 600?°C. Intermittent electrical characterization during thermal storage showed minimal variation in the contact resistance after 2 h and that the specific contact resistivity remained on the order of 10{sup ?5} ?-cm{sup 2}. In addition, the thermally stored multilayer contacts to GaN showed ohmic I-V characteristics when electrically probed at 600?°C. The microstructural analysis with atomic force microscopy showed minimal changes in surface roughness after thermal storage. Observations of the thermochemical reactions after thermal storage using Auger electron spectroscopy chemical depth profiling showed diffusion of Pt and minimal additional Al oxidation. The results support the use of Ti/Al/Pt/Au multilayer metallization for GaN-based sensors and electronic devices that will operate within a high-temperature and oxidizing ambient.

  1. Band offset between cubic GaN and AlN from intra- and interband spectroscopy of superlattices

    SciTech Connect (OSTI)

    Mietze, C.; Lischka, K.; As, D. J. [University of Paderborn, Faculty of Science, Department of Physics, Warburger Strasse 100 D-33098 Paderborn (Germany); DeCuir, E. A. Jr.; Manasreh, M. O. [Department of Electrical Engineering, University of Arkansas, 3217 Bell Engineering Center, Fayetteville, Arkansas 72701 (United States)

    2010-11-01T23:59:59.000Z

    By the analysis of intra- and intersubband transitions in GaN/AlN superlattices the band offset is determined experimentally. Superlattice structures with different period lengths were fabricated by plasma-assisted molecular beam epitaxy 3C-SiC substrates. The structural properties were studied by high resolution X-ray diffraction, revealing a high structural perfection of the superlattice region with several peaks in the X-ray spectra. Infrared absorbance spectroscopy revealed clear intrasubband transitions in the spectral region of 1.55 {mu}m measured at room temperature. Clear intersubband transitions were observed by photoluminescence at room temperature. These transition energies were compared to calculated energies using a 1D Poisson Schroedinger solver. For the calculations standard parameters for cubic GaN and AlN were used, while the band offset between GaN and AlN was varied. Optimal agreement between experimental and theoretical data was obtained for a band offset {Delta}E{sub C}:{Delta} E{sub V} of 55:45.

  2. High linearity GaN HEMT power amplifier with pre-linearization gate diode Shouxuan Xie, Vamsi Paidi, Sten Heikman, Alessandro Chini,

    E-Print Network [OSTI]

    Long, Stephen I.

    GaN/GaN HEMT technology. In order to obtain high linearity, a pre-linearization gate diode is added. Introduction. Our previously described single-ended Class B power amplifier design using GaN HEMT technology is biased at exactly the pinch off point (Class B configuration) [1]. In order to further improve

  3. The reaction of carbon tetrachloride with gallium arsenide ,,001... L. Li., S, Gan, B.-K. Han, H. Qi, and R. F. Hicksa)

    E-Print Network [OSTI]

    Li, Lian

    The reaction of carbon tetrachloride with gallium arsenide ,,001... L. Li., S, Gan, B.-K. Han, H, California 90095 Received 26 June 1997; accepted for publication 30 December 1997 Carbon tetrachloride of steps during the vapor-phase epitaxial growth of III­V compound semiconductors.3,4 Carbon tetrachloride

  4. A planar force-constant model for phonons in wurtzite GaN and AlN: Application to hexagonal GaN/AlN superlattices

    E-Print Network [OSTI]

    Lingjun Wang; Guanghong Wei; Jian Zi

    1998-12-17T23:59:59.000Z

    A planar force-constant model is developed for longitudinal phonons of wurtzite GaN and AlN propagating along the [0001] direction. The proposed model is then applied to the study of the phonon modes in hexagonal GaN/AlN superlattices in the longitudinal polarization. The confinement of the superlattice phonon mode is discussed.

  5. 262 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 14, NO. 6, JUNE 2004 A C-Band High-Dynamic Range GaN HEMT

    E-Print Network [OSTI]

    York, Robert A.

    , Umesh K. Mishra, and Robert A. York Abstract--A C-band low-noise amplifier (LNA) is designed were characterized for circuit design. A single stage low-noise amplifier was designed with the input-Dynamic Range GaN HEMT Low-Noise Amplifier Hongtao Xu, Christopher Sanabria, Alessandro Chini, Stacia Keller

  6. Temperature-Accelerated Degradation of GaN HEMTs under High-Power Stress: Activation Energy of Drain-Current Degradation

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    that allows device characterization through external test equipment [1]. A flow chart of a typical stepTemperature-Accelerated Degradation of GaN HEMTs under High- Power Stress: Activation Energy on this observation, we demonstrate a new scheme to extract the activation energy (Ea) of device degradation from step

  7. Effect of pressure on optical phonon modes and transverse effective charges in GaN and AlN A. R. Gon~i,1

    E-Print Network [OSTI]

    Nabben, Reinhard

    is presented for a three-layer one-dimensional AlN/GaN wurtzite quantum-well structure with GaN as the central. INTRODUCTION GaN/AlN quantum-confined wurtzite heterostructure material combinations are promising candidates effects, and lattice mismatch present in GaN/AlN wurtzite heterostructures. These cou- pling phenomena

  8. Self-Organized GaN Quantum Wire UV Lasers Heon-Jin Choi,, Justin C. Johnson, Rongrui He, Sang-Kwon Lee,, Franklin Kim,

    E-Print Network [OSTI]

    Yang, Peidong

    Self-Organized GaN Quantum Wire UV Lasers Heon-Jin Choi,, Justin C. Johnson, Rongrui He, Sang quantum wire lasers based on the Al-Ga-N system. A novel quantum-wire-in-optical- fiber (Qwof) nanostructure was obtained as a result of spontaneous Al-Ga-N phase separation at the nanometer scale in one

  9. Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J. Jahns

    E-Print Network [OSTI]

    Jahns, Jürgen

    Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J spreading in a mesa-structure GaN-based LED grown on an insulating or semi-insulating substrate. (b. Jahns Current crowding in mesa-structure GaInN/GaN light-emitting diodes (LEDs) grown on insulating

  10. High-temperature molecular beam epitaxial growth of AlGaN/GaN on GaN templates with reduced interface impurity levels

    SciTech Connect (OSTI)

    Koblmueller, G. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany); Chu, R. M.; Raman, A.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States)

    2010-02-15T23:59:59.000Z

    We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage. By exposing the GaN templates to an optimized thermal dissociation step in the plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, to lesser extent, Si impurities were effectively removed from the regrowth interface under preservation of good interface quality. Residual Si was further compensated by C-doped GaN via CBr{sub 4} to yield highly resistive GaN buffer layers. Improved N-rich growth conditions at high growth temperatures were then utilized for subsequent growth of the AlGaN/GaN device structure, yielding smooth surface morphologies and low residual oxygen concentration with large insensitivity to the (Al+Ga)N flux ratio. Room temperature electron mobilities of the two-dimensional electron gas at the AlGaN/GaN interface exceeded >1750 cm{sup 2}/V s and the dc drain current reached {approx}1.1 A/mm at a +1 V bias, demonstrating the effectiveness of the applied methods.

  11. STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN K.K. GAN, W. FERNANDO, H.P. KAGAN, R.D. KASS, A. LAW,

    E-Print Network [OSTI]

    Gan, K. K.

    that the main radiation effect is bulk damage in the VCSEL and PIN with the displacement of atoms. After five and VCSEL arrays coupled to radiation-hard ASICs produced for the current pixel optical link [5], the DORIC1 STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN ARRAYS K.K. GAN, W. FERNANDO, H.P. KAGAN, R

  12. 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...

  13. 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...

  14. Prospective emission efficiency and in-plane light polarization of nonpolar m-plane InxGa1-xN/GaN blue light emitting diodes fabricated on freestanding GaN substrates

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    m-plane In x Ga 1?x N / GaN blue light emitting diodesmea- surements. Since the blue MQW emission is polarized toS. Nakamura and G. Fasol, The Blue Laser Diode ?Springer,

  15. 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. [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan)] [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, Tsukuba-shi, Ibaraki 305-8568 (Japan); Rong, X.; Chen, G.; Wang, X. Q.; Shen, B. [School of Physics, Peking University, Beijing 100871 (China)] [School of Physics, Peking University, Beijing 100871 (China)

    2013-12-02T23:59:59.000Z

    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.

  16. Laser lift-off technique for freestanding GaN substrate using an In droplet formed by thermal decomposition of GaInN and its application to light-emitting diodes

    SciTech Connect (OSTI)

    Iida, Daisuke, E-mail: dft0tfi16@meijo-u.ac.jp; Kawai, Syunsuke; Ema, Nobuaki; Tsuchiya, Takayoshi; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi [Faculty of Science and Technology, Meijo University, Nagoya 468-8502 (Japan); Akasaki, Isamu [Faculty of Science and Technology, Meijo University, Nagoya 468-8502 (Japan); Akasaki Research Center, Nagoya University, Nagoya 464-8603 (Japan)

    2014-08-18T23:59:59.000Z

    We developed a laser lift-off technique for a freestanding GaN substrate using an In droplet formed by thermal decomposition of GaInN. A combination of an In droplet formed by thermal decomposition of GaInN during growth and a pulsed second-harmonic neodymium-doped yttrium aluminum garnet laser (??=?532?nm) realized the lift-off GaN substrate. After laser lift-off of the GaN substrate, it was used to achieve 380?nm ultraviolet light-emitting diodes with light output enhanced 1.7-fold. In this way, the light extraction can be improved by removing the GaN substrate.

  17. Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions

    SciTech Connect (OSTI)

    Zhang Meng; Bhattacharya, Pallab; Guo Wei; Banerjee, Animesh [Department of Electrical Engineering and Computer Science, Solid-State Electronics Laboratory, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)

    2010-03-29T23:59:59.000Z

    Acceptor doping of GaN with Mg during plasma-assisted molecular beam epitaxy, under N-rich conditions and a relatively high growth temperature of 740 deg. C, was investigated. The p-doping level steadily increases with increasing Mg flux. The highest doping level achieved, determined from Hall measurements, is 2.1x10{sup 18} cm{sup -3}. The corresponding doping efficiency and hole mobility are approx4.9% and 3.7 cm{sup 2}/V s at room temperature. Cross-sectional transmission electron microscopy and photoluminescence measurements confirm good crystalline and optical quality of the Mg-doped layers. An InGaN/GaN quantum dot light emitting diode (lambda{sub peak}=529 nm) with p-GaN contact layers grown under N-rich condition exhibits a low series resistance of 9.8 OMEGA.

  18. High quality InAlN single layers lattice-matched to GaN grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Gacevic, Z.; Fernandez-Garrido, S.; Calleja, E. [ISOM, Universidad Politecnica de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Rebled, J. M.; Peiro, F. [LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S. [LENS-MIND-IN2UB, Departament d'Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, CCiT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain)

    2011-07-18T23:59:59.000Z

    We report on properties of high quality {approx}60 nm thick InAlN layers nearly in-plane lattice-matched to GaN, grown on c-plane GaN-on-sapphire templates by plasma-assisted molecular beam epitaxy. Excellent crystalline quality and low surface roughness are confirmed by X-ray diffraction, transmission electron microscopy, and atomic force microscopy. High annular dark field observations reveal a periodic in-plane indium content variation (8 nm period), whereas optical measurements evidence certain residual absorption below the band-gap. The indium fluctuation is estimated to be {+-} 1.2% around the nominal 17% indium content via plasmon energy oscillations assessed by electron energy loss spectroscopy with sub-nanometric spatial resolution.

  19. 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, Ramón; Sitar, Zlatko; Maria, Jon-Paul [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-01-28T23:59:59.000Z

    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.

  20. Effect of Mg codoping on Eu{sup 3+} luminescence in GaN grown by ammonia molecular beam epitaxy

    SciTech Connect (OSTI)

    Takagi, Yasufumi [Central Research Laboratory, Hamamatsu Photonics K. K., Hamamatsu, Shizuoka 434-8601 (Japan); Suwa, Takanobu; Sekiguchi, Hiroto; Wakahara, Akihiro [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Okada, Hiroshi [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan)

    2011-10-24T23:59:59.000Z

    The effect of Mg codoping on the Eu{sup 3+} luminescence in GaN was investigated by photoluminescence measurements. Two notable emission peaks associated with the {sup 5}D{sub 0}{yields}{sup 7}F{sub 2} transition in the Eu{sup 3+} ions were governed by Mg codopants, which corresponded to the change of the dominant peak wavelength from 622.3 to 620.3 nm with an increase in Mg concentration. An optimal amount of Mg also led to enhancement of approximately 20 times of the Eu{sup 3+} luminescence. These results indicated that the Mg codopants selectively activated the optical site of 620.3 nm emission due to the elimination of nonradiative deexcitation paths from the {sup 5}D{sub 0} state.

  1. Downloaded 03 Apr 2013 to 147.173.59.170. This article is copyrighted as indicated in the abstract. Reuse of AIP content is subject to the terms at: http://apl.aip.org/about/rights_and_permissions High conductivity in Si-doped GaN wires

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ;High conductivity in Si-doped GaN wires P. Tchoulfian,1,2,a) F. Donatini,2 F. Levy,1 B. Amstatt,1 P-dependent resistivity measurements have been performed on single Si-doped GaN microwires grown by catalyst-free metal.1063/1.4799167] GaN is a wide band gap III-V semiconductor ($3.4 eV) currently used as the basic material for planar

  2. Deep traps in n-type GaN epilayers grown by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Kamyczek, P.; Placzek-Popko, E.; Zielony, E.; Gumienny, Z. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Zytkiewicz, Z. R. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

    2014-01-14T23:59:59.000Z

    In this study, we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77?K–350?K. Undoped GaN layers were grown using the plasma-assisted molecular beam epitaxy technique on commercial GaN/sapphire templates. The quality of the epilayers was studied by micro-Raman spectroscopy (?-RS) which proved the hexagonal phase and good crystallinity of GaN epilayers as well as a slight strain. The photoluminescence spectrum confirmed a high crystal quality by intense excitonic emission but it also exhibited a blue emission band of low intensity. DLTS signal spectra revealed the presence of four majority traps: two high-temperature and two low-temperature peaks. Using the Laplace DLTS method and Arrhenius plots, the apparent activation energy and capture cross sections were obtained. For two high-temperature majority traps, they were equal to E{sub 1}?=?0.65?eV, ?{sub 1}?=?8.2 × 10{sup ?16} cm{sup 2} and E{sub 2}?=?0.58?eV, ?{sub 2}?=?2.6 × 10{sup ?15} cm{sup 2} whereas for the two low-temperature majority traps they were equal to E{sub 3}?=?0.18?eV, ?{sub 3}?=?9.7 × 10{sup ?18} cm{sup 2} and E{sub 4}?=?0.13?eV, ?{sub 4}?=?9.2 × 10{sup ?18} cm{sup 2}. The possible origin of the traps is discussed and the results are compared with data reported elsewhere.

  3. 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, E-mail: tjkim@khu.ac.kr; Hwang, Soon Yong; Byun, Jun Seok; Barange, Nilesh S.; Park, Han Gyeol; Dong Kim, Young, E-mail: ydkim@khu.ac.kr [Nano-Optical Property Laboratory and Department of Physics, Kyung Hee University, Seoul 130-701 (Korea, Republic of)

    2014-02-15T23:59:59.000Z

    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.

  4. Iron on GaN(0001) pseudo-1?×?1 (1+1/(12) ) investigated by scanning tunneling microscopy and first-principles theory

    SciTech Connect (OSTI)

    Lin, Wenzhi; Mandru, Andrada-Oana; Smith, Arthur R., E-mail: smitha2@ohio.edu [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Takeuchi, Noboru [Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autonoma de Mexico Apartado Postal 14, Ensenada Baja California, Codigo Postal 22800 (Mexico); Al-Brithen, Hamad A. H. [Physics and Astronomy Department, King Abdulah Institute for Nanotechnology, King Saud University, Riyadh, Saudi Arabia, and National Center for Nano Technology, KACST, Riyadh (Saudi Arabia)

    2014-04-28T23:59:59.000Z

    We have investigated sub-monolayer iron deposition on atomically smooth GaN(0001) pseudo-1?×?1 (1+1/(12) ). The iron is deposited at a substrate temperature of 360?°C, upon which reflection high energy electron diffraction shows a transformation to a ?(3)×?(3)-R30° pattern. After cooling to room temperature, the pattern transforms to a 6?×?6, and scanning tunneling microscopy reveals 6?×?6 reconstructed regions decorating the GaN step edges. First-principles theoretical calculations have been carried out for a range of possible structural models, one of the best being a Ga dimer model consisting of 2/9 monolayer of Fe incorporated into 7/3 monolayer of Ga in a relaxed but distorted structure.

  5. Confirmation of intrinsic electron gap states at nonpolar GaN(1-100) surfaces combining photoelectron and surface optical spectroscopy

    SciTech Connect (OSTI)

    Himmerlich, M., E-mail: marcel.himmerlich@tu-ilmenau.de; Eisenhardt, A.; Shokhovets, S.; Krischok, S. [Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, PF 100565, 98684 Ilmenau (Germany); Räthel, J.; Speiser, E.; Neumann, M. D.; Navarro-Quezada, A.; Esser, N. [Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Strasse 9, 12489 Berlin (Germany)

    2014-04-28T23:59:59.000Z

    The electronic structure of GaN(1–100) surfaces is investigated in-situ by photoelectron spectroscopy (PES) and reflection anisotropy spectroscopy (RAS). Occupied surface states 3.1?eV below the Fermi energy are observed by PES, accompanied by surface optical transitions found in RAS around 3.3?eV, i.e., below the bulk band gap. These results indicate that the GaN(1–100) surface band gap is smaller than the bulk one due to the existence of intra-gap states, in agreement with density functional theory calculations. Furthermore, the experiments demonstrate that RAS can be applied for optical surface studies of anisotropic crystals.

  6. Composition and Interface Analysis of InGaN/GaN Multiquantum-Wells on GaN Substrates Using Atom Probe Tomography

    SciTech Connect (OSTI)

    Liu, Fang; Huang, Li; Davis, Robert F.; Porter, Lisa M.; Schreiber, Daniel K.; Kuchibhatla, S. V. N. T.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Preble, Edward; Paskova, Tanya; Evans, K. R.

    2014-09-04T23:59:59.000Z

    In0.20Ga0.80N/GaN multi-quantum wells grown on [0001]-oriented GaN substrates with and without an InGaN buffer layer were characterized using three-dimensional atom probe tomography. In all samples, the upper interfaces of the QWs were slightly more diffuse than the lower interfaces. The buffer layers did not affect the roughness of the interfaces within the quantum well structure, a result attributed to planarization of the surface of the 1st GaN barrier layer which had an average root-mean-square roughness of 0.177 nm. The In and Ga distributions within the MQWs followed the expected distributions for a random alloy with no indications of In clustering.

  7. Preparation of Ag Schottky contacts on n-type GaN bulk crystals grown in nitrogen rich atmosphere by the hydride vapor phase epitaxy technique

    SciTech Connect (OSTI)

    Stübner, R., E-mail: ronald.stuebner@physik.tu-dresden.de; Kolkovsky, Vl.; Weber, J. [Technische Universität Dresden, 01062 Dresden (Germany); Leibiger, Gunnar; Habel, Frank [Freiberger Compound Materials GmbH, 09599 Freiberg (Germany)

    2014-10-14T23:59:59.000Z

    Electrical properties of Schottky contacts on n-type GaN grown in nitrogen rich atmosphere with different N/Ga ratios by hydride vapor phase epitaxy were investigated. We show that tunneling of electrons from the conduction band of GaN to the metal is dominant in our samples. The quality of Schottky contacts does not only depend on surface preparation but also on the growth conditions of the crystals. Schottky contacts on these crystals show an increasing deterioration when higher N/Ga growth ratios are used. We correlate our results with the presence of negatively charged gallium vacancies in the samples. These charges compensate the positively charged donors and lead to a significant increase in series resistance.

  8. Polarization and temperature dependence of photoluminescence of m-plane GaN grown on {gamma}-LiAlO{sub 2} (100) substrate

    SciTech Connect (OSTI)

    Liu, B.; Kong, J. Y.; Zhang, R.; Xie, Z. L.; Fu, D. Y.; Xiu, X. Q.; Chen, P.; Lu, H.; Han, P.; Zheng, Y. D. [Department of Physics, Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China); Zhou, S. M. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2009-08-10T23:59:59.000Z

    We investigated the polarization and temperature dependence of photoluminescence (PL) of m-plane GaN grown on {gamma}-LiAlO{sub 2} (100) substrate. The calculated electronic band structure with kp Hamiltonian points out the energy splitting as well as polarization selection originate from the m-plane GaN epilayer under anisotropic strain. The polarization-angle dependence PL spectra are found to be selected from in-plane x- and z-polarized emission, corresponding to T{sub 1} and T{sub 2} transition. And the intensity distribution of the fitting peaks satisfies the Malus' law. An S-shape energy evolution of near band edge peak on temperatures is observed, which originates from the transition between the localized holes and electrons in triangular potentials induced by basal stacking faults.

  9. Step-flow anisotropy of the m-plane GaN (1100) grown under nitrogen-rich conditions by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Sawicka, Marta; Siekacz, Marcin; Skierbiszewski, Czeslaw [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); TopGaN Ltd., Sokolowska 29/37, PL-01-142 Warszawa (Poland); Turski, Henryk; Krysko, Marcin; DziePcielewski, Igor; Grzegory, Izabella [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); Smalc-Koziorowska, Julita [Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, PL-01-142 Warszawa (Poland); TopGaN Ltd., Sokolowska 29/37, PL-01-142 Warszawa (Poland); Warsaw University of Technology, Faculty of Material Science and Engineering, Woloska 141, PL-02-507 Warszawa (Poland)

    2011-06-15T23:59:59.000Z

    The homoepitaxial growth of m-plane (1100) GaN was investigated by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions. The surface morphologies as a function of sample miscut were studied, providing evidence for a strong growth anisotropy that is a consequence of the anisotropy of Ga adatom diffusion barriers on the m-plane surface recently calculated ab initio[Lymperakis and Neugebauer, Phys. Rev. B 79, 241308(R) (2009)]. We found that substrate miscut toward [0001] implies a step flow toward <1126> while substrate miscut toward [0001] causes formation of atomic steps either perpendicular or parallel to the [0001] direction, under N-rich conditions at 730 deg C. We describe the growth conditions for achieving atomically flat m-plane GaN layers with parallel atomic steps.

  10. Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

    SciTech Connect (OSTI)

    Furtmayr, Florian; Vielemeyer, Martin; Stutzmann, Martin; Eickhoff, Martin [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Arbiol, Jordi [EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, c/ Marti Franques 1, E-08080 Barcelona, CAT (Spain); TEM-MAT, Serveis Cientificotecnics, Universitat de Barcelona, c/ Lluis Sole i Sabaris 1-3, E-08080 Barcelona, CAT (Spain); Estrade, Sonia; Peiro, Francesca; Morante, Joan Ramon [EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, c/ Marti Franques 1, E-08080 Barcelona, CAT (Spain)

    2008-08-01T23:59:59.000Z

    The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations.

  11. Structural properties of free-standing 50 mm diameter GaN waferswith (101_0) orientation grown on LiAlO2

    SciTech Connect (OSTI)

    Jasinski, Jacek; Liliental-Weber, Zuzanna; Maruska, Herbert-Paul; Chai, Bruce H.; Hill, David W.; Chou, Mitch M.C.; Gallagher, John J.; Brown, Stephen

    2005-09-27T23:59:59.000Z

    (10{und 1}0) GaN wafers grown on (100) face of {gamma}-LiAlO{sub 2} were studied using transmission electron microscopy. Despite good lattice matching in this heteroepitaxial system, high densities of planar structural defects in the form of stacking faults on the basal plane and networks of boundaries located on prism planes inclined to the layer/substrate interface were present in these GaN layers. In addition, significant numbers of threading dislocations were observed. High-resolution electron microscopy indicates that stacking faults present on the basal plane in these layers are of low-energy intrinsic I1type. This is consistent with diffraction contrast experiments.

  12. Study of epitaxial lateral overgrowth of semipolar (1 1 ? 2 2) GaN by using different SiO{sub 2} pattern sizes

    SciTech Connect (OSTI)

    Song, Ki-Ryong; Lee, Jae-Hwan; Han, Sang-Hyun; Yi, Hye-Rin; Lee, Sung-Nam, E-mail: snlee@kpu.ac.kr

    2013-12-15T23:59:59.000Z

    Graphical abstract: - Highlights: • We examine comparative studies of semipolar ELO-GaN film. • Semipolar ELO-GaN film was grown by three step growth method. • The achievement of smooth surface morphology of semipolar ELO-GaN. • The crystal and optical properties was significantly improved by ELO process. - Abstract: We investigated the growth mode and the crystal properties of lateral epitaxial overgrowth (LEO) semipolar (1 1 ? 2 2) GaN by using the various SiO{sub 2} pattern sizes of 6, 8, 10 and 12 ?m with the window width of 4.0 ?m. By using three-step growth technique, we successfully obtained the fully-coalescenced semipolar (1 1 ? 2 2) LEO-GaN films regardless of the SiO{sub 2} pattern sizes. However, the coalescence thickness of LEO-GaN film was decreased with decreasing SiO{sub 2} pattern size, indicating that the coalescence of semipolar (1 1 ? 2 2) GaN was easily formed by decreasing the pattern size of SiO{sub 2} mask. The full width at half maximums (FWHMs) of X-ray rocking curves (XRCs) of LEO-GaN films decreased with increasing SiO{sub 2} pattern size. In the pattern size of 4 × 10 ?m, we achieved the minimum XRCs FWHM of 537 and 368 arc s with two different X-ray incident beam directions of [1 1 ? 2 ? 3] and [1 ? 1 0 0], respectively. Moreover, the photoluminescence bandedge emission of semipolar (1 1 ? 2 2) GaN was 45 times increased by LEO process. Based on these results, we concluded that the LEO pattern size of 4 × 10 ?m would effectively decrease crystal defects of semipolar (1 1 ? 2 2) GaN epilayer, resulting in an improvement of the optical properties.

  13. Control of strain in GaN by a combination of H{sub 2} and N{sub 2} carrier gases

    SciTech Connect (OSTI)

    Yamaguchi, Shigeo; Kariya, Michihiko; Kosaki, Masayoshi; Yukawa, Yohei; Nitta, Shugo; Amano, Hiroshi; Akasaki, Isamu

    2001-06-15T23:59:59.000Z

    We study the effect of a combination of N{sub 2} and H{sub 2} carrier gases on the residual strain and crystalline properties of GaN, and we propose its application to the improvement of crystalline quality of GaN/Al{sub 0.17}Ga{sub 0.83}N multiple quantum well (MQW) structures. GaN was grown with H{sub 2} or N{sub 2} carrier gas (H{sub 2}{endash} or N{sub 2}{endash}GaN) on an AlN low-temperature-deposited buffer layer. A (0001) sapphire substrate was used. N{sub 2}{endash}GaN was grown on H{sub 2}{endash}GaN. The total thickness was set to be 1.5 {mu}m, and the ratio of N{sub 2}{endash}GaN thickness to the total thickness, x, ranged from 0 to 1. With increasing x, the tensile stress in GaN increased. Photoluminescence intensity at room temperature was much enhanced. Moreover, the crystalline quality of GaN/Al{sub 0.17}Ga{sub 0.83}N MQW was much higher when the MQW was grown with N{sub 2} on H{sub 2}{endash}GaN than when it was grown with H{sub 2} on H{sub 2}{endash}GaN. These results were due to the achievement of control of strain in GaN using a combination of N{sub 2}{endash}GaN and H{sub 2}{endash}GaN. {copyright} 2001 American Institute of Physics.

  14. Comparative study of GaN mesa etch characteristics in Cl{sub 2} based inductively coupled plasma with Ar and BCl{sub 3} as additive gases

    SciTech Connect (OSTI)

    Rawal, Dipendra Singh, E-mail: dsrawal15@gmail.com; Arora, Henika; Sehgal, Bhupender Kumar; Muralidharan, Rangarajan [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi-110054 (India)

    2014-05-15T23:59:59.000Z

    GaN thin film etching is investigated and compared for mesa formation in inductively coupled plasma (ICP) of Cl{sub 2} with Ar and BCl{sub 3} gas additives using photoresist mask. Etch characteristics are studied as a function of ICP process parameters, viz., ICP power, radio frequency (RF) power, and chamber pressure at fixed total flow rate. The etch rate at each ICP/RF power is 0.1–0.2??m/min higher for Cl{sub 2}/Ar mixture mainly due to higher Cl dissociation efficiency of Ar additive that readily provides Cl ion/radical for reaction in comparison to Cl{sub 2}/BCl{sub 3} mixture. Cl{sub 2}/Ar mixture also leads to better photoresist mask selectivity. The etch-induced roughness is investigated using atomic force microscopy. Cl{sub 2}/Ar etching has resulted in lower root-mean-square roughness of GaN etched surface in comparison to Cl{sub 2}/BCl{sub 3} etching due to increased Ar ion energy and flux with ICP/RF power that enhances the sputter removal of etch product. The GaN surface damage after etching is also evaluated using room temperature photoluminescence and found to be increasing with ICP/RF power for both the etch chemistries with higher degree of damage in Cl{sub 2}/BCl{sub 3} etching under same condition.

  15. 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., E-mail: gdim@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Tsiakatouras, G.; Tsagaraki, K.; Georgakilas, A. [Department of Physics, Microelectronics Research Group, University of Crete, P.O. Box 2208, GR 71003, Greece and IESL, FORTH, P.O. Box 1385, GR71110 Heraklion (Greece); Christofilos, D. [Physics Division, School of Technology, Aristotle University of Thessaloniki, GR54124 Thessaloniki (Greece)

    2014-06-07T23:59:59.000Z

    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.

  16. Sputtering of Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN by electrosprayed nanodroplets

    SciTech Connect (OSTI)

    Borrajo-Pelaez, Rafael; Grustan-Gutierrez, Enric; Gamero-Castaño, Manuel, E-mail: mgameroc@uci.edu [Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697 (United States)

    2013-11-14T23:59:59.000Z

    This article presents a characterization of the damage caused by energetic beams of electrosprayed nanodroplets striking the surfaces of single-crystal semiconductors including Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN. The sputtering yield (number of atoms ejected per projectile's molecule), sputtering rate, and surface roughness are measured as functions of the beam acceleration potential. The maximum values of the sputtering yields range between 1.9 and 2.2 for the technological important but difficult to etch SiC and GaN respectively, and 4.5 for Ge. The maximum sputtering rates for the non-optimized beam flux conditions used in our experiments vary between 409?nm/min for SiC and 2381?nm/min for GaSb. The maximum sputtering rate for GaN is 630?nm/min. Surface roughness increases modestly with acceleration voltage, staying within 2?nm and 20?nm for all beamlet acceleration potentials and materials except Si. At intermediate acceleration potentials, the surface of Si is formed by craters orders of magnitude larger than the projectiles, yielding surface roughness in excess of 60?nm. The effect of projectile dose is studied in the case of Si. This parameter is correlated with the formation of the large craters typical of Si, which suggests that the accumulation of damage following consecutive impacts plays an important role in the interaction between beamlet and target.

  17. As-grown deep-level defects in n-GaN grown by metal-organic chemical vapor deposition on freestanding GaN

    SciTech Connect (OSTI)

    Chen Shang; Ishikawa, Kenji; Hori, Masaru [Nagoya University, Chikusa, Nagoya 464-8603 (Japan); Honda, Unhi; Shibata, Tatsunari; Matsumura, Toshiya; Tokuda, Yutaka [Aichi Institute of Technology, Yakusa, Toyota 470-0392 (Japan); Ueda, Hiroyuki; Uesugi, Tsutomu; Kachi, Tetsu [Toyota Central R and D Laboratories, Inc., Yokomichi, Nagakute 480-1192 (Japan)

    2012-09-01T23:59:59.000Z

    Traps of energy levels E{sub c}-0.26 and E{sub c}-0.61 eV have been identified as as-grown traps in n-GaN grown by metal-organic chemical vapor deposition by using deep level transient spectroscopy of the Schottky contacts fabricated by resistive evaporation. The additional traps of E{sub c}-0.13 and E{sub c}-0.65 eV have been observed in samples whose contacts are deposited by electron-beam evaporation. An increase in concentration of the E{sub c}-0.13 and E{sub c}-0.65 eV traps when approaching the interface between the contact and the GaN film supports our argument that these traps are induced by electron-beam irradiation. Conversely, the depth profiles of as-grown traps show different profiles between several samples with increased or uniform distribution in the near surface below 50 nm. Similar profiles are observed in GaN grown on a sapphire substrate. We conclude that the growth process causes these large concentrations of as-grown traps in the near-surface region. It is speculated that the finishing step in the growth process should be an essential issue in the investigation of the surface state of GaN.

  18. Indium and impurity incorporation in InGaN films on polar, nonpolar, and semipolar GaN orientations grown by ammonia molecular beam epitaxy

    SciTech Connect (OSTI)

    Browne, David A.; Young, Erin C.; Lang, Jordan R.; Hurni, Christophe A.; Speck, James S. [Materials Department, University of California Santa Barbara, Santa Barbara, California 93106 (United States)

    2012-07-15T23:59:59.000Z

    The effects of NH{sub 3} flow, group III flux, and substrate growth temperature on indium incorporation and surface morphology have been investigated for bulk InGaN films grown by ammonia molecular beam epitaxy. The incorporation of unintentional impurity elements (H, C, O) in InGaN films was studied as a function of growth temperature for growth on polar (0001) GaN on sapphire templates, nonpolar (1010) bulk GaN, and semipolar (1122), (2021) bulk GaN substrates. Enhanced indium incorporation was observed on both (1010) and (2021) surfaces relative to c-plane, while reduced indium incorporation was observed on (1122) for co-loaded conditions. Indium incorporation was observed to increase with decreasing growth temperature for all planes, while being relatively unaffected by the group III flux rates for a 1:1 Ga:In ratio. Indium incorporation was found to increase at the expense of a decreased growth rate for higher ammonia flows; however, smooth surface morphology was consistently observed for growth on semipolar orientations. Increased concentrations of oxygen and hydrogen were observed on semipolar and nonpolar orientations with a clear trend of increased hydrogen incorporation with indium content.

  19. 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. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yale Univ., New Haven, CT (United States); Kharche, Neerav [Brookhaven National Lab. (BNL), Upton, NY (United States); Batista, Victor S. [Yale Univ., New Haven, CT (United States); Hybertsen, Mark S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tully, John C. [Yale Univ., New Haven, CT (United States); Muckerman, James T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-04-03T23:59:59.000Z

    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 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 (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.

  20. Strain states of AlN/GaN-stress mitigating layer and their effect on GaN buffer layer grown by ammonia molecular beam epitaxy on 100-mm Si(111)

    SciTech Connect (OSTI)

    Ravikiran, L.; Radhakrishnan, K.; Agrawal, M. [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)] [NOVITAS-Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Dharmarasu, N.; Munawar Basha, S. [Temasek Laboratories, Nanyang Technological University, Singapore 637553 (Singapore)] [Temasek Laboratories, Nanyang Technological University, Singapore 637553 (Singapore)

    2013-09-28T23:59:59.000Z

    The effect of strain states of AlN/GaN-stress mitigating layer (SML) on buried crack density and its subsequent influence on the residual stresses in GaN buffer layers grown using ammonia-molecular beam epitaxy on 100-mm Si(111) substrate has been investigated. Different stages involved in the formation of buried cracks, which are crack initialization, growth of relaxed AlN layer, and subsequent lateral over growth, are identified using in-situ curvature measurements. While the increase of GaN thickness in AlN/GaN-SML enhanced its compressive strain relaxation and resulted in reduced buried crack spacing, the variation of AlN thickness did not show any effect on the crack spacing. Moreover, the decrease in the crack spacing (or increase in the buried crack density) was found to reduce the residual compression in 1st and 2nd GaN layers of AlN/GaN-SML structure. The higher buried crack density relaxed the compressive strain in 1st GaN layer, which further reduced its ability to compensate the tensile stress generated during substrate cool down, and hence resulted in lower residual compressive stress in 2nd GaN layer.

  1. VOLUME 80, NUMBER 14 P H Y S I C A L R E V I E W L E T T E R S 6 APRIL 1998 Clean and As-Covered Zinc-Blende GaN (001) Surfaces: Novel Surface Structures

    E-Print Network [OSTI]

    recently atomically resolved scanning tunneling micrographs have been obtained for wurtzite GaN surfaces [3 in a systematic way. The stable crystal phase of GaN is the wurtzite struc- ture. However, cubic (zinc-blende) Ga appealing for device applica- tions: It has a lower band gap than the wurtzite phase (by 0.2 eV) and can

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

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu; Akyol, Fatih [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Rajan, Siddharth, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2014-10-06T23:59:59.000Z

    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.

  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: szyszka@ihp-microelectronics.com, E-mail: adam.szyszka@pwr.wroc.pl [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Janiszewskiego 11/17, 50-372 Wroclaw (Poland); Lupina, L.; Lupina, G.; Schubert, M. A.; Zaumseil, P. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Haeberlen, M.; Storck, P.; Thapa, S. B. [Siltronic, Hanns-Seidel-Platz 4, 81737 München (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); BTU Cottbus-Senftenberg, Konrad-Zuse-Strasse 1, 03046 Cottbus (Germany)

    2014-08-28T23:59:59.000Z

    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 that—with respect to the basic GaN/oxide/Si system without DBR—the 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. 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.

    2015-04-03T23:59:59.000Z

    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

  5. 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, José H. D. da [Universidade Estadual Paulista, UNESP, Bauru, São Paulo 17033-360 (Brazil)] [Universidade Estadual Paulista, UNESP, Bauru, São Paulo 17033-360 (Brazil); Leite, Douglas M. G. [Universidade Federal de Itajubá, UNIFEI, Itajubá, Minas Gerais 37500-903 (Brazil)] [Universidade Federal de Itajubá, UNIFEI, Itajubá, Minas Gerais 37500-903 (Brazil); Bortoleto, José R. R. [Universidade Estadual Paulista, UNESP, Sorocaba, São Paulo 18087-180 (Brazil)] [Universidade Estadual Paulista, UNESP, Sorocaba, São Paulo 18087-180 (Brazil)

    2013-11-14T23:59:59.000Z

    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.

  6. Study of the growth mechanisms of GaN/(Al, Ga)N quantum dots: Correlation between structural and optical properties

    SciTech Connect (OSTI)

    Sergent, S. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Universite de Nice Sophia Antipolis, Parc Valrose, F-06102 Nice Cedex 2 (France); Damilano, B.; Huault, T.; Brault, J.; Tottereau, O.; Vennegues, P.; Leroux, M.; Semond, F.; Massies, J. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Korytov, M.

    2011-03-01T23:59:59.000Z

    The ammonia-based molecular beam epitaxy of GaN/(Al, Ga)N quantum dots is investigated using reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy and photoluminescence. The main steps of the formation kinetics are identified and the influence of diffusion and evaporation processes on both the quantum dot and the wetting layer morphology is addressed. The correlation between the optical and structural properties of such structures finally allows for the analysis of matter exchanges between the quantum dots and the wetting layer during capping.

  7. Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

    SciTech Connect (OSTI)

    Zhuang, Y. D.; Shields, P. A.; Allsopp, D. W. E., E-mail: d.allsopp@bath.ac.uk [Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom); Bruckbauer, J.; Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2014-11-07T23:59:59.000Z

    Cathodoluminescence (CL) hyperspectral imaging has been performed on GaN nanorods containing a single InGaN quantum disk (SQD) with controlled variations in excitation conditions. Two different nanorod diameters (200 and 280?nm) have been considered. Systematic changes in the CL spectra from the SQD were observed as the accelerating voltage of the electron beam and its position of incidence are varied. It is shown that the dominant optical transition in the SQD varies across the nanorod as a result of interplay between the contributions of the deformation potential and the quantum-confined Stark effect to the transition energy as consequence of radial variation in the pseudomorphic strain.

  8. Point defects as a test ground for the local density approximation +U theory: Mn, Fe, and V{sub Ga} in GaN

    SciTech Connect (OSTI)

    Volnianska, O.; Zakrzewski, T. [Institute of Physics PAS, 02-668 Warsaw (Poland); Boguslawski, P. [Institute of Physics PAS, 02-668 Warsaw (Poland); Institute of Physics, Kazimierz Wielki University, 85-072 Bydgoszcz (Poland)

    2014-09-21T23:59:59.000Z

    Electronic structure of the Mn and Fe ions and of the gallium vacancy V{sub Ga} in GaN was analysed within the GGA + U approach. First, the +U term was treated as a free parameter, and applied to p(N), d(Mn), and d(Fe). The band gap of GaN is reproduced for U(N) ? 4 eV. The electronic structure of defect states was found to be more sensitive to the value of U than that of the bulk states. Both the magnitude and the sign of the U-induced energy shifts of levels depend on occupancies, and thus on the defect charge state. The energy shifts also depend on the hybridization between defect and host states, and thus are different for different level symmetries. In the case of V{sub Ga}, these effects lead to stabilization of spin polarization and the “negative-U{sub eff}” behavior. The values of Us were also calculated using the linear response approach, which gives U(Fe) ? U(Mn) ? 4 eV. This reproduces well the results of previous hybrid functionals calculations. However, the best agreement with the experimental data is obtained for vanishing or even negative U(Fe) and U(Mn)

  9. arXiv:cond-mat/9705111v231Mar1998 Phys. Rev. Lett., in print Clean and As-covered zinc-blende GaN (001) surfaces: Novel surface structures and

    E-Print Network [OSTI]

    understood. Only recently atomically resolved scanning tunneling micrographs have been obtained for wurtzite to improve growth in a systematic way. The stable crystal phase of GaN is the wurtzite struc- ture. However of properties very appealing for device applica- tions: It has a lower bandgap than the wurtzite phase (by 0.2 e

  10. Impact of GaN cap on charges in Al?O?/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations

    SciTech Connect (OSTI)

    ?apajna, M., E-mail: milan.tapajna@savba.sk; Jurkovi?, M.; Válik, L.; Haš?ík, Š.; Gregušová, D.; Kuzmík, J. [Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava (Slovakia); Brunner, F.; Cho, E.-M. [Ferdinand-Braun-Institut, Leibniz Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin (Germany); Hashizume, T. [Research Center for Integrated Quantum Electronics (RCIQE), Hokkaido University, 060-0814 Sapporo, Japan and JST-CREST, 102-0075 Tokyo (Japan)

    2014-09-14T23:59:59.000Z

    Oxide/semiconductor interface trap density (D{sub it}) and net charge of Al?O?/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. D{sub it} distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher D{sub it} (?5–8?×?10¹²eV?¹?cm?²) was found at trap energies ranging from EC-0.5 to 1?eV for structure with GaN cap compared to that (D{sub it}???2–3?×?10¹²eV?¹?cm?²) where the GaN cap was selectively etched away. D{sub it} distributions were then used for simulation of capacitance-voltage characteristics. A good agreement between experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high D{sub it} (>10¹³eV?¹?cm?²) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher D{sub it} centered about EC-0.6?eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al?O? thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed.

  11. High temperature stable W and WSi{sub x} ohmic contacts on GaN and InGaN

    SciTech Connect (OSTI)

    Pearton, S.J.; Abernathy, C.R.; Durbha, A. [Florida Univ., Gainesville, FL (United States)] [and others

    1996-06-01T23:59:59.000Z

    Conventional III-V metallizations chemes such as Au/Ge/Ni, Ti/Pt/Au, and Au/Be were found to display poor thermal stability on both GaN and InGaN, with extensive reaction and contact degradation at {le}500 C. By contrast, W was found to produce low contact resistance ({rho}{sub c}{similar_to}8x10{sup -5}{Omega}cm{sup 2}) to n-GaN. Ga outdiffusion to the surface of thin (500 A) W films was found after annealing at 1,100 C, but not at 1000 C. Interfacial abruptness increased by 300A after 1,100 C annealing. In the case of WSi{sub X} (X=0.45), Ga outdiffusion was absent even at 1,100 C, but again there was interfacial broadening and some phase changes in the WSi{sub X}. On In{sub 0.5}Ga{sub 0.5}N, a minimum specific contact resistivity of 1.5 x10{sup -5}{Omega}cm{sup 2} was obtained for WSi{sub X} annealed at 700 C. These contacts retained a smooth morphology and abrupt interfaces to 800 C. Graded In{sub X}Ga{sub 1-X}N layers have been employed on GaAs/AlGaAs HBTs (heterojunction bipolar transistors), replacing conventional In{sub X}Ga{sub 1-X}As layers. R{sub C} values of 5x10{sup -7}{Omega}cm{sup 2} were obtained for nonalloyed Ti/Pt/Au on the InGaN, and the morphologies were superior to those of InGaAs contact layers. This proves to have significant advantages for fabrication of sub-micron HBTs. Devices with emitter dimensions of 2x5{mu}m{sup 2} displayed gains of 35 for a base doping level of 7x10{sup 19}cm{sup -3} and stable long-term behavior.

  12. Dynamics of thermalization in GaInN/GaN quantum wells grown on ammonothermal GaN

    SciTech Connect (OSTI)

    Binder, J.; Korona, K. P.; Wysmo?ek, A.; Kami?ska, M. [Faculty of Physics, University of Warsaw, ul. Hoza 69, 00-681 Warsaw (Poland); Köhler, K.; Kirste, L.; Ambacher, O. [Fraunhofer Institute for Applied Solid State Physics, Tullastr. 72, 79108 Freiburg (Germany); Zaj?c, M.; Dwili?ski, R. [AMMONO SA, Czerwonego Krzy?a 2/31, 00-377 Warsaw (Poland)

    2013-12-14T23:59:59.000Z

    In this work, we present measurements of the dynamics of photoexcited carriers in GaInN/GaN quantum wells (QWs) grown on ammonothermal GaN, especially thermalization and recombination rates. Emission properties were measured by time-resolved photoluminescence (PL) and electroluminescence spectroscopy. Due to the use of high quality homoepitaxial material, we were able to obtain very valuable data on carrier thermalization. The temperature dependence of the QW energy observed in PL shows characteristic S-shape with a step of about 10?meV. Such a behavior (related to thermalization and localization at potential fluctuations) is often reported for QWs; but in our samples, the effect is smaller than in heteroepitaxial InGaN/GaN QWs due to lower potential fluctuation in our material. Absorption properties were studied by photocurrent spectroscopy measurements. A comparison of emission and absorption spectra revealed a shift in energy of about 60?meV. Contrary to PL, the QW energy observed in absorption decreases monotonically with temperature, which can be described by a Bose-like dependence E(T)?=?E(0) ? ?/(exp(?/T) ? 1), with parameters ??=?(0.11?±?0.01) eV, ??=?(355?±?20)?K, or by a Varshni dependence with coefficients ??=?(10?±?3) × 10{sup ?4}?eV/K and ??=?(1500?±?500) K. Taking into account absorption and emission, the fluctuation amplitude (according to Eliseev theory) was ??=?14?meV. The time resolved PL revealed that in a short period (<1?ns) after excitation, the PL peaks were broadened because of the thermal distribution of carriers. We interpreted this distribution in terms of quasi-temperature (T{sub q}) of the carriers. The initial T{sub q} was of the order of 500?K. The thermalization led to a fast decrease of T{sub q}. The obtained cooling time in the QW was ?{sub C}?=?0.3?ns, which was faster than the observed recombination time ?{sub R}?=?2.2?ns (at 4?K)

  13. Effects of capping on GaN quantum dots deposited on Al{sub 0.5}Ga{sub 0.5}N by molecular beam epitaxy

    SciTech Connect (OSTI)

    Korytov, M. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France) and University of Nice Sophia-Antipolis, Parc Valrose, 06103 Nice (France); Benaissa, M. [CNRST, angle Allal-Fassi/FAR, Madinat al-irfane, 10000 Rabat (Morocco); Brault, J.; Vennegues, P. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Huault, T. [CRHEA-CNRS, rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne, France and RIBER S.A., 31 rue Casimir Perier, BP 70083, 95873 Bezons Cedex (France); Neisius, T. [CP2M, Faculte Saint Jerome, 13397 Marseille Cedex 20 (France)

    2009-04-06T23:59:59.000Z

    The impact of the capping process on the structural and morphological properties of GaN quantum dots (QDs) grown on fully relaxed Al{sub 0.5}Ga{sub 0.5}N templates was studied by transmission electron microscopy. A morphological transition between the surface QDs, which have a pyramidal shape, and the buried ones, which have a truncated pyramid shape, is evidenced. This shape evolution is accompanied by a volume change: buried QDs are bigger than surface ones. Furthermore a phase separation into Al{sub 0.5}Ga{sub 0.5}N barriers was observed in the close vicinity of buried QDs. As a result, the buried QDs were found to be connected with the nearest neighbors by thin Ga-rich zones, whereas Al-rich zones are situated above the QDs.

  14. Impact of barrier thickness on transistor performance in AlN/GaN high electron mobility transistors grown on free-standing GaN substrates

    SciTech Connect (OSTI)

    Deen, David A., E-mail: david.deen@alumni.nd.edu; Storm, David F.; Meyer, David J.; Bass, Robert; Binari, Steven C. [Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375-5347 (United States); Gougousi, Theodosia [Physics Department, University of Maryland Baltimore County, Baltimore, Maryland 21250 (United States); Evans, Keith R. [Kyma Technologies, Raleigh, North Carolina 27617 (United States)

    2014-09-01T23:59:59.000Z

    A series of six ultrathin AlN/GaN heterostructures with varied AlN thicknesses from 1.5–6?nm have been grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. High electron mobility transistors (HEMTs) were fabricated from the set in order to assess the impact of barrier thickness and homo-epitaxial growth on transistor performance. Room temperature Hall characteristics revealed mobility of 1700?cm{sup 2}/V s and sheet resistance of 130 ?/? for a 3?nm thick barrier, ranking amongst the lowest room-temperature sheet resistance values reported for a polarization-doped single heterostructure in the III-Nitride family. DC and small signal HEMT electrical characteristics from submicron gate length HEMTs further elucidated the effect of the AlN barrier thickness on device performance.

  15. 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. [Departamento de Ciencias Básicas, Universidad de Medellín, Medellín (Colombia); Mora-Ramos, M. E., E-mail: memora@uaem.mx [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca, Morelos (Mexico); Duque, C. A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)

    2014-06-07T23:59:59.000Z

    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.

  16. In situ measurements of nitric oxide in coal-combustion exhaust using a sensor based on a widely tunable external-cavity GaN diode laser

    SciTech Connect (OSTI)

    Anderson, T.N.; Lucht, R.P.; Priyadarsan, S.; Annamalai, K.; Caton, J.A. [Purdue University, West Lafayette, IN (United States). School of Mechanical Engineers

    2007-07-15T23:59:59.000Z

    A diode-laser-based sensor has been developed to measure nitric oxide mole fractions using absorption spectroscopy. The sensor is based on sum-frequency mixing of a 395 nm external-cavity diode laser (ECDL) and a 532 run laser in a beta-barium-borate crystal. Using a new tuning scheme, the GaN ECDL wavelength was modulated over 90 GHz without mode hops. The sensor was applied for measurements of the NO mole fraction in the exhaust of a laboratory-scale, 30 kW, coal-fired boiler burner. Absorption measurements were successfully performed despite severe attenuation by scattering from ash particles in the exhaust stream and on the exhaust-section windows. A detection limit (1 sigma) of 4.5 ppm m/root Hz at 700 K was demonstrated in coal-combustion exhaust at a maximum detection rate of 5 Hz.

  17. Dual-polarity GaN micropillars grown by metalorganic vapour phase epitaxy: Cross-correlation between structural and optical properties

    SciTech Connect (OSTI)

    Coulon, P. M. [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France); Université de Nice Sophia-Antipolis (UNS), 28 Ave. Valrose, 06103 Nice (France); Mexis, M.; Teisseire, M.; Vennéguès, P.; Leroux, M.; Zuniga-Perez, J., E-mail: jzp@crhea.cnrs.fr [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France); Jublot, M. [Faculté des Sciences de Saint Jérôme—CP2M, Ave. Escadrille Normandie Niemen, 13397 Marseille (France)

    2014-04-21T23:59:59.000Z

    Self-assembled catalyst-free GaN micropillars grown on (0001) sapphire substrates by metal organic vapor phase epitaxy are investigated. Transmission electron microscopy, as well as KOH etching, shows the systematic presence of two domains of opposite polarity within each single micropillar. The analysis of the initial growth stages indicates that such double polarity originates at the micropillar/substrate interface, i.e., during the micropillar nucleation, and it propagates along the micropillar. Furthermore, dislocations are also generated at the wire/substrate interface, but bend after several hundreds of nanometers. This leads to micropillars several tens of micrometers in length that are dislocation-free. Spatially resolved cathodoluminescence and microphotoluminescence show large differences in the optical properties of each polarity domain, suggesting unequal impurity/dopant/vacancy incorporation depending on the polarity.

  18. Optical and structural study of GaN nanowires grown by catalyst-free molecular beam epitaxy. II. Sub-band-gap luminescence and electron irradiation effects

    SciTech Connect (OSTI)

    Robins, Lawrence H.; Bertness, Kris A.; Barker, Joy M.; Sanford, Norman A.; Schlager, John B. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

    2007-06-01T23:59:59.000Z

    GaN nanowires with diameters of 50-250 nm, grown by catalyst-free molecular beam epitaxy, were characterized by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy at temperatures from 3 to 297 K. Both as-grown samples and dispersions of the nanowires onto other substrates were examined. The properties of the near-band-edge PL and CL spectra were discussed in Part I of this study by [Robins et al. [L. H. Robins, K. A. Bertness, J. M. Barker, N. A. Sanford, and J. B. Schlager, J. Appl. Phys. 101,113505 (2007)]. Spectral features below the band gap, and the effect of extended electron irradiation on the CL, are discussed in Part II. The observed sub-band-gap PL and CL peaks are identified as phonon replicas of the free-exciton transitions, or excitons bound to structural defects or surface states. The defect-related peaks in the nanowires are correlated with luminescence lines previously reported in GaN films, denoted the Y lines [M. A. Reshchikov and H. Morkoc, J. Appl. Phys. 97, 061301 (2005)]. The CL was partially quenched by electron beam irradiation for an extended time; the quenching was stronger for the free and shallow-donor-bound exciton peaks than for the defect-related peaks. The quenching appeared to saturate at high irradiation dose (with final intensity {approx_equal}30% of initial intensity) and was reversible on thermal cycling to room temperature. The electron irradiation-induced quenching of the CL is ascribed to charge injection and trapping phenomena.

  19. August 2013 Jianbang Gan

    E-Print Network [OSTI]

    for development of sustainable advanced lignocellulosic biofuel systems, $6.25 million, 2012-17, US Department of forest biomass based biofuel development on rural communities in the southern United States, $350

  20. * email: nidhi@ece.ucsb.edu phone: +1-805-893-3812 ext 202 Ultra-low contact resistance for Self-aligned HEMT structures on N-polar GaN by MBE

    E-Print Network [OSTI]

    Rodwell, Mark J. W.

    * email: nidhi@ece.ucsb.edu phone: +1-805-893-3812 ext 202 Ultra-low contact resistance for SelfN) are regrown to achieve ultra-low Ohmic contact resistance. All MBE regrowths were done on MOCVD GaN templates of InN. To summarize, ultra-low Ohmic contact resistance of 60 -µm was obtained for a self-aligned devi

  1. Analysis of the AlGaN/GaN vertical bulk current on Si, sapphire, and free-standing GaN substrates

    SciTech Connect (OSTI)

    Perez-Tomas, A.; Fontsere, A.; Llobet, J. [IMB-CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, CAT (Spain); Placidi, M. [IREC, Jardins Dones de Negre 1, 08930 Sant Adria de Besos, Barcelona (Spain); Rennesson, S.; Chenot, S.; Moreno, J. C.; Cordier, Y. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); Baron, N. [CRHEA-CNRS, Rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France); PICOGIGA International, Pl M. Rebuffat, Courtaboeuf 7, 91140 Villejust (France)

    2013-05-07T23:59:59.000Z

    The vertical bulk (drain-bulk) current (I{sub db}) properties of analogous AlGaN/GaN hetero-structures molecular beam epitaxially grown on silicon, sapphire, and free-standing GaN (FS-GaN) have been evaluated in this paper. The experimental I{sub db} (25-300 Degree-Sign C) have been well reproduced with physical models based on a combination of Poole-Frenkel (trap assisted) and hopping (resistive) conduction mechanisms. The thermal activation energies (E{sub a}), the (soft or destructive) vertical breakdown voltage (V{sub B}), and the effect of inverting the drain-bulk polarity have also been comparatively investigated. GaN-on-FS-GaN appears to adhere to the resistive mechanism (E{sub a} = 0.35 eV at T = 25-300 Degree-Sign C; V{sub B} = 840 V), GaN-on-sapphire follows the trap assisted mechanism (E{sub a} = 2.5 eV at T > 265 Degree-Sign C; V{sub B} > 1100 V), and the GaN-on-Si is well reproduced with a combination of the two mechanisms (E{sub a} = 0.35 eV at T > 150 Degree-Sign C; V{sub B} = 420 V). Finally, the relationship between the vertical bulk current and the lateral AlGaN/GaN transistor leakage current is explored.

  2. Molecular beam epitaxy and structural anisotropy of m-plane InN grown on free-standing GaN

    SciTech Connect (OSTI)

    Koblmueller, G.; Hirai, A.; Wu, F.; Gallinat, C. S.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Metcalfe, G. D.; Shen, H.; Wraback, M. [U. S. Army Research Laboratory, Sensors and Electron Devices Directorate, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States)

    2008-10-27T23:59:59.000Z

    This study reports on the growth of high-quality nonpolar m-plane [1100] InN films on free-standing m-plane GaN substrates by plasma-assisted molecular beam epitaxy. Optimized growth conditions (In/N ratio {approx}1 and T=390-430 deg. C) yielded very smooth InN films with undulated features elongated along the [1120] orientation. This directionality is associated with the underlying defect structure shown by the anisotropy of x-ray rocking curve widths parallel to the [1120] (i.e., 0.24 deg. - 0.34 deg.) and [0001] (i.e., 1.2 deg. - 2.7 deg.) orientations. Williamson-Hall analysis and transmission electron microscopy identified the mosaic tilt and lateral coherence length and their associations with different densities of dislocations and basal-plane stacking faults. Ultimately, very low band gap energies of {approx}0.67 eV were measured by optical absorption similar to the best c-plane InN.

  3. Transport and optical properties of c-axis oriented wedge shaped GaN nanowall network grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Bhasker, H. P.; Dhar, S. [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra-400076 (India); Thakur, Varun; Kesaria, Manoj; Shivaprasad, S. M. [Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Bangalore- 560064 (India)

    2014-02-21T23:59:59.000Z

    The transport and optical properties of wedge-shaped nanowall network of GaN grown spontaneously on cplane sapphire substrate by Plasma-Assisted Molecular Beam Epitaxy (PAMBE) show interesting behavior. The electron mobility at room temperature in these samples is found to be orders of magnitude higher than that of a continuous film. Our study reveals a strong correlation between the mobility and the band gap in these nanowall network samples. However, it is seen that when the thickness of the tips of the walls increases to an extent such that more than 70% of the film area is covered, it behaves close to a flat sample. In the sample with lower surface coverage (?40% and ?60%), it was observed that the conductivity, mobility as well as the band gap increase with the decrease in the average tip width of the walls. Photoluminescence (PL) experiments show a strong and broad band edge emission with a large (as high as ? 90 meV) blue shift, compared to that of a continuous film, suggesting a confinement of carriers on the top edges of the nanowalls. The PL peak width remains wide at all temperatures suggesting the existence of a high density of tail states at the band edge, which is further supported by the photoconductivity result. The high conductivity and mobility observed in these samples is believed to be due to a “dissipation less” transport of carriers, which are localized at the top edges (edge states) of the nanowalls.

  4. Anisotropic strain relaxation and the resulting degree of polarization by one- and two-step growth in nonpolar a-plane GaN grown on r-sapphire substrate

    SciTech Connect (OSTI)

    Feng, Shih-Wei, E-mail: swfeng@nuk.edu.tw; Chen, Yu-Yu [Department of Applied Physics, National University of Kaohsiung No.700, Kaohsiung University Road, Nan-Tzu Dist., 811. Kaohsiung, Taiwan (China); Lai, Chih-Ming [Department of Electronic Engineering, Ming Chuan University, Taoyuan, Taiwan (China); Tu, Li-Wei [Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Han, Jung [Department of Electrical Engineering, Yale University, New Haven 06520, Connecticut (United States)

    2013-12-21T23:59:59.000Z

    Anisotropic strain relaxation and the resulting degree of polarization of the electronic transition in nonpolar a-plane GaN using one- and two-step growth are studied. By using two-step growth, a slower coalescence and a longer roughening-recovery process lead to larger anisotropic strain relaxation, a less striated surface, and lower densities of basal stacking fault (BSF) and prismatic stacking fault (PSF). It is suggested that anisotropic in-plane strains, surface striation, and BSF and PSF densities in nonpolar a-GaN are consequences of the rate of coalescence, the period of roughening-recovery process, and the degree of anisotropic strain relaxation. In addition, the two-step growth mode can enhance the degree of polarization of the electronic transition. The simulation results of the k?p perturbation approach show that the oscillator strength and degree of polarization of the electronic transition strongly depend on the in-plane strains upon anisotropic in-plane strain relaxation. The research results provide important information for optimized growth of nonpolar III-nitrides. By using two-step growth and by fabricating the devices on the high-quality nonpolar free-standing GaN substrates, high-efficiency nonpolar a-plane InGaN LEDs can be realized. Nonpolar a-plane InGaN/GaN LEDs can exhibit a strongly polarized light to improve the contrast, glare, eye discomfort and eye strain, and efficiency in display application.

  5. On the ammonolysis of Ga{sub 2}O{sub 3}: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga{sub 2}O{sub 3}-GaN

    SciTech Connect (OSTI)

    Roehrens, D.; Brendt, J.; Samuelis, D. [Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen (Germany); Martin, M., E-mail: martin@rwth-aachen.d [Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen (Germany)

    2010-03-15T23:59:59.000Z

    We investigated the ammonolysis of beta-Ga{sub 2}O{sub 3} at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a beta-Ga{sub 2}O{sub 3} related oxynitride phase was found, and the nitrogen solubility in beta-Ga{sub 2}O{sub 3} was found to be below the detection limit of about 2-3 at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the beta-Ga{sub 2}O{sub 3} phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis. - Graphical abstract: The ammonolysis of beta-Ga{sub 2}O{sub 3} powders forming GaN at temperatures of 600-780 deg. C was monitored by means of XRD, neutron diffraction and X-ray absorption spectroscopy in order to identify the possible intermediates and the solubility limit of nitrogen in the oxide lattice.

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

    SciTech Connect (OSTI)

    Huang, Bohr-Ran [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Liao, Chung-Chi [Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Ke, Wen-Cheng, E-mail: wcke@saturn.yzu.edu.tw; Chang, Yuan-Ching; Huang, Hao-Ping [Department of Mechanical Engineering, Yuan Ze University, Chung-Li 320, Taiwan (China); Chen, Nai-Chuan [Institute of Electro-Optical Engineering and Department of Electronic Engineering, Chang Gung University, Tao-Yuan 333, Taiwan (China)

    2014-03-21T23:59:59.000Z

    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.

  7. Elimination of columnar microstructure in N-face InAlN, lattice-matched to GaN, grown by plasma-assisted molecular beam epitaxy in the N-rich regime

    SciTech Connect (OSTI)

    Ahmadi, Elaheh; Wienecke, Steven; Keller, Stacia; Mishra, Umesh K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Shivaraman, Ravi; Wu, Feng; Kaun, Stephen W.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-02-17T23:59:59.000Z

    The microstructure of N-face InAlN layers, lattice-matched to GaN, was investigated by scanning transmission electron microscopy and atom probe tomography. These layers were grown by plasma-assisted molecular beam epitaxy (PAMBE) in the N-rich regime. Microstructural analysis shows an absence of the lateral composition modulation that was previously observed in InAlN films grown by PAMBE. A room temperature two-dimensional electron gas (2DEG) mobility of 1100 cm{sup 2}/V s and 2DEG sheet charge density of 1.9?×?10{sup 13}?cm{sup ?2} was measured for N-face GaN/AlN/GaN/InAlN high-electron-mobility transistors with lattice-matched InAlN back barriers.

  8. Atom probe analysis of interfacial abruptness and clustering within a single In{sub x}Ga{sub 1-x}N quantum well device on semipolar (1011) GaN substrate

    SciTech Connect (OSTI)

    Prosa, T. J.; Clifton, P. H. [Cameca Instruments Inc., Madison, Wisconsin 53711 (United States); Zhong, H.; Shivaraman, R.; Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Tyagi, A.; DenBaars, S. P.; Nakamura, S. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2011-05-09T23:59:59.000Z

    Pulsed laser atom probe tomography (APT) of In{sub x}Ga{sub 1-x}N single quantum well (SQW) grown on semipolar (1011) GaN orientation estimates the interior atomic composition within the SQW at 6.5{+-}0.7 at. % In, 46.2{+-}0.7 at. % Ga, and 47.3{+-}0.7 at. % N. The atom probe analysis is performed in both 'top-down' and 'cross-section' orientations. Self-consistent Schroedinger-Poisson simulation employing structural and compositional parameters obtained from APT results estimates the polarization field within the SQW at 720 kV/cm. A statistical method for the evaluation of indium homogeneity within the SQW is also considered.

  9. Atom probe analysis of interfacial abruptness and clustering within a single In{sub x}Ga{sub 1-x}N quantum well device on semipolar (10{bar 1}{bar 1}) GaN substrate

    SciTech Connect (OSTI)

    Prosa, T. J.; Clifton, P. H.; Zhong, H.; Tyagi, A.; Shivaraman, R.; DenBaars, S. P.; Nakamura, S.; Speck, J. S.

    2011-01-01T23:59:59.000Z

    Pulsed laser atom probe tomography (APT) of In{sub x}Ga{sub 1?x}N single quantum well (SQW) grown on semipolar (10{bar 1}{bar 1})GaN orientation estimates the interior atomic composition within the SQW at 6.5±0.7?at.?% In, 46.2±0.7?at.?% Ga, and 47.3±0.7?at.?% N. The atom probe analysis is performed in both “top-down” and “cross-section” orientations. Self-consistent Schrödinger–Poisson simulation employing structural and compositional parameters obtained from APT results estimates the polarization field within the SQW at 720 kV/cm. A statistical method for the evaluation of indium homogeneity within the SQW is also considered.

  10. GaN power electronics

    E-Print Network [OSTI]

    Lu, Bin

    Between 5 and 10% of the world's electricity is wasted as dissipated heat in the power electronic circuits needed, for example, in computer power supplies, motor drives or the power inverters of photovoltaic systems. This ...

  11. Impacts of anisotropic lattice relaxation on crystal mosaicity and luminescence spectra of m-plane Al{sub x}Ga{sub 1-x}N films grown on m-plane freestanding GaN substrates by NH{sub 3} source molecular beam epitaxy

    SciTech Connect (OSTI)

    Hoshi, T.; Hazu, K.; Ohshita, K.; Kagaya, M.; Onuma, T.; Chichibu, S. F. [CANTech, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Fujito, K. [Optoelectronics Laboratory, Mitsubishi Chemical Corporation, 1000 Higashi-Mamiana, Ushiku 300-1295 (Japan); Namita, H. [Mitsubishi Chemical Group Science and Technology Research Center, Inc., 8-3-1 Chuo, Ami, Inashiki 300-0332 (Japan)

    2009-02-16T23:59:59.000Z

    In-plane anisotropic lattice relaxation was correlated with the crystal mosaicity and luminescence spectra for m-plane Al{sub x}Ga{sub 1-x}N films grown on a freestanding GaN substrate by NH{sub 3}-source molecular beam epitaxy. The homoepitaxial GaN film exhibited A- and B-excitonic emissions at 8 K, which obeyed the polarization selection rules. For Al{sub x}Ga{sub 1-x}N overlayers, the m-plane tilt mosaic along c-axis was the same as the substrate as far as coherent growth was maintained (x{<=}0.25). However, it became more severe than along the a-axis for lattice-relaxed films (x{>=}0.52). The results are explained in terms of anisotropic lattice and thermal mismatches between the film and the substrate. Nonetheless, all the Al{sub x}Ga{sub 1-x}N films exhibited a near-band-edge emission peak and considerably weak deep emission at room temperature.

  12. ARM - News from the Gan Island Deployment

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadap Documentation TDMADAP : XDCnarrowbandheat fluxChinaNews : AMF Deployment,Media

  13. DFW Airport

    E-Print Network [OSTI]

    Dennis, J. R.

    2011-01-01T23:59:59.000Z

    M ay Ju n Ju l A ug S ep O ct N ov D ec D eg re e D ay s CDD HDD 95.4 ?F (35.2 ?C) 34 ?F (1.1 ?C) Annually 2370 HDD 2568 CDD 7 DFW Airport Overview ? Energy Annual Energy Consumption ? Board Managed Accounts ? ~200... and implement uniform space temperature setpoints ? Training (transfer of knowledge) 9 Continuous Commissioning? - Consolidated Rent-A-Car Center ? Opened in 2000 ? 130,000 sq.ft. of conditioned space ? 1.8 million sq.ft. parking garage ? Houses 10...

  14. Congestion delays at hub airports

    E-Print Network [OSTI]

    St. George, Martin J.

    1986-01-01T23:59:59.000Z

    A deterministic model was developed to study the effects of inefficient scheduling on flight delays at hub airports. The model bases the delay calculation on published schedule data and on user-defined airport capacities. ...

  15. Airline Passengers' Satisfaction with Airports

    E-Print Network [OSTI]

    Kim, Hyun Joo

    2012-02-14T23:59:59.000Z

    cuisine 16 Clean restrooms available 17 Clean airport 6 Comfortable areas to nap, read, and do business 7 D?cor that matches with the local culture 8 Diversity in shops and restaurants 9 Cleanliness (i.e. overall airport, restrooms, etc... airport employees.? Two items regarding cleanliness of overall airport and restrooms were also combined into attribute ?cleanliness,? and the current researcher aggregated three items related to the variety of shopping products and restaurants...

  16. airport market feasibility: Topics by E-print Network

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

    consider other resources your airport might possess that could generate additional revenue. Airport land is an asset Airport operators control if and how the land on an airport...

  17. airport burlingame california: Topics by E-print Network

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

    consider other resources your airport might possess that could generate additional revenue. Airport land is an asset Airport operators control if and how the land on an airport...

  18. AIRPORT LIGHTING Session Highlights

    E-Print Network [OSTI]

    Minnesota, University of

    Administration advisory circulars, available online at www.faa.gov or by mail at the following address: Federal Aviation Administration, Airports 800 Independence Ave. S.W. Washington, D.C. 20591 To qualify for federal AND NAVIGATIONAL AIDS A complete list of federal regulations for airfield lighting is located in Federal Aviation

  19. Boron alloying in GaN Laurian Escalantia)

    E-Print Network [OSTI]

    Hart, Gus

    phase. We performed preliminary calculations using wurtzite supercells and found that wz-BxGa1 xN band of wurtzite structures leads to coupling between conduction band minimum CBM and valence band maximum VBM implies that the zinc-blende structure will have a greater boron solubility than the wurtzite structure

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

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del(ANL-IN-03-032)8Li (59AJ76)ARM2, 2006Observations of the Madden Julian

  1. ARM - Field Campaign - ARM MJO Investigation Experiment on Gan Island

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del(ANL-IN-03-032)8Li (59AJ76)ARM2, 2006Observations of thegovCampaignsARM MJO

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

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of Science (SC)Integrated Codes |IsLove Your Home and It'll Love You Back Love Your Principal

  3. The impact of airline-airport relations on airport management decisions

    E-Print Network [OSTI]

    Cohen, Dayl Arlene

    1985-01-01T23:59:59.000Z

    Airlines, in the past, have had an important influence on airport operations through privileges granted them by the airport lease agreements. Airport administrators and sponsoring agencies have agreed to grant these ...

  4. Emergence of Secondary Airports and Dynamics of Regional Airport Systems in the United States

    E-Print Network [OSTI]

    Bonnefoy, Philippe A

    2006-11-21T23:59:59.000Z

    With the growing demand for air transportation and limited capacity at major airports, there is a need to increase the capacity of airport systems at the metropolitan area level. The increased use of secondary airports has ...

  5. Emergence of secondary airports and dynamics of regional airport systems in the United States

    E-Print Network [OSTI]

    Bonnefoy, Philippe A

    2005-01-01T23:59:59.000Z

    With the growing demand for air transportation and limited capacity at major airports, there is a need to increase the capacity of airport systems at the metropolitan area level. The increased use of secondary airports has ...

  6. Kansai International Airport Alireza Abrishamkar

    E-Print Network [OSTI]

    Prevedouros, Panos D.

    ;Subsidiaries to KIAC KIA Heating & Cooling Supply Co., Ltd. KIA Information & Telecommunications Network Co Co., Ltd. Kansai Airport Agency Co., Ltd. Subsidiaries to KIAC KIA Heating & Cooling Supply Co., Ltd

  7. Implementing Solar Technologies at Airports

    SciTech Connect (OSTI)

    Kandt, A.; Romero, R.

    2014-07-01T23:59:59.000Z

    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.

  8. DRAFT 1999 DRAFT AIRPORT PRIVATIZATION

    E-Print Network [OSTI]

    Entekhabi, Dara

    Professor and Chairman Technology and Policy Program Room E40-245 Massachusetts Institute of Technology PRIVATIZATION ISSUES FOR THE UNITED STATES Richard de Neufville Technology and Policy Program Massachusetts airports into wholly private businesses. Most privatization projects involve substantial regulation

  9. ST. LOUIS AIRPORT/ HAZELWOOD INTERIM

    E-Print Network [OSTI]

    and remote disposal of contaminated soils on various private properties, under removal action authority the Airport resulted in the contamination of numerous private and municipally owned properties. The St. Louis radioactively-contaminated sites are part of the Formerly Utilized Sites Remedial Action Program (FUSRAP

  10. Improving public transportation to Boston Logan International Airport

    E-Print Network [OSTI]

    Cao, Siyuan, M. Eng. Massachusetts Institute of Technology

    2013-01-01T23:59:59.000Z

    Boston Logan International Airport is the largest airport in New England and the 1 9 th busiest airport in the United States, serving 29.3 million passengers (arrivals and departures) in 2012. There are approximately 36,900 ...

  11. Demonstration of Reduced Airport Congestion Through Pushback Rate Control

    E-Print Network [OSTI]

    Simaiakis, Ioannis

    2011-02-02T23:59:59.000Z

    Airport surface congestion results in significant increases in taxi times, fuel burn and emissions at major airports. This paper presents the field tests of a control strategy to airport congestion control at Boston Logan ...

  12. airports: Topics by E-print Network

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

    Summary: radioactively-contaminated sites are part of the Formerly Utilized Sites Remedial Action Program (FUSRAP the Airport resulted in the contamination of numerous...

  13. airport pricing strategies: Topics by E-print Network

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

    provide you with useful new information on project funding Minnesota, University of 88 TUCSON AIRPORT HOTELS 1. Hyatt Place Tucson Airport Engineering Websites Summary: Ph:...

  14. airports aircraft noise: Topics by E-print Network

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

    63 Air freight : the problems of airport restrictions : final report on the Conference of Air Cargo Industry Considerations of Airport Curfews MIT - DSpace Summary: Noise...

  15. airport operations: Topics by E-print Network

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

    Energy Storage, Conversion and Utilization Websites Summary: manager and approve funding and high-level decisions regard- ing airport operations. Most airports in the United...

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

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

    San Antonio Airport Terminal Generating Clean Power EECBG Success Story: New San Antonio Airport Terminal Generating Clean Power January 27, 2011 - 2:03pm Addthis The new...

  17. New airport liquid analysis system undergoes testing at Albuquerque...

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

    New airport liquid analysis system New airport liquid analysis system undergoes testing at Albuquerque International Sunport A new tool that distinguishes potential-threat liquids...

  18. Siting Solar Photovoltaics at Airports: Preprint

    SciTech Connect (OSTI)

    Kandt, A.; Romero, R.

    2014-06-01T23:59:59.000Z

    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.

  19. You will arrive at International Terminal of Haneda Airport. http://www.tokyo-airport-bldg.co.jp/cn/

    E-Print Network [OSTI]

    Hasegawa, Shuji

    You will arrive at International Terminal of Haneda Airport. http://www.tokyo-airport-bldg.co.jp/cn/ http://www.tokyo-airport-bldg.co.jp/kr/ Move to Terminal 1 or 2 (domestic terminal) by free terminal shuttle bus in Airport. Buy a ticket for Monorail and take Monorail to Hamamatsu-Cho Station () (Terminal

  20. Nitride semiconductor Surface and interface characterization and device design

    E-Print Network [OSTI]

    Zhang, Hongtao

    2006-01-01T23:59:59.000Z

    a a where we assume a GaN substrate for the thin film. c 13assuming a GaN GaN substrate. Because the spontaneouslayer are grown on the GaN substrate and because the lattice

  1. Airport Tower Automation With the construction of Bergstrom International Airport in South Austin, the FAA has

    E-Print Network [OSTI]

    Browne, James C.

    Airport Tower Automation With the construction of Bergstrom International Airport in South Austin, air traffic pattern, and incoming airplanes. The control system will be called the "tower. Collisions most often occur during take-offs or landings, so the tower must ensure proper spacing between

  2. Northern New Mexico regional airport market feasibility

    SciTech Connect (OSTI)

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

    1998-06-01T23:59:59.000Z

    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.

  3. Las Cruces International Airport (LRU) Pavement Condition and Analysis

    E-Print Network [OSTI]

    Cal, Mark P.

    Las Cruces International Airport (LRU) Pavement Condition and Analysis Submitted to: Jane M. Lucero ........................................................................................................3. Airport Maintenance 14 .......................................4. Predicted Pavement Conditions Assuming No Maintenance 14 ...............Table 4. Predicted Pavement Conditions (PCI) Assuming

  4. airport strainer box: Topics by E-print Network

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

    based on a runway s length as well as wind indicator and other for federal funding, an airport must be classified in the national plan of integrated airport systems...

  5. Value of Options in Airport Expansion - Example of AICM

    E-Print Network [OSTI]

    Morgado, Frederico

    Investments decisions for airport capacity expansion are usually taken, either when demand exceeds the current capacity and the airport is working under congestion, or when current demand is expected to overcome current ...

  6. 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...

  7. Of airports and architecture : exercises in public form

    E-Print Network [OSTI]

    Fouad, Daniel James

    2006-01-01T23:59:59.000Z

    Airports as an architectural and urban typology typically lack physical and spatial integration with their urban context. Contrary to the city, airports have evolved into semi-autonomous spaces and products of political ...

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

    SciTech Connect (OSTI)

    Edwards, Donna M.; Price, Phillip N. (Lawrence Berkeley National Laboratory, Berkeley, CA); Gordon, Susanna P.; Gadgil, Ashok (Lawrence Berkeley National Laboratory, Berkeley, CA)

    2005-05-01T23:59:59.000Z

    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.

  9. Relative efficiency of Argentinean airports Gustavo Ferro1

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Relative efficiency of Argentinean airports Gustavo Ferro1 , Fabián Garitta2 and Carlos A. Romero3 Key Words: efficiency, airports, Argentina Abstract: The main objectives of this paper are to measure the relative efficiency of Argentinean airports, and to infer possible regulatory consequences

  10. Energy Management Practices at Dalls/Fort Worth International Airport

    E-Print Network [OSTI]

    Dennis, J. R.

    2013-01-01T23:59:59.000Z

    of the Airport?s energy conservation building codes and standards. Proposed Street Light for Southgate Fanwall AHU (TRIP) Energy Management Practices at DFW Airport, October 9, 2013 Demand-Side Management (cont.) ? Continuous Commissioning? ? Optimizes... Management Section ? Structure & Mission ? Supply-Side Management ? Reliability ? Cost (Risk) mitigation ? Environmental stewardship ? Demand-Side Management ? Energy monitoring ? Energy audits ? Energy standards ? Continuous Commissioning...

  11. Noise Load Management at Amsterdam Airport Schiphol

    E-Print Network [OSTI]

    Boucherie, Richard J.

    -airports in Europe. All flight movements are controlled by Air Traffic Control the Netherlands (LVNL), whose main, the Netherlands Stochastic Operations Research, University of Twente, the Netherlands Air Traffic Control driving force for the Dutch economy. All flight movements are controlled by Air Traffic Con- trol

  12. AIRPORT SNOW AND ICE CONTROL Session Highlights

    E-Print Network [OSTI]

    Minnesota, University of

    , and specific to the Federal Aviation Administration (FAA)/Federal Aviation Regulation (FAR) circular under" document. AirTAP is a statewide assistance program for aviation personnel that offers practical instruction be submitted to the FAA for approval. The airport owner's legal staff should review a snow plan before

  13. Assembly of ordered carbon shells on GaN nanowires Eli Suttera

    E-Print Network [OSTI]

    in the thin wires. Given the large surface-to-volume ratio of NWs and the strong effect of sur- face states. Such junctions could form the basis for innovative electronic and optoelectronic devices e.g., photovoltaic cells of catalytic effects in semicon- ductors can be circumvented and C shells can be formed around nanowires whose

  14. Photoluminescence and Raman study of compensation effects in Mg-doped GaN epilayers

    E-Print Network [OSTI]

    Nabben, Reinhard

    by metalorganic vapor phase ep- itaxy MOVPE in an AIX 200 rf reactor. The layers were thermally annealed in N2 performed with either a HeCd Laser or, for higher excitation densities, using the third harmonic at 355 nm of an actively mode-locked Nd:YAG laser giving pulses of 80 ps duration with 76 MHz repetition rate. The samples

  15. Hall photovoltage deep-level spectroscopy of GaN films I. Shalish*

    E-Print Network [OSTI]

    Shalish, Ilan

    in semiconductor Hall voltage is proposed as a method to charac- terize deep levels. An analytical expression nucleation layer at temperatures lower than the typical growth temperature providing a bridge over

  16. Photoelectrochemical undercut etching for fabrication of GaN microelectromechanical systems

    E-Print Network [OSTI]

    MacDonald, Noel C.

    -scale structures for microelectromechanical systems (MEMS), and the fracture properties of mineralized tissue for microelectromechanical systems (MEMS), specifically involving the high-cycle fatigue of micron-scale thin films

  17. On-wafer seamless integration of GaN and Si (100) electronics

    E-Print Network [OSTI]

    Chung, Jinwook

    The high thermal stability of nitride semiconductors allows for the on-wafer integration of (001)Si CMOS electronics and electronic devices based on these semiconductors. This paper describes the technology developed at ...

  18. Metalorganic Chemical Vapor Deposition Route to GaN Nanowires with Triangular

    E-Print Network [OSTI]

    Yang, Peidong

    -free environment at atmospheric pressure. TMG was kept cool in a -10 °C temperature bath. Nitrogen, used a total nitrogen flow rate of 250 sccm. These were supplied via a 4-mm i.d. quartz tube. Hydrogen and ammonia sources were supplied via a 22-mm i.d. outer quartz tube at a total flow rate of 155 sccm

  19. Development of a Bulk GaN Growth Technique for Low Defect Density...

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

    * Frank Delnick * David Ingersoll * Bill Averill * Bob Biefeld * Mike Coltrin * Ryan Egidi * National Energy Technology LaboratoryEnergy Efficiency and Renewable Energy Office...

  20. Ion-beam-induced chemical disorder in GaN. | EMSL

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

    defect formation processes between these layers. Citation: Ishimaru M, Y Zhang, and WJ Weber.2009."Ion-beam-induced chemical disorder in GaN."Journal of Applied Physics...

  1. ROBUST ISOLATED SPEECH RECOGNITION USING BINARY MASKS Seliz Gulsen Karado~gan1

    E-Print Network [OSTI]

    and the observation vectors are quantized with the K-means algorithm using Hamming distance. It is found pattern obtained with the comparison of the target and the noise signal energies with priori information

  2. Analysis of Protein Sequence/Structure Similarity Relationships Hin Hark Gan,*

    E-Print Network [OSTI]

    Schlick, Tamar

    Institute of Mathematical Sciences, The Howard Hughes Medical Institute, § Department of Biology, ¶ New York University Medical School, and Department of Physics, New York University, New York, New York/dissimilarity relationships and provide novel energetic analyses of these relationships. To aid our analysis, we divide

  3. Ferromagnetism in GaN: Gd: A density functional theory study

    SciTech Connect (OSTI)

    Stevenson, Cynthia; Stevenson, Cynthia

    2008-02-04T23:59:59.000Z

    First principle calculations of the electronic structure and magnetic interaction of GaN:Gd have been performed within the Generalized Gradient Approximation (GGA) of the density functional theory (DFT) with the on-site Coulomb energy U taken into account (also referred to as GGA+U). The ferromagnetic p-d coupling is found to be over two orders of magnitude larger than the s-d exchange coupling. The experimental colossal magnetic moments and room temperature ferromagnetism in GaN:Gd reported recently are explained by the interaction of Gd 4f spins via p-d coupling involving holes introduced by intrinsic defects such as Ga vacancies.

  4. MICH]GAN TECHNOLOGICALUNIVERSITY OMB CIRCULAR A-].33 SUPPI,EMENTARYFINAI{CIAI, REPORT

    E-Print Network [OSTI]

    AUDITORS ' REPORITSON COMPIJIA}ICE - The University as an EntiLY - Federal Financial Assistance Programs THE UNIVERSITY AS AN ENTITY To the Board of Control-, Michigan Technological University: We have audited the basic financial statements of MICHIGAN TECHNOLOGICALUNIVERSITY (the .University

  5. Wavelength limits for InGaN quantum wells on GaN

    SciTech Connect (OSTI)

    Pristovsek, Markus, E-mail: markus@pristovsek.de [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)] [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2013-06-17T23:59:59.000Z

    The emission wavelength of coherently strained InGaN quantum wells (QW) is limited by the maximum thickness before relaxation starts. For high indium contents x>40% the resulting wavelength decreases because quantum confinement dominates. For low indium content x<40% the electron hole wave function overlap (and hence radiative emission) is strongly reduced with increasing QW thickness due to the quantum confined Stark effect and imposes another limit. This results in a maximum usable emission wavelength at around 600?nm for QWs with 40%-50% indium content. Relaxed InGaN buffer layers could help to push this further, especially on non- and semi-polar orientations.

  6. Optimal Decentralized Protocol for Electric Vehicle Charging Lingwen Gan Ufuk Topcu Steven Low

    E-Print Network [OSTI]

    Low, Steven H.

    is to shift the load due to electric vehicles to fill the overnight electricity demand valley. In each iteration of the proposed protocol, electric vehicles choose their own charging profiles for the following day according to the price profile broadcast by the utility, and the utility updates the price profile

  7. Piezo-Phototronic Effect on Electroluminescence Properties of p-Type GaN Thin Films

    E-Print Network [OSTI]

    Wang, Zhong L.

    on ZnO nanowires, such as photocells,10 solar cells,11 and light-emitting diodes.12 So far, there have-emitting diodes, laser diodes, flat-panel display devices, and so forth.1-5 Recently, wurtzite-structured Ga

  8. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOE Patents [OSTI]

    Wang, George T. (Albuquerque, NM); Li, Qiming (Albuquerque, NM); Creighton, J. Randall (Albuquerque, NM)

    2010-06-29T23:59:59.000Z

    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.

  9. Seamless On-Wafer Integration of Si(100) MOSFETs and GaN HEMTs

    E-Print Network [OSTI]

    Piner, Edwin L.

    The first on-wafer integration of Si(100) MOSFETs and AlGaN/GaN high electron mobility transistors (HEMTs) is demonstrated. To enable a fully Si-compatible process, we fabricated a novel Si(100)-GaN-Si(100) virtual substrate ...

  10. Observation of whispering gallery modes in nonpolar m-plane GaN microdisks

    SciTech Connect (OSTI)

    Tamboli, Adele C.; Schmidt, Mathew C.; Hirai, Asako; DenBaars, Steven P.; Hu, Evelyn L. [Department of Materials, University of California, Santa Barbara, California 93106-5050 (United States)

    2009-06-22T23:59:59.000Z

    We have fabricated nonpolar GaN/InGaN microdisks using band-gap selective photoelectrochemical etching. These microdisks have a smoother optical cavity than our previous c-plane microdisks, and they support whispering gallery modes with quality factors as high as 2000 after a focused ion beam treatment to the quantum wells. Because of the lack of a Stokes shift in the quantum wells of these m-plane disks, absorption losses play a much more significant role than in our earlier c-plane microdisks, and the light which couples into the modes is emission from the InGaN post rather than the quantum wells within the cavity.

  11. Free Carrier Absorption due to Dislocation Scattering in GaN Quantum Wells

    SciTech Connect (OSTI)

    Vaidya, R. G. [Department of Physics, Karnatak University, Dharwad, Karnataka (India); Department of Physics, Tumkur University, Tumkur, Karnataka, 572102 (India); Sankeshwar, N. S.; Mulimani, B. G. [Department of Physics, Karnatak University, Dharwad, Karnataka (India)

    2011-10-20T23:59:59.000Z

    Free carrier absorption (FCA) is studied in quantum well structures assuming electrons to be scattered by dislocations via strain field. Expression for FCA coefficient, {alpha} is obtained assuming radiation field to be polarized along the plane of quantum well. Numerical results of {alpha}, as function of photon frequency, {Omega} and well width, d are presented. Calculations show, FCA to decrease with increase in {Omega} with a kink observed at {Omega} = 7.79x10{sup 13} s{sup -1} indicating onset of inter subband transitions. {alpha} is found to be proportional to d{sup -3} and to increase with increase in dislocation density.

  12. Local-Orbital Ordering on Cr{sup 3+} Ions Doped in GaN

    SciTech Connect (OSTI)

    Emura, S.; Kimura, S.; Tokuda, K.; Zhou, Yi-Kai; Hasegawa, S.; Asahi, H. [The Institute of Scientific and Industrial research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047 (Japan)

    2010-01-04T23:59:59.000Z

    The X-ray linear dichroism (XLD) at the pre-peaks of Cr K-edge, which corresponds to the transition from 1s to 3d orbital, is explicitly observed for cubic GaCrN and hexagonal GaCrN. This observation of XLD in the cubic structure of GaCrN indicates that CrN{sub 4} tetrahedron in the local coordination suffers inhomogeneous or anisotropic deformation. This deformation is also confirmed through the analysis of the X-ray absorption fine structure of Cr K-edge of the hexagonal GaCrN, indicating the shift of Cr{sup +3} ion along the <111> direction.

  13. Enhancing erbium emission by strain engineering in GaN heteroepitaxial I. W. Feng,1

    E-Print Network [OSTI]

    Jiang, Hongxing

    the GaN:Er epilayer and the substrate, were probed. The emission intensity at 1.54 m increased.54 m emission intensity, induced by lattice mismatch be- tween the GaN:Er epilayer and the substrate report on the MOCVD growth of GaN:Er on various substrates and the resulting optical characteristics

  14. SELF-POWERED CONFORMABLE DEFORMATION SENSOR EXPLOITING THE COLLECTIVE PIEZOELECTRIC EFFECT OF SELF-ORGANIZED GAN

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    , design, fabricate and characterize a thin, conformable low-cost impact detection sensor based additivity of their nanoscale intrinsic properties, which enables to appeal to classical fabrication research effort is put towards the integration of new electronic functionalities in everyday-life objects

  15. Airport testing an explosives detection portal

    SciTech Connect (OSTI)

    Rhykerd, C.; Linker, K.; Hannum, D.; Bouchier, F.; Parmeter, J.

    1998-08-01T23:59:59.000Z

    At the direction of the US Congress, following the Pan Am 103 and TWA 800 crashes, the Federal Aviation Administration funded development of non-invasive techniques to screen airline passengers for explosives. Such an explosives detection portal, developed at Sandia National Laboratories, was field tested at the Albuquerque International airport in September 1997. During the 2-week field trial, 2,400 passengers were screened and 500 surveyed. Throughput, reliability, maintenance and sensitivity were studied. Follow-up testing at Sandia and at Idaho National Engineering and Environmental Laboratory was conducted. A passenger stands in the portal for five seconds while overhead fans blow air over his body. Any explosive vapors or dislodged particles are collected in vents at the feet. Explosives are removed from the air in a preconcentrator and subsequently directed into an ion mobility spectrometer for detection. Throughput measured 300 passengers per hour. The non-invasive portal can detect subfingerprint levels of explosives residue on clothing. A survey of 500 passengers showed a 97% approval rating, with 99% stating that such portals, if effective, should be installed in airports to improve security. Results of the airport test, as well as operational issues, are discussed.

  16. airport demonstration project: Topics by E-print Network

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

    unable to attend, we hope it will provide you with useful new information on project funding Minnesota, University of 2 DEMONSTRATION OF REDUCED AIRPORT CONGESTION THROUGH...

  17. airport extension project: Topics by E-print Network

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

    unable to attend, we hope it will provide you with useful new information on project funding Minnesota, University of 2 Key Findings of 2013 ATRS Global Airport Performance...

  18. airport ground transportation: Topics by E-print Network

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

    control problem consists of coordinating the movements of airplanes on the airport Hoffmann, Jrg -FR 6.2 9 Improving Aircraft Sequencing and Separation at a Small Aircraft...

  19. airport facilities: Topics by E-print Network

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

    Summary: radioactively-contaminated sites are part of the Formerly Utilized Sites Remedial Action Program (FUSRAP the Airport resulted in the contamination of numerous...

  20. airport gardermoenaquifer thermal: Topics by E-print Network

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

    Summary: radioactively-contaminated sites are part of the Formerly Utilized Sites Remedial Action Program (FUSRAP the Airport resulted in the contamination of numerous...