Sample records for al wa ga

  1. Dopant-Free GaN/AlN/AlGaN Radial Nanowire Heterostructures as High

    E-Print Network [OSTI]

    Li, Yat

    Dopant-Free GaN/AlN/AlGaN Radial Nanowire Heterostructures as High Electron Mobility Transistors, 2006 ABSTRACT We report the rational synthesis of dopant-free GaN/AlN/AlGaN radial nanowire-organic chemical vapor deposition (MOCVD). Transmission electron microscopy (TEM) studies reveal that the GaN/ AlN/AlGaN

  2. AlGaN/GaN-based power semiconductor switches

    E-Print Network [OSTI]

    Lu, Bin, Ph. D. Massachusetts Institute of Technology

    2013-01-01T23:59:59.000Z

    AlGaN/GaN-based high-electron-mobility transistors (HEMTs) have great potential for their use as high efficiency and high speed power semiconductor switches, thanks to their high breakdown electric field, mobility and ...

  3. Advantages of the Blue InGaN/GaN Light-Emitting Diodes with an AlGaN/GaN/AlGaN Quantum Well Structured Electron Blocking Layer

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Advantages of the Blue InGaN/GaN Light-Emitting Diodes with an AlGaN/GaN/AlGaN Quantum Well ABSTRACT: InGaN/GaN light-emitting diodes (LEDs) with p-(AlGaN/GaN/AlGaN) quantum well structured electron. The proposed QWEBL LED structure, in which a p-GaN QW layer is inserted in the p-AlGaN electron blocking layer

  4. Role of Electrochemical Reactions in the Degradation Mechanisms of AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Role of Electrochemical Reactions in the Degradation Mechanisms of AlGaN/GaN HEMTs Feng Gao1, USA tpalacios@mit.edu; (617) 324-2395 Keywords: AlGaN/GaN HEMTs, reliability, moisture, electro-chemical reactions Abstract The nature of structural degradation in AlGaN/GaN high electron mobility transistors

  5. Effect of dislocations on electron mobility in AlGaN/GaN and AlGaN/AlN/GaN heterostructures

    SciTech Connect (OSTI)

    Kaun, Stephen W.; Burke, Peter G.; Kyle, Erin C. H.; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wong, Man Hoi; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2012-12-24T23:59:59.000Z

    Al{sub x}Ga{sub 1-x}N/GaN (x = 0.06, 0.12, 0.24) and AlGaN/AlN/GaN heterostructures were grown on 6 H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with threading dislocation densities of {approx}2 Multiplication-Sign 10{sup 10}, {approx}5 Multiplication-Sign 10{sup 8}, and {approx}5 Multiplication-Sign 10{sup 7} cm{sup -2}, respectively. All growths were performed under Ga-rich conditions by plasma-assisted molecular beam epitaxy. Dominant scattering mechanisms with variations in threading dislocation density and sheet concentration were indicated through temperature-dependent Hall measurements. The inclusion of an AlN interlayer was also considered. Dislocation scattering contributed to reduced mobility in these heterostructures, especially when sheet concentration was low or when an AlN interlayer was present.

  6. Analysis of InGaN light-emitting diodes with GaN-AlGaN and AlGaN-GaN composition-graded barriers

    SciTech Connect (OSTI)

    Yang, Yujue; Wang, Junxi; Li, Jinmin; Zeng, Yiping, E-mail: ypzeng@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2014-06-21T23:59:59.000Z

    The effects of InGaN-based light-emitting diodes (LEDs) with Al composition increasing and decreasing GaN-AlGaN barriers along the growth direction are studied numerically. Simulation results suggest that the LEDs with GaN-AlGaN composition-decreased barriers show more significant enhancement of light-output power and internal quantum efficiency than LEDs with composition-increasing GaN-AlGaN barriers when compared with the conventional LED with GaN barriers, due to the improvement in hole injection efficiency and electron blocking capability. Moreover, the optical performance is further improved by replacing GaN-AlGaN barriers with AlGaN-GaN barriers of the same Al composition-decreasing range, which are mainly attributed to the modified band diagrams. In addition, the major causes of the different efficiency droop behaviors for all the designed structures are explained by the electron leakage current and the different increase rates of hole concentration with injection current.

  7. GaAs/InGaP/AlGaAs quantum-well infrared photodetectors

    SciTech Connect (OSTI)

    Keshagupta, P.; Radpour, F. [Univ. of Cincinnati, OH (United States)

    1994-12-31T23:59:59.000Z

    In this paper, a new quantum-well infrared photodetector (QWIP) based on bound-to-miniband transitions in a GaAs/InGaP quantum well with GaAs/AlGaAs short superlattice barriers is presented and compared with the conventional GaAs/InGaP QWIPs. Results of the theoretical calculations of the detector parameters and the preliminary fabrication results of an embedded-well to miniband (EWTMB) GaAs/InGaP/AlGaAs quantum well/superlattice detector are presented. The advantages of the proposed design include improvement of the material quality, ability to adjust the peak wavelength in 8--12 {micro}m range, and in the lower dark current.

  8. Structural, morphological, and optical properties of AlGaN/GaN heterostructures with AlN buffer and interlayer

    E-Print Network [OSTI]

    Ozbay, Ekmel

    N buffer layer BL grown on an Al2O3 substrate and an AlN IL grown under the AlGaN ternary layer TL. In the present study, we investigate the effects of an AlN BL on an Al2O3 substrate and an AlN IL between an AlGaNStructural, morphological, and optical properties of AlGaN/GaN heterostructures with AlN buffer

  9. Red emitting photonic devices using InGaP/InGaAlP material system

    E-Print Network [OSTI]

    Kangude, Yamini

    2005-01-01T23:59:59.000Z

    In this thesis, two red emitting photonic devices are presented using the InGaP/InGaAlP material system. InGaP/InGaAlP material system provides large flexibility in the band gap energy while being lattice matched to GaAs ...

  10. Low frequency noise in AlGaN/InGaN/GaN double heterostructure field effect transistors

    E-Print Network [OSTI]

    Pala, Nezih

    Torr and consisted of a 1.4 lm undoped GaN buffer layer on i-SiC substrate, * Corresponding authorLow frequency noise in AlGaN/InGaN/GaN double heterostructure field effect transistors N. Pala a November 2002 Abstract Low-frequency noise in AlGaN/InGaN/GaN double heterostructure field effect

  11. Free carrier accumulation at cubic AlGaN/GaN heterojunctions Q. Y. Wei,1

    E-Print Network [OSTI]

    As, Donat Josef

    ) substrate,7 with GaN and AlGaN layer thickness of 600 nm and 30 nm, respectively. The layer thicknessFree carrier accumulation at cubic AlGaN/GaN heterojunctions Q. Y. Wei,1 T. Li,1 J. Y. Huang,1 F. A (Received 24 February 2012; accepted 19 March 2012; published online 3 April 2012) Cubic Al0.3Ga0.7N/GaN

  12. AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by PEALD

    E-Print Network [OSTI]

    Boyer, Edmond

    AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by PEALD R. Meunier1 , A, 38054 Grenoble Cedex 9, France 2 LAAS-CNRS, 7 Avenue du Colonel Roche, 31400 Toulouse, France AlGaN /GaN behavior. Those trapped charges can be associated to the carbon contamination of the AlGaN surface

  13. Electron mobility enhancement in AlN/GaN/AlN heterostructures with InGaN nanogrooves

    E-Print Network [OSTI]

    improve the room-temperature carrier mobility in wurtzite AlN/GaN/AlN heterostructures, which is limited consider a narrow groove made of InxGa1-xN with small In content x inside a wurtzite AlN/GaN/AlN heteroN 2 nm /GaN 3 nm /AlN 3 nm . A well-known feature of wurtzite heterostructures is a strong buit

  14. Intersubband absorption in AlN/GaN/AlGaN coupled quantum wells

    SciTech Connect (OSTI)

    Driscoll, Kristina; Bhattacharyya, Anirban; Moustakas, Theodore D.; Paiella, Roberto; Zhou, Lin; Smith, David J. [Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary's Street, Boston, Massachusetts 02215 (United States); Department of Physics and School of Materials, Arizona State University, Tempe, Arizona 85287 (United States)

    2007-10-01T23:59:59.000Z

    AlN/GaN/AlGaN coupled quantum wells grown by molecular beam epitaxy have been developed and characterized via intersubband absorption spectroscopy. In these structures, an AlGaN layer of sufficiently low Al content is used to achieve strong interwell coupling without the need for ultrathin inner barriers. At the same time, AlN is used in the outer barriers to provide the large quantum confinement required for near-infrared intersubband transitions. The composition of the inner barriers also provides a continuously tunable parameter to control the coupling strength. Double intersubband absorption peaks are measured in each sample, at photon energies in good agreement with theoretical expectations.

  15. Self-aligned AlGaN/GaN transistors for sub-mm wave applications

    E-Print Network [OSTI]

    Saadat, Omair I

    2010-01-01T23:59:59.000Z

    This thesis describes work done towards realizing self-aligned AlGaN/GaN high electron mobility transistors (HEMTs). Self-aligned transistors are important for improving the frequency of AlGaN/GaN HEMTs by reducing source ...

  16. Continuous-wave operation of extremely low-threshold GaAs/AlGaAs broad-area injection laser on (110) Si substrate at room temperature

    SciTech Connect (OSTI)

    Chen, H.Z.; Ghaffari, A.; Wang, H.; Morkoc, H.; Yariv, A.

    1987-10-01T23:59:59.000Z

    Room-temperature continuous-wave operation of large-area (120 ..mu..m x 980 ..mu..m) GaAs/AlGaAs graded-refractive-index separate-confinement heterostructure lasers on (100)Si substrates has been obtained. Minimum threshold-current densities of 214 A/cm/sup 2/ (1900-..mu..m cavity length), maximum slope efficiencies of about 0.8 W/A (600-..mu..m cavity length), and optical power in excess of 270 mW/facet (900-..mu..m cavity length) have been observed under pulsed conditions.

  17. AlGaN/GaN/AlN quantum-well field-effect transistors with highly resistive AlN epilayers

    E-Print Network [OSTI]

    Jiang, Hongxing

    AlGaN/GaN/AlN quantum-well field-effect transistors with highly resistive AlN epilayers Z. Y. Fana 66506-2601 Received 23 November 2005; accepted 5 January 2006; published online 16 February 2006 AlGaN/GaN/AlN quantum-well field-effect transistors have been demonstrated. By replacing a semi-insulating GaN epilayer

  18. 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.

  19. Violet to deep-ultraviolet InGaN/GaN and GaN/AlGaN quantum structures for UV electroabsorption modulators

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Violet to deep-ultraviolet InGaN/GaN and GaN/AlGaN quantum structures for UV electroabsorption In this paper, we present four GaN based polar quantum structures grown on c-plane embedded in p-i-n diode GaN/AlGaN quantum structures for operation in the deep-UV spectral region and the other three

  20. Monolithic Millimeter-wave Distributed Amplifiers using AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    York, Robert A.

    Monolithic Millimeter-wave Distributed Amplifiers using AlGaN/GaN HEMTs Rajkumar Santhakumar, Yi have been designed and fabricated using AlGaN/GaN HEMTs. One of them uses a standard HEMT for the unit-gate distributed amplifier achieves a CW peak output power of 1W and a PAE of about 16% at 4GHz. Index Terms -- GaN

  1. GaN/AlGaN heterojunction infrared detector responding in 814 and 2070 m ranges

    E-Print Network [OSTI]

    Perera, A. G. Unil

    GaN/AlGaN heterojunction infrared detector responding in 8­14 and 20­70 m ranges G. Ariyawansa, M October 2006 A GaN/AlGaN heterojunction interfacial work function internal photoemission infrared detector, the work demonstrates 54 m 5.5 THz operation of the detector based on 1s­2p± transition of Si donors in GaN

  2. Reactive codoping of GaAlInP compound semiconductors

    DOE Patents [OSTI]

    Hanna, Mark Cooper (Boulder, CO); Reedy, Robert (Golden, CO)

    2008-02-12T23:59:59.000Z

    A GaAlInP compound semiconductor and a method of producing a GaAlInP compound semiconductor are provided. The apparatus and method comprises a GaAs crystal substrate in a metal organic vapor deposition reactor. Al, Ga, In vapors are prepared by thermally decomposing organometallic compounds. P vapors are prepared by thermally decomposing phospine gas, group II vapors are prepared by thermally decomposing an organometallic group IIA or IIB compound. Group VIB vapors are prepared by thermally decomposing a gaseous compound of group VIB. The Al, Ga, In, P, group II, and group VIB vapors grow a GaAlInP crystal doped with group IIA or IIB and group VIB elements on the substrate wherein the group IIA or IIB and a group VIB vapors produced a codoped GaAlInP compound semiconductor with a group IIA or IIB element serving as a p-type dopant having low group II atomic diffusion.

  3. AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors using barium strontium titanate

    E-Print Network [OSTI]

    York, Robert A.

    AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors using barium strontium; published 13 October 2004) Use of high-k gate dielectrics in AlGaN/GaN heterostructure field transconductance and pinchoff voltage. To achieve this, AlGaN/GaN metal-oxide-semiconductor heterostructure field

  4. In this paper, an AlGaN/GaN high electron mobility transistor (HEMT) device based on a

    E-Print Network [OSTI]

    Yang, Kyounghoon

    205 Abstract In this paper, an AlGaN/GaN high electron mobility transistor (HEMT) device basedBm at 2 GHz have been demonstrated from the fabricated device. 1. Introduction In recent years, AlGaN/GaN noise amplifier and switch. Superior results have been reported in microwave power performance of AlGaN/GaN

  5. A New Architecture for AlGaN/GaN HEMT Frequency Doubler Using Active Integrated Antenna Design Approach

    E-Print Network [OSTI]

    Itoh, Tatsuo

    A New Architecture for AlGaN/GaN HEMT Frequency Doubler Using Active Integrated Antenna Design presents a new architecture for an AlGaN/GaN HEMT frequency doubler using the active integrated antenna. The antenna operates as a fundamental frequency reflector in this circuit. Using AlGaN/GaN with 1mm gate

  6. Generation-Recombination Defects In AlGaN/GaN HEMT On SiC Substrate,

    E-Print Network [OSTI]

    Boyer, Edmond

    Generation-Recombination Defects In AlGaN/GaN HEMT On SiC Substrate, Evidenced By Low Frequency Aristide Briand, 92.195 Meudon, France Abstract. Wide bandgap devices such as AlGaN/GaN High Electron of GR- bulges related respectively to AlGaN/GaN interface and quantum well are identified. Each GR

  7. AlGaAs/InGaAs/AlGaAs Double Barrier

    E-Print Network [OSTI]

    Perera, A. G. Unil

    -state Er. Tunneling Quantum Dot Sensors for Multi-band Infrared and Terahertz Radiation Detection G radiation detection are demonstrated. In T-QDIP structures, photoabsorption takes place in InGaAs QDs (due

  8. Graphene induced remote surface scattering in graphene/AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Liu, Xiwen; Li, Dan; Wang, Bobo; Liu, Bin; Chen, Famin; Jin, Guangri; Lu, Yanwu, E-mail: ywlu@bjtu.edu.cn [Department of Physics, Beijing Jiaotong University, Beijing 100044 (China)

    2014-10-20T23:59:59.000Z

    The mobilities of single-layer graphene combined with AlGaN/GaN heterostructures on two-dimensional electron gases in graphene/AlGaN/GaN double heterojunction are calculated. The impact of electron density in single-layer graphene is also studied. Remote surface roughness (RSR) and remote interfacial charge (RIC) scatterings are introduced into this heterostructure. The mobilities limited by RSR and RIC are an order of magnitude higher than that of interface roughness and misfit dislocation. This study contributes to designing structures for generation of higher electron mobility in graphene/AlGaN/GaN double heterojunction.

  9. GaAs, AlGaAs and InGaP Tunnel Junctions for Multi-Junction Solar Cells Under Concentration: Resistance Study

    SciTech Connect (OSTI)

    Wheeldon, Jeffrey F.; Valdivia, Christopher E.; Walker, Alex; Kolhatkar, Gitanja; Hall, Trevor J.; Hinzer, Karin [Centre for Research in Photonics, University of Ottawa, Ottawa, ON (Canada); Masson, Denis; Riel, Bruno; Fafard, Simon [Cyrium Technologies Inc., Ottawa, ON (Canada); Jaouad, Abdelatif; Turala, Artur; Ares, Richard; Aimez, Vincent [Centre de Recherche en Nanofabrication et en Nanocaracterisation CRN2, Universite de Sherbrooke, Sherbrooke, QC (Canada)

    2010-10-14T23:59:59.000Z

    The following four TJ designs, AlGaAs/AlGaAs, GaAs/GaAs, AlGaAs/InGaP and AlGaAs/GaAs are studied to determine minimum doping concentration to achieve a resistance of <10{sup -4} {omega}{center_dot}cm{sup 2} and a peak tunneling current suitable for MJ solar cells up to 1500-suns concentration (operating current of 21 A/cm{sup 2}). Experimentally calibrated numerical models are used to determine how the resistance changes as a function of doping concentration. The AlGaAs/GaAs TJ design is determined to require the least doping concentration to achieve the specified resistance and peak tunneling current, followed by the GaAs/GaAs, and AlGaAs/AlGaAs TJ designs. The AlGaAs/InGaP TJ design can only achieve resistances >5x10{sup -4} {omega}cm{sup 2}.

  10. Switchable piezoelectric transduction in AlGaN/GaN MEMS resonators

    E-Print Network [OSTI]

    Weinstein, Dana

    This work presents a new switching mechanism in piezoelectric transduction of AlGaN/GaN bulk acoustic resonators. A piezoelectric transducer is formed in the AlGaN, between a top Schottky electrode and a 2D electron gas ...

  11. Effect of buffer structures on AlGaN/GaN high electron mobility transistor reliability

    SciTech Connect (OSTI)

    Liu, L. [University of Florida, Gainesville; Xi, Y. Y. [University of Florida, Gainesville; Ren, F. [University of Florida; Pearton, S. J. [University of Florida; Laboutin, O. [Kopin Corporation, Taunton, MA; Cao, Yu [Kopin Corporation, Taunton, MA; Johnson, Wayne J. [Kopin Corporation, Taunton, MA; Kravchenko, Ivan I [ORNL

    2012-01-01T23:59:59.000Z

    AlGaN/GaN high electron mobility transistors (HEMTs) with three different types of buffer layers, including a GaN/AlGaN composite layer, or 1 or 2 lm GaN thick layers, were fabricated and their reliability compared. The HEMTs with the thick GaN buffer layer showed the lowest critical voltage (Vcri) during off-state drain step-stress, but this was increased by around 50% and 100% for devices with the composite AlGaN/GaN buffer layers or thinner GaN buffers, respectively. The Voff - state for HEMTs with thin GaN and composite buffers were 100 V, however, this degraded to 50 60V for devices with thick GaN buffers due to the difference in peak electric field near the gate edge. A similar trend was observed in the isolation breakdown voltage measurements, with the highest Viso achieved based on thin GaN or composite buffer designs (600 700 V), while a much smaller Viso of 200V was measured on HEMTs with the thick GaN buffer layers. These results demonstrate the strong influence of buffer structure and defect density on AlGaN/GaN HEMT performance and reliability.

  12. Radiation Hard AlGaN Detectors and Imager

    SciTech Connect (OSTI)

    None

    2012-05-01T23:59:59.000Z

    Radiation hardness of AlGaN photodiodes was tested using a 65 MeV proton beam with a total proton fluence of 3x10{sup 12} protons/cm{sup 2}. AlGaN Deep UV Photodiode have extremely high radiation hardness. These new devices have mission critical applications in high energy density physics (HEDP) and space explorations. These new devices satisfy radiation hardness requirements by NIF. NSTec is developing next generation AlGaN optoelectronics and imagers.

  13. N-Face GaN/AlGaN HEMTs Fabricated Through Layer Transfer Technology

    E-Print Network [OSTI]

    Chung, Jinwook

    We present a new method to fabricate N-face GaN/AlGaN high electron mobility transistors (HEMTs). These devices are extremely promising for ultrahigh frequency applications where low contact resistances and excellent carrier ...

  14. Breakdown mechanism in AlGaN/GaN HEMTs on Si substrate

    E-Print Network [OSTI]

    Lu, Bin

    AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates have attracted a great interest for power electronics applications. Despite the low cost of the Si substrate, the breakdown voltage (V[subscript ...

  15. AlGaN/GaN Metal Oxide Semiconductor Field Effect Transistors using Titanium Dioxide P. J. HANSEN

    E-Print Network [OSTI]

    York, Robert A.

    AlGaN/GaN Metal Oxide Semiconductor Field Effect Transistors using Titanium Dioxide P. J. HANSEN 1 epitaxially on AlGaN/GaN HFET structures by molecular beam epitaxy (MBE). Growth was first performed on GaN templates to establish epitaxial growth conditions. X-ray diffraction showed [001] TiO2 || [1010]GaN

  16. Negative capacitance in GaN/AlGaN heterojunction dual-band detectors L. E. Byrum,1

    E-Print Network [OSTI]

    Dietz, Nikolaus

    Negative capacitance in GaN/AlGaN heterojunction dual-band detectors L. E. Byrum,1 G. Ariyawansa,1 online 2 September 2009 A study of trap states in n+ -GaN/AlGaN heterostructures using electrical related absorption centers attributed to shallow Si-donor pinned to the AlGaN barrier , N-vacancy/ C

  17. Comparison of compressive and tensile relaxed composition-graded GaAsP and ,,Al...InGaP substrates

    E-Print Network [OSTI]

    Comparison of compressive and tensile relaxed composition-graded GaAsP and ,,Al...InGaP substrates, around 104 cm-2 . The structures, grown on GaP or GaAs, consist of graded In-fraction InGaP and AlInGaP. High surface roughness and branch defects in Al InGaP lead to the lowest quality virtual substrates we

  18. Determination of two-dimensional electron and hole gas carriers in AlGaN/GaN/AlN heterostructures grown by Metal

    E-Print Network [OSTI]

    Ozbay, Ekmel

    on nominally undoped Al0.25Ga0.75N/GaN/AlN heterostructures grown on sapphire substrates prepared by metal undoped Al0.25Ga0.75N/GaN/ AlN heterostructures grown on sapphire substrate. © 2007 Elsevier B.V. All of AlGaN on a thick GaN epilayer on a semi- insulating substrate. Spontaneous and strain induced

  19. AlGaAs/InGaAsN/GaAs PnP double heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P.C.; Baca, A.G.; Li, N.Y.; Sharps, P.R.; Hou, H.Q.; Laroche, J.R.; Ren, F.

    2000-01-11T23:59:59.000Z

    The authors have demonstrated a functional MOCVD-grown AlGaAs/InGaAsN/GaAsPnP DHBT that is lattice matched to GaAs and has a peak current gain ({beta}) of 25. Because of the smaller bandgap (E{sub g}=1.20eV)of In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} used for the base layer, this device has a low V{sub ON} of 0.79 V, 0.25 V lower than in a comparable Pnp AlGaAs/GaAs HBT. The BV{sub CEO} is 12 V, consistent with its GaAs collector thickness and doping level.

  20. Asymmetric interfacial abruptness in N-polar and Ga-polar GaN/AlN/GaN heterostructures

    SciTech Connect (OSTI)

    Mazumder, B.; Hurni, C. A.; Zhang, J. Y.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Wong, M. H.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2012-08-27T23:59:59.000Z

    In this letter, we report on the interfacial abruptness of GaN/AlN/GaN heterostructures with pulsed laser atom probe tomography (APT). The samples were grown by plasma-assisted molecular beam epitaxy (MBE) under both metal-rich and N-rich conditions on both Ga-polar (0001) GaN templates and N-polar (0001) GaN substrates. An NH{sub 3} assisted MBE technique was involved to grow similar Ga-polar and N-polar structures on GaN:Fe substrates and GaN/Al{sub 2}O{sub 3} templates, respectively, for a comparison study. We find in all cases the interface with net positive polarization charge was chemically abrupt, whereas the interface with net negative polarization charge was diffuse. We discuss the implications on device design and performance. These data validate the efficiency of APT in studying interfaces for better performance in devices.

  1. 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

  2. Multi-bands photoconductive response in AlGaN/GaN multiple quantum wells

    SciTech Connect (OSTI)

    Chen, G.; Rong, X.; Xu, F. J.; Tang, N. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Wang, X. Q., E-mail: wangshi@pku.edu.cn; Shen, B., E-mail: bshen@pku.edu.cn [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Fu, K.; Zhang, B. S. [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Ruoshui Road 398, 215123 Suzhou (China); Hashimoto, H.; Yoshikawa, A. [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)

    2014-04-28T23:59:59.000Z

    Based on the optical transitions among the quantum-confined electronic states in the conduction band, we have fabricated multi-bands AlGaN/GaN quantum well infrared photodetectors. Crack-free AlGaN/GaN multiple quantum wells (MQWs) with atomically sharp interfaces have been achieved by inserting an AlN interlayer, which releases most of the tensile strain in the MQWs grown on the GaN underlayer. With significant reduction of dark current by using thick AlGaN barriers, photoconductive responses are demonstrated due to intersubband transition in multiple regions with center wavelengths of 1.3, 2.3, and 4??m, which shows potential applications on near infrared detection.

  3. 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.

  4. Simplified 2DEG carrier concentration model for composite barrier AlGaN/GaN HEMT

    SciTech Connect (OSTI)

    Das, Palash, E-mail: d.palash@gmail.com; Biswas, Dhrubes, E-mail: d.palash@gmail.com [Indian Institute of Technology Kharagpur, Kharagpur - 721302, West Bengal (India)

    2014-04-24T23:59:59.000Z

    The self consistent solution of Schrodinger and Poisson equations is used along with the total charge depletion model and applied with a novel approach of composite AlGaN barrier based HEMT heterostructure. The solution leaded to a completely new analytical model for Fermi energy level vs. 2DEG carrier concentration. This was eventually used to demonstrate a new analytical model for the temperature dependent 2DEG carrier concentration in AlGaN/GaN HEMT.

  5. High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module with Drain and Feedback Loop

    E-Print Network [OSTI]

    Itoh, Tatsuo

    High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module with Drain and Feedback Loop amplifier module using AlGaN/GaN high electron mobility transistor (HEMT) has been developed that covers radars and communications systems. GaN-based HEMT's for high power applications at microwave frequencies

  6. AlGaN/GaN HFET Single-Ended Frequency Doubler Younkyu Chung and Tatsuo Itoh

    E-Print Network [OSTI]

    Itoh, Tatsuo

    AlGaN/GaN HFET Single-Ended Frequency Doubler Younkyu Chung and Tatsuo Itoh Department-mail: ykchung@ee.ucla.edu Abstract - This paper presents the first single-ended AlGaN/GaN heterojunction field, respectively. For the frequency doubler with 1mm gate periphery AlGaN/GaN HFET, conversion gain of 0.17 d

  7. From Schottky to Ohmic graphene contacts to AlGaN/GaN heterostructures: Role of the AlGaN layer microstructure

    SciTech Connect (OSTI)

    Fisichella, G. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy); Department of Electronic Engineering, University of Catania, 95124 Catania (Italy); Greco, G.; Roccaforte, F.; Giannazzo, F. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy)

    2014-08-11T23:59:59.000Z

    The electrical behaviour of graphene (Gr) contacts to Al{sub x}Ga{sub 1?x}N/GaN heterostructures has been investigated, focusing, in particular, on the impact of the AlGaN microstructure on the current transport at Gr/AlGaN interface. Two Al{sub 0.25}Ga{sub 0.75}N/GaN heterostructures with very different quality in terms of surface roughness and defectivity, as evaluated by atomic force microscopy (AFM) and transmission electron microscopy, were compared in this study, i.e., a uniform and defect-free sample and a sample with a high density of typical V-defects, which locally cause a reduction of the AlGaN thickness. Nanoscale resolution current voltage (I-V) measurements by an Au coated conductive AFM tip were carried out at several positions both on the bare and Gr-coated AlGaN surfaces. Rectifying contacts were found onto both bare AlGaN surfaces, but with a more inhomogeneous and lower Schottky barrier height (?{sub B}???0.6?eV) for AlGaN with V-defects, with respect to the case of the uniform AlGaN (?{sub B}???0.9?eV). Instead, very different electrical behaviours were observed in the presence of the Gr interlayer between the Au tip and AlGaN, i.e., a Schottky contact with reduced barrier height (?{sub B} ? 0.4?eV) for the uniform AlGaN and an Ohmic contact for the AlGaN with V-defects. Interestingly, excellent lateral uniformity of the local I-V characteristics was found in both cases and can be ascribed to an averaging effect of the Gr electrode over the AlGaN interfacial inhomogeneities. Due to the locally reduced AlGaN layer thickness, V defect act as preferential current paths from Gr to the 2DEG and can account for the peculiar Ohmic behaviour of Gr contacts on defective AlGaN.

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

    SciTech Connect (OSTI)

    Watanabe, T.; Ohta, J.; Kondo, T.; Ohashi, M.; Ueno, K.; Kobayashi, A. [Institute of Industrial Science (IIS), The University of Tokyo, 4-6-1 Komaba, Tokyo 153-8505 (Japan); Fujioka, H., E-mail: hfujioka@iis.u-tokyo.ac.jp [Institute of Industrial Science (IIS), The University of Tokyo, 4-6-1 Komaba, Tokyo 153-8505 (Japan); CREST, Japan Science and Technology Corporation (JST), 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan)

    2014-05-05T23:59:59.000Z

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

  9. AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by Plasma-Enhanced ALD

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    AlGaN/GaN MIS-HEMT Gate Structure Improvement Using Al2O3 Deposited by Plasma-Enhanced ALD R(0)438782894 Abstract - In this work we evaluate the influence of the Al2O3 ALD deposition technique on AlGaN/GaN MIS drastically reduced with a measured average of 1e-11 A/mm for a drain-source bias of 5V. 1. Introduction AlGaN

  10. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Killat, N., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk; Uren, M. J.; Kuball, M., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk [Center for Device Thermography and Reliability (CDTR), H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Keller, S.; Kolluri, S.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of Santa Barbara California, Santa Barbara, California 93106 (United States)

    2014-08-11T23:59:59.000Z

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  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. Effect of polarization on intersubband transition in AlGaN/GaN multiple quantum wells

    SciTech Connect (OSTI)

    Chen, G.; Li, Z. L.; Wang, X. Q.; Huang, C. C.; Rong, X.; Xu, F. J.; Tang, N.; Qin, Z. X.; Shen, B. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)] [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Sang, L. W.; Sumiya, M. [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Optical and Electronic Materials Unit, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Chen, Y. H. [Laboratory of Semiconductor Material Science, Institute of Semiconductors, CAS, Beijing 100083 (China)] [Laboratory of Semiconductor Material Science, Institute of Semiconductors, CAS, Beijing 100083 (China); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)] [Department of Physics, Tsinghua University, Beijing 100871 (China)

    2013-05-13T23:59:59.000Z

    Intersubband transitions (ISBT) of AlGaN/GaN multiple quantum wells (MQWs) with wavelength towards atmospheric window (3-5 {mu}m) have been investigated. A Ga-excess epitaxial method is used in the molecular beam epitaxy leading to ultra-sharp interface and negligible elements inter-diffusion. The absorption peak wavelength of the ISBT was successfully tuned in the range of 3-4 {mu}m by modifying the GaN well thickness from 2.8 to 5.5 nm. It was further found that the polarization charge density of the AlGaN/GaN MQWs was about -0.034 C/m{sup 2} which gave rise to blueshift of the ISBT wavelength and thus partially compensated its redshift with increasing well thickness.

  13. First principles phase diagram calculations for the wurtzitestructure systems AlN--GaN, GaN--InN, and AlN--InN

    E-Print Network [OSTI]

    Burton, Benjamin P.

    First principles phase diagram calculations for the wurtzite­structure systems AlN--GaN, GaN for the wurtzite­structure quasibinary systems AlN--GaN, GaN--InN, and AlN--InN. Cluster expansion Hamiltonians. Miscibility gaps are predicted for all three quasibinaries, with consolute points, #X C , T C #, for AlN--GaN

  14. Low-threshold (--600 A/cm/sup 2/ at room temperature) GaAs/AlGaAs lasers on Si (100)

    SciTech Connect (OSTI)

    Chen, H.Z.; Ghaffari, A.; Wang, H.; Morkoc, H.; Yariv, A.

    1987-10-26T23:59:59.000Z

    Low-threshold graded-refractive-index GaAs/AlGaAs laser structures were grown on Si (100) by molecular beam epitaxy and tested at room temperature under a probe station. Broad area devices having widths of 110--120 ..mu..m and cavity lengths of --500--1210 ..mu..m exhibited threshold current densities as low as 600 A/cm/sup 2/ and total slope efficiencies of as high as 0.75 W/A. The thresholds fell in the range of 600--1000 A/cm/sup 2/ in three different wafers, and it is assumed that the quality of the facets accounts for most of the spread in results.

  15. Nucleation of GaN/AlN quantum dots

    SciTech Connect (OSTI)

    Adelmann, C; Daudin, B; Oliver, R; Briggs, G; Rudd, R

    2003-10-13T23:59:59.000Z

    We study the nucleation of GaN islands grown by plasma-assisted molecular-beam epitaxy on AlN in a Stranski-Krastanov mode. In particular, we assess the variation of their height and density as a function of GaN coverage. We show that the GaN growth passes four stages: initially, the growth is layer-by-layer; subsequently, bidimensional precursor islands form, which transform into genuine three-dimensional islands. During the latter stage, the height and the density of the islands increase with GaN coverage until the density saturates. During further GaN growth, the density remains constant and a bimodal height distribution appears. The variation of island height and density as a function of substrate temperature is discussed in the framework of an equilibrium model for Stranski-Krastanov growth [R. E. Rudd et al., Phys. Rev. Lett. 90, 146101 (2003)].

  16. AlGaN/GaN HEMT With 300-GHz fmax

    E-Print Network [OSTI]

    Chung, Jinwook W.

    We report on a gate-recessed AlGaN/GaN high-electron mobility transistor (HEMT) on a SiC substrate with a record power-gain cutoff frequency (f[subscript max]). To achieve this high f[subscript max], we combined a low-damage ...

  17. Gate-First AlGaN/GaN HEMT Technology for High-Frequency Applications

    E-Print Network [OSTI]

    Piner, Edwin L.

    This letter describes a gate-first AlGaN/GaN high-electron mobility transistor (HEMT) with a W/high-k dielectric gate stack. In this new fabrication technology, the gate stack is deposited before the ohmic contacts, and ...

  18. Schottky-Drain Technology for AlGaN/GaN High-Electron Mobility Transistors

    E-Print Network [OSTI]

    Lu, Bin

    In this letter, we demonstrate 27% improvement in the buffer breakdown voltage of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on Si substrate by using a new Schottky-drain contact technology. Schottky-drain ...

  19. Investigation of Strain in AlGaN/GaN Multi Quantum Wells by Complementary Techniques

    SciTech Connect (OSTI)

    Devaraju, G.; Sathish, N.; Pathak, A. P. [School of Physics, University of Hyderabad, Central University (P.0), Hyderabad 500 046 (India); Dhamodaran, S. [Department of Physics, Indian Institute of Technology, IIT P O, Kanpur UP 208016 (India); Gaca, J.; Wojcik, M. [Institute of Electronic Materials Technology, 01-919 Warsaw, ul. Wolczynska 133 (Poland); Turos, A. [Institute of Electronic Materials Technology, 01-919 Warsaw, ul. Wolczynska 133 (Poland); Soltan Institute for Nuclear Studies, Swierk/Otwock, Warsaw (Poland); Arora, B. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400 005 (India)

    2009-03-10T23:59:59.000Z

    Al{sub 0.49}Ga{sub 0.51}N(12 nm)/GaN (13 nm) Multi Quantum Wells of 15 periods are grown on sapphire by MOCVD technique. GaN/AlN, each of thickness 200 nm and 20 nm respectively, are used as buffer layers between substrate and epilayer to incorporate the strain in epilayers. It is a well established technique to engineer the band gap in Al{sub x}Ga{sub 1-x}N by adjusting alloy composition. These samples are used in visible and UV light emitters. In the present study, we employ a photoluminescence technique to estimate the composition and luminescence peak positions of AlGaN and GaN. Crystallinity and quality of interfaces have been studied by Rocking curve scan. The Threading Dislocations formed at the GaN buffer layer travel across the entire layers to the surface to form good quality films. Photo-luminescence results show a very sharp GaN peak at 3.4 eV, as observed and reported by others, which shows that samples are free from point defects.

  20. The Effect of the Thermal Boundary Resistance on Self-Heating of AlGaN/GaN HFETs

    E-Print Network [OSTI]

    The Effect of the Thermal Boundary Resistance on Self-Heating of AlGaN/GaN HFETs 1. Introduction, performance of these devices has been limited by self-heating [1] [6]. Thus, accurate modeling of heat diffusion and self-heating effects in AlGaN/GaN heterostructures and device optimization based

  1. Ferromagnetic semiconductors based upon AlGaP M. E. Overberg,a)

    E-Print Network [OSTI]

    Hebard, Arthur F.

    band-gap ternary InGaP, which is lattice matched to GaAs. An immediate application of the DMS, with its wide band-gap binary GaP, AlP and ternary InGaP, AlGaP, AlInP components, is used for devices

  2. September 16-21, 2007 Las Vegas, Nevada Gate recess technology on AlGaN/GaN HFET with InGaN as etch-stop layer

    E-Print Network [OSTI]

    Pala, Nezih

    0 2 V(V) C(pF) Before etching (material) After etching (device) G AlGaN substrate i-GaN DS AlN AlGaN substrate AlN i-GaN AlGaN S G DAlGaNAlGaN InGaNInGaN Standard gate recess InGaN stop layer gate recess InGaNICNS 7 September 16-21, 2007 ­ Las Vegas, Nevada Gate recess technology on AlGaN/GaN HFET with InGaN

  3. AlGaAs/GaAs photovoltaic converters for high power narrowband radiation

    SciTech Connect (OSTI)

    Khvostikov, Vladimir; Kalyuzhnyy, Nikolay; Mintairov, Sergey; Potapovich, Nataliia; Shvarts, Maxim; Sorokina, Svetlana; Andreev, Viacheslav [Ioffe Physical-Technical Institute, 26 Polytechnicheskaya, St. Petersburg, 194021 (Russian Federation); Luque, Antonio [Ioffe Physical-Technical Institute, 26 Polytechnicheskaya, St. Petersburg, 194021, Russia and Instituto de Energia Solar, Universidad Politecnica de Madrid, Madrid (Spain)

    2014-09-26T23:59:59.000Z

    AlGaAs/GaAs-based laser power PV converters intended for operation with high-power (up to 100 W/cm{sup 2}) radiation were fabricated by LPE and MOCVD techniques. Monochromatic (? = 809 nm) conversion efficiency up to 60% was measured at cells with back surface field and low (x = 0.2) Al concentration 'window'. Modules with a voltage of 4 V and the efficiency of 56% were designed and fabricated.

  4. Analytical modeling of AlGaN/AlN/GaN heterostructures including effects of distributed surface donor states

    SciTech Connect (OSTI)

    Goyal, Nitin, E-mail: nitin@unik.no [Carinthian Tech Research CTR AG, Europastraße 4/1, Technologiepark Villach, A-9524 Villach/St. Magdalen (Austria); Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway); Fjeldly, Tor A. [Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway)

    2014-07-14T23:59:59.000Z

    In this paper, a physics based analytical model is presented for calculation of the two-dimensional electron gas density and the bare surface barrier height of AlGaN/AlN/GaN material stacks. The presented model is based on the concept of distributed surface donor states and the self-consistent solution of Poisson equation at the different material interfaces. The model shows good agreement with the reported experimental data and can be used for the design and characterization of advanced GaN devices for power and radio frequency applications.

  5. 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

  6. MBE growth and applications of cubic AlN/GaN quantum wells

    E-Print Network [OSTI]

    As, Donat Josef

    MBE growth and applications of cubic AlN/GaN quantum wells Donat J. As* and Christian Mietze Keywords cubic AlN, GaN, interband and intersubband transitions, MBE, resonant tunneling * Corresponding regions. In this contribution, the latest achievement in the MBE of phase-pure cubic GaN, AlN, and AlN/GaN

  7. 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

  8. Sheet resistance under Ohmic contacts to AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Haj?asz, M., E-mail: m.hajlasz@m2i.nl [Materials innovation institute (M2i), Mekelweg 2, 2628 CD, Delft (Netherlands); MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Donkers, J. J. T. M.; Sque, S. J.; Heil, S. B. S. [NXP Semiconductors Research, High Tech Campus 46, 5656 AE, Eindhoven (Netherlands); Gravesteijn, D. J. [NXP Semiconductors Research, High Tech Campus 46, 5656 AE, Eindhoven (Netherlands); MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands); Rietveld, F. J. R. [NXP Semiconductors, Gerstweg 2, 6534 AE, Nijmegen (Netherlands); Schmitz, J. [MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede (Netherlands)

    2014-06-16T23:59:59.000Z

    For the determination of specific contact resistance in semiconductor devices, it is usually assumed that the sheet resistance under the contact is identical to that between the contacts. This generally does not hold for contacts to AlGaN/GaN structures, where an effective doping under the contact is thought to come from reactions between the contact metals and the AlGaN/GaN. As a consequence, conventional extraction of the specific contact resistance and transfer length leads to erroneous results. In this Letter, the sheet resistance under gold-free Ti/Al-based Ohmic contacts to AlGaN/GaN heterostructures on Si substrates has been investigated by means of electrical measurements, transmission electron microscopy, and technology computer-aided design simulations. It was found to be significantly lower than that outside of the contact area; temperature-dependent electrical characterization showed that it exhibits semiconductor-like behavior. The increase in conduction is attributed to n-type activity of nitrogen vacancies in the AlGaN. They are thought to form during rapid thermal annealing of the metal stack when Ti extracts nitrogen from the underlying semiconductor. The high n-type doping in the region between the metal and the 2-dimensional electron gas pulls the conduction band towards the Fermi level and enhances horizontal electron transport in the AlGaN. Using this improved understanding of the properties of the material underneath the contact, accurate values of transfer length and specific contact resistance have been extracted.

  9. Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

    SciTech Connect (OSTI)

    Sztein, Alexander, E-mail: asztein@umail.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106 (United States); Bowers, John E.; DenBaars, Steven P.; Nakamura, Shuji [Materials Department, University of California, Santa Barbara, California 93106 (United States); Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States)

    2014-01-27T23:59:59.000Z

    A novel polarization field engineering based strategy to simultaneously achieve high electrical conductivity and low thermal conductivity in thermoelectric materials is demonstrated. Polarization based electric fields are used to confine electrons into two-dimensional electron gases in GaN/AlN/Al{sub 0.2}Ga{sub 0.8}N superlattices, resulting in improved electron mobilities as high as 1176 cm{sup 2}/Vs and in-plane thermal conductivity as low as 8.9?W/mK. The resulting room temperature ZT values reach 0.08, a factor of four higher than InGaN and twelve higher than GaN, demonstrating the potential benefits of this polarization based engineering strategy for improving the ZT and efficiencies of thermoelectric materials.

  10. Height stabilization of GaSb/GaAs quantum dots by Al-rich capping

    SciTech Connect (OSTI)

    Smakman, E. P., E-mail: e.p.smakman@tue.nl; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (Netherlands); DeJarld, M.; Martin, A. J.; Millunchick, J. [Department of Material Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Luengo-Kovac, M.; Sih, V. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2014-09-01T23:59:59.000Z

    GaSb quantum dots (QDs) in a GaAs matrix are investigated with cross-sectional scanning tunneling microscopy (X-STM) and photoluminescence (PL). We observe that Al-rich capping materials prevent destabilization of the nanostructures during the capping stage of the molecular beam epitaxy (MBE) growth process and thus preserves the QD height. However, the strain induced by the absence of destabilization causes many structural defects to appear around the preserved QDs. These defects originate from misfit dislocations near the GaSb/GaAs interface and extend into the capping layer as stacking faults. The lack of a red shift in the QD PL suggests that the preserved dots do not contribute to the emission spectra. We suggest that a better control over the emission wavelength and an increase of the PL intensity is attainable by growing smaller QDs with an Al-rich overgrowth.

  11. GaN/ZnO and AlGaN/ZnO heterostructure LEDs: growth, fabrication, optical and electrical characterization

    E-Print Network [OSTI]

    Wetzel, Christian M.

    GaN/ZnO and AlGaN/ZnO heterostructure LEDs: growth, fabrication, optical and electrical 12180-3590, U.S.A. ABSTRACT The wide bandgap polar semiconductors GaN and ZnO and their related alloys fields, and surface terminations. With a small lattice mismatch of ~1.8 % between GaN and Zn

  12. Optical spectroscopy of quantum confined states in GaAs/AlGaAs quantum well tubes

    SciTech Connect (OSTI)

    Shi, Teng; Fickenscher, Melodie; Smith, Leigh; Jackson, Howard [Department of Physics, University of Cincinnati, Cincinnati, OH 45221 (United States); Yarrison-Rice, Jan [Department of Physics, Miami University, Oxford, OH 45056 (United States); Gao, Qiang; Tan, Hoe; Jagadish, Chennupati [Department of Electronic Materials and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Etheridge, Joanne [Monash Centre for Electron Microscopy, Monash University, Victoria, 3800 (Australia); Wong, Bryan M. [Materials Chemistry Department, Sandia National Laboratories, Livermore, CA 94551 (United States)

    2013-12-04T23:59:59.000Z

    We have investigated the quantum confinement of electronic states in GaAs/Al{sub x}Ga{sub 1?x}As nanowire heterostructures which contain radial GaAs quantum wells of either 4nm or 8nm. Photoluminescence and photoluminescence excitation spectroscopy are performed on single nanowires. We observed emission and excitation of electron and hole confined states. Numerical calculations of the quantum confined states using the detailed structural information on the quantum well tubes show excellent agreement with these optical results.

  13. Midinfrared intersubband absorption in GaN/AlGaN superlattices on Si(111) templates

    SciTech Connect (OSTI)

    Kandaswamy, P. K.; Monroy, E. [CEA/CNRS group 'Nanophysique et semiconducteurs', INAC/SP2M/NPSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Machhadani, H.; Sakr, S.; Tchernycheva, M.; Julien, F. H. [Photis, Institut d'Electronique Fondamentale, Universite Paris-Sud, 91405 Orsay Cedex (France); Bougerol, C. [CEA/CNRS group 'Nanophysique et semiconducteurs', Institut Neel, 25 rue des Martyrs, 38042 Grenoble Cedex 9 (France)

    2009-10-05T23:59:59.000Z

    We report on the observation of midinfrared intersubband absorption in Si-doped GaN/AlGaN superlattices grown by plasma-assisted molecular-beam epitaxy on semi-insulating GaN-on-Si(111) templates. TM-polarized absorption attributed to transition between the first two electronic levels in the quantum wells peaked in the range from 2 to 9 {mu}m. The relative spectral width remains around 20% in the whole midinfrared spectral range. Doping is predicted to have a large influence on the intersubband absorption energy due to screening of polarization-induced internal electric field.

  14. Local stress-induced effects on AlGaAs/AlOx oxidation front shape

    SciTech Connect (OSTI)

    Chouchane, F.; Almuneau, G., E-mail: almuneau@laas.fr; Arnoult, A.; Lacoste, G.; Fontaine, C. [CNRS, LAAS, 7 avenue du colonel Roche, F-31400 Toulouse (France); Univ de Toulouse, UPS, LAAS, F-31400 Toulouse (France); Cherkashin, N. [Univ de Toulouse, UPS, LAAS, F-31400 Toulouse (France); CNRS, CEMES, 29 Rue Jeanne Marvig, 31055 Toulouse Cedex 4 (France)

    2014-07-28T23:59:59.000Z

    The lateral oxidation of thick AlGaAs layers (>500?nm) is studied. An uncommon shape of the oxide tip is evidenced and attributed to the embedded stress distribution, inherent to the oxidation reaction. Experimental and numerical studies of the internal strain in oxidized Al{sub x}Ga{sub 1?x}As/GaAs structures were carried out by dark-field electron holography and finite element methods. A mapping of the strain distribution around the AlGaAs/oxide interface demonstrates the main role of internal stress on the shaping of the oxide front. These results demonstrate the high relevance of strain in oxide-confined III-V devices, in particular, with over-500-nm thick AlOx confinement layers.

  15. High density plasma damage in InGaP/GaAs as AlGaAs/GaAs high electron mobility transistors

    SciTech Connect (OSTI)

    Lee, J.W.; Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Ren, F.; Kopf, R.F.; Kuo, J.M. [Bell Labs., Murray Hill, NJ (United States). Lucent Technologies; Shul, R.J. [Sandia National Labs., Albuquerque, NM (United States); Constantine, C.; Johnson, D. [Plasma-Therm Inc., St. Petersburg, FL (United States)

    1998-11-01T23:59:59.000Z

    The introduction of plasma damage in InGaP/GaAs and AlGaAs/GaAs high electron mobility transistors (HEMTs) has been investigated using both inductively coupled plasma and electron cyclotron resonance Ar discharges. The saturated drain-source current is found to be decreased through introduction of compensating deep levels into the InGaP or AlGaAs donor layer. The degradation of device performance is a strong function of ion energy and ion flux, and an advantage of both high density plasma tools is that ion energy can be reduced by increasing the plasma density. Increasing process pressure and source power, and decreasing radio-frequency chuck power produce the lowest amounts of plasma damage in HEMTs.

  16. High-field quasi-ballistic transport in AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Danilchenko, B. A.; Tripachko, N. A. [Institute of Physics, NASU, Pr. Nauki 46, Kiev 03028 (Ukraine); Belyaev, A. E. [Institute of Semiconductor Physics, NASU, Pr. Nauki 45, Kiev 03028 (Ukraine); Vitusevich, S. A., E-mail: s.vitusevich@fz-juelich.de; Hardtdegen, H.; Lüth, H. [Peter Grünberg Institute (PGI-8,PGI-9), Forschungszentrum Jülich, Jülich D-52425 (Germany)

    2014-02-17T23:59:59.000Z

    Mechanisms of electron transport formation in 2D conducting channels of AlGaN/GaN heterostructures in extremely high electric fields at 4.2?K have been studied. Devices with a narrow constriction for the current flow demonstrate high-speed electron transport with an electron velocity of 6.8?×?10{sup 7}?cm/s. Such a velocity is more than two times higher than values reported for conventional semiconductors and about 15% smaller than the limit value predicted for GaN. Superior velocity is attained in the channel with considerable carrier reduction. The effect is related to a carrier runaway phenomenon. The results are in good agreement with theoretical predictions for GaN-based materials.

  17. GaN/AlN Quantum Dots for Single Qubit Emitters M. Winkelnkemper

    E-Print Network [OSTI]

    Nabben, Reinhard

    GaN/AlN Quantum Dots for Single Qubit Emitters M. Winkelnkemper , R. Seguin, S. Rodt, A. Hoffmann-plane GaN/AlN quantum dots (QDs) with focus on their potential as sources of single polarized photons emission lines from single InGaN/GaN [4­11] and GaN/AlN QDs grown on the c-plane [12­16] and a-plane [17

  18. 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.

  19. AlGaN/GaN High-Electron-Mobility Transistor Employing an Additional Gate for High-Voltage Switching Applications

    E-Print Network [OSTI]

    Seo, Kwang Seok

    AlGaN/GaN High-Electron-Mobility Transistor Employing an Additional Gate for High-Voltage Switching 16, 2004; accepted May 10, 2005; published September 8, 2005) We have proposed and fabricated an AlGaN/GaN: GaN, AlGaN, HEMT, switch 1. Introduction GaN has attracted attention for high-power and high

  20. Cubic AlGaN/GaN Hetero-Junction Field-Effect Transistors with Normally-on and Normally-off

    E-Print Network [OSTI]

    As, Donat Josef

    Cubic AlGaN/GaN Hetero-Junction Field-Effect Transistors with Normally-on and Normally-effect transistors (HFETs) in GaN technology. HFET structures were fabricated of non-polar cubic AlGaN/GaN hetero insulation of 3C-SiC was realized by Ar+ implantation before c-AlGaN/GaN growth. HFETs with normally

  1. Engineering of AlGaN-Delta-GaN Quantum-Well Gain Media for Mid-and Deep-Ultraviolet Lasers

    E-Print Network [OSTI]

    Gilchrist, James F.

    Engineering of AlGaN-Delta-GaN Quantum-Well Gain Media for Mid- and Deep-Ultraviolet Lasers Volume.1109/JPHOT.2013.2248705 1943-0655/$31.00 Ó2013 IEEE #12;Engineering of AlGaN-Delta-GaN Quantum-Well Gain@Lehigh.Edu). Abstract: The gain characteristics of AlGaN-delta-GaN quantum wells (QWs) with varying delta-GaN positions

  2. Manipulation of emission energy in GaAs/AlGaAs core-shell nanowires with radial heterostructure

    SciTech Connect (OSTI)

    Barbosa, B. G.; Arakaki, H.; Souza, C. A. de; Pusep, Yu. A. [Instituto de Fisica de São Carlos, Universidade de São Paulo, 13560-970 Sao Carlos, SP (Brazil)

    2014-03-21T23:59:59.000Z

    Photoluminescence was studied in GaAs/AlGaAs nanowires (NWs) with different radial heterostructures. We demonstrated that manipulation of the emission energy may be achieved by appropriate choice of the shell structure. The emission at highest energy is generated in the NWs with tunneling thin AlGaAs inner shell and thin GaAs outer shell due to recombination of the photoexcited electrons confined in the outer shell with the holes in the core. Lower energy emission was shown to occur in the NWs with thick outer shell grown in the form of a short-period GaAs/AlGaAs multiple quantum well structure. In this case, the tunneling probability through the multiple quantum wells controls the energy emitted by the NWs. The doping of core results in dominated low energy emission from the GaAs core.

  3. Gas-source molecular beam epitaxial growth and characterization of the (Al,In,Ga)NP/GaP material system and Its applications to light-emitting diodes

    E-Print Network [OSTI]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    ? G, Kcal/mol GaP GaN AlN o Substrate temperature, C Figurenm-thick GaN 0.006 P 0.994 layer on substrate temperature.substrate temperature for Reactions formation of AlP, GaP, GaN and

  4. IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 51, NO. 2, FEBRUARY 2003 653 AlGaN/GaN HFET Power Amplifier Integrated With

    E-Print Network [OSTI]

    Itoh, Tatsuo

    the first demonstration of a GaN-based HFET was done on a sapphire substrate in 1993 [1]­[3]. This is due crystal quality compared to that of the sapphire substrate. Thanks to steadfast progress in AlGaN/GaN HFETIEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 51, NO. 2, FEBRUARY 2003 653 AlGaN/GaN

  5. A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    York, Robert A.

    WE4A-5 A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs Jane J a GaN-based broadband power amplifier using AlGaN/GaN-HEMTs, grown on sapphire substrates amplifier using GaN- HEMTs-on-Sapphire. I INTRODUCTION GaN HEMTs have enormous potential for realizing high

  6. Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

    SciTech Connect (OSTI)

    Chen, Haoran; Yang, Lin'an, E-mail: layang@xidian.edu.cn; Hao, Yue [State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071 (China)

    2014-08-21T23:59:59.000Z

    The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of In{sub x}Ga{sub 1?x}N at around x?=?0.06.

  7. IEEE ELECTRON DEVICE LETTERS, VOL. 21, NO. 12, DECEMBER 2000 549 Dual-Gate AlGaN/GaN Modulation-Doped

    E-Print Network [OSTI]

    Rodwell, Mark J. W.

    IEEE ELECTRON DEVICE LETTERS, VOL. 21, NO. 12, DECEMBER 2000 549 Dual-Gate AlGaN/GaN Modulation--We demonstrate dual-gate AlGaN/GaN modula- tion-doped field-effect transistors (MODFETs) with gate-lengths of 0 power amplifiers. Index Terms--AlGaN/GaN, broadband power amplifiers, dual-gate FETs. I. INTRODUCTION

  8. Nonpolar cubic AlGaN/GaN heterojunction field-effect transistor on Ar+ implanted 3CSiC ,,001...

    E-Print Network [OSTI]

    As, Donat Josef

    through the substrate. Cubic AlGaN/GaN heterostructures were grown in a RibeNonpolar cubic AlGaN/GaN heterojunction field-effect transistor on Ar+ implanted 3C­SiC ,,001... E HFET was fabricated of nonpolar cubic AlGaN/GaN grown on Ar+ implanted 3C­SiC 001 by molecular beam

  9. 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.

  10. 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.

  11. Cubic GaN/AlN multiple quantum well photodetector

    SciTech Connect (OSTI)

    DeCuir, E. A. Jr.; Manasreh, M. O. [Department of Electrical Engineering, University of Arkansas, 3217 Bell Engineering Center, Fayetteville, Arkansas 72701 (United States); Tschumak, Elena; Schoermann, J.; As, D. J.; Lischka, K. [Department of Physics, University of Paderborn, Paderborn 33095 (Germany)

    2008-05-19T23:59:59.000Z

    Photodetectors based on intersubband transitions in molecular beam epitaxially grown cubic GaN/AlN multiple quantum wells were fabricated and tested. The presence of the intersubband transition was confirmed by using the optical absorption technique for structures with different well widths. Samples were polished into waveguide configuration on which the devices were fabricated. The photoresponse spectra were collected in the temperature range of 77-215 K under the influence of small bias voltages. All devices exhibit photovoltaic effect where the photoresponse is observed at zero bias voltage. Theoretical calculations of the intersubband transition were performed and found to be in agreement with the observed results.

  12. 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.

  13. Surface donor states distribution post SiN passivation of AlGaN/GaN heterostructures

    SciTech Connect (OSTI)

    Goyal, Nitin, E-mail: nitin@unik.no [Carinthian Tech Research CTR AG, Europastraße 4/1, Technologiepark Villach, A- 9524 Villach/St. Magdalen (Austria); Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway); Fjeldly, Tor A. [Department of Electronics and Telecommunication, Norwegian University of Science and Technology, Trondheim NO7034 (Norway)

    2014-07-21T23:59:59.000Z

    In this paper, we present a physics based analytical model to describe the effect of SiN passivation on two-dimensional electron gas density and surface barrier height in AlGaN/GaN heterostructures. The model is based on an extraction technique to calculate surface donor density and surface donor level at the SiN/AlGaN interface. The model is in good agreement with the experimental results and promises to become a useful tool in advanced design and characterization of GaN based heterostructures.

  14. Contribution of alloy clustering to limiting the two-dimensional electron gas mobility in AlGaN/GaN and InAlN/GaN heterostructures: Theory and experiment

    SciTech Connect (OSTI)

    Ahmadi, Elaheh; Mishra, Umesh K. [Electrical and Computer Engineering Department, University of California, Santa Barbara, California 93106 (United States); Chalabi, Hamidreza [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305 (United States); Kaun, Stephen W.; Shivaraman, Ravi; Speck, James S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-10-07T23:59:59.000Z

    The influence of alloy clustering on fluctuations in the ground state energy of the two-dimensional electron gas (2DEG) in AlGaN/GaN and InAlN/GaN heterostructures is studied. We show that because of these fluctuations, alloy clustering degrades the mobility even when the 2DEG wavefunction does not penetrate the alloy barrier unlike alloy disorder scattering. A comparison between the results obtained for AlGaN/GaN and InAlN/GaN heterostructures shows that alloy clustering limits the 2DEG mobility to a greater degree in InAlN/GaN heterostructures. Our study also reveals that the inclusion of an AlN interlayer increases the limiting mobility from alloy clustering. Moreover, Atom probe tomography is used to demonstrate the random nature of the fluctuations in the alloy composition.

  15. Large linear magnetoresistance in a GaAs/AlGaAs heterostructure

    SciTech Connect (OSTI)

    Aamir, Mohammed Ali, E-mail: aamir@physics.iisc.ernet.in; Goswami, Srijit, E-mail: aamir@physics.iisc.ernet.in; Ghosh, Arindam [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India); Baenninger, Matthias; Farrer, Ian; Ritchie, David A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Tripathi, Vikram [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Pepper, Michael [Department of Electrical and Electronic Engineering, University College, London WC1E 7JE (United Kingdom)

    2013-12-04T23:59:59.000Z

    We report non-saturating linear magnetoresistance (MR) in a two-dimensional electron system (2DES) at a GaAs/AlGaAs heterointerface in the strongly insulating regime. We achieve this by driving the gate voltage below the pinch-off point of the device and operating it in the non-equilibrium regime with high source-drain bias. Remarkably, the magnitude of MR is as large as 500% per Tesla with respect to resistance at zero magnetic field, thus dwarfing most non-magnetic materials which exhibit this linearity. Its primary advantage over most other materials is that both linearity and the enormous magnitude are retained over a broad temperature range (0.3 K to 10 K), thus making it an attractive candidate for cryogenic sensor applications.

  16. Modeling of GaN/AlN heterostructure-based nano pressure sensors

    E-Print Network [OSTI]

    Sinha, Niraj

    We quantify the influence of thermopiezoelectric effects in nano-sized Al[subscript x]Ga[subscript 1-x]N/GaN heterostructures for pressure sensor applications based on the barrier height modulation principle. We use a ...

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

    SciTech Connect (OSTI)

    Christy, Dennis; Watanabe, Arata; Egawa, Takashi [Research Center for Nano-Device and System, Nagoya Institute of Technology, Nagoya, 466-8555 (Japan)

    2014-10-15T23:59:59.000Z

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

  18. Characterization of AlGaN/GaN Heterostructure Field Effect Transistors (HFETs) with Variable Thickness Channel and Substrate Type

    SciTech Connect (OSTI)

    Hussein, A. SH.; Hassan, Z.; Hassan, H. Abu; Thahab, S. M. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2010-07-07T23:59:59.000Z

    In this study, AlGaN/GaN-based heterostructure field effect transistor (HFET) was simulated by using ISE TCAD software. The effects of varying thickness, substrate type and doping channel levels were investigated. The device output characteristics of drain current and voltage with various gate biases were presented. A maximum drain current and extrinsic transconductance were achieved with AlGaN HFET grown on AlN/SiC substrate. The device performance can be improved by optimizing the substrate type and heavily doped channel layer which will reduce the contact resistance and enhance the transconductance. All results are comparable with the experimental results obtained by other researchers.

  19. Influence of substrate quality on structural properties of AlGaN/GaN superlattices grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Schubert, F. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); Merkel, U.; Schmult, S. [TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany); Mikolajick, T. [NaMLab gGmbH, Nöthnitzer Straße 64, 01187 Dresden (Germany); TU Dresden, Institute of Semiconductors and Microsystems, Nöthnitzer Straße 64, 01187 Dresden (Germany)

    2014-02-28T23:59:59.000Z

    Short-period AlGaN/GaN superlattices were established as versatile test structures to investigate the structural properties of molecular beam epitaxy (MBE)-grown GaN and AlGaN layers and their dependence on the GaN substrate quality. X-ray diffractometry data of the investigated superlattices allow access to relevant structural parameters such as aluminum mole fraction and layer thicknesses. The occurrence of theoretically predicted intense high-order satellite peaks and pronounced interface fringes in the diffraction pattern reflects abrupt interfaces and perfect 2-dimensional growth resulting in smooth surfaces. The data unambiguously demonstrate that the structural quality of the MBE grown layers is limited by the structural properties of the GaN substrate.

  20. 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.

  1. Reduction of gap states of ternary IIIV semiconductor surfaces by sulfur passivation: Comparative studies of AlGaAs and InGaP

    E-Print Network [OSTI]

    Kim, Sehun

    studies of AlGaAs and InGaP J. M. Seo School of Physics and Technology, Jeonbuk National University on liquid-phase-epitaxy-grown n-type InGaP and AlGaAs surfaces have been studied using x-ray photoelectron treatment in air. For InGaP, sulfur atoms initially reacted with both surface In and Ga atoms and reacted

  2. Pulsed Current-Voltage-Temperature Characteristics of AlGaN/GaN High Electron Mobility Transistor under Isothermal Conditions

    E-Print Network [OSTI]

    Seo, Kwang Seok

    , such as current collapse (power slump), the self-heating effect and the power scaling problem. In this paper, we have studied the self-heating effect using pulsed current-voltage (IV) and current- voltage self-heating affects the AlGaN/GaN HEMT's operation. It can be thought that a reason for the power

  3. Self-Heating Effects in GaN/AlGaN Heterostructure Field-Effect Transistors and Device Structure Optimization

    E-Print Network [OSTI]

    Self-Heating Effects in GaN/AlGaN Heterostructure Field-Effect Transistors and Device Structure time, performance of these devices has been limited by self-heating and other problems associated-3]. At the same time, performance of these devices has been limited by self-heating and other problems associated

  4. Output Harmonic Termination Techniques for AlGaN/GaN HEMT Power Amplifiers Using Active Integrated Antenna Approach

    E-Print Network [OSTI]

    Itoh, Tatsuo

    Output Harmonic Termination Techniques for AlGaN/GaN HEMT Power Amplifiers Using Active Integrated 1200, Los Angeles, CA 90045 Abstract -- In this paper, effects of output harmonic terminations on PAE termination, we observe a substantial increase in PAE and output power. Further, we demonstrate the high

  5. Wavelength dependence of the threshold in an InGaP-InAlGaP vertical cavity surface emitting laser

    SciTech Connect (OSTI)

    Chow, W.W.; Schneider, R.P. Jr.; Lott, J.A.; Choquette, K.D. (Sandia National Laboratories, Albuquerque, New Mexico 87185-0350 (United States))

    1994-07-11T23:59:59.000Z

    The wavelength dependence of the threshold in an InGaP-InAlGaP vertical cavity surface emitting laser is investigated using a microscopic theory of the semiconductor gain medium. Good agreement is found between experiment and theory for the minimum threshold lasing wavelength for a range of laser structures.

  6. High Breakdown ( > \\hbox {1500 V} ) AlGaN/GaN HEMTs by Substrate-Transfer Technology

    E-Print Network [OSTI]

    Lu, Bin

    In this letter, we present a new technology to increase the breakdown voltage of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on Si substrates. This new technology is based on the removal of the original Si ...

  7. Ga[sub 13], Al[sub 13], GaAl[sub 12], and chromium-pillared montmorillonites: Acidity and reactivity for cumene conversion

    SciTech Connect (OSTI)

    Bradley, S.M.; Kydd, R.A. (Univ. of Calgary, Alberta (Canada))

    1993-05-01T23:59:59.000Z

    A comparison has been made of the acidic characters of a series of metal polyoxocation pillar interlayered clay minerals (M-PILCs) by studying the infrared spectra of adsorbed pyridine. These comparisons were made for Ga[sub 13]-, Al[sub 13]- and GaAl[sub 12]-PILCs, and for Na[sup +]-exchanged montmorillonite (Na-STx-1). The Ga[sub 13]-PILC, was found to exhibit the strongest Lewis acid sites, followed by the AL[sub 13]-, and GaAl[sub 12]-PILCs and then by the Ns-STx-1. The relative number of Lewis acid sites, however, was found to be much greater for the GaAl[sub 12]-PILC, particularly after calcination at higher temperatures, indicating that the Ga[sub 13] Lewis acid sites did not have as high a thermal stability. The Broensted acidic characters for the pillared clays depend on the pillar, and follow the general decreasing order of abundance of GaAl[sub 12]-, Al[sub 13], and Ga[sub 13]-PILC when expressed as absorbance per unit mass. When the acidities per unit surface area were estimated, however, the Ga[sub 13]-PILCs were found to have the greatest number. This indicated that while the pillars contribute to the PILC acidities primarily through increasing the exposed phyllosilicate sheet surface areas, there is also a significant effect arising from the acidic characters of the pillars themselves. The dehydrogenation activities of Ga[sub 13]-, GaAl[sub 12]-, Al[sub 13]-, and Na-STx-1, in addition to a chromium polyoxocation-PILC, were compared by observing the products formed upon reaction with the model compound cumene. The Ga[sub 13]- and chromium-PILCs and the Na-Stx-1 exhibited almost exclusively dehydrogenation activities, whereas the Al[sub 13]- and GaAl[sub 12]-PILCs exhibited both cracking and dehydrogenation behaviors. These results prove that the pillars themselves can very strongly effect the catalytic activities of the PILCs. 3 refs., 6 figs., 2 tabs.

  8. GaN-based two-dimensional surface-emitting photonic crystal lasers with AlN/GaN distributed Bragg reflector

    E-Print Network [OSTI]

    Fan, Shanhui

    GaN-based two-dimensional surface-emitting photonic crystal lasers with AlN/GaN distributed Bragg 14 December 2007; published online 11 January 2008 GaN-based two-dimensional 2D surface-emitting photonic crystal PC lasers with AlN/GaN distributed Bragg reflectors are fabricated and demonstrated

  9. 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.

  10. Generation and transportation mechanisms for two-dimensional hole gases in GaN/AlGaN/GaN double heterostructures

    SciTech Connect (OSTI)

    Nakajima, Akira, E-mail: a-nakajima@aist.go.jp; Ogura, Masahiko; Makino, Toshiharu; Nishizawa, Shin-ichi; Ohashi, Hiromichi; Yamasaki, Satoshi [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Liu, Pucheng; Kakushima, Kuniyuki; Iwai, Hiroshi [Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori, Yokohama, Kanagawa 226-8503 (Japan)

    2014-04-21T23:59:59.000Z

    The electrical properties of two-dimensional hole gases (2DHGs) in GaN/AlGaN/GaN double heterostructures were investigated. The layers were grown on sapphire substrates and a high-quality bulk GaN substrate. The coexistence of 2DHG and 2D electron gases on both sides of the AlGaN layer was confirmed by Hall effect measurements at 80–460?K. It was also verified that the 2DHGs were generated by negative polarization at the undoped GaN/AlGaN interface, which did not have a doped Mg acceptor. It was also demonstrated that the 2DHG density could be controlled by varying the AlGaN layer thickness and was inversely related to the 2DHG mobility. The measured relation indicated that the 2DHG mobility is mainly limited by phonon scatterings at around room temperature. As a result, the maximum 2DHG mobility of 16 cm{sup 2}/Vs at 300?K was achieved with a density of 1?×?10{sup 13}?cm{sup ?2}.

  11. 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.

  12. Effects of high-temperature AIN buffer on the microstructure of AlGaN/GaN HEMTs

    SciTech Connect (OSTI)

    Coerekci, S., E-mail: scorekci@kirklareli.edu.tr [K Latin-Small-Letter-Dotless-I rklareli University, Department of Physics (Turkey); Oeztuerk, M. K. [Gazi University, Department of Physics (Turkey); Yu, Hongbo [Bilkent University, Nanotechnology Research Center (Turkey); Cakmak, M.; Oezcelik, S. [Gazi University, Department of Physics (Turkey); Oezbay, E. [Bilkent University, Nanotechnology Research Center, Department of Physics, Department of Electrical and Electronics Engineering (Turkey)

    2013-06-15T23:59:59.000Z

    Effects on AlGaN/GaN high-electron-mobility transistor structure of a high-temperature AlN buffer on sapphire substrate have been studied by high-resolution x-ray diffraction and atomic force microscopy techniques. The buffer improves the microstructural quality of GaN epilayer and reduces approximately one order of magnitude the edge-type threading dislocation density. As expected, the buffer also leads an atomically flat surface with a low root-mean-square of 0.25 nm and a step termination density in the range of 10{sup 8} cm{sup -2}. Due to the high-temperature buffer layer, no change on the strain character of the GaN and AlGaN epitaxial layers has been observed. Both epilayers exhibit compressive strain in parallel to the growth direction and tensile strain in perpendicular to the growth direction. However, an high-temperature AlN buffer layer on sapphire substrate in the HEMT structure reduces the tensile stress in the AlGaN layer.

  13. Low Phase-Noise 5 GHz AlGaN/GaN HEMT Oscillator Integrated with BaxSr1-xTiO3 Thin Films

    E-Print Network [OSTI]

    York, Robert A.

    Low Phase-Noise 5 GHz AlGaN/GaN HEMT Oscillator Integrated with BaxSr1-xTiO3 Thin Films Hongtao Xu -- A C-band MMIC oscillator in GaN HEMT technology with BaxSr1-xTiO3 (BST) film capacitors integrated with the common gate HEMT to generate negative resistance. The oscillator, based on AlGaN/GaN HEMT with 0.7um gate

  14. Large optical cavity AlGaAs injection lasers with multiple active regions

    SciTech Connect (OSTI)

    Katz, J.; Bar-Chaim, N.; Margalit, S.; Yariv, A.

    1980-08-01T23:59:59.000Z

    A new type of AlGaAs injection laser is described. The structure consists of alternating p- and n-type layers of GaAs and Al/sub x/ Ga/sub 1-x/As . The electrical mode of operation of the device is that of a Shockley diode (SCR). Optically the device operates as a large optical cavity. Single transverse mode operation was observed with optical cavities larger than 4 ..mu..m.

  15. Electrical Degradation of InAlAs/InGaAs Metamorphic

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    Electrical Degradation of InAlAs/InGaAs Metamorphic High-Electron Mobility Transistors S. D · Introduction · Electrical Degradation of mHEMTs · Degradation of TLMs · Degradation Mechanisms #12;Metamorphic Degradation of InAlAs/InGaAs mHEMTs Little known about reliability of mHEMTs Observations in InP HEMTs

  16. Efficiency-Droop Suppression by Using Large-Bandgap AlGaInN Thin Barrier

    E-Print Network [OSTI]

    Gilchrist, James F.

    Efficiency-Droop Suppression by Using Large-Bandgap AlGaInN Thin Barrier Layers in InGaN Quantum DOI: 10.1109/JPHOT.2013.2255028 1943-0655/$31.00 Ó2013 IEEE #12;Efficiency-Droop Suppression by Using with the consideration of carrier transport effect for efficiency droop suppression. The lattice-matched Al

  17. Analysis of AlN/AlGaN/GaN metal-insulator-semiconductor structure by using capacitance-frequency-temperature mapping

    SciTech Connect (OSTI)

    Shih, Hong-An; Kudo, Masahiro; Suzuki, Toshi-kazu [Center for Nano Materials and Technology, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2012-07-23T23:59:59.000Z

    AlN/AlGaN/GaN metal-insulator-semiconductor (MIS) structure is analyzed by using capacitance-frequency-temperature (C-f-T) mapping. Applying sputtering-deposited AlN, we attained AlN/AlGaN/GaN MIS heterostructure field-effect transistors with much suppressed gate leakage currents, but exhibiting frequency dispersion in C-V characteristics owing to high-density AlN/AlGaN interface states. In order to investigate the interface states deteriorating the device performance, we measured temperature-dependent frequency dispersion in the C-V characteristics. As a result, we obtained C-f-T mapping, whose analysis gives the activation energies of electron trapping, namely the interface state energy levels, for a wide range of the gate biases. This analysis method is auxiliary to the conventional conductance method, serving as a valuable tool for characterization of wide-bandgap devices with deep interface states. From the analysis, we can directly evaluate the gate-control efficiency of the devices.

  18. Reduced thermal resistance in AlGaN/GaN multi-mesa-channel high electron mobility transistors

    SciTech Connect (OSTI)

    Asubar, Joel T., E-mail: joel@rciqe.hokudai.ac.jp; Yatabe, Zenji; Hashizume, Tamotsu [Research Center for Integrated Quantum Electronics (RCIQE) and Graduate School of Information Science and Technology, Hokkaido University, Sapporo (Japan); Japan Science and Technology Agency (JST), CREST, 102-0075 Tokyo (Japan)

    2014-08-04T23:59:59.000Z

    Dramatic reduction of thermal resistance was achieved in AlGaN/GaN Multi-Mesa-Channel (MMC) high electron mobility transistors (HEMTs) on sapphire substrates. Compared with the conventional planar device, the MMC HEMT exhibits much less negative slope of the I{sub D}-V{sub DS} curves at high V{sub DS} regime, indicating less self-heating. Using a method proposed by Menozzi and co-workers, we obtained a thermal resistance of 4.8?K-mm/W at ambient temperature of ?350?K and power dissipation of ?9?W/mm. This value compares well to 4.1?K-mm/W, which is the thermal resistance of AlGaN/GaN HEMTs on expensive single crystal diamond substrates and the lowest reported value in literature.

  19. Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures directly on sapphire substrates

    E-Print Network [OSTI]

    Manfra, Michael J.

    Dislocation and morphology control during molecular-beam epitaxy of AlGaN/GaN heterostructures-dimensional arrays Appl. Phys. Lett. 100, 203117 (2012) Partially filled intermediate band of Cr-doped GaN films Appl at telecommunication wavelengths J. Appl. Phys. 111, 093721 (2012) GaN epitaxy on Cu(110) by metal organic chemical

  20. Specific features of kinetics of molecular beam epitaxy of compounds in the GaN-AlN system

    SciTech Connect (OSTI)

    Alekseev, A. N.; Byrnaz, A. E.; Krasovitsky, D. M.; Pavlenko, M. V.; Petrov, S. I., E-mail: support@semiteq.ru; Pogorel'sky, Yu. V.; Sokolov, I. A.; Sokolov, M. A.; Stepanov, M. V.; Shkurko, A. P.; Chalyi, V. P. [ZAO Svetlana-ROST (Russian Federation)

    2007-09-15T23:59:59.000Z

    The effect of growth conditions (V/III ratio, substrate temperature) on the properties of materials in AlN-GaN systems is discussed. A concept of the growth of the AlN/AlGaN/GaN multilayer heterostructure, which provides the improvement of crystal quality and surface morphology of the layers, is suggested and realized. The improvement of the properties of GaN in the AlN/AlGaN/GaN/AlGaN multilayer heterostructure is confirmed by a considerable increase in electron mobility in the two-dimensional electron gas formed at the upper heterointerface GaN/Al{sub 0.3}Ga{sub 0.7}N.

  1. Selective oxidation of buried AlGaAs for fabrication of vertical-cavity lasers

    SciTech Connect (OSTI)

    Choquette, K.D.; Geib, K.M.; Chui, H.C.; Hou, H.Q. [Sandia National Labs., Albuquerque, NM (United States). Photonics Research Dept.; Hull, R. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science

    1996-06-01T23:59:59.000Z

    The authors discuss the selective conversion of buried layers of AlGaAs to a stable oxide and the implementation of this oxide into high performance vertical-cavity surface emitting lasers (VCSELs). The rate of lateral oxidation is shown to be linear with an Arrhenius temperature dependence. The measured activation energies vary with Al composition, providing a high degree of oxidation selectivity between AlGaAs alloys. Thus buried oxide layers can be selectively fabricated within the VCSEL through small compositional variations in the AlGaAs layers. The oxidation of AlGaAs alloys, as opposed to AlAs, is found to provide robust processing of reliable lasers. The insulating and low refractive index oxide provides enhanced electrical and optical confinement for ultralow threshold currents in oxide-apertured VCSELs.

  2. Spatial distribution of structural degradation under high-power stress in AlGaN/GaN high electron mobility transistors

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    and high temperature, the latter being a result of de- vice self-heating. A complicating factor degradation of AlGaN/GaN high electron mobility transistors was investigated under high-power electrical electrical degradation that was mostly driven by an electric field across the AlGaN barrier. Under high

  3. Electron density and currents of AlN/GaN high electron mobility transistors with thin GaN/AlN buffer layer

    SciTech Connect (OSTI)

    Bairamis, A.; Zervos, Ch.; Georgakilas, A., E-mail: alexandr@physics.uoc.gr [Microelectronics Research Group, IESL, Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1385, GR-71110 Heraklion, Crete (Greece); Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete (Greece); Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G. [Microelectronics Research Group, IESL, Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1385, GR-71110 Heraklion, Crete (Greece)

    2014-09-15T23:59:59.000Z

    AlN/GaN high electron mobility transistor (HEMT) structures with thin GaN/AlN buffer layer have been analyzed theoretically and experimentally, and the effects of the AlN barrier and GaN buffer layer thicknesses on two-dimensional electron gas (2DEG) density and transport properties have been evaluated. HEMT structures consisting of [300?nm GaN/ 200?nm AlN] buffer layer on sapphire were grown by plasma-assisted molecular beam epitaxy and exhibited a remarkable agreement with the theoretical calculations, suggesting a negligible influence of the crystalline defects that increase near the heteroepitaxial interface. The 2DEG density varied from 6.8?×?10{sup 12} to 2.1 × 10{sup 13} cm{sup ?2} as the AlN barrier thickness increased from 2.2 to 4.5?nm, while a 4.5?nm AlN barrier would result to 3.1?×?10{sup 13} cm{sup ?2} on a GaN buffer layer. The 3.0?nm AlN barrier structure exhibited the highest 2DEG mobility of 900?cm{sup 2}/Vs for a density of 1.3?×?10{sup 13} cm{sup ?2}. The results were also confirmed by the performance of 1??m gate-length transistors. The scaling of AlN barrier thickness from 1.5?nm to 4.5?nm could modify the drain-source saturation current, for zero gate-source voltage, from zero (normally off condition) to 0.63?A/mm. The maximum drain-source current was 1.1?A/mm for AlN barrier thickness of 3.0?nm and 3.7?nm, and the maximum extrinsic transconductance was 320 mS/mm for 3.0?nm AlN barrier.

  4. Low-frequency noise in AlN/AlGaN/GaN metal-insulator-semiconductor devices: A comparison with Schottky devices

    SciTech Connect (OSTI)

    Le, Son Phuong; Nguyen, Tuan Quy; Shih, Hong-An; Kudo, Masahiro; Suzuki, Toshi-kazu, E-mail: tosikazu@jaist.ac.jp [Center for Nano Materials and Technology, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2014-08-07T23:59:59.000Z

    We have systematically investigated low-frequency noise (LFN) in AlN/AlGaN/GaN metal-insulator-semiconductor (MIS) devices, where the AlN gate insulator layer was sputtering-deposited on the AlGaN surface, in comparison with LFN in AlGaN/GaN Schottky devices. By measuring LFN in ungated two-terminal devices and heterojunction field-effect transistors (HFETs), we extracted LFN characteristics in the intrinsic gated region of the HFETs. Although there is a bias regime of the Schottky-HFETs in which LFN is dominated by the gate leakage current, LFN in the MIS-HFETs is always dominated by only the channel current. Analyzing the channel-current-dominated LFN, we obtained Hooge parameters ? for the gated region as a function of the sheet electron concentration n{sub s} under the gate. In a regime of small n{sub s}, both the MIS- and Schottky-HFETs exhibit ??n{sub s}{sup ?1}. On the other hand, in a middle n{sub s} regime of the MIS-HFETs, ? decreases rapidly like n{sub s}{sup ??} with ????2-3, which is not observed for the Schottky-HFETs. In addition, we observe strong increase in ??n{sub s}{sup 3} in a large n{sub s} regime for both the MIS- and Schottky-HFETs.

  5. Rapid silicon outdiffusion from SiC substrates during molecular-beam epitaxial growth of AlGaN/GaN/AlN transistor structures

    SciTech Connect (OSTI)

    Hoke, W.E.; Torabi, A.; Mosca, J.J.; Hallock, R.B.; Kennedy, T.D. [Raytheon RF Components, 362 Lowell Street, Andover, Massachusetts 01810 (United States)

    2005-10-15T23:59:59.000Z

    AlGaN/GaN/AlN transistor structures were grown onto SiC substrates by molecular-beam epitaxy. Under aluminum-rich growth conditions for the AlN nucleation layer, undesirable n-type conduction is observed near the GaN/AlN interface for even thick (>1000 A) AlN layers. Silicon is identified as the unwanted dopant from secondary-ion mass spectroscopy measurements. Atomic force microscopy surface maps reveal free aluminum metal on AlN surfaces grown under modest aluminum-rich conditions. It is proposed that rapid silicon migration is caused by molten aluminum reacting with the SiC substrate resulting in dissolved silicon that rapidly migrates through the growing AlN layer. This behavior is significantly reduced using a growth flux ratio of aluminum to reactive nitrogen close to unity. The resulting buffer leakage current of the GaN high electron mobility transistor structure is reduced by more than four orders of magnitude.

  6. Stimulated emission and optical gain in AlGaN heterostructures grown on bulk AlN substrates

    SciTech Connect (OSTI)

    Guo, Wei, E-mail: wguo2@ncsu.edu; Bryan, Zachary; Kirste, Ronny; Bryan, Isaac; Hussey, Lindsay; Bobea, Milena; Haidet, Brian; Collazo, Ramón; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Xie, Jinqiao; Mita, Seiji [HexaTech, Inc., 991 Aviation Pkwy, Suite 800, Morrisville, North Carolina 27560 (United States); Gerhold, Michael [Engineering Science Directorate, Army Research Office, P.O. BOX 12211, Research Triangle Park, North Carolina 27703 (United States)

    2014-03-14T23:59:59.000Z

    Optical gain spectra for ?250?nm stimulated emission were compared in three different AlGaN-based structures grown on single crystalline AlN substrates: a single AlGaN film, a double heterostructure (DH), and a Multiple Quantum Well (MQW) structure; respective threshold pumping power densities of 700, 250, and 150?kW/cm{sup 2} were observed. Above threshold, the emission was transverse-electric polarized and as narrow as 1.8?nm without a cavity. The DH and MQW structures showed gain values of 50–60?cm{sup ?1} when pumped at 1?MW/cm{sup 2}. The results demonstrated the excellent optical quality of the AlGaN-based heterostructures grown on AlN substrates and their potential for realizing electrically pumped sub-280?nm laser diodes.

  7. Fabrication of Two-Dimensional Photonic Crystals in AlGaInP/GaInP Membranes by Inductively Coupled Plasma Etching

    E-Print Network [OSTI]

    Chen, A.

    The fabrication process of two-dimensional photonic crystals in an AlGaInP/GaInP multi-quantum-well membrane structure is developed. The process includes high resolution electron-beam lithography, pattern transfer into ...

  8. Advanced Gate Technologies for State-of-the-art f[subscript T] in AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    Chung, Jinwook

    In this paper, the lower-than-expected frequency performance observed in many AlGaN/GaN high electron mobility transistors (HEMTs) has been attributed to a significant drop of the intrinsic small-signal transconductance ...

  9. Nanocomposites of Semimetallic ErAs Nanoparticles Epitaxially Embedded within InGaAlAs-based Semiconductors for Thermoelectric Materials

    E-Print Network [OSTI]

    GaAlAs-based Semiconductors for Thermoelectric Materials J.M.O. Zide', G. Zeng2, J.H. Bahk2, W. Kim3, S. L. Singer3, DAs nanoparticles which are epitaxially embedded within InGaAlAs-based semiconductors. The properties. In one geometry, barriers of InGaAlAs, a wider bandgap semiconductor, are introduced into an Er

  10. Abstract--Frequency dispersion of transconductance and output conductance in AlInN/GaN high electron mobility

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    1 Abstract--Frequency dispersion of transconductance and output conductance in AlInN/GaN high is compared to experimental data for several bias conditions and different types of dispersion. Index Terms--AlInN/GaN in recent years on nearly lattice-matched AlInN/GaN high electron mobility transistors (HEMTs

  11. Self-heating study of an AlGaN/GaN-based heterostructure field-effect transistor using ultraviolet micro-Raman scattering

    E-Print Network [OSTI]

    Holtz, Mark

    Self-heating study of an AlGaN/GaN-based heterostructure field-effect transistor using ultraviolet We report micro-Raman studies of self-heating in an AlGaN/GaN heterostructure field-effect transistorC substrate, at the same lateral position. Combined, we depth profile the self-heating. Measured T in the 2DEG

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

    SciTech Connect (OSTI)

    Killat, N., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk; Montes Bajo, M.; Kuball, M., E-mail: Nicole.Killat@bristol.ac.uk, E-mail: Martin.Kuball@bristol.ac.uk [Center for Device Thermography and Reliability (CDTR), H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Paskova, T. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States) [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Materials Science and Engineering Department, North Carolina State University, Raleigh, North Carolina 27695 (United States); Evans, K. R. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States)] [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Leach, J. [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States) [Kyma Technologies, Inc., Raleigh, North Carolina 27617 (United States); Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Li, X.; Özgür, Ü.; Morkoç, H. [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Chabak, K. D.; Crespo, A.; Gillespie, J. K.; Fitch, R.; Kossler, M.; Walker, D. E.; Trejo, M.; Via, G. D.; Blevins, J. D. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)] [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)

    2013-11-04T23:59:59.000Z

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

  13. Cavity design for improved electrical injection in InAlGaP/AlGaAs visible (639--661 nm) vertical-cavity surface-emitting laser diodes

    SciTech Connect (OSTI)

    Schneider, R.P. Jr.; Lott, J.A. (Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 (United States))

    1993-08-16T23:59:59.000Z

    A novel optical cavity design for improved electrical injection in visible vertical-cavity surface-emitting laser (VCSEL) diodes employing an InGaP/InAlGaP strained quantum-well active optical cavity and AlAs/Al[sub 0.5]Ga[sub 0.5]As distributed Bragg reflectors (DBRs) is described. The cavity design was determined by measuring the lasing threshold current density of visible edge-emitting laser diodes with AlAs/Al[sub 0.5]Ga[sub 0.5]As DBR cladding layers. By inserting InAlP spacer layers between the active region and the DBR cladding, significant improvement in the performance of the edge-emitting lasers was achieved. This approach was then applied to the design of visible VCSEL diodes, and resulted in the first demonstration of room-temperature electrically injected lasing, over the wavelength range 639--661 nm. The visible VCSELs, with a diameter of 20 [mu]m, exhibit pulsed output power of 3.4 mW at 650 nm, and continue to lase at a duty cycle of 40%. The threshold current was 30 mA, with a low threshold voltage (2.7 V) and low series resistance ([lt]15 [Omega]).

  14. Molecular dynamics simulation comparison of atomic scale intermixing at the amorphous Al2O3/semiconductor interface for a-Al2O3/Ge, a-Al2O3/InGaAs,

    E-Print Network [OSTI]

    Kummel, Andrew C.

    /semiconductor interface for a-Al2O3/Ge, a-Al2O3/InGaAs, and a-Al2O3/InAlAs/InGaAs Evgueni A. Chagarov *, Andrew oxides Ge InGaAs InAlAs Oxide­semiconductor stack High-K oxide a b s t r a c t The structural properties of a-Al2O3/Ge, a-Al2O3/In0.5Ga0.5As and a-Al2O3/In0.5Al0.5As/InGaAs interfaces were investigated

  15. Terahertz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Edmunds, C.; Malis, O., E-mail: omalis@purdue.edu [Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States); Shao, J. [Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Shirazi-HD, M. [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Manfra, M. J. [Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-07-14T23:59:59.000Z

    We demonstrate THz intersubband absorption (15.6–26.1?meV) in m-plane AlGaN/GaN quantum wells. We find a trend of decreasing peak energy with increasing quantum well width, in agreement with theoretical expectations. However, a blue-shift of the transition energy of up to 14?meV was observed relative to the calculated values. This blue-shift is shown to decrease with decreasing charge density and is, therefore, attributed to many-body effects. Furthermore, a??40% reduction in the linewidth (from roughly 8 to 5?meV) was obtained by reducing the total sheet density and inserting undoped AlGaN layers that separate the wavefunctions from the ionized impurities in the barriers.

  16. GaN/AlN Quantum Wells and Quantum Dots for Unipolar Devices at Telecommunication Wavelengths

    SciTech Connect (OSTI)

    Julien, Francois H.; Tchernycheva, Maria; Doyennette, Laetitia; Nevou, Laurent; Lupu, Anatole; Warde, Elias [Institut d'Electronique Fondamentale, Universite Paris Sud, UMR 8622 CNRS, 91405 Orsay (France); Guillot, Fabien; Monroy, Eva; Bellet-Amalric, Edith [Equipe mixte CEACNRS-UJF, DRFMC/SP2M/PSC, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble (France); Vardi, Alon; Bahir, Gad [Departement of Electrical Engineering, Technion-Israel Institute of Technology, Haifa 3200 (Israel)

    2007-04-10T23:59:59.000Z

    We report on the latest achievements in terms of growth and optical investigation of ultrathin GaN/AlN isolated and coupled quantum wells grown by plasma-assisted molecular-beam epitaxy. We also present the observation of intraband absorption in self-organized GaN quantum dots and on the application to infrared photodetection at telecommunication wavelengths.

  17. Strain relaxation in GaN/Al{sub x}Ga{sub 1-x}N superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect (OSTI)

    Kotsar, Y.; Bellet-Amalric, E.; Das, A.; Monroy, E. [CEA-Grenoble, INAC/SP2M/NPSC, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Doisneau, B. [SIMaP, Grenoble INP, Domaine Universitaire, BP 75, 38402 Saint Martin d'Heres (France); Sarigiannidou, E. [LMGP, Grenoble INP, 3 Parvis Louis Neel, BP 257, 38016 Grenoble cedex 1 (France)

    2011-08-01T23:59:59.000Z

    We have investigated the misfit relaxation process in GaN/Al{sub x}Ga{sub 1-x}N (x = 0.1, 0.3, 0.44) superlattices (SL) deposited by plasma-assisted molecular beam epitaxy. The SLs under consideration were designed to achieve intersubband absorption in the mid-infrared spectral range. We have considered the case of growth on GaN (tensile stress) and on AlGaN (compressive stress) buffer layers, both deposited on GaN-on-sapphire templates. Using GaN buffer layers, the SL remains almost pseudomorphic for x = 0.1, 0.3, with edge-type threading dislocation densities below 9 x 10{sup 8} cm{sup -2} to 2 x 10{sup 9} cm{sup -2}. Increasing the Al mole fraction to 0.44, we observe an enhancement of misfit relaxation resulting in dislocation densities above 10{sup 10} cm{sup -2}. In the case of growth on AlGaN, strain relaxation is systematically stronger, with the corresponding increase in the dislocation density. In addition to the average relaxation trend of the SL, in situ measurements indicate a periodic fluctuation of the in-plane lattice parameter, which is explained by the different elastic response of the GaN and AlGaN surfaces to the Ga excess at the growth front. The results are compared with GaN/AlN SLs designed for near-infrared intersubband absorption.

  18. High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module Y. Chung, S. Cai, W. Lee, Y. Lin, C. P. Wen, K. L. Wang, and T. Itoh

    E-Print Network [OSTI]

    Itoh, Tatsuo

    High Power Wideband AlGaN/GaN HEMT Feedback Amplifier Module Y. Chung, S. Cai, W. Lee, Y. Lin, C. P wideband feedback amplifier module using AlGaN/GaN high electron mobility transistor (HEMT) has been of 12 V (Vds) and a gate voltage of -3 V (Vgs). A feedback amplifier with AlGaN/GaN HEMT GaN-based HEMT

  19. Determination of subband energies and 2DEG characteristics of Al{sub x}Ga{sub 1?x}N/GaN heterojunctions using variational method

    SciTech Connect (OSTI)

    Manouchehri, Farzin; Valizadeh, Pouya; Kabir, M. Z., E-mail: kabir@encs.concordia.ca [Department of Electrical and Computer Engineering, Concordia University, Montreal, H3G 1M8 (Canada)

    2014-03-15T23:59:59.000Z

    A physics-based model based on the variational method for analyzing the two dimensional electron gas (2DEG) characteristics of polar AlGaN/GaN heterojunctions is developed. The 2DEG carrier concentration, the first and second energy subbands, and the position of the Fermi energy level are calculated for various barrier thicknesses, Al mole fractions, background dopant concentrations, and gate voltages for gated AlGaN/GaN heterojunctions. The results are in good agreement with the data reported based on self-consistent method. Whereas the aforementioned report has dealt with specific values of Al mole fraction, barrier thickness, and unintentional doping level, the present work provides a basis for calculating the 2DEG characteristics for the full range of these parameters. Furthermore, according to the proposed model, the applicability of the triangular approximation of the quantum well in AlGaN/GaN heterojunctions is evaluated.

  20. Selective epitaxial growth of monolithically integrated GaN-based light emitting diodes with AlGaN/GaN driving transistors

    SciTech Connect (OSTI)

    Liu, Zhaojun; Ma, Jun; Huang, Tongde; Liu, Chao; May Lau, Kei, E-mail: eekmlau@ust.hk [Photonics Technology Center, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2014-03-03T23:59:59.000Z

    In this Letter, we report selective epitaxial growth of monolithically integrated GaN-based light emitting diodes (LEDs) with AlGaN/GaN high-electron-mobility transistor (HEMT) drivers. A comparison of two integration schemes, selective epitaxial removal (SER), and selective epitaxial growth (SEG) was made. We found the SER resulted in serious degradation of the underlying LEDs in a HEMT-on-LED structure due to damage of the p-GaN surface. The problem was circumvented using the SEG that avoided plasma etching and minimized device degradation. The integrated HEMT-LEDs by SEG exhibited comparable characteristics as unintegrated devices and emitted modulated blue light by gate biasing.

  1. Active Q switching in a GaAs/AlGaAs multiquantum well laser with an intracavity monolithic loss modulator

    SciTech Connect (OSTI)

    Arakawa, Y.; Larsson, A.; Paslaski, J.; Yariv, A.

    1986-03-03T23:59:59.000Z

    Active Q switching in a GaAs/AlGaAs multiquantum well laser with an intracavity electroabsorption monolithic loss modulator is demonstrated. In this device, an efficient loss modulation is achieved through the quantum confined Stark effect in a modulator section and the enhanced carrier induced band shrinkage effect in an optical amplifier section. It is found that a picosecond pulse as narrow as 18.6 ps full width at half-maximum is generated and a high repetition rate of more than 3 GHz is obtained.

  2. 1.9 kV AlGaN/GaN Lateral Schottky Barrier Diodes on Silicon

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

    Zhu, Mingda [University of Notre Dame, IN (United States); Song, Bo [Cornell University, Ithaca, NY (United States); Qi, Meng [University of Notre Dame, IN (United States); Hu, Zongyang [University of Notre Dame, IN (United States); Nomoto, Kazuki [University of Notre Dame, IN (United States); Yan, Xiaodong [University of Notre Dame, IN (United States); Cao, Yu [IQE, Westborough, MA (United States); Johnson, Wayne [IQE, Westborough, MA (United States); Kohn, Erhard [University of Notre Dame, IN (United States); Jena, Debdeep [Cornell University, Ithaca, NY (United States); Xing, Grace Huili [Cornell University, Ithaca, NY (United States)

    2015-04-01T23:59:59.000Z

    In this letter, we present AlGaN/GaN lateral Schottky barrier diodes on silicon with recessed anodes and dual field plates. A low specific on-resistance RON,SP (5.12 m?{center_dot}cm2), a low turn-on voltage (1.9 kV), were simultaneously achieved in devices with a 25 ?m anode/cathode separation, resulting in a power figure-of-merit (FOM) BV2/RON,SP of 727 MW{center_dot}cm2. The record high breakdown voltage of 1.9 kV is attributed to the dual field plate structure.

  3. Effects of rapid thermal annealing on the electrical properties of the AlGaN/AlN/GaN heterostructure field-effect transistors with Ti/Al/Ni/Au gate electrodes

    SciTech Connect (OSTI)

    Zhao, Jingtao; Lin, Zhaojun, E-mail: linzj@sdu.edu.cn; Luan, Chongbiao; Zhou, Yang; Yang, Ming [School of Physics, Shandong University, Jinan 250100 (China); Lv, Yuanjie; Feng, Zhihong [National Key Laboratory of Application Specific Integrated Circuit (ASIC), Hebei Semiconductor Research Institute, Shijiazhuang 050051 (China)

    2014-08-25T23:59:59.000Z

    In this study, we investigated the electrical properties of the AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with Ti/Al/Ni/Au gate electrodes using the measured capacitance-voltage, current-voltage characteristics, and micro-Raman spectroscopy. We found that the uneven distribution of the strain caused by the Schottky metals was a major factor that generates the polarization Coulomb field scattering in AlGaN/AlN/GaN HFETs, and after appropriate rapid thermal annealing (RTA) processes, the polarization Coulomb field scattering was greatly weakened and the two-dimensional electron gas electron mobility was improved. We also found that the Schottky barrier height and the DC characteristics of the devices became better after appropriate RTA. Of course, the electrical performances mentioned above became deteriorated after excessive annealing.

  4. Growth, microstructure, and luminescent properties of direct-bandgap InAlP on relaxed InGaAs on GaAs substrates

    E-Print Network [OSTI]

    an impact on the luminescence spectrum. While similar to InGaP in many ways, the greater tendency for phase as the InGaP system, but still has desirable properties. In0.48Al0.52P is lattice- matched to GaAs and has

  5. 2DEG electrodes for piezoelectric transduction of AlGaN/GaN MEMS resonators

    E-Print Network [OSTI]

    Weinstein, Dana

    A 2D electron gas (2DEG) interdigitated transducer (IDT) in Gallium Nitride (GaN) resonators is introduced and demonstrated. This metal-free transduction does not suffer from the loss mechanisms associated with more commonly ...

  6. OMVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics (title change from A)

    SciTech Connect (OSTI)

    HAN,JUNG; FIGIEL,JEFFREY J.; PETERSEN,GARY A.; MYERS JR.,SAMUEL M.; CRAWFORD,MARY H.; BANAS,MICHAEL ANTHONY; HEARNE,SEAN JOSEPH

    2000-01-18T23:59:59.000Z

    We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GrdnN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

  7. Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe

    E-Print Network [OSTI]

    A. E. Nikolaenko; E. A. Chekhovich; M. N. Makhonin; I. W. Drouzas; A. B. Vankov; J. Skiba-Szymanska; M. S. Skolnick; P. Senellart; A. Lemaitre; A. I. Tartakovskii

    2009-01-15T23:59:59.000Z

    Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.

  8. SiO2 Passivation Effects on the Leakage Current in Dual-Gate AlGaN/GaN High Electron Mobility Transistors

    E-Print Network [OSTI]

    Seo, Kwang Seok

    was grown on c-plane sapphire substrate by MOCVD. Undoped 30 nm-thick Al0.26Ga0.74N and Fe-doped 3 m GaN substrate 3 nm undoped GaN 0.26 0.74 Source DrainMain-GateSiO2 2DEG SiO2 SiO2 Additional Gate 5 m3 m3 m 3 mSiO2 Passivation Effects on the Leakage Current in Dual-Gate AlGaN/GaN High Electron Mobility

  9. High performance double pulse doped pseudomorphic AlGaAs/InGaAs transistors grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Hoke, W.E.; Lyman, P.S.; Labossier, W.H.; Brierley, S.K.; Hendriks, H.T.; Shanfield, S.R.; Aucoin, L.M.; Kazior, T.E. [Raytheon Research Division, Lexington, MA (United States)] [Raytheon Research Division, Lexington, MA (United States)

    1992-05-01T23:59:59.000Z

    Double pulse doped AlGaAs/InGaAs pseudomorphic high electron mobility transistors have been grown by molecular-beam epitaxy on GaAs substrates. Hall mobilities in excess of 7100 cm{sup 2}/V s at 300 K and 25000 cm{sup 2}/V s at 77 K are obtained with a sheet density of 3 x 10{sup 12} cm{sup {minus}2}. Photoluminescence measurements indicate that two electronic subbands are occupied, and the subband energies are determined. The doping pulses are resolved in secondary ion mass spectrometry measurements. Using a double recess process, transistors have been fabricated that have produced state of the art microwave performance. At 10 GHz a 1.2 mm device has simultaneously achieved a power added efficiency of 70%, output power of 0.97 W, and gain of 10 dB. 17 refs., 5 figs., 1 tab.

  10. Plasmonic terahertz detectors based on a high-electron mobility GaAs/AlGaAs heterostructure

    SciTech Connect (OSTI)

    Bia?ek, M., E-mail: marcin.bialek@fuw.edu.pl; Witowski, A. M.; Grynberg, M.; ?usakowski, J. [Faculty of Physics, University of Warsaw, ul. Ho?a 69, 00-681 Warsaw (Poland); Orlita, M.; Potemski, M. [Laboratoire National des Champs Magnetiques Intenses, CNRS-UJF-UPS-INSA, 25, avenue des Martyrs, 38042 Grenoble (France); Czapkiewicz, M. [Institute of Physics, PAS, al. Lotników 32/46, 02-668 Warsaw (Poland); Wróbel, J. [Institute of Physics, PAS, al. Lotników 32/46, 02-668 Warsaw (Poland); Faculty of Mathematics and Natural Sciences, Rzeszów University, al. Rejtana 16A, 35-959 Rzeszów (Poland); Umansky, V. [Weizmann Institute of Science, Rehevot 76100 (Israel)

    2014-06-07T23:59:59.000Z

    In order to characterize magnetic field (B) tunable THz plasmonic detectors, spectroscopy experiments were carried out at liquid helium temperatures and high magnetic fields on devices fabricated on a high electron mobility GaAs/AlGaAs heterostructure. The samples were either gated (the gate of a meander shape) or ungated. Spectra of a photovoltage generated by THz radiation were obtained as a function of B at a fixed THz excitation from a THz laser or as a function of THz photon frequency at a fixed B with a Fourier spectrometer. In the first type of measurements, the wave vector of magnetoplasmons excited was defined by geometrical features of samples. It was also found that the magnetoplasmon spectrum depended on the gate geometry which gives an additional parameter to control plasma excitations in THz detectors. Fourier spectra showed a strong dependence of the magnetoplasmon resonance amplitude on the conduction-band electron filling factor which was explained within a model of the electron gas heating with THz radiation. The study allows to define both the advantages and limitations of plasmonic devices based on high-mobility GaAs/AlGaAs heterostructures for THz detection at low temperatures and high magnetic fields.

  11. 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.

  12. Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

    SciTech Connect (OSTI)

    Ledentsov, N. N., E-mail: nikolay.ledentsov@v-i-systems.com; Shchukin, V. A. [VI Systems GmbH, Hardenbergstr. 7, Berlin D-10623 (Germany); Lyytikäinen, J.; Okhotnikov, O. [Optoelectronics Research Centre, Tampere University of Technology, Tampere FI-33720 (Finland); Shernyakov, Yu. M.; Payusov, A. S.; Gordeev, N. Yu.; Maximov, M. V. [A. F. Ioffe Physical Technical Institute of the Russian Academy of Sciences, Politekhnicheskaya 26, St. Petersburg 194021 (Russian Federation); Schlichting, S.; Nippert, F.; Hoffmann, A. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, Berlin D-10623 (Germany)

    2014-11-03T23:59:59.000Z

    We report on green (550–560?nm) electroluminescence (EL) from (Al{sub 0.5}Ga{sub 0.5}){sub 0.5}In{sub 0.5}P-(Al{sub 0.8}Ga{sub 0.2}){sub 0.5}In{sub 0.5}P double p-i-n heterostructures with monolayer-scale GaP insertions in the cladding layers and light-emitting diodes based thereupon. The structures are grown side-by-side on high-index and (100) GaAs substrates by molecular beam epitaxy. At moderate current densities (?500?A/cm{sup 2}), the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)-grown strictures, the EL spectra of (211) and (311)-grown devices are shifted towards shorter wavelengths (?550?nm at room temperature). At high current densities (>1?kA/cm{sup 2}), a much higher EL intensity is achieved for the devices grown on high-index substrates. The integrated intensity of (311)-grown structures gradually saturates at current densities above 4?kA/cm{sup 2}, whereas no saturation is revealed for (211)-grown structures up to the current densities above 14?kA/cm{sup 2}. We attribute the effect to the surface orientation-dependent engineering of the GaP band structure, which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p-doped (Al{sub 0.8}Ga{sub 0.2}){sub 0.5}In{sub 0.5}P cladding layers.

  13. Study of the breakdown failure mechanisms for power AlGaN/GaN HEMTs implemented using a RF compatible process

    E-Print Network [OSTI]

    Ng, Wai Tung

    ]. Mishra et al. proposed a SiO2/Si3N4 bi-layer structure as the gate insulator [6]. Even though these MISStudy of the breakdown failure mechanisms for power AlGaN/GaN HEMTs implemented using a RF Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology

  14. 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

  15. Short-period superlattices of AlN/Al0.08Ga0.92N grown on AlN substrates S. A. Nikishin,a)

    E-Print Network [OSTI]

    Holtz, Mark

    Group Inc., 1154 Stealth Street, Livermore, California 94550 (Received 10 August 2004; accepted 8 from high dislocation densities that reduce quantum efficiency and lifetime of light emitting diodes (LEDs) and solar blind pho- todetectors. Short period superlattices (SPSLs) of AlN/Al0.08Ga0.92N

  16. Ultrasensitive detection of Hg{sup 2+} using oligonucleotide-functionalized AlGaN/GaN high electron mobility transistor

    SciTech Connect (OSTI)

    Cheng, Junjie [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Li, Jiadong; Miao, Bin; Wu, Dongmin, E-mail: dmwu2008@sinano.ac.cn [i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wang, Jine; Pei, Renjun, E-mail: rjpei2011@sinano.ac.cn [Division of Nanobiomedicine, Key Laboratory for Nano-Bio Interface Research, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-08-25T23:59:59.000Z

    An oligonucleotide-functionalized ion sensitive AlGaN/GaN high electron mobility transistor (HEMT) was fabricated to detect trace amounts of Hg{sup 2+}. The advantages of ion sensitive AlGaN/GaN HEMT and highly specific binding interaction between Hg{sup 2+} and thymines were combined. The current response of this Hg{sup 2+} ultrasensitive transistor was characterized. The current increased due to the accumulation of Hg{sup 2+} ions on the surface by the highly specific thymine-Hg{sup 2+}-thymine recognition. The dynamic linear range for Hg{sup 2+} detection has been determined in the concentrations from 10{sup ?14} to 10{sup ?8} M and a detection limit below 10{sup ?14} M level was estimated, which is the best result of AlGaN/GaN HEMT biosensors for Hg{sup 2+} detection till now.

  17. Two-dimensional electron gases in strained quantum wells for AlN/GaN/AlN double heterostructure field-effect transistors on AlN

    SciTech Connect (OSTI)

    Li, Guowang; Song, Bo; Ganguly, Satyaki; Zhu, Mingda; Wang, Ronghua; Yan, Xiaodong; Verma, Jai; Protasenko, Vladimir; Grace Xing, Huili; Jena, Debdeep, E-mail: djena@nd.edu [Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)

    2014-05-12T23:59:59.000Z

    Double heterostructures of strained GaN quantum wells (QWs) sandwiched between relaxed AlN layers provide a platform to investigate the quantum-confined electronic and optical properties of the wells. The growth of AlN/GaN/AlN heterostructures with varying GaN quantum well thicknesses on AlN by plasma molecular beam epitaxy (MBE) is reported. Photoluminescence spectra provide the optical signature of the thin GaN QWs. Reciprocal space mapping in X-ray diffraction shows that a GaN layer as thick as ?28 nm is compressively strained to the AlN layer underneath. The density of the polarization-induced two-dimensional electron gas (2DEG) in the undoped heterostructures increases with the GaN QW thickness, reaching ?2.5?×?10{sup 13}/cm{sup 2}. This provides a way to tune the 2DEG channel density without changing the thickness of the top barrier layer. Electron mobilities less than ?400 cm{sup 2}/Vs are observed, leaving ample room for improvement. Nevertheless, owing to the high 2DEG density, strained GaN QW field-effect transistors with MBE regrown ohmic contacts exhibit an on-current density ?1.4?A/mm, a transconductance ?280 mS/mm, and a cut off frequency f{sub T}?104?GHz for a 100-nm-gate-length device. These observations indicate high potential for high-speed radio frequency and high voltage applications that stand to benefit from the extreme-bandgap and high thermal conductivity of AlN.

  18. Dielectric function and optical properties of quaternary AlInGaN alloys

    SciTech Connect (OSTI)

    Sakalauskas, E.; Gobsch, G. [Institut fuer Physik, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Reuters, B.; Khoshroo, L. Rahimzadeh; Kalisch, H.; Vescan, A. [GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); Heuken, M. [GaN Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath (Germany); Roeppischer, M.; Cobet, C. [Leibniz-Institut fuer Analytische Wissenschaften - ISAS - e.V., Albert-Einstein-Str. 9, 12489 Berlin (Germany); Goldhahn, R. [Institut fuer Physik, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Institut fuer Experimentelle Physik, Otto-von-Guericke-Universitaet Magdeburg, PF 4120, 39016 Magdeburg (Germany)

    2011-07-01T23:59:59.000Z

    The optical properties of quaternary Al{sub x}In{sub y}Ga{sub 1-x-y}N alloy films with 0.16AlInGaN layers were grown by metal-organic vapor phase epitaxy on thick GaN/sapphire templates. High-resolution x-ray diffraction measurements revealed the pseudomorphic growth of the AlInGaN films on the GaN buffer. Rutherford backscattering and wavelength-dispersive x-ray spectroscopy analysis were used in order to determine the composition of the alloys. The ordinary dielectric function (DF) of the AlInGaN samples was determined in the range of 1-10 eV by spectroscopic ellipsometry (SE) at room temperature (synchrotron radiation: BESSY II). The sharp onset of the imaginary part of the DF defines the direct absorption edge of the alloys. At higher photon energies, pronounced peaks are observed in the DF indicating a promising optical quality of the material. These features are correlated to the critical points of the band structure (van Hove singularities). An analytical model, which permits us to accurately describe the dielectric function (or optical constants) in the range of 1-10 eV, is also presented. The band-gap and high-energy interband transition values are obtained by fitting the experimental DF with the analytical model. The strain influence on the bandgap is evaluated by using the kxp formalism. Furthermore, an empirical expression is proposed which allows us to calculate the AlInGaN band-gap and high-energy inter-band transitions in the whole compositional range (x, y). The band-gap values obtained from the empirical expression are in good agreement with both the calculated ab initio and the experimental values determined by SE.

  19. 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.

  20. 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

  1. Influence of substrate miscut angle on surface morphology and luminescence properties of AlGaN

    SciTech Connect (OSTI)

    Kusch, Gunnar, E-mail: gunnar.kusch@strath.ac.uk; Edwards, Paul R.; Bruckbauer, Jochen; Martin, Robert W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Li, Haoning; Parbrook, Peter J. [Tyndall National Institute, University College Cork, Lee Maltings, Dyke Parade, Cork (Ireland); School of Engineering, University College Cork, College Road, Cork (Ireland); Sadler, Thomas C. [Tyndall National Institute, University College Cork, Lee Maltings, Dyke Parade, Cork (Ireland)

    2014-03-03T23:59:59.000Z

    The influence of substrate miscut on Al{sub 0.5}Ga{sub 0.5}?N layers was investigated using cathodoluminescence (CL) hyperspectral imaging and secondary electron imaging in an environmental scanning electron microscope. The samples were also characterized using atomic force microscopy and high resolution X-ray diffraction. It was found that small changes in substrate miscut have a strong influence on the morphology and luminescence properties of the AlGaN layers. Two different types are resolved. For low miscut angle, a crack-free morphology consisting of randomly sized domains is observed, between which there are notable shifts in the AlGaN near band edge emission energy. For high miscut angle, a morphology with step bunches and compositional inhomogeneities along the step bunches, evidenced by an additional CL peak along the step bunches, are observed.

  2. Inverted-V chirped phased arrays of gain-guided GaAs/GaAlAs diode lasers

    SciTech Connect (OSTI)

    Kapon, E.; Lindsey, C.P.; Smith, J.S.; Margalit, S.; Yariv, A.

    1984-12-15T23:59:59.000Z

    Inverted-V chirped arrays of multiple quantum well GaAs/GaAlAs lasers were grown by molecular beam epitaxy. These arrays consisted of seven gain-guided lasers whose stripe widths decreased, from the central laser to the outermost ones, symmetrically. This structure makes it possible to discriminate against the higher order array supermodes, which results in diffraction limited beams with a single lobe directed perpendicular to the laser facet. Single lobed far-field patterns, 3/sup 0/--4/sup 0/ wide, were obtained from inverted-V chirped arrays operated up to 1.5I/sub th/. The supermode structure of these arrays was identified by studying their spectrally resolved near fields.

  3. 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

  4. AlGaAs/GaAs quantum well infrared detectors and modulators

    E-Print Network [OSTI]

    Dave, Digant Praful

    1990-01-01T23:59:59.000Z

    of boundary condition (1) we find that F=D=O Applying the boundary conditions (2) and (3) to the Schrodinger equation we get four ordinary equations. at x=-a -Asin(qa) + Bcos(qa) = Ce-" qAcos(qa) + qBsin(qa) = sCe ~ (4 7) (4 6) atx= a Asin... been extensively used for quantum well applications and studies is because of the excellent lattice match that exists between GaAs and AIAs. This feature is quite clear from the Fig. 2. They have less than 0. 13/o of lattice mismatch. The lattice...

  5. Vertical-external-cavity surface-emitting 625-nm laser upon optical pumping of an InGaP/AlGaInP nanostructure with a Bragg mirror

    SciTech Connect (OSTI)

    Kozlovskii, Vladimir I; Lavrushin, B M; Skasyrsky, Yan K [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation); Tiberi, M D [Principia Light Works Inc., Woodland Hills, CA (United States)

    2009-08-31T23:59:59.000Z

    Pulsed lasing is obtained in a multilayer quantum-well InGaP/AlGaInP structure in a cavity with an external mirror and a Bragg AlAs/AlGaAs mirror pumped by the 532-nm second harmonic from a diode-pumped Q-switched Nd:YAG laser. Lasing is obtained at the TEM{sub 00} fundamental transverse mode of the cavity at a wavelength of 625 nm. The pulse beam power was 3.1 W and the radiation divergence achieved a diffraction limit of 10-12 mrad for 5-ns pulses with a repetition rate of 6 kHz. (lasers)

  6. On the importance of AlGaN electron blocking layer design for GaN-based light-emitting diodes

    SciTech Connect (OSTI)

    Sheng Xia, Chang, E-mail: xiachsh@crosslight.com.cn; Simon Li, Z. M.; Sheng, Yang [Crosslight Software Inc., China Branch, Suite 906, Building JieDi, 2790 Zhongshan Bei Road, Shanghai 200063 (China)] [Crosslight Software Inc., China Branch, Suite 906, Building JieDi, 2790 Zhongshan Bei Road, Shanghai 200063 (China)

    2013-12-02T23:59:59.000Z

    There has been confusion regarding the usefulness of AlGaN electron blocking layer (EBL) in GaN-based light-emitting diodes (LEDs) with some published experimental data indicating that the LEDs without EBL performed better than those with it. InGaN/GaN LEDs have been investigated numerically to analyze its actual effect in these devices. Simulation results show that hole blocking effect of EBL mainly determines the effectiveness of using it which is more sensitive to its Al composition, band offset ratio, and polarization charges. It is found that the choice of Al composition is critical for EBL to improve the optical performance of GaN-based LEDs.

  7. AlGaAs lasers with micro-cleaved mirrors suitable for monolithic integration

    SciTech Connect (OSTI)

    Blauvelt, H.; Bar-Chaim, N.; Fekete, D.; Margalit, S.; Yariv, A.

    1982-02-15T23:59:59.000Z

    A technique has been developed for cleaving the mirrors of AlGaAs lasers without cleaving the substrate. Micro-cleaving involves cleaving a suspended heterostructure cantilever by ultrasonic vibrations. Lasers with microcleaved mirrors have threshold currents and quantum efficiencies identical to those of similar devices with conventionally cleaved mirrors.

  8. Very high frequency GaAlAs laser field-effect transistor monolithic integrated circuit

    SciTech Connect (OSTI)

    Ury, I.; Lau, K.Y.; Bar-Chaim, N.; Yariv, A.

    1982-07-15T23:59:59.000Z

    A very low threshold GaAlAs buried heterostructure laser has been monolithically integrated with a recessed structure metal-semiconductor field-effect transistor on a semi-insulating substrate. At cw operation, the device has a direct modulation bandwidth of at least 4 GHz.

  9. Wet chemical etch solutions for Al{sub x}Ga{sub 1{minus}x}P

    SciTech Connect (OSTI)

    Lee, J.W.; Santana, C.J.; Abernathy, C.R.; Pearton, S.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Ren, F. [AT and T Bell Labs., Murray Hill, NJ (United States)

    1996-01-01T23:59:59.000Z

    Heterostructures based on AlGaInP alloy compounds are very attractive for visible semiconductor lasers, heterojunction bipolar transistors (HBTs), and high-electron-mobility transistors (HEMTs) lattice matched to GaAs substrates. Several wet etching solutions for AlGaP of different compositions have been studied. Al{sub 0.5}Ga{sub 0.5}P is found to etch in HF, H{sub 3}PO{sub 4}, hyphosphorous acid (HOPH{sub 2}:O), HCl, KOH, and 1% Br{sub 2}-methanol (MeOH). Etching of Al{sub 0.5}Ga{sub 0.5}P in HCl is reaction limited with an activation energy of {approximately}54.4 kJ/mol. At fixed conditions, the etch rates of Al{sub x}Ga{sub 1{minus}x}P vary exponentially with x in HF and HCl, while in 1% Br{sub 2}-MeOH and mixtures of HCl and HNO{sub 3} the etch rates follow a linear dependence on AlP mole fraction. HF has been found to be a good etchant for AlGaP over InGaP or AlInP with high selectivity, while HCl is useful for the reverse case. The use of 1% Br{sub 2}-MeOH or the mixtures of HCl and HNO{sub 3} provides little selectivity between AlGaP, InGaP, AlInP, and GaAs.

  10. Short-period superlattices of AlN/Al{sub 0.08}Ga{sub 0.92}N grown on AlN substrates

    SciTech Connect (OSTI)

    Nikishin, S.A.; Borisov, B.A.; Chandolu, A.; Kuryatkov, V.V.; Temkin, H.; Holtz, M.; Mokhov, E.N.; Makarov, Yu.; Helava, H. [Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409-3102 (United States); Nano Tech Center/Department of Physics, Texas Tech University, Lubbock, Texas 79409 (United States); Fox Group Inc., 1154 Stealth Street, Livermore, California 94550 (United States)

    2004-11-08T23:59:59.000Z

    High-quality short-period superlattices of AlN/Al{sub 0.08}Ga{sub 0.92}N have been grown by gas-source molecular-beam epitaxy with ammonia on Al face of AlN (0001) substrates. A significant reduction was achieved in the dislocation density, down to 3x10{sup 8} cm{sup -2}. Complete removal of residual Al{sub 2}O{sub 3} surface oxide is needed in order to obtain low dislocation density in homoepitaxy on AlN. We show that the presence of Al{sub 2}O{sub 3} islands with the surface coverage as low as 0.2% results in increased dislocation density.

  11. 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.

  12. Comparison of plasma chemistries for inductively coupled plasma etching of InGaAlP alloys

    SciTech Connect (OSTI)

    Hong, J.; Lee, J.W.; Abernathy, C.R.; Lambers, E.S.; Pearton, S.J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Shul, R.J. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Hobson, W.S. [Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)] [Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)

    1998-05-01T23:59:59.000Z

    Two plasma chemistries, i.e., CH{sub 4}/H{sub 2}/Ar and Cl{sub 2}/Ar, were compared for the etching of InGaP, AlInP, and AlGaP under inductively coupled plasma (ICP) conditions. While the etching with CH{sub 4}/H{sub 2}/Ar discharges appears to be ion driven, Cl{sub 2}/Ar discharges showed an additional strong chemical enhancement. The highest etch rate ({approximately}1 {mu}m/min) for InGaP was achieved at high ICP source power ({ge}750 W) with the Cl{sub 2}/Ar chemistry. Cl{sub 2}/Ar discharges provided very smooth surfaces in all three materials with root-mean-square roughness measured by atomic force microscopy around 2 nm. This result may be due to the efficient ion-assisted product desorption in this chemistry. The etched near-surface region of InGaP ({approximately}100 {Angstrom}) with Cl{sub 2}/Ar maintained almost the same stoichiometry as that of the unetched control. By contrast, the CH{sub 4}/H{sub 2}/Ar plasma chemistry produced somewhat rougher surfaces and depletion of phosphorous (P) from the surface of InGaP. {copyright} {ital 1998 American Vacuum Society.}

  13. Investigation of trap states under Schottky contact in GaN/AlGaN/AlN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Ma, Xiao-Hua, E-mail: xhma@xidian.edu.cn, E-mail: yhao@xidian.edu.cn; Chen, Wei-Wei; Hou, Bin; Zhu, Jie-Jie [School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710071 (China); Key Lab of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071 (China); Zhang, Kai; Zhang, Jin-Cheng; Zheng, Xue-Feng; Hao, Yue, E-mail: xhma@xidian.edu.cn, E-mail: yhao@xidian.edu.cn [Key Lab of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071 (China)

    2014-03-03T23:59:59.000Z

    Forward gate-bias stress experiments are performed to investigate the variation of trap states under Schottky contact in GaN-based high electron mobility transistors. Traps with activation energy E{sub T} ranging from 0.22?eV to 0.31?eV are detected at the gate-semiconductor interface by dynamic conductance technique. Trap density decreases prominently after stressing, particularly for traps with E{sub T}?>?0.24?eV. X-ray photoelectron spectroscopy measurements reveal a weaker Ga-O peak on the stressed semiconductor surface. It is postulated that oxygen is stripped by Ni to form NiO upon electrical stress, contributing to the decrease in O{sub N} donor sates under the gate contact.

  14. Al fraction induced effects on the capacitance characteristics -GaN/AlxGa1-xN IR detectors

    E-Print Network [OSTI]

    Dietz, Nikolaus

    substrate. As shown in Fig. 1(a), the device structures consist of a 0.2 m n+ -GaN top contact (emitter.1117/12.828156 Proc. of SPIE Vol. 7467 74670W-1 #12;(a) Sapphire Substrate n GaN Bottom Contact AlxGa1-xN Barrier n GaNAl fraction induced effects on the capacitance characteristics of n+ -GaN/AlxGa1-xN IR detectors

  15. Optical anisotropy in [0001] oriented GaN/Al{sub x}Ga{sub 1?x}N quantum wells under pressure

    SciTech Connect (OSTI)

    Bardyszewski, W. [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ul. Ho?a 69, 00-681 Warszawa (Poland); ?epkowski, S. P. [Institute of High Pressure Physics, Unipress, Polish Academy of Sciences, ul. Soko?owska 29/37, 01-142 Warszawa (Poland)

    2013-12-04T23:59:59.000Z

    We investigate the influence of external pressure on optical anisotropy of GaN/Al{sub x}Ga{sub 1?x}N quantum wells (QWs) grown along the c-crystallographic direction. Our theoretical study reveals that for sufficiently narrow GaN/Al{sub x}Ga{sub 1?x}N QWs, lattice matched to GaN substrate a pressure-dependent switching of polarization of emitted light occurs. This switching of polarization is manifested by the change of sign of the degree of polarization of photoluminescence spectra. We note that the results of our model critically depend on the deformation potential values and therefore can be used for verification of existing literature values of these parameters.

  16. Two-dimensional electron and hole gases in In{sub x}Ga{sub 1?x}N/Al{sub y}Ga{sub 1?y}N/GaN heterostructure for enhancement mode operation

    SciTech Connect (OSTI)

    Yan, Junda; Wang, Quan; Qu, Shenqi; Xiao, Hongling; Peng, Enchao; Kang, He; Wang, Cuimei; Feng, Chun; Yin, Haibo; Jiang, Lijuan [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Wang, Xiaoliang, E-mail: xlwang@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Beijing (China); ISCAS-XJTU Joint Laboratory of Functional Materials and Devices for Informatics, P.O. Box 912, Beijing 100083 (China); Li, Baiquan [Beijing Huajin Chuangwei Technology Co., Ltd., Beijing (China); Wang, Zhanguo [Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Beijing (China); Hou, Xun [ISCAS-XJTU Joint Laboratory of Functional Materials and Devices for Informatics, P.O. Box 912, Beijing 100083 (China)

    2014-08-07T23:59:59.000Z

    In this paper, a numerical study of In{sub x}Ga{sub 1?x}N/Al{sub y}Ga{sub 1?y}N/GaN heterostructure is presented. The dependence of two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) sheet densities on variables, such as In{sub x}Ga{sub 1?x}N layer thickness and In content, and Al{sub y}Ga{sub 1?y}N barrier layer thickness and Al content, are systematically investigated. The effect of P-type doping in In{sub x}Ga{sub 1?x}N on 2DEG and 2DHG sheet densities in this heterostructure is also studied. It is shown that the strong reverse electric field in In{sub x}Ga{sub 1?x}N cap layer contributes to the depletion of 2DEG at the Al{sub y}Ga{sub 1-y}N/GaN interface. When In{sub x}Ga{sub 1?x}N layer thickness and In content increases, 2DEG sheet density decreases significantly. P-type doping shows less influence on 2DEG compared to the polarization electric field in In{sub x}Ga{sub 1?x}N layer. In addition, there exist critical values for all the variables beyond which 2DHG appears at the interface of In{sub x}Ga{sub 1?x}N/Al{sub y}Ga{sub 1?y}N. Once 2DHG appears, it will prevent 2DEG from being further depleted. With proper design of Al{sub y}Ga{sub 1?y}N layer, the coexistence of 2DEG and 2DHG in In{sub x}Ga{sub 1?x}N/Al{sub y}Ga{sub 1?y}N/GaN structure can be avoided, showing that this structure has great potential in the fabrication of enhancement mode (E-mode) high electron mobility transistors.

  17. 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.

  18. Strain relaxation in short-period polar GaN/AlN superlattices

    SciTech Connect (OSTI)

    Kandaswamy, P. K.; Jalabert, D.; Monroy, E. [Equipe Mixte CEA-CNRS Nanophysique et Semiconducteurs, INAC/SP2M/NPSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Bougerol, C. [Equipe Mixte CEA-CNRS Nanophysique et Semiconducteurs, Institut Neel, 25 rue des Martyrs, 38042 Grenoble (France); Ruterana, P. [CIMAP, CNRS-ENSICAEN-CEA-UCBN, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France)

    2009-07-01T23:59:59.000Z

    We have investigated the strain relaxation mechanisms in short-period polar GaN/AlN superlattices deposited by plasma-assisted molecular-beam epitaxy, and designed to display intersubband transitions at 1.55 mum. In a first stage, we have identified the growth conditions to minimize strain relaxation, using a Ga excess to reduce the (0001) surface free energy of both GaN and AlN. Under these growth conditions, crack propagation is not observed, even for the tensile-strained superlattices grown on GaN templates. The initial misfit relaxation in the vicinity of the buffer occurs by the formation of a-type dislocations. The final strain state of the superlattice, reached after 10-20 periods, is independent of the substrate (either GaN or AlN templates). Once the steady-state conditions are reached, we observe a periodic partial relaxation of quantum wells and barriers. High-resolution transmission electron microscopy indicates that the periodic relaxation can be related to the presence of basal and prismatic stacking faults creating clusters with an in-plane length of tens of nanometers. The effect of these defects on the optical performance of the superlattices is discussed by simulation of electronic structure using an 8x8kcentre dotp Schroedinger-Poisson solver. In the presence of basal stacking faults at the quantum well interfaces, the deviation of the e{sub 1}-e{sub 2} intersubband transition with respect to the nominal value is expected to be smaller than the measured absorption line width.

  19. Photoluminescence from InGaAs/GaAs quantum well regrown on a buried patterned oxidized AlAs layer

    SciTech Connect (OSTI)

    Chouchane, F.; Makhloufi, H.; Calvez, S.; Fontaine, C.; Almuneau, G., E-mail: almuneau@laas.fr [CNRS, LAAS, 7 Avenue du Colonel Roche, F-31400 Toulouse (France); Université de Toulouse, UPS, F-31400 Toulouse (France)

    2014-02-10T23:59:59.000Z

    We present a quasi-planar technological approach for forming a flexible and versatile confinement scheme based on oxidation of AlGaAs buried layers combined to an epitaxial regrowth. This method improves the electrical and optical confinements compared to the lateral oxidation since it allows to define confinement areas from a planar surface. This technique is suitable for the realization of advanced integrated photonic components arrays with close device-to-device spacing such as two-dimensional arrays of vertical-cavity surface-emitting lasers. Our results prove that the oxidation and epitaxial regrowth can be sequenced in a process flow, leading to viable confinement while preserving good radiative properties.

  20. The critical role of growth temperature on the structural and electrical properties of AlGaN/GaN high electron mobility transistor heterostructures grown on Si(111)

    SciTech Connect (OSTI)

    Baron, N. [CRHEA-CNRS, rue Bernard Gregory, Parc de Sophia Antipolis, 06560 Valbonne (France); PICOGIGA International, Place Marcel Rebuffat, Parc de Villejust, 91971 Courtaboeuf (France); Cordier, Y.; Chenot, S.; Vennegues, P.; Tottereau, O.; Leroux, M.; Semond, F.; Massies, J. [CRHEA-CNRS, rue Bernard Gregory, Parc de Sophia Antipolis, 06560 Valbonne (France)

    2009-02-01T23:59:59.000Z

    This work is dedicated to the study of the growth by ammonia source molecular beam epitaxy of Al{sub x}Ga{sub 1-x}N/GaN high electron mobility transistors on (111) oriented silicon substrates. The effect of growth conditions on the structural and electrical properties of the heterostructures was investigated. It is shown that even a slight variation in the growth temperature of the thick GaN buffer on AlN/GaN stress mitigating layers has a drastic influence on these properties via a counterintuitive effect on the dislocation density. Both in situ curvature measurements and ex situ transmission electron microscopy and x-ray diffraction experiments indicate that the relaxation rate of the lattice mismatch stress increases with the growth temperature but finally results in a higher dislocations density. Furthermore, a general trend appears between the final wafer curvature at room temperature and the threading dislocation density. Finally, the influence of the dislocation density on the GaN buffer insulating properties and the two-dimensional electron gas transport properties at the Al{sub x}Ga{sub 1-x}N/GaN interface is discussed.

  1. InGaP/InGaAlP double-heterostructure and multiquantum-well laser diodes grown by molecular-beam epitaxy

    SciTech Connect (OSTI)

    Tanaka, H.; Kawamura, Y.; Nojima, S.; Wakita, K.; Asahi, H.

    1987-03-01T23:59:59.000Z

    Room-temperature continuous-wave (cw) operation is achieved in the MBE (molecular-beam epitaxy)-grown InGaP/InGaAlP double-heterostructure (DH) visible laser diodes with a threshold current of 110 mA. The lasing wavelength and threshold current density under pulsed operation are 666 nm and as low as 3.9 kA/cm/sup 2/, respectively. This result is achieved by the introduction of H/sub 2/ into the growth chamber during growth, the continuous growth from one layer to the next layer, and the introduction of a GaAs buffer layer. InGaP/InGaAlP quantum well structures are also grown. From photoluminescence measurements, the conduction-band discontinuity ..delta..E/sub c/ is estimated to be 0.43 of the band-gap difference ..delta..E/sub g/. Furthermore, the multiquantum-well (MQW) structure is found to be stable under thermal treatment at temperatures as high as 750 /sup 0/C. Room-temperature pulsed operation of InGaP/InGaAlP MQW laser diodes is achieved for the first time. The lasing wavelength is 658 nm with a threshold current density of 7.6 kA/cm/sup 2/. cw operation is also achieved in the MQW laser diodes at -125 /sup 0/C.

  2. Deep ultraviolet photoluminescence of Tm-doped AlGaN alloys

    SciTech Connect (OSTI)

    Nepal, N.; Zavada, J. M. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Lee, D. S.; Steckl, A. J. [Nanoelectronics Laboratory, University of Cincinnati, Cincinnati, Ohio 45221 (United States); Sedhain, A.; Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409 (United States)

    2009-03-16T23:59:59.000Z

    The ultraviolet (UV) photoluminescence (PL) properties of Tm-doped Al{sub x}Ga{sub 1-x}N (0.39{<=}x{<=}1) alloys grown by solid-source molecular beam epitaxy were probed using above-bandgap excitation from a laser source at 197 nm. The PL spectra show dominant UV emissions at 298 and 358 nm only for samples with x=1 and 0.81. Temperature dependence of the PL intensities of these emission lines reveals exciton binding energies of 150 and 57 meV, respectively. The quenching of these UV emissions appears related to the thermal activation of the excitons bound to rare-earth structured isovalent (RESI) charge traps, which transfer excitonic energy to Tm{sup 3+} ions resulting in the UV emissions. A model of the RESI trap levels in AlGaN alloys is presented.

  3. Gate-Recessed InAlN/GaN HEMTs on SiC Substrate With Al[subscript 2]O[subscript 3] Passivation

    E-Print Network [OSTI]

    Guo, Shiping

    We studied submicrometer (L[subscript G] = 0.15-0.25 à ¿m) gate-recessed InAlN/AlN/GaN high-electron mobility transistors (HEMTs) on SiC substrates with 25-nm Al[subscript 2]O[subscript 3] passivation. The combination of ...

  4. Fermi energy dependence of linewidth enhancement factor of GaAlAs buried heterostructure lasers

    SciTech Connect (OSTI)

    Arakawa, Y.; Yariv, A.

    1985-11-01T23:59:59.000Z

    The linewidth enhancement factor ..cap alpha.. is measured in a number of GaAlAs lasers with different internal losses. It is found that ..cap alpha.. decreases monotonically with the increase of the loss (Fermi energy level) in agreement with the theoretical prediction. On the basis of these results the design of cavity length and mirror reflection in order to reduce the spectral linewidth of the laser output is discussed.

  5. The emission of polarized light from GaN/AlN self-assembled quantum dots subject to variable excitation conditions and uniaxial interfacial stresses

    E-Print Network [OSTI]

    Vardi, Amichay

    The emission of polarized light from GaN/AlN self-assembled quantum dots subject to variable. In this work, GaN/AlN self-assembled QDs were grown by the Stranski-Krastanov method on a Si(111) substrate expansion coefficient mismatch between the Si substrate and GaN/AlN film containing vertically stacked QDs

  6. Molecular-beam epitaxial growth and characterization of inverted, pulse-doped AlGaAs/InGaAs transistor structures

    SciTech Connect (OSTI)

    Hoke, W.E.; Lyman, P.S.; Brierley, S.K. [Raytheon Research Division, Lexington, MA (United States)] [and others] [Raytheon Research Division, Lexington, MA (United States); and others

    1993-05-01T23:59:59.000Z

    Inverted, pulse-doped AlGaAs/InGaAs pseudomorphic high electron mobility transistor structures were grown by molecular-beam epitaxy. Growth conditions were optimized to improve the quality of the selectively doped AlGaAs layer and to minimize dopant diffusion into the InGaAs channel. The sheet densities and mobilities of the inverted structure were found to be essentially equivalent to those obtained with the normal structure. Shubnikov-de Haas measurements exhibited strong oscillations in the magnetoresistance and plateaus in the Hall resistance. Four optical transitions from the lowest bound electron and hole quantum well states were observed in room-temperature photoluminescence spectra. 15 refs., 4 figs.

  7. Evanescent-wave pumped room-temperature single-mode GaAs/AlGaAs core-shell nanowire lasers

    SciTech Connect (OSTI)

    Wei, Wei; Zhang, Xia, E-mail: xzhang@bupt.edu.cn; Ren, Xiaomin [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 66, Beijing 100876 (China); Liu, Yange, E-mail: ygliu@nankai.edu.cn; Wang, Zhi [Key Laboratory of Optical Information and Technology, Ministry of Education and Institute of Modern Optics, Nankai University, Tianjin 300071 (China)

    2014-06-02T23:59:59.000Z

    Evanescent-wave pumped room-temperature single-mode GaAs/AlGaAs core-shell nanowire lasers are proposed and demonstrated. The nanowires are axially excited by evanescent wave outside a microfiber with a diameter about 10??m via a ns-pulse laser. The lasing emission with a low effective threshold less than 90 nJ is achieved at 868.62?nm along with a linewidth of ?1.8?nm. Moreover, multiple lasing lines in a wavelength range from 852.56?nm to 882.48?nm are observed. The mechanism of diverse lasing wavelengths is revealed. Furthermore, the proposed GaAs/AlGaAs nanowire laser has advantages such as simple structure, easy to operate, and controllable lasing wavelength, tending to be practical in optical communications and integrated photonic circuits.

  8. Yellow-green emission for ETS-LEDs and lasers based on a strainedInGaP quantum well heterostructure grown on a transparent, compositionally graded AlInGaP buffer

    E-Print Network [OSTI]

    Yellow-green emission for ETS-LEDs and lasers based on a strained­InGaP quantum well heterostructure grown on a transparent, compositionally graded AlInGaP buffer Lisa McGill, Juwell Wu, and Eugene phosphide (InGaP) quantum well on a transparent In0.22(Al0.2Ga0.8)0.78P/ x[Inx(Al0.2Ga0.8)1-xP]/GaP virtual

  9. Transient grating measurements of ambipolar diffusion and carrier recombination in InGaP/InAlP multiple quantum wells and InGaP bulk

    SciTech Connect (OSTI)

    Prasad, M.; Martinez, O.E.; Menoni, C.S. [Colorado State Univ., Fort Collins, CO (United States)

    1994-03-01T23:59:59.000Z

    The ambipolar diffusion coefficient and carrier recombination lifetime in InGaP/InAlP multiple quantum wells and InGaP epitaxial layers grown by gas source molecular beam epitaxy have been determined by measuring the diffraction efficiency decay of transient gratings induced by picosecond laser pulses. The multiple quantum well room temperature ambipolar diffusion coefficient of carrier transport parallel to the growth plane was measured to be approximately half that of the bulk material. 17 refs., 2 figs.

  10. Investigation of buffer traps in AlGaN/GaN-on-Si devices by thermally stimulated current spectroscopy and back-gating measurement

    SciTech Connect (OSTI)

    Yang, Shu; Zhou, Chunhua; Jiang, Qimeng; Chen, Kevin J., E-mail: eekjchen@ust.hk [Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Lu, Jianbiao; Huang, Baoling [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)] [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2014-01-06T23:59:59.000Z

    Thermally stimulated current (TSC) spectroscopy and high-voltage back-gating measurement are utilized to study GaN buffer traps specific to AlGaN/GaN lateral heterojunction structures grown on a low-resistivity Si substrate. Three dominating deep-level traps in GaN buffer with activation energies of ?E{sub T1}???0.54?eV, ?E{sub T2}???0.65?eV, and ?E{sub T3}???0.75?eV are extracted from TSC spectroscopy in a vertical GaN-on-Si structure. High back-gate bias applied to the Si substrate could influence the drain current in an AlGaN/GaN-on-Si high-electron-mobility transistor in a way that cannot be explained with a simple field-effect model. By correlating the trap states identified in TSC with the back-gating measurement results, it is proposed that the ionization/deionization of both donor and acceptor traps are responsible for the generation of buffer space charges, which impose additional modulation to the 2DEG channel.

  11. 238 IEEE ELECTRON DEVICE LETTERS, VOL. 25, NO. 5, MAY 2004 Polyimide Passivated AlGaNGaN HFETs With

    E-Print Network [OSTI]

    Shen, Shyh-Chiang

    238 IEEE ELECTRON DEVICE LETTERS, VOL. 25, NO. 5, MAY 2004 Polyimide Passivated AlGaN­GaN HFETs, degrading RF performance. A passivation scheme utilizing a polyimide film as the passivating layer. This data suggests that polyimide can be an effective passivation film for reducing surface states. Index

  12. 11-GHz direct modulation bandwidth GaAlAs window laser on semi-insulating substrate operating at room temperature

    SciTech Connect (OSTI)

    Lau, K.Y.; Bar-Chaim, N.; Ury, I.; Yariv, A.

    1984-08-15T23:59:59.000Z

    We have demonstrated a direct modulation bandwidth of up to 11 GHz in a window GaAlAs buried heterostructure laser fabricated on a semi-insulating substrate, operating at room temperature.

  13. Aluminum nitride transitional layer for reducing dislocation density and cracking of AlGaN epitaxial films

    DOE Patents [OSTI]

    Allerman, Andrew A.; Crawford, Mary H.; Lee, Stephen R.

    2013-01-08T23:59:59.000Z

    A denticulated Group III nitride structure that is useful for growing Al.sub.xGa.sub.1-xN to greater thicknesses without cracking and with a greatly reduced threading dislocation (TD) density.

  14. Visible (657 nm) InGaP/InAlGaP strained quantum well vertical-cavity surface-emitting laser

    SciTech Connect (OSTI)

    Schneider, R.P. Jr.; Bryan, R.P.; Lott, J.A. (Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 (United States)); Olbright, G.R. (Photonics Research, Inc., Broomfield, Colorado 80021 (United States))

    1992-04-13T23:59:59.000Z

    We report the first visible (657 nm) vertical-cavity surface-emitting laser. The photopumped undoped structure was grown using low-pressure metalorganic vapor-phase epitaxy in a single-growth sequence on misoriented GaAs substrates. The optical cavity consists of an In{sub 0.54}Ga{sub 0.46}P/In{sub 0.48}(Al{sub 0.7}Ga{sub 0.3}){sub 0.52} P strained quantum-well active region and a lattice-matched In{sub 0.48}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.52} P (0.7{le}{ital y}{le}1.0) graded spacer region, while the distributed Bragg reflectors are composed of Al{sub 0.5}Ga{sub 0.5}As/AlAs quarter-wave stacks. Room-temperature optically pumped lasing was achieved with a very low-threshold power, clearly demonstrating the viability of this new technology. These results provide the foundation for visible semiconductor laser-diode arrays for a number of applications including laser projection displays, holographic memories, and plastic fiber communication.

  15. Near-infrared wavelength intersubband transitions in GaN/AlN short period superlattices

    SciTech Connect (OSTI)

    DeCuir, E. A. Jr.; Fred, Emil; Passmore, B. S.; Muddasani, A.; Manasreh, M. O.; Xie Jinqiao; Morkoc, Hadis; Ware, M. E.; Salamo, G. J. [Department of Electrical Engineering, University of Arkansas, 3217 Bell Engineering Center, Fayetteville, Arkansas 72701 (United States); Department of Electrical and Computer Engineering, Virginia Commonwealth University, 601 W. Main St., Richmond, Virginia 23284-3072 (United States); Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

    2006-10-09T23:59:59.000Z

    Intersubband transitions in GaN/AlN short period superlattices prepared by molecular beam epitaxy were investigated using the optical absorption technique. The peak position wavelengths of these transitions are found to span the spectral range of 1.35-2.90 {mu}m for samples cut into 45 deg. waveguides with GaN quantum well thicknesses ranging between 1.70 and 2.41 nm. The Fermi energy levels are estimated from the carrier concentrations, which were measured using an electrochemical capacitance-voltage profiler. The well widths were inferred from comparing the measured peak position energy of the intersubband transitions and the bound state energy levels calculated using the transfer matrix method.

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

    SciTech Connect (OSTI)

    Hille, P., E-mail: Pascal.Hille@physik.uni-giessen.de; Müßener, J.; Becker, P.; Teubert, J.; Schörmann, J.; Eickhoff, M. [I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen (Germany)] [I. Physikalisches Institut, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen (Germany); Mata, M. de la [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, CAT (Spain)] [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, CAT (Spain); Rosemann, N.; Chatterjee, S. [Faculty of Physics and Materials Science Center, Philipps Universität Marburg, Renthof 5, 35032 Marburg (Germany)] [Faculty of Physics and Materials Science Center, Philipps Universität Marburg, Renthof 5, 35032 Marburg (Germany); Magén, C. [Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragon-ARAID, Universidad de Zaragoza, 50018 Zaragoza (Spain)] [Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragon-ARAID, Universidad de Zaragoza, 50018 Zaragoza (Spain); Arbiol, J. [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, CAT (Spain) [Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, CAT (Spain); Institucio Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, CAT (Spain)

    2014-03-10T23:59:59.000Z

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

  17. Carrier dynamics in Beryllium doped low-temperature-grown InGaAs/InAlAs

    SciTech Connect (OSTI)

    Globisch, B., E-mail: Bjoern.Globisch@hhi.fraunhofer.de; Dietz, R. J. B.; Stanze, D.; Göbel, T.; Schell, M. [Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, Einsteinufer 37, 10587 Berlin (Germany)

    2014-04-28T23:59:59.000Z

    The electron and hole dynamics in low-temperature-grown InGaAs/InAlAs multiple quantum well structures are studied by optical pump-probe transmission measurements for Beryllium (Be) doping levels between 3?×?10{sup 17}?cm{sup ?3} and 4?×?10{sup 18}?cm{sup ?3}. We investigate electron dynamics in the limit cases of unsaturated and completely saturated electron trapping. By expanding a rate equation model in these limits, the details of carrier dynamics are revealed. Electrons are trapped by ionized arsenic antisites, whereas recombination occurs between trapped electrons and holes trapped by negatively charged Be dopants.

  18. Spectral and dynamic characteristics of buried-heterostructure single quantum well (Al,Ga)As lasers

    SciTech Connect (OSTI)

    Derry, P.L.; Chen, T.R.; Zhuang, Y.H.; Paslaski, J.; Mittelstein, M.; Vahala, K.; Yariv, A.

    1988-07-25T23:59:59.000Z

    We demonstrate that, as predicted, (Al,Ga)As single quantum well (SQW) lasers have substantially narrower spectral linewidths than bulk double-heterostructure lasers. We have observed a further major reduction (>3 x ) in the linewidth of these SQW lasers when the facet reflectivities are enhanced. This observation is explained theoretically on the basis of the very low losses in coated SQW lasers and the value of the spontaneous emission factor at low threshold currents. We also report on the modulation frequency response parameter of these SQW lasers.

  19. Narrow stripe AlGaAs lasers using double current confinement

    SciTech Connect (OSTI)

    Blauvelt, H.; Margalit, S.; Yariv, A.

    1982-11-15T23:59:59.000Z

    Gain guided AlGaAs lasers in which the current is restricted to flow between two narrow stripes have been fabricated. The double current confinement configuration, which is fabricated by a selective meltback-growth technique, enables the current injection to be restricted to a very narrow section of the active layer. These lasers exhibit very strong antiguiding and operate in many longitudinal modes, which are characteristics of narrow stripe lasers. Potential applications of the twin vertical stripe configuration include arrays of optically coupled lasers and, if a real index waveguiding mechanism can be combined with double current confinement, low threshold lasers.

  20. Single-growth embedded epitaxy AlGaAs injection lasers with extremely low threshold currents

    SciTech Connect (OSTI)

    Katz, J.; Margalit, S.; Wilt, D.; Chen, P.C.; Yariv, A.

    1980-12-01T23:59:59.000Z

    A new type of strip-geometry AlGaAs double-heterostructure laser with an embedded optical waveguide has been developed. The new structure is fabricated using a single step of epitaxial growth. Lasers with threshold currents as low as 9.5 mA (150 ..mu..m long) were obtained. These lasers exhibit operation in a single spatial and longitudinal mode, have differential quantum efficiencies exceeding 45%, and a characteristic temperature of 175/sup 0/ C. They emit more than 12 mW/facet of optical power without any kinks.

  1. Gain broadening mechanism in various GaAlAs laser structures

    SciTech Connect (OSTI)

    Ruehle, W.; Brosson, P.

    1980-11-01T23:59:59.000Z

    Coupling of an external grating to a GaAlAs laser results in a strong enhancement of the selected mode and a reduction of the nonselected modes. The spectral form of this reduction is measured with a new sensitive experimental arrangement for three types of laser structures: proton bombarded stripe geometry, V-groove and CSP lasers. This spectral form is determined by the gain curve of the laser only and is independent on the position of the selected mode, i.e., no spectral hole burning is observed at room temperature.

  2. Optical ridge waveguides in AlGaAs and LiNbO3 

    E-Print Network [OSTI]

    Terry, Roger Mark

    1993-01-01T23:59:59.000Z

    the properties of ridge waveguides in AlGaAs, and also to develop and characterize low loss optical waveguides in LiNbOs that combine ridge geometry with the photoelastic efFect. A model that predicts strain contours and related ref'ractive index distribution... waveguides is important. This would establish profiles of the index distribution and guided modal fields, and permit adjustments of ridge height and film thickness for obtaining maximum coupling efilciencies. A computer model using the relaxation method...

  3. Temperature stability of intersubband transitions in AlN/GaN quantum wells

    SciTech Connect (OSTI)

    Berland, Kristian; Stattin, Martin; Farivar, Rashid; Sultan, D. M. S.; Hyldgaard, Per; Larsson, Anders; Wang, Shu Min; Andersson, Thorvald G. [Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-41296 Goeteborg (Sweden)

    2010-07-26T23:59:59.000Z

    Temperature dependence of intersubband transitions in AlN/GaN multiple quantum wells grown with molecular beam epitaxy is investigated both by absorption studies at different temperatures and modeling of conduction-band electrons. For the absorption study, the sample is heated in increments up to 400 deg. C. The self-consistent Schroedinger-Poisson modeling includes temperature effects of the band gap and the influence of thermal expansion on the piezoelectric field. We find that the intersubband absorption energy decreases only by approx6 meV at 400 deg. C relative to its room temperature value.

  4. Highly reliable InGaP/InGaAlP visible light emitting inner stripe lasers with 667 nm lasing wavelength

    SciTech Connect (OSTI)

    Okuda, H.; Ishikawa, M.; Shiozawa, H.; Watanabe, Y.; Itaya, K.; Nitta, K.; Hatakoshi, G.; Kokubun, Y.; Uematsu, Y.

    1989-06-01T23:59:59.000Z

    In order to obtain highly reliable InGaP/InGaAlP inner stripe (IS) lasers, the authors have clarified the relation between the maximum CW operation temperature and other laser characteristics, such as the pulsed threshold current, characteristic temperature, series resistance, and thermal resistance. The Al composition of the cladding layer, the carrier concentration of the p-cladding layer, and the thicknesses of the active layer and cladding layer have been optimized. It was found that an Al composition of 0.7 was the most suitable for the cladding layer, and the optimized carrier concentration was 4 x 10/sup 17/ cm/sup -3/. A maximum temperature of 90/sup 0/C was obtained for a 0.1 /mu/m active layer thickness and a 0.6 /mu/m cladding layer thickness. This is the highest value for InGaP/InGaAlP IS lasers, to our knowledge. In the case of a 0.06 /mu/m active layer thickness and a 0.8 /mu/m cladding layer thickness, a maximum temperature of 75/sup 0/C was obtained. IS lasers with facet coating have been stably operating for more than 8000 h at 40/sup 0/C and 3 mW and for more than 4000 h at 50/sup 0/C and 3 mW.

  5. First principles calculation of polarization induced interfacial charges in GaN/AlN heterostructures

    E-Print Network [OSTI]

    Rohan Mishra; Oscar D. Restrepo; Siddharth Rajan; Wolfgang Windl

    2011-05-17T23:59:59.000Z

    We propose a new method to calculate polarization induced interfacial charges in semiconductor heterostructures using classical electrostatics applied to real-space band diagrams from first principles calculations and apply it to GaN/AlN heterostructures with ultrathin AlN layers (4-6 monolayers). We show that the calculated electric fields and interfacial charges are independent of the exchange-correlation functionals used (local-density approximation and hybrid functionals). We also find the calculated interfacial charge of (6.8 +/- 0.4) x 10^13 cm-2 to be in excellent agreement with experiments and the value of 6.58 x 10^13 cm-2 calculated from bulk polarization constants, validating the use of bulk constants even for very thin films.

  6. Fabrication of quantum point contacts by engraving GaAsAlGaAs heterostructures with a diamond tip

    E-Print Network [OSTI]

    Hohls, Frank

    by hot-filament chemical vapor deposition of polycrystalline diamond onto a prepat- terned siliconFabrication of quantum point contacts by engraving GaAsÕAlGaAs heterostructures with a diamond tip for publication 17 July 2002 We use the all-diamond tip of an atomic force microscope for the direct engraving

  7. Si-CMOS-Like Integration of AlGaN/GaN Dielectric-Gated High-Electron-Mobility Transistors

    E-Print Network [OSTI]

    Johnson, Derek Wade

    2014-07-31T23:59:59.000Z

    the engineering of high mobility, high carrier density channels at III-Nitride heterointerfaces. In order to seize market share from silicon, the cost of manufacturing GaN-based devices must be further reduced. With the successful realization of 200mm Ga...

  8. Si-CMOS-Like Integration of AlGaN/GaN Dielectric-Gated High-Electron-Mobility Transistors 

    E-Print Network [OSTI]

    Johnson, Derek Wade

    2014-07-31T23:59:59.000Z

    the engineering of high mobility, high carrier density channels at III-Nitride heterointerfaces. In order to seize market share from silicon, the cost of manufacturing GaN-based devices must be further reduced. With the successful realization of 200mm Ga...

  9. Electric-field-dependent electroreflectance spectra of visible-band-gap (InAlGa)P quantum-well structures

    SciTech Connect (OSTI)

    Fritz, I.J.; Blum, O.; Schneider, R.P. Jr.; Howard, A.J.; Follstaedt, D.M. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

    1994-04-04T23:59:59.000Z

    We present results from the first studies of electric-field effects on optical transitions in visible-band-gap InGaP/InAlGaP multiple-quantum-well (MQW) structures. These structures, grown at 775 [degree]C by metalorganic vapor phase epitaxy on (100) GaAs substrates misoriented 6[degree] towards P(111)[r angle][l angle]111[r angle]A, consist of nominally undoped MQWs surrounded by doped In[sub 0.49]Al[sub 0.51]P cladding layers to form [ital p]-[ital i]-[ital n] diodes. The Stark shifts of various allowed and forbidden quantum-well transitions were observed in bias-dependent electroreflectance spectra of In[sub 0.49]Ga[sub 0.51]P/In[sub 0.49](Al[sub 0.5]Ga[sub 0.5])[sub 0.51]P MQW samples with 10-nm-thick layers. We find the magnitude of these shifts to depend on the details of the Mg doping profile, confirming the importance of Mg diffusion and unintentional background doping in these materials. Our results show that (InAlGa)P materials are promising for visible-wavelength electro-optic modulator applications.

  10. Band engineering of GaN/AlN quantum wells by Si dopants

    SciTech Connect (OSTI)

    Zhuo, Xiaolong; Ni, Jianchao; Li, Jinchai; Lin, Wei; Cai, Duanjun; Li, Shuping, E-mail: lsp@xmu.edu.cn, E-mail: jykang@xmu.edu.cn; Kang, Junyong, E-mail: lsp@xmu.edu.cn, E-mail: jykang@xmu.edu.cn [Fujian Key Laboratory of Semiconductor Materials and Applications, Department of Physics, Xiamen University, Xiamen 361005 (China)

    2014-03-28T23:59:59.000Z

    The electronic properties of GaN/AlN quantum wells are engineered by Si doped in different positions with the aid of the first-principle calculations. The local potential where the dopant located is dragged down as a result of negative center induced by the Si atom, leading to a different shift of the potential, and further affects the band bending and carrier distribution. The band profiles are depicted by analyzing the projected densities of states, it is found that the different positions of Si doping lead to a different band bending owing to the modified polarization fields. The spatial distributions of electrons and holes plotted by the partial charge densities reveal that electrons and holes experience redistribution by Si dopant in different positions. The above results demonstrate that the effect of polarization on the band bending has been significantly modulated by Si doped in different positions. Such modification of electronic structure is especially valuable for the fabrication of GaN/AlN QWs under desired control.

  11. A geometrical model for the description of the AlN shell morphology in GaN-AlN core-shell nanowires

    SciTech Connect (OSTI)

    Hestroffer, Karine; Daudin, Bruno [CEA-CNRS Group Nanophysique et Semiconducteurs, Institut Néel/CNRS-Université J. Fourier and CEA Grenoble, INAC, SP2M, 17 rue des Martyrs, 38 054 Grenoble (France)] [CEA-CNRS Group Nanophysique et Semiconducteurs, Institut Néel/CNRS-Université J. Fourier and CEA Grenoble, INAC, SP2M, 17 rue des Martyrs, 38 054 Grenoble (France)

    2013-12-28T23:59:59.000Z

    A geometrical model based on the one formulated by Foxon et al.[J. Cryst. Growth 311, 3423 (2009)] is developed to describe the morphology of AlN shells in GaN-AlN core-shell nanowires grown by plasma-assisted molecular beam epitaxy. The shell aspect ratio is studied as a function of the atomic beam flux incidence angles and of the ratio between Al and N species. The comparison between experimental data and the developed geometrical model suggests the diffusion of about 55% of Al atoms from the side walls to the top surface.

  12. 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.

  13. Impacts of SiN passivation on the degradation modes of AlGaN/GaN high electron mobility transistors under reverse-bias stress

    SciTech Connect (OSTI)

    Chen, Wei-Wei; Ma, Xiao-Hua, E-mail: xhma@xidian.edu.cn, E-mail: yhao@xidian.edu.cn; Hou, Bin; Zhu, Jie-Jie [School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710071 (China); Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071 (China); Chen, Yong-He; Zheng, Xue-Feng; Zhang, Jin-Cheng; Hao, Yue, E-mail: xhma@xidian.edu.cn, E-mail: yhao@xidian.edu.cn [Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071 (China)

    2014-10-27T23:59:59.000Z

    Impacts of SiN passivation on the degradation modes of AlGaN/GaN high electron mobility transistors are investigated. The gate leakage current decreases significantly upon removing the SiN layer and no clear critical voltage for the sudden degradation of the gate leakage current can be observed in the reverse-bias step-stress experiments. Gate-lag measurements reveal the decrease of the fast-state surface traps and the increase of slow-state traps after the passivation layer removal. It is postulated that consistent surface charging relieves the electric field peak on the gate edge, thus the inverse piezoelectric effect is shielded.

  14. Scattering due to Schottky barrier height spatial fluctuation on two dimensional electron gas in AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Li, Huijie; Liu, Guipeng, E-mail: liugp@semi.ac.cn; Wei, Hongyuan; Jiao, Chunmei; Wang, Jianxia; Zhang, Heng; Dong Jin, Dong; Feng, Yuxia; Yang, Shaoyan, E-mail: sh-yyang@semi.ac.cn; Wang, Lianshan; Zhu, Qinsheng; Wang, Zhan-Guo [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People's Republic of China and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)] [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People's Republic of China and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2013-12-02T23:59:59.000Z

    A scattering mechanism related to the Schottky barrier height (SBH) spatial fluctuation of the two dimensional electron gas (2DEG) in AlGaN/GaN heterostructures is presented. We find that the low field mobility is on the order of 10{sup 4}–10{sup 6} cm{sup 2}/Vs. The 2DEG transport properties are found to be influenced by both the mobility and 2DEG density variations caused by the SBH fluctuation. Our results indicate that a uniform Schottky contact is highly desired to minimize the influence of SBH inhomogeneity on the device performance.

  15. Anisotropic scattering effect of the inclined misfit dislocation on the two-dimensional electron gas in Al(In)GaN/GaN heterostructures

    SciTech Connect (OSTI)

    Jin, Dong-Dong [Key Laboratory of Semiconductor Materials Science, and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Department of Physics, Tsinghua University, Beijing 100084 (China); Wang, Lian-shan, E-mail: ls-wang@semi.ac.cn; Yang, Shao-Yan, E-mail: sh-yyang@semi.ac.cn; Li, Hui-jie; Zhang, Heng; Wang, Jian-xia; Xiang, Ruo-fei; Wei, Hong-yuan; Jiao, Chun-mei; Liu, Xiang-Lin; Zhu, Qin-Sheng, E-mail: qszhu@semi.ac.cn; Wang, Zhan-Guo [Key Laboratory of Semiconductor Materials Science, and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Zhang, Liu-Wan [Department of Physics, Tsinghua University, Beijing 100084 (China)

    2014-01-28T23:59:59.000Z

    In this paper, a theory is developed to study the anisotropic scattering effect of the inclined misfit dislocation on the two-dimensional electron gas in Al(In)GaN/GaN heterostructures. The inclined misfit dislocation, which differs from the well-known vertical threading dislocation, has a remarkable tilt angle from the vertical. The predicted electron mobility shows a remarkable anisotropy. It has a maximum mobility value along the direction perpendicular to the projection of the inclined dislocation line, and a minimum mobility value along the direction parallel to the projection. The degree of the anisotropic scattering effect will be even greater with the increase of the tilt angle.

  16. 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.

  17. The influence of the AlN barrier thickness on the polarization Coulomb field scattering in AlN/GaN heterostructure field-effect transistors

    SciTech Connect (OSTI)

    Lv, Yuanjie; Feng, Zhihong, E-mail: ga917vv@163.com; Gu, Guodong; Han, Tingting; Yin, Jiayun; Liu, Bo; Cai, Shujun [National Key Laboratory of Application Specific Integrated Circuit (ASIC), Hebei Semiconductor Research Institute, Shijiazhuang 050051 (China); Lin, Zhaojun; Ji, Ziwu; Zhao, Jingtao [School of Physics, Shandong University, Jinan 250100 (China)

    2014-07-14T23:59:59.000Z

    The electron mobility scattering mechanisms in AlN/GaN heterostuctures with 3?nm and 6?nm AlN barrier thicknesses were investigated by temperature-dependent Hall measurements. The effect of interface roughness (IFR) scattering on the electron mobility was found to be enhanced by increasing AlN barrier thickness. Moreover, using the measured capacitance-voltage and current-voltage characteristics of the fabricated heterostructure field-effect transistors (HFETs) with different Schottky areas on the two heterostuctures, the variations of electron mobility with different gate biases were investigated. Due to enhanced IFR scattering, the influence of polarization Coulomb field (PCF) scattering on electron mobility was found to decrease with increasing AlN barrier layer thickness. However, the PCF scattering remained an important scattering mechanism in the AlN/GaN HFETs.

  18. Effects of Mg-doped AlN/AlGaN superlattices on properties of p-GaN contact layer and performance of deep ultraviolet light emitting diodes

    SciTech Connect (OSTI)

    Al tahtamouni, T. M., E-mail: talal@yu.edu.jo [Department of Physics, Yarmouk University, Irbid 21163 (Jordan); Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)] [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2014-04-15T23:59:59.000Z

    Mg-doped AlN/AlGaN superlattice (Mg-SL) and Mg-doped AlGaN epilayers have been investigated in the 284 nm deep ultraviolet (DUV) light emitting diodes (LEDs) as electron blocking layers. It was found that the use of Mg-SL improved the material quality of the p-GaN contact layer, as evidenced in the decreased density of surface pits and improved surface morphology and crystalline quality. The performance of the DUV LEDs fabricated using Mg-SL was significantly improved, as manifested by enhanced light intensity and output power, and reduced turn-on voltage. The improved performance is attributed to the enhanced blocking of electron overflow, and enhanced hole injection.

  19. High ion density plasma etching of InGaP, AlInP, and AlGaP in CH{sub 4}/H{sub 2}/Ar

    SciTech Connect (OSTI)

    Lee, J.W.; Pearton, S.J.; Santana, C.J.; Mileham, J.R.; Lambers, E.S.; Abernathy, C.R. [Univ. of Florida, Gainesville, FL (United States); Ren, F.; Hobson, W.S. [AT and T Bell Labs., Murray Hill, NJ (United States)

    1996-03-01T23:59:59.000Z

    High microwave power (1,000 W) electron cyclotron resonance CH{sub 4}/H{sub 2}/Ar discharges produce etch rates for In{sub 0.5}Ga{sub 0.5}P, Al{sub 0.5}In{sub 0.5}P{sub 0.5}, and Al{sub 0.5}Ga{sub 0.5}P of {approximately} 2,000 {angstrom}/min at moderate RF power levels (150 W) and low pressure (1.5 mTorr). This is approximately a factor of five faster than for conventional reactive ion etching conditions where much higher ion energies are necessary. The etched surfaces are smooth over a wide range of CH{sub 4}-to-H{sub 2} ratios and microwave powers. AlInP is more resistant to preferential loss of P from the near-surface during etching than is InGaP. While the etching is ion-driven, pure Ar discharges produce rough surfaces and the CH{sub 4}/H{sub 2} is necessary in the achievement of acceptable morphologies. The InGaAlP/GaAs heterostructure is being increasingly utilized in diode lasers, light emitting diodes, field-effect transistors, and heterojunction bipolar transistors.

  20. A5.2 Raman and IR reflectance studies of AlGaN C. Wetzel and I. Akasaki

    E-Print Network [OSTI]

    Wetzel, Christian M.

    center phonon modes in wurtzite AlxGa1-xN (0 x 1) [1-5] (for GaN [6] and AlN [7] refer to the dedicated chapters). Selection rules in wurtzite allow a splitting of longitudinal and transversal modes into A1 of the TO modes, but a one mode behavior of the LO modes. Through symmetry arguments the wurtzite situation can

  1. 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

  2. Highly tunable quantum Hall far-infrared photodetector by use of GaAs/Al{sub x}Ga{sub 1?x}As-graphene composite material

    SciTech Connect (OSTI)

    Tang, Chiu-Chun [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Ling, D. C. [Department of Physics, Tamkang University, Tamsui Dist., New Taipei City 25137, Taiwan (China); Chi, C. C.; Chen, Jeng-Chung [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2014-11-03T23:59:59.000Z

    We have developed a highly tunable, narrow band far-infrared (FIR) photodetector which utilizes the characteristic merits of graphene and two-dimensional electron gas (2DEG) in GaAs/Al{sub x}Ga{sub 1?x}As heterostructure in the Quantum Hall states (QHS). The heterostructure surface is covered with chemical vapor-deposited graphene, which functions as a transparent top-gate to vary the electron density of the 2DEG. FIR response observed in the vicinity of integer QH regime can be effectively tuned in a wide range of 27–102?cm{sup ?1} with a bias voltage less than ?1?V. In addition, we have found that the presence of graphene can genuinely modulate the photoresponse. Our results demonstrate a promising direction for realizing a tunable long-wavelength FIR detector using QHS in GaAs 2DEG/ graphene composite material.

  3. Mid-infrared electro-luminescence and absorption from AlGaN/GaN-based multi-quantum well inter-subband structures

    SciTech Connect (OSTI)

    Hofstetter, Daniel, E-mail: Daniel.Hofstetter@unine.ch [University of Neuchâtel, Institute of Physics, 51 Avenue de Bellevaux, Neuchâtel, CH–2009 (Switzerland); Bour, David P. [Avogy, Inc., 677 River Oaks Parkway, San Jose, California 95134 (United States); Kirste, Lutz [Fraunhofer Institute for Applied Solid State Physics (IAF), Tullastrasse 72, D-79108 Freiburg i. Brsg. (Germany)

    2014-06-16T23:59:59.000Z

    We present electro-modulated absorption and electro-luminescence measurements on chirped AlGaN/GaN-based multi-quantum well inter-subband structures grown by metal-organic vapour phase epitaxy. The absorption signal is a TM-polarized, 70?meV wide feature centred at 230?meV. At medium injection current, a 58?meV wide luminescence peak corresponding to an inter-subband transition at 1450?cm{sup ?1} (180?meV) is observed. Under high injection current, we measured a 4?meV wide structure peaking at 92.5?meV in the luminescence spectrum. The energy location of this peak is exactly at the longitudinal optical phonon of GaN.

  4. Influence of the surface potential on electrical properties of Al{sub x}Ga{sub 1-x}N/GaN heterostructures with different Al-content: Effect of growth method

    SciTech Connect (OSTI)

    Koehler, K.; Mueller, S.; Aidam, R.; Waltereit, P.; Pletschen, W.; Kirste, L.; Menner, H. P.; Bronner, W.; Leuther, A.; Quay, R.; Mikulla, M.; Ambacher, O. [Fraunhofer-Institut fuer Angewandte Festkoerperphysik, Tullastrasse 72, 79108 Freiburg (Germany); Granzner, R.; Schwierz, F.; Buchheim, C. [Institut fuer Mikro- und Nanotechnologien, Technische Universitaet Ilmenau, PF 100565, 98684 Ilmenau (Germany); Goldhahn, R. [Institut fuer Experimentelle Physik, Otto-von-Guericke-Universitaet, Universitaetsplatz 2, 39106 Magdeburg (Germany)

    2010-03-15T23:59:59.000Z

    The influence of the growth method on the surface potential and thus on the sheet carrier concentration of GaN capped Al{sub x}Ga{sub 1-x}N/GaN heterostructures was evaluated. Nominally undoped low pressure metal-organic vapor-phase (MOVPE) and plasma-assisted molecular beam epitaxial (PA-MBE) grown structures with an Al-content between 12% and 30% yield carrier concentrations from 3.6x10{sup 12} to 1.2x10{sup 13} cm{sup -2}. A difference of the concentrations for a fixed Al-content was found between the different epitaxial techniques. This result indicates unambiguously different surface potentials determined quantitatively from the carrier concentration, and is verified in addition by the results of photoreflectance spectroscopy. The GaN surface potentials of MOVPE and PA-MBE grown samples amounts to (0.26{+-}0.04) and (0.61{+-}0.10) eV irrespective of the Al-content of the barrier layer. After device fabrication, we find that due to the identical surface potential defined by the Ni Schottky gate, the threshold voltage for a given Al-content is the same for samples grown with different techniques. Thus, the interplay between epitaxy and process technology defines the threshold voltage.

  5. InAlN/GaN Bragg reflectors grown by plasma-assisted 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); Hosseini, D.; Peiro, F. [Departament d'Electronica, LENS-MIND-IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S. [Departament d'Electronica, LENS-MIND-IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, SCT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain)

    2010-12-01T23:59:59.000Z

    We report on molecular beam epitaxy growth and characterization of ten-period lattice-matched InAlN/GaN distributed Bragg reflectors (DBRs), with peak reflectivity centered around 400 nm. Thanks to the well tuned ternary alloy composition, crack-free surfaces have been obtained, as confirmed by both optical and transmission electron microscopy (TEM). Their good periodicity and well-defined interfaces have been confirmed by both x-ray diffraction and TEM measurements. Peak reflectivity values as high as 60% with stop bands of 30 nm have been demonstrated. Optical measurements revealed that discrepancy between the obtained (60%) and the theoretically expected ({approx}75%) reflectivity is a consequence of significant residual absorption ({approx}35%). TEM measurements revealed the coexistence of zinc-blende and wurtzite phases, as well as planar defects, mainly in GaN. These defects are suggested as the potential source of the undesired absorption and/or scattering effects that lowered the DBRs' peak reflectivity.

  6. Effect of exciton oscillator strength on upconversion photoluminescence in GaAs/AlAs multiple quantum wells

    SciTech Connect (OSTI)

    Kojima, Osamu, E-mail: kojima@phoenix.kobe-u.ac.jp; Okumura, Shouhei; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Akahane, Kouichi [National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2014-11-03T23:59:59.000Z

    We report upconversion photoluminescence (UCPL) in GaAs/AlAs multiple quantum wells. UCPL from the AlAs barrier is caused by the resonant excitation of the excitons in the GaAs well. When the quantum well has sufficient miniband width, UCPL is hardly observed because of the small exciton oscillator strength. The excitation-energy and excitation-density dependences of UCPL intensity show the exciton resonant profile and a linear increase, respectively. These results demonstrate that the observed UCPL caused by the saturated two-step excitation process requires a large number of excitons.

  7. Comprehensive magnetotransport characterization of two dimensional electron gas in AlGaN/GaN high electron mobility transistor structures leading to the assessment of interface roughness

    SciTech Connect (OSTI)

    Mishra, Manna Kumari [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi-110054 (India); Netaji Subhas Institute of Technology, Dwarka, New Delhi-110078 (India); Sharma, Rajesh K., E-mail: rksharma@sspl.drdo.in; Manchanda, Rachna; Bag, Rajesh K.; Muralidharan, Rangarajan [Solid State Physics Laboratory, Lucknow Road, Timarpur, Delhi-110054 (India); Thakur, Om Prakash [Netaji Subhas Institute of Technology, Dwarka, New Delhi-110078 (India)

    2014-09-15T23:59:59.000Z

    Magnetotransport in two distinct AlGaN/GaN HEMT structures grown by Molecular Beam Epitaxy (MBE) on Fe-doped templates is investigated using Shubnikov de-Haas Oscillations in the temperature range of 1.8–6 K and multicarrier fitting in the temperature range of 1.8–300 K. The temperature dependence of the two dimensional electron gas mobility is extracted from simultaneous multicarrier fitting of transverse and longitudinal resistivity as a function of magnetic field and the data is utilized to estimate contribution of interface roughness to the mobility and the corresponding transport lifetime. The quantum scattering time obtained from the analysis of Shubnikov de Haas Oscillations in transverse magnetoresistance along with the transport lifetime time were used to estimate interface roughness amplitude and lateral correlation length. The results indicate that the insertion of AlN over layer deposited prior to the growth of GaN base layer on Fe doped GaN templates for forming HEMT structures reduced the parallel conduction but resulted in an increase in interface roughness.

  8. Effects of threading dislocations on drain current dispersion and slow transients in unpassivated AlGaN/GaN/Si heterostructure field-effect transistors

    SciTech Connect (OSTI)

    Ghosh, Saptarsi, E-mail: saptarsi123@gmail.com; Dinara, Syed Mukulika; Mukhopadhyay, Partha; Jana, Sanjay K.; Bag, Ankush; Kabi, Sanjib [Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Chakraborty, Apurba [Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Chang, Edward Yi [Department of Material Science and Engineering, National Chiao Tung University, Hsinchu 30050, Taiwan (China); Biswas, Dhrubes [Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2014-08-18T23:59:59.000Z

    Current transient analysis combined with response to pulsed bias drives have been used to explore the possibilities of threading dislocations affecting the current dispersion characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs). A growth strategy is developed to modulate the dislocation density among the heterostructures grown on silicon by plasma-assisted molecular-beam epitaxy. Slow pulsed I-V measurements show severe compressions and appear to be significantly dependent on the threading dislocation density. By analyzing the corresponding slow detrapping process, a deep-level trap with emission time constant in the order of seconds was identified as the cause. Among the specimens, both in the epilayers and at the surface, the number of dislocations was found to have a notable influence on the spatial distribution of deep-level trap density. The observations confirm that the commonly observed degraded frequency performance among AlGaN/GaN HFETs in the form of DC-radio frequency dispersions can at least partly be correlated with threading dislocation density.

  9. Quasi-bound states and continuum absorption background of polar Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots

    SciTech Connect (OSTI)

    Elmaghraoui, D., E-mail: elmaghraouidonia@yahoo.fr; Triki, M. [Laboratoire de physique de la matière condensé, Faculté des sciences de Tunis, Campus universitaire 2092 El Manar (Tunisia); Jaziri, S. [Laboratoire de physique de la matière condensé, Faculté des sciences de Tunis, Campus universitaire 2092 El Manar (Tunisia); Laboratoire de Physique des Matériaux, Faculté des Sciences de Bizerte 7021 Jarzouna (Tunisia); Leroux, M.; Brault, J. [Centre de Recherche sur l'Hetero-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, Rue B. Gregory, 06560 Valbonne (France)

    2014-07-07T23:59:59.000Z

    A theoretical interpretation of the photoluminescence excitation spectra of self-organized polar GaN/(Al,Ga)N quantum dots is presented. A numerical method assuming a realistic shape of the dots and including the built-in electric field effects is developed to calculate their energy structure and hence their optical absorption. The electron and hole spectra show the existence of a set of quasi-bound states that does not originate from the wetting layer and plays a crucial role in the observed absorption spectrum of the GaN/(Al,Ga)N dots. Transitions involving these quasi-bound states and wetting layer states give a sufficient explanation for the observed continuum absorption background. The properties of this absorption band, especially its extension, depend strongly on the dot's size. Our simulation provides a natural explanation of the experimental luminescence excitation spectra of ensembles of dots of different heights. Our theoretical model can be convenient for future optical studies including systems with more complicated potentials.

  10. Near-infrared intersubband absorption in nonpolar cubic GaN/AlN superlattices

    SciTech Connect (OSTI)

    DeCuir, E. A. Jr.; Fred, E.; Manasreh, M. O.; Schoermann, J.; As, D. J.; Lischka, K. [Department of Electrical Engineering, University of Arkansas, Fayetteville, Arkansas 72701 and Department of Physics, University of Arkansas, Fayetteville, Arkansas 7270 (United States); Department of Physics, University of Paderborn, Paderborn 33095 (Germany)

    2007-07-23T23:59:59.000Z

    Optical absorption spectra related to intersubband transitions in molecular beam epitaxially grown nonpolar cubic-GaN/AlN superlattices were observed in the spectral range of 1.5-2.00 {mu}m. The background doping was measured using an electrochemical capacitance-voltage technique and found to be on the order of 10{sup 18} cm{sup -3}. This doping level yields a Fermi energy level slightly above the ground state energy level enabling intersubband transitions to occur. The existence of the intersubband transition is verified in several samples with different well widths. The observed peak position energy of the intersubband transition is compared to those calculated using a transfer matrix method.

  11. Temperature dependence of the threshold current for InGaAlP visible laser diodes

    SciTech Connect (OSTI)

    Ishikawa, M.; Shiozawa, H.; Itaya, K.; Hatakoshi, G.; Uematsu, Y. (Research and Development Center, Toshiba Corp., Saiwai-ku, Kawasaki 210 (JP))

    1991-01-01T23:59:59.000Z

    The temperature dependence of the threshold current for InGaAlP visible light laser diodes is investigated from the aspect of gain-current characteristics. The cavity length dependence of light output power versus current characteristic was evaluated for a 40 {mu}m width InGaP-InBaAlP broad-stripe laser in the temperature range between {minus} 70 and 90{degrees} C, which had about a 670 nm oscillation wavelength at room temperature. The threshold-current density dependence on the cavity length shows that a linear-gain approximation is suitable for this system. A minimum threshold-current density at 860 A/cm{sup 2} was achieved at room temperature with a cavity length of 1160 {mu}m, which is the lowest value ever reported for this material. The linear-gain parameters {beta} and {ital J}{sub 0} depended on the temperature with the characteristic temperature of about 200 K, which is considered to be the intrinsic characteristic temperature of the threshold current for this active-layer material. The internal quantum efficiency, derived from the cavity length dependence of the differential quantum efficiency, decreased in the temperature range higher than {minus}10{degrees} C, which affected the excess threshold-current increase and the decrease in the characteristic temperature at this temperature range. The theoretical calculation, considering a one-dimensional band structure model, showed that this excess increase of the threshold current was found to be attributed to the electron overflow current into the p-type cladding layer.

  12. Characterization of catastrophic optical damage in Al-free InGaAs/InGaP 0.98 {mu}m high-power lasers

    SciTech Connect (OSTI)

    Park, K.H.; Lee, J.K.; Jang, D.H.; Cho, H.S.; Park, C.S.; Pyun, K.E. [Compound Semiconductor Research Department, Electronics and Telecommunications Research Institute, Yusong P.O. Box 106, Taejon 305-600 (Korea)] [Compound Semiconductor Research Department, Electronics and Telecommunications Research Institute, Yusong P.O. Box 106, Taejon 305-600 (Korea); Jeong, J.Y. [Department of Radio Engineering, Korea University, 5-1 Ka, Anam-Dong, Sungbuk-ku, Seoul 136-701 (Korea)] [Department of Radio Engineering, Korea University, 5-1 Ka, Anam-Dong, Sungbuk-ku, Seoul 136-701 (Korea); Nahm, S. [Department of Material Science and Engineering, Korea University, 5-1 Ka, Anam-Dong, Sungbuk-ku, Seoul 136-701 (Korea)] [Department of Material Science and Engineering, Korea University, 5-1 Ka, Anam-Dong, Sungbuk-ku, Seoul 136-701 (Korea); Jeong, J. [Department of Radio Engineering, Korea University, 5-1 Ka, Anam-Dong, Sungbuk-ku, Seoul 136-701 (Korea)] [Department of Radio Engineering, Korea University, 5-1 Ka, Anam-Dong, Sungbuk-ku, Seoul 136-701 (Korea)

    1998-11-01T23:59:59.000Z

    Catastrophic optical damage (COD) in Al-free InGaAs/InGaP 0.98 {mu}m lasers has been investigated using real-time electroluminescence (EL) and transmission electron microscopy (TEM). From EL images, we observed that multiple bright spots initiated from one of the facets and then propagated to the center of the cavity during the COD process. It is clarified by the TEM analysis that the propagation of bright spots resulted in 60-nm-wide Moir{acute e} fringe along the cavity and the crystalline phase of the active area became polycrystalline. Highly nonradiative polycrystalline phase of the active area is the major cause of COD failure in the Al-free 0.98 {mu}m lasers. {copyright} {ital 1998 American Institute of Physics.}

  13. Resonant circular photogalvanic effect in GaN/AlGaN heterojunctions B. Wittmann,1 L. E. Golub,2 S. N. Danilov,1 J. Karch,1 C. Reitmaier,1 Z. D. Kvon,3 N. Q. Vinh,4 A. F. G. van der Meer,4

    E-Print Network [OSTI]

    Ganichev, Sergey

    Resonant circular photogalvanic effect in GaN/AlGaN heterojunctions B. Wittmann,1 L. E. Golub,2 S circular photogalvanic effect is observed in wurtzite 0001 -oriented GaN low-dimensional structures excited electrons at resonant intersubband optical transitions in a GaN/AlGaN heterojunction. The signal reverses

  14. 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

  15. Physics of gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors

    SciTech Connect (OSTI)

    Goswami, Arunesh; Trew, Robert J.; Bilbro, Griff L. [ECE Department, Box 7911, North Carolina State University, Raleigh, North Carolina 27695-7911 (United States)

    2014-10-28T23:59:59.000Z

    A physics based model of the gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors is demonstrated. The model is based on the space charge limited current flow dominated by the effects of deep traps in the InAlN surface layer. The model predicts accurately the gate-leakage measurement data of the N-polar InAlN/GaN device with InAlN cap layer. In the pinch-off state, the gate leakage current conduction through the surface of the device in the drain access region dominates the current flow through the two dimensional electron gas channel. One deep trap level and two levels of shallow traps are extracted by fitting the model results with measurement data.

  16. AlGaN/GaN High Electron Mobility Transistor degradation under on-and off-state stress

    E-Print Network [OSTI]

    Florida, University of

    power operation of GaN HEMTs can also result in substantial self-heating, which will reduce the 2DEG of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32611, United States c Department ATLAS/Blaze simula- tions show that the maximum electric field is similar for all gate lengths

  17. 5:OOpm -5:15pm Temperature Dependence of Breakdown Voltage in InAlAsDnGaAs HEMTs

    E-Print Network [OSTI]

    del Alamo, Jesús A.

    in the channel. Our work shows that an extension of the tunneling-limited breakdown model to finite temperatures the breakdown path, we began our analysis by looking at 2- and 3-terminal measurements of the breakdown voltage5:OOpm -5:15pm MC6 Temperature Dependence of Breakdown Voltage in InAlAsDnGaAs HEMTs: Theory

  18. 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.

  19. Efficient charge carrier injection into sub-250?nm AlGaN multiple quantum well light emitting diodes

    SciTech Connect (OSTI)

    Mehnke, Frank, E-mail: mehnke@physik.tu-berlin.de; Kuhn, Christian; Guttmann, Martin; Reich, Christoph; Kolbe, Tim; Rass, Jens; Wernicke, Tim [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin (Germany); Kueller, Viola; Knauer, Arne; Lapeyrade, Mickael; Einfeldt, Sven; Weyers, Markus [Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Kneissl, Michael [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin (Germany); Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2014-08-04T23:59:59.000Z

    The design and Mg-doping profile of AlN/Al{sub 0.7}Ga{sub 0.3}N electron blocking heterostructures (EBH) for AlGaN multiple quantum well (MQW) light emitting diodes (LEDs) emitting below 250?nm was investigated. By inserting an AlN electron blocking layer (EBL) into the EBH, we were able to increase the quantum well emission power and significantly reduce long wavelength parasitic luminescence. Furthermore, electron leakage was suppressed by optimizing the thickness of the AlN EBL while still maintaining sufficient hole injection. Ultraviolet (UV)-C LEDs with very low parasitic luminescence (7% of total emission power) and external quantum efficiencies of 0.19% at 246?nm have been realized. This concept was applied to AlGaN MQW LEDs emitting between 235?nm and 263?nm with external quantum efficiencies ranging from 0.002% to 0.93%. After processing, we were able to demonstrate an UV-C LED emitting at 234?nm with 14.5??W integrated optical output power and an external quantum efficiency of 0.012% at 18.2?A/cm{sup 2}.

  20. 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.

  1. Effect of surface passivation by SiN/SiO{sub 2} of AlGaN/GaN high-electron mobility transistors on Si substrate by deep level transient spectroscopy method

    SciTech Connect (OSTI)

    Gassoumi, Malek, E-mail: malek.gassoumi@fsm.rnu.tn; Mosbahi, Hana; Zaidi, Mohamed Ali [Universite deMonastir, Laboratoire de Micro-Optoelectroniques et Nanostructures, Faculte des Sciences de Monastir (Tunisia); Gaquiere, Christophe [Universite des Sciences et Technologies de Lille, Institut d'Electronique de Microelectronique et de Nanotechnologie IEMN, Departement hyperfrequences et Semiconducteurs (France); Maaref, Hassen [Universite deMonastir, Laboratoire de Micro-Optoelectroniques et Nanostructures, Faculte des Sciences de Monastir (Tunisia)

    2013-07-15T23:59:59.000Z

    Device performance and defects in AlGaN/GaN high-electron mobility transistors have been correlated. The effect of SiN/SiO{sub 2} passivation of the surface of AlGaN/GaN high-electron mobility transistors on Si substrates is reported on DC characteristics. Deep level transient spectroscopy (DLTS) measurements were performed on the device after the passivation by a (50/100 nm) SiN/SiO{sub 2} film. The DLTS spectra from these measurements showed the existence of the same electron trap on the surface of the device.

  2. Characteristics of AlN/GaN nanowire Bragg mirror grown on (001) silicon by molecular beam epitaxy

    SciTech Connect (OSTI)

    Heo, Junseok; Bhattacharya, Pallab [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States)] [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109-2122 (United States); Zhou, Zifan [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States)] [Department of Electrical and Computer Engineering, University of Michigan-Dearborn, Dearborn, Michigan 48128 (United States); Guo, Wei [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States)] [Microsystems Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States); Ooi, Boon S. [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)] [Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2013-10-28T23:59:59.000Z

    GaN nanowires containing AlN/GaN distributed Bragg reflector (DBR) heterostructures have been grown on (001) silicon substrate by molecular beam epitaxy. A peak reflectance of 70% with normal incidence at 560 nm is derived from angle resolved reflectance measurements on the as-grown nanowire DBR array. The measured peak reflectance wavelength is significantly blue-shifted from the ideal calculated value. The discrepancy is explained by investigating the reflectance of the nanoscale DBRs with a finite difference time domain technique. Ensemble nanowire microcavities with In{sub 0.3}Ga{sub 0.7}N nanowires clad by AlN/GaN DBRs have also been characterized. Room temperature emission from the microcavity exhibits considerable linewidth narrowing compared to that measured for unclad In{sub 0.3}Ga{sub 0.7}N nanowires. The resonant emission is characterized by a peak wavelength and linewidth of 575 nm and 39 nm, respectively.

  3. Photoluminescence linewidths in metalorganic vapor phase epitaxially grown ordered and disordered InAlGaP alloys

    SciTech Connect (OSTI)

    Schneider, R.P. Jr.; Jones, E.D.; Lott, J.A.; Bryan, R.P. (Sandia National Laboratories, Albuquerque, New Mexico 87185-5800 (United States))

    1992-12-01T23:59:59.000Z

    The dependence of the photoluminescent properties of In{sub 0.48}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.52}P alloys (0{le}{ital y}{le}0.5) on growth temperature and substrate misorientation off GaAs(100) has been studied. Samples were grown using low-pressure metalorganic vapor phase epitaxy. By studying the dependence of ordering behavior in InGaP as a function of substrate misorientation and growth temperature simultaneously, a very large range in low-temperature photoluminescence emission energy---135 meV---has been obtained. The photoluminescence linewidth exhibits a strong, continuous dependence on the extent of atomic ordering (the emission energy) in the alloys. The results indicate that inhomogeneity in the microstructure of the material (i.e., between ordered'' domains and the disordered'' matrix) is the dominant photoluminescence broadening mechanism. This investigation has allowed a significant optimization of the optical properties of these materials, including the narrowest low-temperature photoluminescent linewidths reported for all of the In(Al{sub {ital y}}Ga{sub 1{minus}{ital y}})P alloys exhibiting direct band gaps (4.2 meV for InGaP).

  4. Radiation response analysis of wide-gap p-AlInGaP for superhigh-efficiency space photovoltaics

    SciTech Connect (OSTI)

    Khan, Aurangzeb; Marupaduga, S.; Anandakrishnan, S.S.; Alam, M.; Ekins-Daukes, N.J.; Lee, H.S.; Sasaki, T.; Yamaguchi, M.; Takamoto, T.; Agui, T.; Kamimura, K.; Kaneiwa, M.; Imazumi, M. [Department of Electrical and Computer Engineering, University of South Alabama, Mobile, Alabama 36688 (United States); Toyota Technological Institute, Nagoya (Japan); Sharp Corporation, Nara (Japan); JAXA, Tsukuba (Japan)

    2004-11-29T23:59:59.000Z

    We present here the direct observation of the majority and minority carrier defects generation from wide-band-gap (2.04 eV) and thick (2 {mu}m) p-AlInGaP diodes and solar cells structures before and after 1 MeV electron irradiation by deep level transient spectroscopy (DLTS). One dominant hole-emitting trap H1 (E{sub V}+0.37{+-}0.05 eV) and two electron-emitting traps, E1 (E{sub C}-0.22{+-}0.04 eV) and E3 (E{sub C}-0.78{+-}0.05 eV) have been observed in the temperature range, which we could scan by DLTS. Detailed analysis of the minority carrier injection annealing experiment reveals that the H1 center has shown the same annealing characteristics, which has been previously observed in all phosphide-based materials such as InP, InGaP, and InGaAsP. The annealing property of the radiation-induced defects in p-AlInGaP reveals that multijunction solar cells and other optoelectronic devices such as light-emitting diodes based on this material could be considerably better to Si and GaAs in a radiation environment.

  5. High-temperature luminescence in an n-GaSb/n-InGaAsSb/p-AlGaAsSb light-emitting heterostructure with a high potential barrier

    SciTech Connect (OSTI)

    Petukhov, A. A., E-mail: andrey-rus29@rambler.ru; Zhurtanov, B. E.; Kalinina, K. V.; Stoyanov, N. D.; Salikhov, H. M.; Mikhailova, M. P.; Yakovlev, Yu. P. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)] [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-09-15T23:59:59.000Z

    The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface ({Delta}E{sub c} = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence (EL) spectrum. In the entire temperature range under study, T = 290-480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated as a result of the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the EL intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290-345 K, and a linear increase is observed at T > 345 K. This work for the first time reports an increase in the emission power of a light-emitting diode structure with increasing temperature. It is shown that this rise is caused by a decrease in the threshold energy of the impact ionization due to narrowing of the band gap of the active region.

  6. Gas-source molecular beam epitaxial growth and characterization of the (Al,In,Ga)NP/GaP material system and Its applications to light-emitting diodes

    E-Print Network [OSTI]

    Odnoblyudov, Vladimir

    2006-01-01T23:59:59.000Z

    on metamorphic growth of InGaP layers on GaP substrates, astemperature amber photoluminescence from InGaP QWs, grownon a metamorphic InGaP layer. References: Fred Shubert E. ,

  7. Effects of bias and temperature on the intersubband absorption in very long wavelength GaAs/AlGaAs quantum well infrared photodetectors

    SciTech Connect (OSTI)

    Liu, X. H.; Zhou, X. H., E-mail: xhzhou@mail.sitp.ac.cn; Li, N.; Liao, K. S.; Huang, L.; Li, Q.; Li, Z. F.; Chen, P. P.; Lu, W. [National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu-Tian Road, Shanghai 200083 (China); Wang, L.; Sun, Q. L. [Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

    2014-03-28T23:59:59.000Z

    The temperature- and bias-dependent photocurrent spectra of very long wavelength GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations. It is found that the peak response wavelength will shift as the bias and temperature change. Aided by band structure calculations, we propose a model of the double excited states and explain the experimental observations very well. In addition, the working mechanisms of the quasi-bound state confined in the quantum well, including the processes of tunneling and thermionic emission, are also investigated in detail. We confirm that the first excited state, which belongs to the quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. These obtained results provide a full understanding of the bound-to-quasi-bound state and the bound-to-quasi-continuum state transition, and thus allow for a better optimization of QWIPs performance.

  8. Submilliampere threshold current pseudomorphic InGaAs/AlGaAs buried-heterostructure quantum well lasers grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Eng, L.E.; Chen, T.R.; Sanders, S.; Zhuang, Y.H.; Zhao, B.; Yariv, A. (Department of Applied Physics, California Institute of Technology, Pasadena, California 91125 (US)); Morkoc, H. (The Coordinated Science Laboratory, University of Illinois, Urbana, Illinois 61801)

    1989-10-02T23:59:59.000Z

    We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad-area threshold current densities of 114 A/cm{sup 2} at 990 nm were measured for 1540-{mu}m-long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried-heterostructure device with a 2-{mu}m-wide stripe and 425-{mu}m-long cavity. With reflective coatings the best device showed 0.9 mA threshold current ({ital L}=225 {mu}m). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.

  9. Current collapse imaging of Schottky gate AlGaN/GaN high electron mobility transistors by electric field-induced optical second-harmonic generation measurement

    SciTech Connect (OSTI)

    Katsuno, Takashi, E-mail: e1417@mosk.tytlabs.co.jp; Ishikawa, Tsuyoshi; Ueda, Hiroyuki; Uesugi, Tsutomu [Toyota Central R and D Laboratories Inc., Nagakute, Aichi 480-1192 (Japan); Manaka, Takaaki; Iwamoto, Mitsumasa [Department of Physical Electronics, Tokyo Institute of Technology, Meguro, Tokyo 152-8552 (Japan)

    2014-06-23T23:59:59.000Z

    Two-dimensional current collapse imaging of a Schottky gate AlGaN/GaN high electron mobility transistor device was achieved by optical electric field-induced second-harmonic generation (EFISHG) measurements. EFISHG measurements can detect the electric field produced by carriers trapped in the on-state of the device, which leads to current collapse. Immediately after (e.g., 1, 100, or 800??s) the completion of drain-stress voltage (200?V) in the off-state, the second-harmonic (SH) signals appeared within 2??m from the gate edge on the drain electrode. The SH signal intensity became weak with time, which suggests that the trapped carriers are emitted from the trap sites. The SH signal location supports the well-known virtual gate model for current collapse.

  10. Improvement of near-infrared absorption linewidth in AlGaN/GaN superlattices by optimization of delta-doping location

    SciTech Connect (OSTI)

    Edmunds, C.; Cervantes, M.; Malis, O. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Tang, L.; Shao, J.; Li, D. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); Gardner, G. [Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Zakharov, D. N. [Birck Nanotechnology Center, West Lafayette, Indiana 47907 (United States); Manfra, M. J. [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, 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)

    2012-09-03T23:59:59.000Z

    We report a systematic study of the near-infrared intersubband absorption in AlGaN/GaN superlattices grown by plasma-assisted molecular-beam epitaxy as a function of Si-doping profile with and without {delta}-doping. The transition energies are in agreement with theoretical calculations including many-body effects. A dramatic reduction of the intersubband absorption linewidth is observed when the {delta}-doping is placed at the end of the quantum well. This reduction is attributed to the improvement of interface roughness. The linewidth dependence on interface roughness is well reproduced by a model that considers the distribution of well widths measured with transmission electron microscopy.

  11. Thermal stability and in situ SiN passivation of InAlN/GaN high electron mobility heterostructures

    SciTech Connect (OSTI)

    Lugani, L.; Carlin, J.-F.; Py, M. A.; Grandjean, N. [ICMP, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2014-09-15T23:59:59.000Z

    We investigate the thermal stability of nearly lattice-matched InAlN layers under metal organic vapor phase epitaxy conditions for temperatures >800?°C and show that they are not fully stable. In particular, InAlN top layers undergo degradation during high temperature annealing due to a surface related process, which causes the loss of crystal quality. This strongly impacts the transport properties of InAlN/GaN HEMT heterostructures; in particular, the mobility is significantly reduced. However, we demonstrate that high thermal stability can be achieved by capping with a GaN layer as thin as 0.5?nm. Those findings enabled us to realize in situ passivated HEMT heterostructures with state of the art transport properties.

  12. WA_1995_001_US_AUTO_MATERIALS_PARTNERSHIPS_Waiver_of_Patent_...

    Office of Environmental Management (EM)

    WA1995001USAUTOMATERIALSPARTNERSHIPSWaiverofPatent.pdf WA1995001USAUTOMATERIALSPARTNERSHIPSWaiverofPatent.pdf WA1995001USAUTOMATERIALSPARTNERSHIPSWaiver...

  13. Large internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko, Gerald Hnig, Christian Kindel, Sven Rodt, Andr Strittmatter et al.

    E-Print Network [OSTI]

    Nabben, Reinhard

    Large internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko, Gerald Hönig, Christian transitions in wurtzite InGaN/GaN coupled quantum dot nanowire heterostructures with polarization internal dipole moment in InGaN/GaN quantum dots Irina A. Ostapenko,a Gerald Hönig, Christian Kindel, Sven

  14. Investigation of large Stark shifts in InGaN/GaN multiple quantum wells Guibao Xu, Guan Sun, Yujie J. Ding, Hongping Zhao, Guangyu Liu et al.

    E-Print Network [OSTI]

    Gilchrist, James F.

    Investigation of large Stark shifts in InGaN/GaN multiple quantum wells Guibao Xu, Guan Sun, Yujie overgrowth on residual strain and In incorporation in a-plane InGaN/GaN quantum wells on r- sapphire substrates J. Appl. Phys. 113, 023506 (2013) Anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple

  15. 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.

  16. Room-temperature cw operation of InGaP/InGaAlP visible light laser diodes on GaAs substrates grown by metalorganic chemical vapor deposition

    SciTech Connect (OSTI)

    Ishikawa, M.; Ohba, Y.; Sugawara, H.; Yamamoto, M.; Nakanisi, T.

    1986-01-20T23:59:59.000Z

    Room-temperature cw operation for InGaP/InGaAlP double heterostructure (DH) laser diodes on GaAs substrates was achieved for the first time. The DH wafers were grown by low-pressure metalorganic chemical vapor deposition using methyl metalorganics. A lasing wavelength of 679 nm and a threshold current of 109 mA at 24C were obtained for an inner stripe structure laser diode with a 250- m-long and 7- m stripe geometry. The laser operated at up to 51C. The characteristic temperature T0 was 87 K at around room temperature. The lowest threshold current density, 5.0 kA/cmS, was obtained with a 20- m stripe width laser diode under room-temperature pulsed operation.

  17. Quasiperiodic AlGaAs superlattices for neuromorphic networks and nonlinear control systems

    E-Print Network [OSTI]

    K. V. Malyshev

    2015-02-08T23:59:59.000Z

    The application of quasiperiodic AlGaAs superlattices as a nonlinear element of the FitzHugh-Nagumo neuromorphic network is proposed and theoretically investigated on the example of Fibonacci and figurate superlattices. The sequences of symbols for the figurate superlattices were produced by decomposition of the Fibonacci superlattices' symbolic sequences. A length of each segment of the decomposition was equal to the corresponding figurate number. It is shown that a nonlinear network based upon Fibonacci and figurate superlattices provides better parallel filtration of a half-tone picture than a network based upon traditional diodes which have cubic voltage-current characteristics. It was found that the figurate superlattice F011(1) as a nonlinear network's element provides the filtration error almost twice less than the conventional "cubic" diode. These advantages are explained by a wavelike shape of the decreasing part of the quasiperiodic superlattice's voltage-current characteristic, which leads to multistability of the network's cell. This multistability promises new interesting nonlinear dynamical phenomena. A variety of wavy forms of voltage-current characteristics opens up new interesting possibilities for quasiperiodic superlattices and especially for figurate superlattices in many areas - from nervous system modeling to nonlinear control systems development

  18. New plasma chemistries for dry etching of InGaAlP alloys: BI{sub 3} and BBr{sub 3}

    SciTech Connect (OSTI)

    Hong, J.; Cho, H.; Maeda, T.; Abernathy, C.R.; Pearton, S.J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Shul, R.J. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Hobson, W.S. [Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)] [Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)

    1998-09-01T23:59:59.000Z

    Inductively coupled plasma etching of InGaP, AlInP and AlGaP in BI{sub 3} or BBr{sub 3} discharges was investigated as a function of source power, dc chuck bias and plasma composition. InGaP etches at the fastest rates ({gt}6000thinsp{Angstrom}thinspmin{sup {minus}1}) in both chemistries, followed by AlGaP. It is found that AlInP provides an excellent etch stop for the other two materials in both mixtures. The InGaP surface morphology improves with increasing BI{sub 3} or BBr{sub 3} content, and with increasing dc chuck bias. The etched features for this material are highly anisotropic. Etch selectivities for InGaP over SiO{sub 2} and SiN{sub x} of {ge}8 are obtained in both plasma chemistries, and there is no etch incubation time with either mixture, indicating that both can scavenge the native oxide on InGaP, AlGaP and AlInP. {copyright} {ital 1998 American Vacuum Society.}

  19. A15 superconductors through direct solid-state precipitation: V/sub 3/Ga and Nb/sub 3/Al

    SciTech Connect (OSTI)

    Hong, M.

    1980-09-01T23:59:59.000Z

    A solid-state precipitation process was used to prepare superconducting tapes containing an A15 phase, V/sub 3/Ga or Nb/sub 3/Al, in a ductile niobium or vanadium containing BCC matrix. Ingots weighing as large as 30 to 50 gms of V-(14 approx. 19 at. %) Ga and Nb-(13 approx. 22 at. %) Al were prepared by arc-melting, homogenized, quenched, warm-rolled over 99% into tape, and aged at temperatures in the range 600/sup 0/C to 1000/sup 0/C to precipitate the superconducting A15 phase. The features demonstrated by the process are very attractive for practical applications. In the V-Ga system, transmission electron microscopy (TEM) studies revealed the A15 precipitates in an elongated form. However, for the Nb-Al samples, deformed and aged at 750/sup 0/C, TEM studies revealed A15 precipitation in fine equi-axed particles which formed as a semi-continuous network over sub-grain boundaries formed by the recovery of deformation-induced dislocations. In the V-Ga system, the maximum critical transition temperature (approx. 15 K) was found in materials aged at temperatures of 750/sup 0/C or below. At these aging temperatures the T/sub c/ initially increased with aging time and passed through a distinct maximum. The source of the exceptionally high T/sub c/ is discussed. In the Nb-Al system, the aging response of the T/sub c/ of the tested samples was somewhat different; the T/sub c/ increased with aging time to a plateau, and then increased again to a second plateau. The maximum T/sub c/ measured was approx. 17 K. Promising high-field overall critical currents were obtained in the Nb-Al system (overall J/sub c/ approx. 10/sup 4/ A/cm/sup 2/ in a magnetic field of 140 KG at 4.2 K).

  20. Degradation of AlGaN/GaN high-electron mobility transistors in the current-controlled off-state breakdown

    SciTech Connect (OSTI)

    Kuzmik, J., E-mail: jan.kuzmik@savba.sk; Jurkovi?, M.; Gregušová, D.; ?apajna, M. [Institute of Electrical Engineering SAS, Dubravska cesta 9, 841 04 Bratislava (Slovakia); Brunner, F.; Cho, M.; Würfl, J. [Ferdinand-Braun-Institute, Leibnitz Institute für Höchfrequenztechnik, Gustav-Kirchoff-Strasse 4, 12489 Berlin (Germany); Meneghesso, G. [Department of Information Engineering, University of Padova, via Gradenigo, 6/B 35131 Padova (Italy)

    2014-04-28T23:59:59.000Z

    We investigate degradation mechanisms in AlGaN/GaN HEMTs which were repeatedly driven into the current-controlled off-state breakdown or subject to 60 s voltage- or current-controlled off state stresses. The current-controlled sweep in to the breakdown allows the sustainability of breakdown that can not be observed in the voltage controlled sweep. Only temporal changes were observed in the HEMT dc performance after repetitive sweeps, which were explained by charging/discharging of the HEMT surface at the gate-to-drain access region and in the GaN buffer below the gate. Similar changes were observed also if high-voltage stress has been applied on the drain; however, permanent degradation appears after 60 s current-controlled breakdown stress. In this case, the drain leakage current, as well as the breakdown current, increases significantly. On the other hand, the breakdown voltage, as well as the gate characteristics, remains unaltered. We suggest that the avalanche-injection process is governing the off-state breakdown event with a dominant role of the potential barrier at the channel-buffer interface.

  1. Depth-resolved ultra-violet spectroscopic photo current-voltage measurements for the analysis of AlGaN/GaN high electron mobility transistor epilayer deposited on Si

    SciTech Connect (OSTI)

    Ozden, Burcu; Yang, Chungman; Tong, Fei; Khanal, Min P.; Mirkhani, Vahid; Sk, Mobbassar Hassan; Ahyi, Ayayi Claude; Park, Minseo, E-mail: park@physics.auburn.edu [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

    2014-10-27T23:59:59.000Z

    We have demonstrated that the depth-dependent defect distribution of the deep level traps in the AlGaN/GaN high electron mobility transistor (HEMT) epi-structures can be analyzed by using the depth-resolved ultra-violet (UV) spectroscopic photo current-voltage (IV) (DR-UV-SPIV). It is of great importance to analyze deep level defects in the AlGaN/GaN HEMT structure, since it is recognized that deep level defects are the main source for causing current collapse phenomena leading to reduced device reliability. The AlGaN/GaN HEMT epi-layers were grown on a 6 in. Si wafer by metal-organic chemical vapor deposition. The DR-UV-SPIV measurement was performed using a monochromatized UV light illumination from a Xe lamp. The key strength of the DR-UV-SPIV is its ability to provide information on the depth-dependent electrically active defect distribution along the epi-layer growth direction. The DR-UV-SPIV data showed variations in the depth-dependent defect distribution across the wafer. As a result, rapid feedback on the depth-dependent electrical homogeneity of the electrically active defect distribution in the AlGaN/GaN HEMT epi-structure grown on a Si wafer with minimal sample preparation can be elucidated from the DR-UV-SPIV in combination with our previously demonstrated spectroscopic photo-IV measurement with the sub-bandgap excitation.

  2. Study of gate oxide traps in HfO[subscript 2]/AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors by use of ac transconductance method

    E-Print Network [OSTI]

    Sun, X.

    We introduce an ac-transconductance method to profile the gate oxide traps in a HfO[subscript 2] gated AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors (MOS-HEMTs) that can exchange carriers with metal ...

  3. Anti-site disorder and improved functionality of Mn?NiX (X = Al, Ga, In, Sn) inverse Heusler alloys

    SciTech Connect (OSTI)

    Paul, Souvik; Kundu, Ashis; Ghosh, Subhradip, E-mail: subhra@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati, Assam 781039 (India); Sanyal, Biplab [Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala (Sweden)

    2014-10-07T23:59:59.000Z

    Recent first-principles calculations have predicted Mn?NiX (X = Al, Ga, In, Sn) alloys to be magnetic shape memory alloys. Moreover, experiments on Mn?NiGa and Mn?NiSn suggest that the alloys deviate from the perfect inverse Heusler arrangement and that there is chemical disorder at the sublattices with tetrahedral symmetry. In this work, we investigate the effects of such chemical disorder on phase stabilities and magnetic properties using first-principles electronic structure methods. We find that except Mn?NiAl, all other alloys show signatures of martensitic transformations in presence of anti-site disorder at the sublattices with tetrahedral symmetry. This improves the possibilities of realizing martensitic transformations at relatively low fields and the possibilities of obtaining significantly large inverse magneto-caloric effects, in comparison to perfect inverse Heusler arrangement of atoms. We analyze the origin of such improvements in functional properties by investigating electronic structures and magnetic exchange interactions.

  4. Electronic structure of Al- and Ga-doped ZnO films studied by hard X-ray photoelectron spectroscopy

    SciTech Connect (OSTI)

    Gabás, M.; Ramos Barrado, José R. [Lab. de Materiales and Superficies, Dpto. de Física Aplicada I, Universidad de Málaga, 29071 Málaga (Spain); Torelli, P. [Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, I-34149 Trieste (Italy); Barrett, N. T. [CEA, DSM/IRAMIS/SPCSI, F-91191 Gif-sur-Yvette Cedex (France); Sacchi, M. [Synchrotron SOLEIL, BP 48, 91192 Gif-sur-Yvette, France and Institut des NanoSciences de Paris, UPMC Paris 06, CNRS UMR 7588, 4 Place Jussieu, 75005 Paris (France)

    2014-01-01T23:59:59.000Z

    Al- and Ga-doped sputtered ZnO films (AZO, GZO) are semiconducting and metallic, respectively, despite the same electronic valence structure of the dopants. Using hard X-ray photoelectron spectroscopy we observe that both dopants induce a band in the electronic structure near the Fermi level, accompanied by a narrowing of the Zn 3d/O 2p gap in the valence band and, in the case of GZO, a substantial shift in the Zn 3d. Ga occupies substitutional sites, whereas Al dopants are in both substitutional and interstitial sites. The latter could induce O and Zn defects, which act as acceptors explaining the semiconducting character of AZO and the lack of variation in the optical gap. By contrast, mainly substitutional doping is consistent with the metallic-like behavior of GZO.

  5. Cl{sub 2}-based dry etching of the AlGaInN system in inductively coupled plasmas

    SciTech Connect (OSTI)

    Cho, Hyun; Vartuli, C.B.; Abernathy, C.R.; Donovan, S.M.; Pearton, S.J. [Florida Univ., Gainesville, FL (United States). Dept. of Materials Science and Engineering; Shul, R.J.; Han, J. [Sandia National Labs., NM (United States)

    1997-12-01T23:59:59.000Z

    Cl{sub 2}-based Inductively Coupled Plasmas with low additional dc self- biases(-100V) produce convenient etch rates(500-1500 A /min) for GaN, AlN, InN, InAlN and InGaN. A systematic study of the effects of additive gas(Ar, N{sub 2}, H{sub 2}), discharge composition and ICP source power and chuck power on etch rate and surface morphology has been performed. The general trends are to go through a maximum in etch rate with percent Cl{sub 2} in the discharge for all three mixtures, and to have an increase(decrease) in etch rate with source power(pressure). Since the etching is strongly ion-assisted, anisotropic pattern transfer is readily achieved. Maximum etch selectivities of approximately 6 for InN over the other nitrides were obtained.

  6. Strain control of AlGaN/GaN high electron mobility transistor structures on silicon (111) by plasma assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Aidam, Rolf; Diwo, Elke; Rollbuehler, Nicola; Kirste, Lutz; Benkhelifa, Fouad [Fraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg (Germany)

    2012-06-01T23:59:59.000Z

    This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN-based high electron mobility transistor structures grown on 4 in. Si (111) substrates. In situ measurements of wafer curvature during growth proved to be a very powerful method to analyze the buffer layer's thickness dependent strain. The Ga/N ratio at the beginning of growth of the GaN buffer layer is the critical parameter to control the compressive strain of the entire grown structure. An engineered amount of compressive strain must be designed into the structure to perfectly compensate for the tensile strain caused by differences in the thermal expansion coefficient between the epi-layer and substrate during sample cool down from growth temperatures. A maximum film thickness of 4.2 {mu}m was achieved without the formation of any cracks and a negligible bow of the wafers below 10 {mu}m. Measurement of the as-grown wafers revealed depth profiles of the charge carrier concentration comparable to values achieved on SiC substrates and mobility values of the two dimensional electron gas in the range 1230 to 1350 cm{sup 2}/Vs at a charge carrier concentration of 6.5-7 10{sup 12}/cm{sup 2}. First results on processed wafers with 2 {mu}m thick buffer layer indicate very promising results with a resistance of the buffer, measured on 200 {mu}m long contacts with 15 {mu}m pitch, in the range of R > 10{sup 9}{Omega} at 100 V and breakdown voltages up to 550 V.

  7. Drift velocity of electrons in quantum wells of selectively doped In{sub 0.5}Ga{sub 0.5}As/Al{sub x}In{sub 1-x}As and In{sub 0.2}Ga{sub 0.8}As/Al{sub x}Ga{sub 1-x}As heterostructures in high electric fields

    SciTech Connect (OSTI)

    Pozela, J., E-mail: pozela@pfi.lt; Pozela, K.; Raguotis, R.; Juciene, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute (Lithuania)

    2011-06-15T23:59:59.000Z

    The field dependence of drift velocity of electrons in quantum wells of selectively doped In{sub 0.5}Ga{sub 0.5}As/Al{sub x}In{sub 1-x}As and In{sub 0.2}Ga{sub 0.8}As/Al{sub x}Ga{sub 1-x}As heterostructures is calculated by the Monte Carlo method. The influence of varying the molar fraction of Al in the composition of the Al{sub x}Ga{sub 1-x}As and Al{sub x}In{sub 1-x}As barriers of the quantum well on the mobility and drift velocity of electrons in high electric fields is studied. It is shown that the electron mobility rises as the fraction x of Al in the barrier composition is decreased. The maximum mobility in the In{sub 0.5}Ga{sub 0.5}As/In{sub 0.8}Al{sub 0.2}As quantum wells exceeds the mobility in a bulk material by a factor of 3. An increase in fraction x of Al in the barrier leads to an increase in the threshold field E{sub th} of intervalley transfer (the Gunn effect). The threshold field is E{sub th} = 16 kV/cm in the In{sub 0.5}Ga{sub 0.5}As/Al{sub 0.5}In{sub 0.5}As heterostructures and E{sub th} = 10 kV/cm in the In{sub 0.2}Ga{sub 0.8}As/Al{sub 0.3}Ga{sub 0.7}As heterostructures. In the heterostructures with the lowest electron mobility, E{sub th} = 2-3 kV/cm, which is lower than E{sub th} = 4 kV/cm in bulk InGaAs.

  8. Ab initio studies of early stages of AlN and GaN growth on 4H-SiC

    SciTech Connect (OSTI)

    Wachowicz, E.; K?dro?, N. [Institute of Experimental Physics, University of Wroclaw, PL-50-204 Wroclaw (Poland); Sznajder, M. [Institute of Physics, University of Rzeszow, PL -35-959 Rzeszow, Poland and Faculty of Physics, University of Warsaw, PL-00-681 Warsaw (Poland); Majewski, J. A. [Faculty of Physics, University of Warsaw, PL-00-681 Warsaw (Poland)

    2013-12-04T23:59:59.000Z

    Processes of aluminum and gallium adsorption on Si- and C-terminated 4H-SiC(0001) surfaces have been studied within the DFT framework. Al and Ga coverages ranging from a submonolayer to one monolayer have been considered. The results show that Al binds more strongly to both surfaces than Ga and the binding of both metals is stronger to the C-terminated than to Si-terminated surface of SiC. The lateral lattice sites occupied by Al and Ga atoms at one monolayer are different and it is due to a different charge transfer from metal to the substrate.

  9. Monolithic integration of AlGaInP laser diodes on SiGe/Si substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Kwon, O.; Boeckl, J. J.; Lee, M. L.; Pitera, A. J.; Fitzgerald, E. A.; Ringel, S. A. [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2006-07-01T23:59:59.000Z

    Room temperature operation of visible AlGaInP laser diodes epitaxially integrated on Si was demonstrated. Compressively strained laser heterostructures were grown by molecular beam epitaxy (MBE) on low dislocation density SiGe/Si substrates, where the threading dislocation density of the top relaxed Ge layers was measured in the range of 2x10{sup 6} cm{sup -2}. A threshold current density of J{sub th}{approx}1.65 kA/cm{sup 2} for the as-cleaved, gain-guided AlGaInP laser grown on SiGe/Si was obtained at the peak emission wavelength of 680 nm under pulsed mode current injection. These results show that not only can high quality AlGaInP materials grown by MBE be achieved on Si via relaxed SiGe interlayers, but the prototype demonstration of laser diode operation on Si illustrates that very defect sensitive optoelectronics in the III-P system can indeed be integrated with Si substrates by heteroepitaxial methods.

  10. 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.

  11. 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.

  12. Inhomogeneous distribution of defect-related emission in Si-doped AlGaN epitaxial layers with different Al content and Si concentration

    SciTech Connect (OSTI)

    Kurai, Satoshi, E-mail: kurai@yamaguchi-u.ac.jp; Ushijima, Fumitaka; Yamada, Yoichi [Department of Material Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611 (Japan); Miyake, Hideto; Hiramatsu, Kazumasa [Department of Electrical and Electronic Engineering, Mie University, 1577 Kurimamachiya, Tsu, Mie 514-8507 (Japan)

    2014-02-07T23:59:59.000Z

    The spatial distribution of luminescence in Si-doped AlGaN epitaxial layers that differ in Al content and Si concentration has been studied by cathodoluminescence (CL) mapping in combination with scanning electron microscopy. The density of surface hillocks increased with decreasing Al content and with increasing Si concentration. The mechanisms giving rise to those hillocks are likely different. The hillocks induced surface roughening, and the compositional fluctuation and local donor-acceptor-pair (DAP) emission at hillock edges in AlGaN epitaxial layers were enhanced irrespective of the origin of the hillocks. The intensity of local DAP emission was related to Si concentration, as well as to hillock density. CL observation revealed that DAP emission areas were present inside the samples and were likely related to dislocations concentrated at hillock edges. Possible candidates for acceptors in the observed DAP emission that are closely related in terms of both Si concentration and hillock edges with large deformations are a V{sub III}-Si{sub III} complex and Si{sub N}, which are unfavorable in ordinary III-nitrides.

  13. Inductively Coupled Plasma and Electron Cyclotron Resonance Plasma Etching of InGaAlP Compound Semiconductor System

    SciTech Connect (OSTI)

    Abernathy, C.R.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Pearton, S.J.; Shul, R.J.

    1998-11-04T23:59:59.000Z

    Current and future generations of sophisticated compound semiconductor devices require the ability for submicron scale patterning. The situation is being complicated since some of the new devices are based on a wider diversity of materials to be etched. Conventional IUE (Reactive Ion Etching) has been prevalent across the industry so far, but has limitations for materials with high bond strengths or multiple elements. IrI this paper, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma), for the etching of ternary compound semiconductors (InGaP, AIInP, AlGaP) which are employed for electronic devices like heterojunction bipolar transistors (HBTs) or high electron mobility transistors (HEMTs), and photonic devices such as light-emitting diodes (LEDs) and lasers. High density plasma sources, opeiating at lower pressure, are expected to meet target goals determined in terms of etch rate, surface morphology, surface stoichiometry, selectivity, etc. The etching mechanisms, which are described in this paper, can also be applied to other III-V (GaAs-based, InP-based) as well as III-Nitride since the InGaAIP system shares many of the same properties.

  14. Free-standing Al[subscript x]Ga[subscript 1?x]As heterostructures by gas-phase etching of germanium

    E-Print Network [OSTI]

    Cole, Garrett D.

    We outline a facile fabrication technique for the realization of free-standing Al[subscript x]Ga[subscript 1?x]As heterostructures of arbitrary aluminum content. Utilizing xenon difluoride (XeF[subscript 2]) we rapidly and ...

  15. 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 ...

  16. SEATILE, WA October 1972

    E-Print Network [OSTI]

    'lnpml"nL. in r " arch in the fishery sciences, including hiology, tpchnology, and ngin ring. The publications al'P writtpn bv scientisL and oth r staff meml){'rs of the 'ational ceanic and Atmosph 'ric Administration.' for oth r scipnlific and t(> hnieal publications in the marine sciences. Individual copi s ar a

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

    SciTech Connect (OSTI)

    Goldenberg, Eda, E-mail: goldenberg@unam.bilkent.edu.tr [UNAM – National Nanotechnology Research Center, Bilkent University, Ankara 06800 (Turkey); Ozgit-Akgun, Cagla; Biyikli, Necmi [Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 (Turkey); Kemal Okyay, Ali [Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800 (Turkey)

    2014-05-15T23:59:59.000Z

    Gallium nitride (GaN), aluminum nitride (AlN), and Al{sub x}Ga{sub 1?x}N films have been deposited by hollow cathode plasma-assisted atomic layer deposition at 200?°C on c-plane sapphire and Si substrates. The dependence of film structure, absorption edge, and refractive index on postdeposition annealing were examined by x-ray diffraction, spectrophotometry, and spectroscopic ellipsometry measurements, respectively. Well-adhered, uniform, and polycrystalline wurtzite (hexagonal) GaN, AlN, and Al{sub x}Ga{sub 1?x}N films were prepared at low deposition temperature. As revealed by the x-ray diffraction analyses, crystallite sizes of the films were between 11.7 and 25.2?nm. The crystallite size of as-deposited GaN film increased from 11.7 to 12.1 and 14.4?nm when the annealing duration increased from 30?min to 2?h (800?°C). For all films, the average optical transmission was ?85% in the visible (VIS) and near infrared spectrum. The refractive indices of AlN and Al{sub x}Ga{sub 1?x}N were lower compared to GaN thin films. The refractive index of as-deposited films decreased from 2.33 to 2.02 (??=?550?nm) with the increased Al content x (0???x???1), while the extinction coefficients (k) were approximately zero in the VIS spectrum (>400?nm). Postdeposition annealing at 900?°C for 2?h considerably lowered the refractive index value of GaN films (2.33–1.92), indicating a significant phase change. The optical bandgap of as-deposited GaN film was found to be 3.95?eV, and it decreased to 3.90?eV for films annealed at 800?°C for 30?min and 2?h. On the other hand, this value increased to 4.1?eV for GaN films annealed at 900?°C for 2?h. This might be caused by Ga{sub 2}O{sub 3} formation and following phase change. The optical bandgap value of as-deposited Al{sub x}Ga{sub 1?x}N films decreased from 5.75 to 5.25?eV when the x values decreased from 1 to 0.68. Furthermore, postdeposition annealing did not affect the bandgap of Al-rich films.

  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. Systematic study of near-infrared intersubband absorption of polar and semipolar GaN/AlN quantum wells

    SciTech Connect (OSTI)

    Machhadani, H. [Institut d'Electronique Fondamentale, Universite Paris-Sud, UMR 8622 CNRS, 91405 Orsay (France); Semiconductor Materials, Department of Physics, Chemistry, and Biology (IFM), Linkoeping University, S-58183 Linkoeping (Sweden); Beeler, M.; Kotsar, Y.; Monroy, E. [CEA-CNRS Group Nanophysique et Semiconducteurs, INAC/SP2M/NPSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Sakr, S.; Warde, E.; Tchernycheva, M.; Julien, F. H. [Institut d'Electronique Fondamentale, Universite Paris-Sud, UMR 8622 CNRS, 91405 Orsay (France); Chauvat, M. P.; Ruterana, P. [CIMAP, UMR 6252, CNRS-ENSICAEN-CEA-UCBN, 6 Bd Marechal Juin, 14050 Caen (France); Nataf, G.; De Mierry, Ph. [CRHEA, UPR 10, 1 rue Bernard Gregory, Sophia Antipolis, 06560 Valbonne (France)

    2013-04-14T23:59:59.000Z

    We report on the observation of intersubband absorption in GaN/AlN quantum well superlattices grown on (1122)-oriented GaN. The absorption is tuned in the 1.5-4.5 {mu}m wavelength range by adjusting the well thickness. The semipolar samples are compared with polar samples with identical well thickness grown during the same run. The intersubband absorption of semipolar samples shows a significant red shift with respect to the polar ones due to the reduction of the internal electric field in the quantum wells. The experimental results are compared with simulations and confirm the reduction of the polarization discontinuity along the growth axis in the semipolar case. The absorption spectral shape depends on the sample growth direction: for polar quantum wells the intersubband spectrum is a sum of Lorentzian resonances, whereas a Gaussian shape is observed in the semipolar case. This dissimilarity is explained by different carrier localization in these two cases.

  20. Microstructure and interface control of GaN/MgAl{sub 2}O{sub 4} grown by metalorganic chemical vapor deposition: Substrate-orientation dependence

    SciTech Connect (OSTI)

    He, G.; Chikyow, T. [Advanced Electric Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Chichibu, Shigefusa F. [CANTech, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan)

    2011-07-15T23:59:59.000Z

    GaN films with single-crystal and polycrystalline structure were deposited on (111) and (100) MgAl{sub 2}O{sub 4} substrates by metalorganic chemical vapor deposition using a substrate modified by chemical etching and thermal passivation. The interface structure and chemical bonding state of the GaN/MgAl{sub 2}O{sub 4} interface was investigated using angle-resolved x-ray photoelectron spectroscopy and resulting valence band spectra. Our results indicate that the Al{sub 2}O{sub 3} buffered layer induced by thermal passivation of the (111) substrate remains unchanged during GaN deposition, which is primarily responsible for the epitaxial growth of GaN on (111) MgAl{sub 2}O{sub 4} substrate. However, for the as-processed (100) substrate, interfacial reactions take place between the formed MgO-terminated surface and GaN films and GaN with a polycrystalline structure on (100) substrate forms. From the interface engineering viewpoint, the appropriate interface modification will allow control of the interface reaction to obtain high-quality GaN films for future optoelectronic devices.

  1. 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}?

  2. 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.

  3. Direct modulation and active mode locking of ultrahigh speed GaAlAs lasers at frequencies up to 18 GHz

    SciTech Connect (OSTI)

    Lau, K.Y.; Yariv, A.

    1985-02-15T23:59:59.000Z

    It is demonstrated that an ultrahigh speed window buried heterostructure GaAlAs laser fabricated on a semi-insulating substrate can be used as a narrowband signal transmitter in the Ku band frequency range (12--20 GHz). The modulation efficiency can be increased over a limited bandwidth by a weak optical feedback. A stronger optical feedback enables one to actively mode lock the laser diode at a very high repetition rate up to 17.5 GHz, producing pulses approx.12 ps long.

  4. Stark effect in ensembles of polar (0001) Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots and comparison with semipolar (11?22) ones

    SciTech Connect (OSTI)

    Leroux, M.; Brault, J.; Kahouli, A.; Damilano, B.; Mierry, P. de; Korytov, M. [Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, CNRS, Rue Bernard Grégory, 06560 Valbonne (France); Maghraoui, D. [Laboratoire de Physique de la Matière Condensée, Faculté des Sciences de Tunis, 2092 El Manar (Tunisia); Kim, Je-Hyung; Cho, Yong-Hoon [Department of Physics and KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701 (Korea, Republic of)

    2014-07-21T23:59:59.000Z

    This work presents a continuous-wave photoluminescence study of Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots grown by ammonia-assisted molecular beam epitaxy on sapphire, either on the wurtzite polar (0001) or the semipolar (11?22) plane. Due to interface polarization discontinuities, the polar dots are strongly red-shifted by the Stark effect and emit in the visible range. Carrier injection screening of the polarization charges has been studied. A model relying on average dot heights and dot height variances, as measured by transmission electron microscopy, is proposed. It can account for the injection dependent luminescence energies and efficiencies. The electric field discontinuity deduced from the fittings is in good agreement with theoretical expectations for our barrier composition. On the contrary, semipolar quantum dot ensembles always emit above the gap of GaN strained to Al{sub 0.5}Ga{sub 0.5}N. Their luminescence linewidth is significantly lower than that of polar ones, and their energy does not shift with injection. Our study then confirms the expected strong decrease of the Stark effect for (11?22) grown (Al,Ga)N/GaN heterostructures.

  5. Fabrication of InAs quantum dots in AlAs/GaAs DBR pillar microcavities for single photon sources

    SciTech Connect (OSTI)

    Zhang Bingyang; Solomon, Glenn S.; Pelton, Matthew; Plant, Jocelyn; Santori, Charles; Vuckovic, Jelena; Yamamoto, Yoshihisa [Quantum Entanglement Project, ICORP, JST, Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4085 (United States)

    2005-04-01T23:59:59.000Z

    We report the molecular beam epitaxy growth of low-density strain-induced InAs quantum dots (QD) embedded in an AlAs/GaAs distributed Bragg reflector structure for a triggered photon source. By optimal selection of growth temperature, InAs deposited thickness and other experimental parameters, it is possible to grow low density (10/{mu}m{sup 2}) InAs quantum dots with a suitable emission wavelength for a triggered photon source. The empirical formulas for the refractive indices of AlAs and GaAs materials at high temperature over a wide wavelength range are constructed by combining high resolution x-ray diffraction, dynamic optical reflectivity, and optical reflectivity spectrum techniques. Utilizing the electron-beam lithography and electron-cyclotron-resonance plasma etching techniques, a micropost microcavity with the top diameter of 0.6 {mu}m and the post height of 4.2 {mu}m has been fabricated. Narrow, spectrally limited single QD emission embedded in a micropost microcavity is observed in the photoluminescence.

  6. WA_1994010__SCHWITZER_U.S._INC_Waiver_of_Domestic_and_Foreig...

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

    Publications WA1994007KYOCERAINDUSTRIALCERAMICSCORPORATIONWaivero.pdf WA1994011EATONCORPORATIONWaiverofDomesticandForeign.pdf WA02028TRANECOWaiverofDomesti...

  7. WA_02_021_H2GEN_INNOVATIONS_Waiver_of_Domestic_and_Foreign_P...

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

    WA02046QUESTAAIRTECHNOLOGIESWaiverofDomesticandFor.pdf WA02055PRAXAIRWaiverofDomesticandForeignPatentRigh.pdf WA04034NUVERAFUELCELLSINCWaiver...

  8. Infrared photorefractive passive phase conjugation with BaTiO/sub 3/: Demonstrations with GaAlAs and 1. 09-. mu. m Ar/sup +/ lasers

    SciTech Connect (OSTI)

    Cronin-Golomb, M.; Lau, K.Y.; Yariv, A.

    1985-09-15T23:59:59.000Z

    We report photorefractive passive phase conjugation of GaAlAs laser radiation at 815--865 nm and Ar/sup +/ laser radiation at 1090 nm. A ring passive phase conjugate mirror was used with BaTiO/sub 3/ as the real-time holographic gain medium. With GaAlAs lasers phase conjugate reflectivities of up to 16% uncorrected for Fresnel losses were recorded. Effects of the strong associated feedback to the laser and attempts at mode locking are described. At 1090 nm the reflectivity remains approximately the same, but with a significantly longer time constant.

  9. Luminescence and superradiance in electron-beam-excited Al{sub x}Ga{sub 1?x}N

    SciTech Connect (OSTI)

    Bokhan, P. A.; Gugin, P. P.; Zakrevsky, Dm. E.; Malin, T. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, 13, Lavrentieva av., Novosibirsk 630090 (Russian Federation); Zhuravlev, K. S.; Osinnykh, I. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, 13, Lavrentieva av., Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090 (Russian Federation); Solomonov, V. I.; Spirina, A. V. [Institute of Electrophysics, Ural Division of the Russian Academy of Sciences, 106, Amundsen str., Ekaterinburg 620016 (Russian Federation)

    2014-09-21T23:59:59.000Z

    Luminescence and superradiance characteristics of 0.5–1.2-?m thick Al{sub x}Ga{sub 1?x}N films grown by molecular-beam epitaxy on sapphire substrates were studied under excitation of the films with low-energy (<20?keV) and high-energy (170?keV) electron beams. In both cases, the luminescence spectra looked quite similarly; they exhibited a band-edge luminescence with x-dependent wavelength ranging from 365?nm to 310?nm and a broadband emission taking over the whole visible spectral region. Superradiance within the broad band was obtained by pumping the samples with powerful an electron beam in the form of an open-discharge-generated filament.

  10. 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.

  11. InGaN/GaN multi-quantum well and LED growth on wafer-bonded sapphire-on-polycrystalline AlN substrates by metalorganic chemical vapor deposition.

    SciTech Connect (OSTI)

    Crawford, Mary Hagerott; Olson, S. M. (Aonex Technologies Inc., Pasadena, CA); Banas, M.; Park, Y. -B. (Aonex Technologies Inc., Pasadena, CA); Ladous, C. (Aonex Technologies Inc., Pasadena, CA); Russell, Michael J.; Thaler, Gerald; Zahler, J. M. (Aonex Technologies Inc., Pasadena, CA); Pinnington, T. (Aonex Technologies Inc., Pasadena, CA); Koleske, Daniel David; Atwater, Harry A. (Aonex Technologies Inc., Pasadena, CA)

    2008-06-01T23:59:59.000Z

    We report growth of InGaN/GaN multi-quantum well (MQW) and LED structures on a novel composite substrate designed to eliminate the coefficient of thermal expansion (CTE) mismatch problems which impact GaN growth on bulk sapphire. To form the composite substrate, a thin sapphire layer is wafer-bonded to a polycrystalline aluminum nitride (P-AlN) support substrate. The sapphire layer provides the epitaxial template for the growth; however, the thermo-mechanical properties of the composite substrate are determined by the P-AlN. Using these substrates, thermal stresses associated with temperature changes during growth should be reduced an order of magnitude compared to films grown on bulk sapphire, based on published CTE data. In order to test the suitability of the substrates for GaN LED growth, test structures were grown by metalorganic chemical vapor deposition (MOCVD) using standard process conditions for GaN growth on sapphire. Bulk sapphire substrates were included as control samples in all growth runs. In situ reflectance monitoring was used to compare the growth dynamics for the different substrates. The material quality of the films as judged by X-ray diffraction (XRD), photoluminescence and transmission electron microscopy (TEM) was similar for the composite substrate and the sapphire control samples. Electroluminescence was obtained from the LED structure grown on a P-AlN composite substrate, with a similar peak wavelength and peak width to the control samples. XRD and Raman spectroscopy results confirm that the residual strain in GaN films grown on the composite substrates is dramatically reduced compared to growth on bulk sapphire substrates.

  12. Built-in electric field and radiative efficiency of polar (0001) and semipolar (11–22) Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots

    SciTech Connect (OSTI)

    Brault, J.; Kahouli, A.; Leroux, M.; Damilano, B.; Elmaghraoui, D.; Vennéguès, P.; Guillet, T.; Brimont, C. [Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, CNRS, Rue B.Grégory 06560 Valbonne (France); Laboratoire de Physique de la Matière Condensée, Faculté des Sciences de Tunis, 2092 El Manar (Tunisia)

    2013-12-04T23:59:59.000Z

    We compare the optical properties of ensembles of polar (0001) and semipolar (11–22) Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots grown by molecular beam epitaxy The polar quantum dot emission shows a huge Stark shift. Using dot height distributions measured by transmission electron microscopy, a simple model allows accounting for the PL energies and lineshapes, and to the screening of the Stark field. The semipolar quantum dots emission show a much weaker Stark effect. High room temperature quantum yields attest the efficiency of 3D-confinement.

  13. Atomic layer deposition of Al{sub 2}O{sub 3} on GaSb using in situ hydrogen plasma exposure

    SciTech Connect (OSTI)

    Ruppalt, Laura B.; Cleveland, Erin R.; Champlain, James G.; Prokes, Sharka M.; Brad Boos, J.; Park, Doewon; Bennett, Brian R. [Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2012-12-03T23:59:59.000Z

    In this report, we study the effectiveness of hydrogen plasma surface treatments for improving the electrical properties of GaSb/Al{sub 2}O{sub 3} interfaces. Prior to atomic layer deposition of an Al{sub 2}O{sub 3} dielectric, p-GaSb surfaces were exposed to hydrogen plasmas in situ, with varying plasma powers, exposure times, and substrate temperatures. Good electrical interfaces, as indicated by capacitance-voltage measurements, were obtained using higher plasma powers, longer exposure times, and increasing substrate temperatures up to 250 Degree-Sign C. X-ray photoelectron spectroscopy reveals that the most effective treatments result in decreased SbO{sub x}, decreased Sb, and increased GaO{sub x} content at the interface. This in situ hydrogen plasma surface preparation improves the semiconductor/insulator electrical interface without the use of wet chemical pretreatments and is a promising approach for enhancing the performance of Sb-based devices.

  14. 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.

  15. Design and fabrication of InGaN/GaN heterojunction bipolar transistors for microwave power amplifiers

    E-Print Network [OSTI]

    Keogh, David Martin

    2006-01-01T23:59:59.000Z

    T. Henderson, “High- Speed InGaP/GaAs HBT’s Using a SimpleA typical AlGaAs/GaAs HBT or InGaP/GaAs HBT has the opposite

  16. AlGaN UV LED and Photodiodes Radiation Hardness and Space Qualifications and Their Applications in Space Science and High Energy Density Physics

    SciTech Connect (OSTI)

    Sun, K. X.

    2011-05-31T23:59:59.000Z

    This presentation provides an overview of robust, radiation hard AlGaN optoelectronic devices and their applications in space exploration & high energy density physics. Particularly, deep UV LED and deep UV photodiodes are discussed with regard to their applications, radiation hardness and space qualification. AC charge management of UV LED satellite payload instruments, which were to be launched in late 2012, is covered.

  17. The effects of small metal additions ,,Co,Cu,Ga,Mn,Al,Bi,Sn... on the magnetocaloric properties of the Gd5Ge2Si2 alloy

    E-Print Network [OSTI]

    Kletetschka, Gunther

    .1 X=Fe,Cu,Co,Ga,Mn, or Al alloys are superior magnetic refrigerants compared to the undoped Gd5Ge2Si2 magnetic refrigerant because of its large "giant" magnetocaloric effect Sm between 270 and 300 K.1 more useful magnetic refrigerant than the undoped Gd5Ge2Si2 compound. Further, it was concluded

  18. Broadband emission in InAs/InGaAlAs quantum-dash-in-well laser Boon S. Ooi1, a

    E-Print Network [OSTI]

    -broadband sources are generated using nonlinear-optical transformations of ultra-short laser pulses and photonicBroadband emission in InAs/InGaAlAs quantum-dash-in-well laser Boon S. Ooi1, a , Hery S. Djie1: Quantum dash, Quantum dot, Broadband emission, Semiconductor Laser. Abstract. We report on the development

  19. Tunable two-dimensional plasmon resonances in an InGaAs/InP high electron mobility transistor

    E-Print Network [OSTI]

    Peale, Robert E.

    of materials systems such as GaAs/AlGaAs,3 InGaP/InGaAs/GaAs,4 GaN/AlGaN,2,5 and Si Ref. 1 have been explored

  20. WA_98_005_WESTINGHOUSE_POWER_GENERATION_A_FORMER_DIVISION_OF...

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

    5WESTINGHOUSEPOWERGENERATIONAFORMERDIVISIONOF.pdf WA98005WESTINGHOUSEPOWERGENERATIONAFORMERDIVISIONOF.pdf WA98005WESTINGHOUSEPOWERGENERATIONAFORMERDIVISION...

  1. WA_98_006_WESTINGHOUSE_POWER_GENERATION_A_FORMER_DIVISION_OF...

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

    6WESTINGHOUSEPOWERGENERATIONAFORMERDIVISIONOF.pdf WA98006WESTINGHOUSEPOWERGENERATIONAFORMERDIVISIONOF.pdf WA98006WESTINGHOUSEPOWERGENERATIONAFORMERDIVISION...

  2. WA_00_007_COMBUSTION_ENGINEERING_INC_Waiver_of_Domestic_and_...

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

    07COMBUSTIONENGINEERINGINCWaiverofDomesticand.pdf WA00007COMBUSTIONENGINEERINGINCWaiverofDomesticand.pdf WA00007COMBUSTIONENGINEERINGINCWaiverofDomestica...

  3. WA_1994_034_AIR_PRODUCTS_AND_CHEMICALS_INC_Waiver_of_Domesti...

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

    4034AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti.pdf WA1994034AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti.pdf WA1994034AIRPRODUCTSANDCHEMICALSINCWaiverofDom...

  4. WA_99_017_AIR_PRODUCTS_AND_CHEMICALS_Waiver_of_Domestic_and_...

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

    9017AIRPRODUCTSANDCHEMICALSWaiverofDomesticand.pdf WA99017AIRPRODUCTSANDCHEMICALSWaiverofDomesticand.pdf WA99017AIRPRODUCTSANDCHEMICALSWaiverofDomesti...

  5. WA_1995_009_AIR_PRODUCTS_AND_CHEMICALS_INC_Waiver_of_Domesti...

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

    9AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti.pdf WA1995009AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti.pdf WA1995009AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti...

  6. WA_96_016_AIR_PRODUCTS_AND_CHEMICALS_INC_Waiver_of_Domestic_...

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

    16AIRPRODUCTSANDCHEMICALSINCWaiverofDomestic.pdf WA96016AIRPRODUCTSANDCHEMICALSINCWaiverofDomestic.pdf WA96016AIRPRODUCTSANDCHEMICALSINCWaiverofDomest...

  7. WA_1995_014_AIR_PRODUCTS_AND_CHEMICALS_INC_Waiver_of_Domesti...

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

    14AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti.pdf WA1995014AIRPRODUCTSANDCHEMICALSINCWaiverofDomesti.pdf WA1995014AIRPRODUCTSANDCHEMICALSINCWaiverofDomest...

  8. WA_04_028_AIR_PRODUCTS_AND_CHEMICALS_Waiver_of_patent_Rights...

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

    8AIRPRODUCTSANDCHEMICALSWaiverofpatentRights.pdf WA04028AIRPRODUCTSANDCHEMICALSWaiverofpatentRights.pdf WA04028AIRPRODUCTSANDCHEMICALSWaiverofpatentRigh...

  9. Excitonic complexes in single zinc-blende GaN/AlN quantum dots grown by droplet epitaxy

    E-Print Network [OSTI]

    As, Donat Josef

    -assembled wurtzite GaN QDs1 and up to 300 K in site-controlled wurtzite nanowire QDs.2 Less mature than their wurtzite counterparts, single self-assembled zinc- blende (ZB) GaN QDs already show good prospects in terms to 100 K.5 They even present several advantages over self-assembled wurtzite GaN QDs: shorter radiative

  10. Step-by-step capping and strain state of GaN/AlN quantum dots studied by grazing-incidence diffraction anomalous fine structure

    SciTech Connect (OSTI)

    Coraux, J.; Favre-Nicolin, V.; Renevier, H. [Commissariat l'Energie Atomique, Departement de Recherche Fondamentale sur la Matiere Condensee, SP2M/NRS, 17 rue des martyrs, 38054 Grenoble Cedex 9 (France); Universite Joseph Fourier, BP 53, 38041, Grenoble Cedex 9 (France); Proietti, M. G. [Departamento de Fisica de la Materia Condensada, Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, c. Pedro Cerbuna 12, 50009 Zaragoza (Spain); Daudin, B. [Commissariat l'Energie Atomique, Departement de Recherche Fondamentale sur la Matiere Condensee, SP2M/NRS, 17 rue des martyrs, 38054 Grenoble Cedex 9 (France)

    2006-05-15T23:59:59.000Z

    The investigation of small-size embedded nanostructures, by a combination of complementary anomalous diffraction techniques, is reported. GaN quantum dots (QD's), grown by molecular beam epitaxy in a modified Stranski-Krastanow mode, are studied in terms of strain and local environment, as a function of the AlN cap layer thickness, by means of grazing-incidence anomalous diffraction. That is, the x-ray photon energy is tuned across the Ga absorption K edge which makes diffraction chemically selective. Measurement of hkl scans, close to the AlN (3030) Bragg reflection, at several energies across the Ga K edge, allows the extraction of the Ga partial structure factor, from which the in-plane strain of GaN QD's is deduced. From the fixed-Q energy-dependent diffracted intensity spectra, measured for diffraction-selected isostrain regions corresponding to the average in-plane strain state of the QD's, quantitative information regarding the composition and out-of-plane strain has been obtained. We recover the in-plane and out-of-plane strains in the dots. The comparison to the biaxial elastic strain in a pseudomorphic layer indicates a tendency to an overstrained regime.

  11. 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.

  12. Probing channel temperature profiles in Al{sub x}Ga{sub 1?x}N/GaN high electron mobility transistors on 200?mm diameter Si(111) by optical spectroscopy

    SciTech Connect (OSTI)

    Kyaw, L. M., E-mail: a0048661@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), Singapore 117602 (Singapore); Bera, L. K.; Dolmanan, S. B.; Tan, H. R.; Bhat, T. N.; Tripathy, S., E-mail: tripathy-sudhiranjan@imre.a-star.edu.sg [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), Singapore 117602 (Singapore); Liu, Y.; Bera, M. K.; Singh, S. P.; Chor, E. F. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2014-08-18T23:59:59.000Z

    Using micro-Raman and photoluminescence (PL) techniques, the channel temperature profile is probed in Al{sub x}Ga{sub 1-x}N/GaN high electron mobility transistors (HEMTs) fabricated on a 200?mm diameter Si(111) substrate. In particular, RuO{sub x}-based gate is used due to the semitransparent nature to the optical excitation wavelengths, thus allowing much accurate thermal investigations underneath the gate. To determine the channel temperature profile in devices subjected to different electrical bias voltages, the GaN band-edge PL peak shift calibration with respect to temperature is used. PL analyses show a maximum channel temperature up to 435?K underneath the gate edge between gate and drain, where the estimated thermal resistance in such a HEMT structure is about 13.7 KmmW{sup ?1} at a power dissipation of ?10?W/mm. The temperature profiles from micro-Raman measurements are also addressed from the E{sub 2}-high optical phonon peak shift of GaN, and this method also probes the temperature-induced peak shifts of optical phonon from Si thus showing the nature of thermal characteristics at the AlN/Si substrate interface.

  13. Anisotropic elastic scattering of stripe/line-shaped scatters to two-dimensional electron gas: Model and illustrations in a nonpolar AlGaN/GaN hetero-junction

    SciTech Connect (OSTI)

    Zhang, Jinfeng, E-mail: jfzhang@xidian.edu.cn; Li, Yao; Yan, Ran; Nie, Yuhu; Zhang, Jincheng; Hao, Yue, E-mail: yhao@xidian.edu.cn [State Key Discipline Laboratory of Wide Bandgap Semiconductor Technologies, School of Microelectronics, Xidian University, Xi'an 710071 (China); Liu, Guipeng [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2014-09-07T23:59:59.000Z

    In a semiconductor hetero-junction, the stripe/line-shaped scatters located at the hetero-interface lead to the anisotropic transport of two-dimensional electron gas (2DEG). The elastic scattering of infinitely long and uniform stripe/line-shaped scatters to 2DEG is theoretically investigated based on a general theory of anisotropic 2DEG transport [J. Schliemann and D. Loss, Phys. Rev. B 68(16), 165311 (2003)], and the resulting 2DEG mobility along the applied electrical field is modeled to be a function of the angle between the field and the scatters. The anisotropy of the scattering and the mobility originate in essence from that the stripe/line-shaped scatters act upon the injecting two-dimensional wave vector by changing only its component perpendicular to the scatters. Three related scattering mechanisms in a nonpolar AlGaN/GaN hetero-junction are discussed as illustrations, including the striated morphology caused interface roughness scattering, and the polarization induced line charge dipole scattering and the misfit dislocation scattering at the AlGaN/GaN interface. Different anisotropic behaviors of the mobility limited by these scattering mechanisms are demonstrated, but analysis shows that all of them are determined by the combined effects of the anisotropic bare scattering potential and the anisotropic dielectric response of the 2DEG.

  14. Mechanochemical-thermal preparation and structural studies of mullite-type Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} solid solutions

    SciTech Connect (OSTI)

    Da Silva, K.L. [Institute of Physical and Theoretical Chemistry, Technische Universitaet Braunschweig, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany); Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 3a, 30167 Hannover (Germany); Department of Physics, State University of Maringa, Av. Colombo 5790, 87020-900 Maringa (Brazil); Sepelak, V., E-mail: vladimir.sepelak@kit.ed [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Duevel, A. [Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 3a, 30167 Hannover (Germany); Paesano, A. [Department of Physics, State University of Maringa, Av. Colombo 5790, 87020-900 Maringa (Brazil); Hahn, H. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Litterst, F.J. [Institute of Condensed Matter Physics, Technische Universitaet Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig (Germany); Heitjans, P. [Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 3a, 30167 Hannover (Germany); Becker, K.D. [Institute of Physical and Theoretical Chemistry, Technische Universitaet Braunschweig, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany)

    2011-05-15T23:59:59.000Z

    A series of Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} solid solutions (0{<=}x{<=}1), prepared by mechanochemical processing of Bi{sub 2}O{sub 3}/Ga{sub 2}O{sub 3}/Al{sub 2}O{sub 3} mixtures and subsequent annealing, was investigated by XRD, EDX, and {sup 27}Al MAS NMR. The structure of the Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} solid solutions is found to be orthorhombic, space group Pbam (No. 55). The lattice parameters of the Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} series increase linearly with increasing gallium content. Rietveld refinement of the XRD data as well as the analysis of the {sup 27}Al MAS NMR spectra show a preference of gallium cations for the tetrahedral sites in Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9}. As a consequence, this leads to a far from random distribution of Al and Ga cations across the whole series of solid solutions. -- Graphical Abstract: Mullite-type Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} mixed crystals (0{<=}x{<=}1) prepared by a combined mechanochemical-thermal route possess a non-random distribution of Ga{sup 3+} and Al{sup 3+} cations over the sites of tetrahedral (T) and octahedral [O] coordination, characterized by the preference of Ga{sup 3+} (Al{sup 3+}) for tetrahedral (octahedral) sites. Display Omitted Highlights: {yields} Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} (0{<=}x{<=}1) were synthesized via mechanochemical-thermal route. {yields} The lattice parameters of Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} increase linearly with gallium content. {yields} Quantitative information on the cation distribution in Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} is derived. {yields} Ga{sup 3+} and Al{sup 3+} show the preference for tetrahedral and octahedral sites, respectively.

  15. Variable-gap selective photocells based on Ga/sub 1-x/Al/sub x/As:Ge:Te p-n structures

    SciTech Connect (OSTI)

    Bessolov, V.N.; Danilova, T.N.; Imenkov, A.N.; Tsarenkov, B.V.; Yakovlev, Y.P.

    1980-08-01T23:59:59.000Z

    Doping of Ga/sub 1-x/Al/sub x/As solid solutions with Ge and Te increased the steepness of the fundamental absorption edge and this reduced the width of the quantum photosensitivity spectra of variable-gap selective p-n junction photocells made by depositing epitaxial films of these solid solutions on n-type GaAs substrates. The current-voltage and load characteristics of the photocells were detemined. The efficiency of conversion of the optical into electrical energy was 0.42--0.43 for the photocells with wider photosensitivity spectra and 0.3 for those with the narrowest spectra.

  16. Experimental study of frequency multipliers based on a GaAs/AlAs semiconductor superlattices in the terahertz frequency range

    SciTech Connect (OSTI)

    Paveliev, D. G., E-mail: pavelev@rf.unn.ru; Koshurinov, Y. I.; Ivanov, A. S. [Lobachevskii State University of Nizhny Novgorod (Russian Federation); Panin, A. N.; Vax, V. L.; Gavrilenko, V. I.; Antonov, A. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Zhukov, A. E. [Russian Academy of Sciences, St. Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation)

    2012-01-15T23:59:59.000Z

    Frequency multipliers based on a GaAs/AlAs semiconductor quantum superlattice have been experimentally studied. The power spectrum of the harmonics in the output signal from a multiplier with an input-signal frequency of 140-160 GHz has been measured. Planar diodes with a small active region (an area of 1-2 {mu}m{sup 2}) have been used in this study. For fabrication of the diodes, structures of heavily doped superlattices with the miniband width 24 meV have been used, these structures were grown by the molecular-beam epitaxy method. Measurements have been conducted using a BOMEM DA3.36 Fourier spectrometer equipped with a detector based on a bolometer cooled to the temperature of liquid helium. The results of the measurements have been used to plot the dependences of the power of the harmonics on the frequency in the range from 0.4 to 8.1 THz. It has been found that the character of the microwave-power distribution over the number of harmonics is close to the spectrum of a sequence of sign-alternating pulses which appear in the diode circuit when the applied voltage of the input signal exceeds the threshold of the diode. The minimal time of establishment of the pulse front and pulse duration are equal to 123 and 667 fs, respectively.

  17. 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.

  18. X-ray determination of threading dislocation densities in GaN/Al{sub 2}O{sub 3}(0001) films grown by metalorganic vapor phase epitaxy

    SciTech Connect (OSTI)

    Kopp, Viktor S., E-mail: victor.kopp@pdi-berlin.de; Kaganer, Vladimir M. [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin (Germany); Baidakova, Marina V.; Lundin, Wsevolod V.; Nikolaev, Andrey E.; Verkhovtceva, Elena V.; Yagovkina, Maria A. [Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Politekhnicheskaya 26, 194021 St.-Petersburg (Russian Federation); Cherkashin, Nikolay [CEMES-CNRS and Université de Toulouse, 29 rue J. Marvig, 31055 Toulouse (France)

    2014-02-21T23:59:59.000Z

    Densities of a- and a+c-type threading dislocations for a series of GaN films grown in different modes by metalorganic vapor phase epitaxy are determined from the x-ray diffraction profiles in skew geometry. The reciprocal space maps are also studied. Theory of x-ray scattering from crystals with dislocations is extended in order to take into account contribution from both threading and misfit dislocations. The broadening of the reciprocal space maps along the surface normal and the rotation of the intensity distribution ellipse is attributed to misfit dislocations at the interface. We find that the presence of a sharp AlN/GaN interface leads to an ordering of misfit dislocations and reduces strain inhomogeneity in GaN films.

  19. Estimation of the internal electric field inside (11-22) semipolar GaN/Al{sub 0.5}Ga{sub 0.5}N nanostructures and the radiative efficiency at low temperature

    SciTech Connect (OSTI)

    Kahouli, Abdelkarim, E-mail: abdelkarim.kahouli@yahoo.fr; Kriouche, Nasser [Université de Nice Sophia Antipolis, 06108 Nice Cedex 2 (France)

    2014-05-21T23:59:59.000Z

    We report on time-integrated and resolved photoluminescence data on self-assembled semipolar (11-22) GaN nanostructures embedded in Al{sub 0.5}Ga{sub 0.5}N. It is confirmed that the internal electric field is reduced for semipolar (11-22) orientation. It is shown in particular that the value of the electric field is 450–500?kV/cm for this orientation. The photoluminescence decay time of excitons is used as a probe of the reduction of the internal electric field in the case of semipolar GaN nanostructures. The measured decays are not only controlled by radiative lifetimes, which depend on the fields inside GaN nanostructures, but also on the nonradiative escape of carriers through barriers. The correspondent decay time is found equal to 330 ps. By the study of the decay time as a function of the emission energy, we can determine the evolution of the internal quantum efficiency as a function of the nanostructures height (energy) and to have access to the nonradiative lifetime at low temperature.

  20. Analysis of the causes of the decrease in the electroluminescence efficiency of AlGaInN light-emitting-diode heterostructures at high pumping density

    SciTech Connect (OSTI)

    Rozhansky, I. V., E-mail: igor@quantum.ioffe.ru; Zakheim, D. A. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2006-07-15T23:59:59.000Z

    The study is devoted to theoretical explanation of a decrease in the electroluminescence efficiency as the pump current increases, which is characteristic of light-emitting-diode (LED) heterostructures based on AlInGaN. Numerical simulation shows that the increase in the external quantum efficiency at low current densities J {approx} 1 A/cm{sup 2} is caused by the competition between radiative and nonradiative recombination. The decrease in the quantum efficiency at current densities J > 1 A/cm{sup 2} is caused by a decrease in the efficiency of hole injection into the active region. It is shown that the depth of the acceptor energy level in the AlGaN emitter, as well as low electron and hole mobilities in the p-type region, plays an important role in this effect. A modified LED heterostructure is suggested in which the efficiency decrease with the pump current should not occur.

  1. Nanoscale-accuracy transfer printing of ultra-thin AlInGaN light-emitting diodes onto mechanically flexible substrates

    SciTech Connect (OSTI)

    Trindade, A. J., E-mail: antonio.trindade@strath.ac.uk; Guilhabert, B.; Massoubre, D.; Laurand, N.; Gu, E.; Watson, I. M.; Dawson, M. D. [Institute of Photonics, SUPA, University of Strathclyde, 106 Rottenrow, Glasgow G4 0NW (United Kingdom)] [Institute of Photonics, SUPA, University of Strathclyde, 106 Rottenrow, Glasgow G4 0NW (United Kingdom); Zhu, D.; Humphreys, C. J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)] [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)

    2013-12-16T23:59:59.000Z

    The transfer printing of 2 ?m-thick aluminum indium gallium nitride (AlInGaN) micron-size light-emitting diodes with 150?nm (±14?nm) minimum spacing is reported. The thin AlInGaN structures were assembled onto mechanically flexible polyethyleneterephthalate/polydimethylsiloxane substrates in a representative 16 × 16 array format using a modified dip-pen nano-patterning system. Devices in the array were positioned using a pre-calculated set of coordinates to demonstrate an automated transfer printing process. Individual printed array elements showed blue emission centered at 486?nm with a forward-directed optical output power up to 80??W (355 mW/cm{sup 2}) when operated at a current density of 20?A/cm{sup 2}.

  2. Band offsets determination and interfacial chemical properties of the Al2O3/GaSb system

    E-Print Network [OSTI]

    Yener, Aylin

    of a high quality dielectric/substrate interface. Native oxides of III­V com- pounds lead to the formation Sb is formed at the oxide/GaSb interface, which leads to a high leakage current.8 To overcome treatment. In contrast, NH4 2S and HCl solutions inhibit the Sb oxide formation. The lowest amount of Ga

  3. A 77 GHz Transceiver for Automotive Radar System Using a120nm In AlAs/In GaAs Metamorphic HEMTs

    E-Print Network [OSTI]

    Kwon, Youngwoo

    A 77 GHz Transceiver for Automotive Radar System Using a120nm 0.4 0.35 In AlAs/In GaAs Metamorphic-mail:ykwon@snu.ac.kr) Abstract -- In this work, we demonstrate a compact 77GHz single-chip transceiver for an automotive radar at the transmitter and a 5dB conversion gain at the receiver. Index Terms -- Automotive radar, 77GHz, MHEMT, MMIC

  4. Importance of growth temperature on achieving lattice-matched and strained InAlN/GaN heterostructure by plasma-assisted molecular beam epitaxy

    SciTech Connect (OSTI)

    Jeganathan, K., E-mail: kjeganathan@yahoo.com [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli-620 024, Tamil Nadu (India); Shimizu, M., E-mail: mitsu.shimizu@aist.go.jp [Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan. (Japan)

    2014-09-15T23:59:59.000Z

    We investigate the role of growth temperature on the optimization of lattice-matched In{sub 0.17}Al{sub 0.83}N/GaN heterostructure and its structural evolutions along with electrical transport studies. The indium content gradually reduces with the increase of growth temperature and approaches lattice-matched with GaN having very smooth and high structural quality at 450ºC. The InAlN layers grown at high growth temperature (480ºC) retain very low Indium content of ? 4 % in which cracks are mushroomed due to tensile strain while above lattice matched (>17%) layers maintain crack-free compressive strain nature. The near lattice-matched heterostructure demonstrate a strong carrier confinement with very high two-dimensional sheet carrier density of ?2.9 × 10{sup 13} cm{sup ?2} with the sheet resistance of ?450 ?/? at room temperature as due to the manifestation of spontaneous polarization charge differences between InAlN and GaN layers.

  5. Polarization induced hole doping in graded Al{sub x}Ga{sub 1-x}N (x = 0.7 {approx} 1) layer grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Li, Shibin; Zhang, Ting; Wu, Jiang; Yang, Yajie; Wang, Zhiming; Wu, Zhiming; Chen, Zhi; Jiang, Yadong [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)] [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

    2013-02-11T23:59:59.000Z

    Polarization induced hole doping on the order of {approx}10{sup 18} cm{sup -3} is achieved in linearly graded Al{sub x}Ga{sub 1-x}N (x = 0.7 {approx} 1) layer grown by molecular beam epitaxy. Graded Al{sub x}Ga{sub 1-x}N and conventional Al{sub 0.7}Ga{sub 0.3}N layers grown on AlN are beryllium (Be) doped via epitaxial growth. The hole concentration in graded Al{sub x}Ga{sub 1-x}N:Be (x = 0.7 {approx} 1) layers demonstrates that polarization generates hole charges from Be dopant. The Al{sub 0.7}Ga{sub 0.3}N layer is not conductive owing to the absence of carriers generated from the Be dopant without the inducement of polarization. Polarization doping provides an approach to high efficiency p-type doping in high Al composition AlGaN.

  6. Optical properties of a-plane (Al, Ga)N/GaN multiple quantum wells grown on strain engineered Zn{sub 1-x}Mg{sub x}O layers by molecular beam epitaxy

    SciTech Connect (OSTI)

    Xia, Y.; Vinter, B.; Chauveau, J.-M. [CRHEA-CNRS, Rue Bernard Gregory, 06560 Valbonne (France); University of Nice Sophia-Antipolis, 06103 Nice (France); Brault, J.; Nemoz, M.; Teisseire, M.; Leroux, M. [CRHEA-CNRS, Rue Bernard Gregory, 06560 Valbonne (France)

    2011-12-26T23:59:59.000Z

    Nonpolar (1120) Al{sub 0.2}Ga{sub 0.8}N/GaN multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (1120) Zn{sub 0.74}Mg{sub 0.26}O templates on r-plane sapphire substrates. The quantum wells exhibit well-resolved photoluminescence peaks in the ultra-violet region, and no sign of quantum confined Stark effect is observed in the complete multiple quantum well series. The results agree well with flat band quantum well calculations. Furthermore, we show that the MQW structures are strongly polarized along the [0001] direction. The origin of the polarization is discussed in terms of the strain anisotropy dependence of the exciton optical oscillator strengths.

  7. The Study of Energy Band Gap of In{sub x}Al{sub y}Ga{sub 1-x-y}N Quaternary Alloys using UV-VIS Spectroscopy

    SciTech Connect (OSTI)

    Raof, N. H. Abd.; Ng, S. S.; Hassan, H. Abu; Hassan, Z. [Nano-Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

    2009-06-01T23:59:59.000Z

    Quaternary In{sub x}Al{sub y}Ga{sub 1-x-y}N alloys with indium (In) mole fraction x ranging from 0.01 to 0.10 and constant aluminum (Al) mole fraction y = 0.06, were grown by molecular beam epitaxy. The energy band gaps of InAlGaN alloys were investigated using UV-VIS spectroscopy under room temperature. The energy band gap decreases with increasing In composition from 0.01 to 0.08. This trend is expected since the incorporation of In lowers the energy band gap of Al{sub 0.06}Ga{sub 0.94}N(3.72 eV). However, for InAlGaN with In composition of 0.1, the band gap shows a sudden increase in energy. This is probably due to local alloy compositional fluctuations in the epilayer, contributed by incomplete substitutions of Ga atoms by the In atoms, thus retaining a much richer GaN structure. Finally, we investigate the bowing parameter appears also to be very sensitive on In content. We obtained b 50.08 for quaternary InAlGaN alloys.

  8. WA_00_025_PRAXAIR_INC_Waiver_Request.pdf | Department of Energy

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

    25PRAXAIRINCWaiverRequest.pdf WA00025PRAXAIRINCWaiverRequest.pdf WA00025PRAXAIRINCWaiverRequest.pdf More Documents & Publications WA00001PRAXAIRINCWaiverofDo...

  9. Optical properties of the Si-doped GaN/Al{sub 2}O{sub 3} films

    SciTech Connect (OSTI)

    Zayats, N. S.; Gentsar, P. O., E-mail: gentsar@isp.kiev.ua; Boiko, V. G.; Litvin, O. S.; Vuychik, M. V.; Stronski, A. V.; Yanchuk, I. B. [National Academy of Sciences of Ukraine, Lashkarev Institute of Semiconductor Physics (Ukraine)

    2009-05-15T23:59:59.000Z

    Morphological and optical studies of the Si-doped GaN films (doping level N{sub Si} = 1.5 x 10{sup 19} cm{sup -3}) grown by vapor-phase epitaxy from metalorganic compounds on a sapphire substrate oriented along the c axis are conducted. For the grown GaN films, the following characteristics are obtained: energy of electron transition E{sub 0}, absorption coefficient {alpha}, refractive index n, and frequencies of transverse and longitudinal optical lattice vibrations characteristic of the crystalline GaN films.

  10. Thermoelectric power generator module of 1616 Bi2Te3 and 0.6% ErAs:,,InGaAs...1-x,,InAlAs...x segmented elements

    E-Print Network [OSTI]

    Bowers, John

    Thermoelectric power generator module of 16Ã16 Bi2Te3 and 0.6% ErAs:,,InGaAs...1-x; published online 26 August 2009 We report the fabrication and characterization of thermoelectric power temperature was at 610 K. The thermoelectric properties of InGaAs 1-x InAlAs x were characterized from 300 up

  11. Thermal Boundary Resistance and Heat Diffusion in AlGaN/GaN HFETs Konstantin A. Filippov and Alexander A. Balandin

    E-Print Network [OSTI]

    , and radar applications [1-3]. At the same time, performance of these devices has been limited by self-heating [1, 4]. Thus, accurate modeling of heat diffusion and self-heating effects in Al

  12. Growth and properties of AlGaInP resonant cavity light emitting diodes on Ge/SiGe/Si substrates

    SciTech Connect (OSTI)

    Kwon, O.; Boeckl, J.; Lee, M.L.; Pitera, A.J.; Fitzgerald, E.A.; Ringel, S.A. [Department of Electrical Engineering, Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Electrical and Computer Engineering, Ohio State University, 2015 Neil Avenue, Columbus, Ohio 43210 (United States)

    2005-02-01T23:59:59.000Z

    Visible AlGaInP resonant cavity light emitting diodes (RCLEDs) were grown by molecular beam epitaxy and fabricated on low-dislocation density, SiGe/Si metamorphic substrates. A comparison with identical devices grown on GaAs and Ge substrates shows that not only did the RCLED device structure successfully transfer to the SiGe/Si substrate, but also a higher optical output power was obtained. This result is attributed to enhanced lateral current spreading by the low residual dislocation density ({approx}1x10{sup 6} cm{sup -2}) network within the virtual Ge substrate and the superior thermal conductivity of the underlying Si wafer. In addition, the growth of an AlGaAs current spreading layer and a modified top metal contact were incorporated in the RCLED on SiGe to optimize device performance. The measured electroluminescent output power was 166 {mu}W at a 665 nm peak wavelength under 500 mA current injection. Extremely narrow electroluminescence linewidths were achieved with a full width half maximum value of 3.63 nm under 50 mA current injection. These results demonstrate great promise for the monolithic integration of visible band optical sources with Si-based electronic circuitry.

  13. Role of the dielectric for the charging dynamics of the dielectric/barrier interface in AlGaN/GaN based metal-insulator-semiconductor structures under forward gate bias stress

    SciTech Connect (OSTI)

    Lagger, P., E-mail: peter.lagger@infineon.com [Infineon Technologies Austria AG, Siemensstraße 2, 9500 Villach (Austria); Institute of Solid State Electronics, Vienna University of Technology, Floragasse 7, 1040 Wien (Austria); Steinschifter, P.; Reiner, M.; Stadtmüller, M.; Denifl, G.; Ostermaier, C. [Infineon Technologies Austria AG, Siemensstraße 2, 9500 Villach (Austria); Naumann, A.; Müller, J.; Wilde, L.; Sundqvist, J. [Fraunhofer IPMS-CNT, Königsbrücker Straße 178, 01099 Dresden (Germany); Pogany, D. [Institute of Solid State Electronics, Vienna University of Technology, Floragasse 7, 1040 Wien (Austria)

    2014-07-21T23:59:59.000Z

    The high density of defect states at the dielectric/III-N interface in GaN based metal-insulator-semiconductor structures causes tremendous threshold voltage drifts, ?V{sub th}, under forward gate bias conditions. A comprehensive study on different dielectric materials, as well as varying dielectric thickness t{sub D} and barrier thickness t{sub B}, is performed using capacitance-voltage analysis. It is revealed that the density of trapped electrons, ?N{sub it}, scales with the dielectric capacitance under spill-over conditions, i.e., the accumulation of a second electron channel at the dielectric/AlGaN barrier interface. Hence, the density of trapped electrons is defined by the charging of the dielectric capacitance. The scaling behavior of ?N{sub it} is explained universally by the density of accumulated electrons at the dielectric/III-N interface under spill-over conditions. We conclude that the overall density of interface defects is higher than what can be electrically measured, due to limits set by dielectric breakdown. These findings have a significant impact on the correct interpretation of threshold voltage drift data and are of relevance for the development of normally off and normally on III-N/GaN high electron mobility transistors with gate insulation.

  14. Analysis of different tunneling mechanisms of In{sub x}Ga{sub 1?x}As/AlGaAs tunnel junction light-emitting transistors

    SciTech Connect (OSTI)

    Wu, Cheng-Han [Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China); Wu, Chao-Hsin, E-mail: chaohsinwu@ntu.edu.tw [Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China); Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China)

    2014-10-27T23:59:59.000Z

    The electrical and optical characteristics of tunnel junction light-emitting transistors (TJLETs) with different indium mole fractions (x?=?5% and 2.5%) of the In{sub x}Ga{sub 1?x}As base-collector tunnel junctions have been investigated. Two electron tunneling mechanisms (photon-assisted or direct tunneling) provide additional currents to electrical output and resupply holes back to the base region, resulting in the upward slope of I-V curves and enhanced optical output under forward-active operation. The larger direct tunneling probability and stronger Franz-Keldysh absorption for 5% TJLET lead to higher collector current slope and less optical intensity enhancement when base-collector junction is under reverse-biased.

  15. Near-infrared intersubband absorption in molecular-beam epitaxy-grown lattice-matched InAlN/GaN superlattices

    SciTech Connect (OSTI)

    Malis, O.; Edmunds, C. [Department of Physics, Binghamton University, Binghamton, New York 13902 (United States); Manfra, M. J.; Sivco, D. L. [Bell Laboratories, Alcatel-Lucent, Murray Hill, New Jersey 07974 (United States)

    2009-04-20T23:59:59.000Z

    Strong near-infrared intersubband absorption is observed directly at room temperature in silicon-doped lattice-matched InAlN/GaN superlattices grown by molecular-beam epitaxy on GaN templates grown by hydride vapor-phase epitaxy. X-ray diffraction characterization of the heterostructures indicates excellent layer thickness uniformity and low interface roughness. For 2-4.5 nm quantum wells, the intersubband transition energies span the technologically relevant range between 2.3 and 2.9 {mu}m. The experimental results are in good agreement with calculations of the transition energies using a conduction band offset of 1 eV and spontaneous polarization of 3 MV/cm.

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

    SciTech Connect (OSTI)

    Sheu, J.K.; Lee, M.L.; Tun, C.J.; Lin, S.W. [Institute of Electro-Optical Science and Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electro-Optical Engineering, Southern Taiwan University of Technology, No.1, Nantai St, Yung-Kang City, Tainan 710, Taiwan (China); Institute of Optical Science, National Central University, Jhongli 32001, Taiwan (China)

    2006-01-23T23:59:59.000Z

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

  17. 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.

  18. 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.

  19. Advance Patent Waiver W(A)2005-006 | Department of Energy

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

    W(A)2005-006 More Documents & Publications Advance Patent Waiver W(A)2008-022 WA04079PRAXAIRINCWaiverofPatentRightsUnderaSubcon.pdf Advance Patent Waiver W(A)2011-063...

  20. Growth, microstructure, and luminescent properties of direct-bandgap InAlP on relaxed InGaAs on GaAs substrates

    E-Print Network [OSTI]

    Beaton, D. A.

    Direct-bandgap InAlP alloy has the potential to be an active material in nitride-free yellow-green and amber optoelectronics with applications in solid-state lighting, display devices, and multi-junction solar cells. We ...

  1. PO Box 2349 White Salmon, WA 98672

    E-Print Network [OSTI]

    PO Box 2349 White Salmon, WA 98672 509.493.4468 www.newbuildings.org COMMERCIAL ROOFTOP HVAC ENERGY from utility-sponsored field service measures on small (typically 3-10 tons) commercial rooftop unitary utility-funded RTU service programs. New Buildings Institute (NBI) staff has been managing the research

  2. WA_04_080_HYBRID_POWER_GENERATION_SYSTEMS_Waiver_of_Patent_R...

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

    80HYBRIDPOWERGENERATIONSYSTEMSWaiverofPatentR.pdf WA04080HYBRIDPOWERGENERATIONSYSTEMSWaiverofPatentR.pdf WA04080HYBRIDPOWERGENERATIONSYSTEMSWaiverofPaten...

  3. WA_00_010_ROCKWELL_SCIENCE_CENTER_A_Subcontractor_of_SILICON...

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

    NTERASubcontractorofSILICON.pdf More Documents & Publications WA03011ROCKWELLAUTOMATIONWaiverofPatentRightsUnder.pdf WA01034INGERSOLL-RANDENERGYSYSTEMSWaiverof...

  4. WA_96_004_GE_CORPORATE_RESEARCH_and_DEVELOPMENT_Waiver_of_Dome...

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

    RATERESEARCHandDEVELOPMENTWaiverofDome.pdf More Documents & Publications WA1993012GENERALELECTRICCOMPANY--CORPORATERESEARCHAND.pdf WA1994013GENERALELECTRICCOMPANY...

  5. WA_03_021_DELPHI_AUTOMOTIVE_SYSTEMS_Waiver_of_Patent_Rights_...

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

    1DELPHIAUTOMOTIVESYSTEMSWaiverofPatentRights.pdf WA03021DELPHIAUTOMOTIVESYSTEMSWaiverofPatentRights.pdf WA03021DELPHIAUTOMOTIVESYSTEMSWaiverofPatentRight...

  6. WA_04_082_DELPHI_AUTOMOTIVE_SYSTEMS_Waiver_of_Patent_Rights_...

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

    82DELPHIAUTOMOTIVESYSTEMSWaiverofPatentRights.pdf WA04082DELPHIAUTOMOTIVESYSTEMSWaiverofPatentRights.pdf WA04082DELPHIAUTOMOTIVESYSTEMSWaiverofPatentRigh...

  7. WA_04_033_CARGILL_Waiver_of_Patent_Rights_to_CARGILL_DOWN_L.pdf...

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

    tentRightstoCARGILLDOWNL.pdf More Documents & Publications WA00022CARGILLDOWPOLYMERSLLCWaiverofDomesticandFo.pdf WA05022DOWCHEMICALCOMPANYWaiverofdomestica...

  8. WA_1993_003_EATON_CORPORATION_Waiver_of_Domestic_and_Foreign...

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    3003EATONCORPORATIONWaiverofDomesticandForeign.pdf WA1993003EATONCORPORATIONWaiverofDomesticandForeign.pdf WA1993003EATONCORPORATIONWaiverofDomesticandFor...

  9. WA_1994_011_EATON_CORPORATION_Waiver_of_Domestic_and_Foreign...

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

    1EATONCORPORATIONWaiverofDomesticandForeign.pdf WA1994011EATONCORPORATIONWaiverofDomesticandForeign.pdf WA1994011EATONCORPORATIONWaiverofDomesticandForeign...

  10. WA_04_083_AIR_PRODUCTS_AND_CHEMICALS_Waiver_of_Patent_Rights...

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    83AIRPRODUCTSANDCHEMICALSWaiverofPatentRights.pdf WA04083AIRPRODUCTSANDCHEMICALSWaiverofPatentRights.pdf WA04083AIRPRODUCTSANDCHEMICALSWaiverofPatentRig...

  11. WA_04_025_AIR_LIQUIDE_AMERICA_Waiver_of_Patent_Rights_under_...

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    25AIRLIQUIDEAMERICAWaiverofPatentRightsunder.pdf WA04025AIRLIQUIDEAMERICAWaiverofPatentRightsunder.pdf WA04025AIRLIQUIDEAMERICAWaiverofPatentRightsund...

  12. WA_02_046_QUESTA_AIR_TECHNOLOGIES_Waiver_of_Domestic_and_For...

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

    6QUESTAAIRTECHNOLOGIESWaiverofDomesticandFor.pdf WA02046QUESTAAIRTECHNOLOGIESWaiverofDomesticandFor.pdf WA02046QUESTAAIRTECHNOLOGIESWaiverofDomesticandF...

  13. WA_99_022_AIR_PRODUCTS_AND_CHEMICAL_Waiver_of_Domestic_and_F...

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    9022AIRPRODUCTSANDCHEMICALWaiverofDomesticandF.pdf WA99022AIRPRODUCTSANDCHEMICALWaiverofDomesticandF.pdf WA99022AIRPRODUCTSANDCHEMICALWaiverofDomestic...

  14. WA_02_015_AIR_PRODUCTS_AND_CHEMICALS_INC_Waiver_of_Patent_Ri...

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

    15AIRPRODUCTSANDCHEMICALSINCWaiverofPatentRi.pdf WA02015AIRPRODUCTSANDCHEMICALSINCWaiverofPatentRi.pdf WA02015AIRPRODUCTSANDCHEMICALSINCWaiverofPatent...

  15. WA_04_063_AIR_PRODUCTS_AND_CHEMICALS_Waiver_of_Patent_Rights...

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

    63AIRPRODUCTSANDCHEMICALSWaiverofPatentRights.pdf WA04063AIRPRODUCTSANDCHEMICALSWaiverofPatentRights.pdf WA04063AIRPRODUCTSANDCHEMICALSWaiverofPatentRig...

  16. WA_01_005__PRAXAIR_INC_Waiver_of_Domestic_and_Foreign_patent...

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

    1005PRAXAIRINCWaiverofDomesticandForeignpatent.pdf WA01005PRAXAIRINCWaiverofDomesticandForeignpatent.pdf WA01005PRAXAIRINCWaiverofDomesticandForeign...

  17. WA_01_022_PRAXAIR_INC_AND_BP_AMOCO_Waiver_of_Domestic_and_Fo...

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

    1022PRAXAIRINCANDBPAMOCOWaiverofDomesticandFo.pdf WA01022PRAXAIRINCANDBPAMOCOWaiverofDomesticandFo.pdf WA01022PRAXAIRINCANDBPAMOCOWaiverofDomestic...

  18. 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.

  19. High magnetic field studies of charged exciton localization in GaAs/Al{sub x}Ga{sub 1?x}As quantum wells

    SciTech Connect (OSTI)

    Jadczak, J.; Bryja, L., E-mail: leszek.bryja@pwr.edu.pl; Ryczko, K.; Kubisa, M.; Wójs, A. [Institute of Physics, Wroc?aw University of Technology, 50-370 Wroclaw (Poland); Potemski, M. [Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, Grenoble (France); Liu, F. [Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund (Germany); Yakovlev, D. R.; Bayer, M. [Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund (Germany); Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Nicoll, C. A.; Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 OHE (United Kingdom)

    2014-09-15T23:59:59.000Z

    We report on low temperature, polarization resolved, high magnetic field (up to 23?T) photoluminescence experiments on high mobility asymmetric GaAs quantum wells. At high magnetic fields, we detect two strong emission lines of the neutral and positively charged excitons (X and X{sup +}) and a series of weaker lines of the excitons bound to ionized acceptors (AX{sup ?}). From polarization energy splittings of these lines, we determine the hole Landé factors (g{sub h}) of different complexes. For X and X{sup +}, g{sub h} initially grows with magnetic field and then saturates at g{sub h}?=?0.88 and 1.55, respectively; for AX{sup ?}'s, g{sub h} begins from a high value (from 6 to 11 at zero field) and decreases with the field growth. This contrasting behavior is traced to the structure of valence band Landau levels, calculated numerically in the Luttinger model, beyond axial approximation. This points to the coexistence (in the same well) of mobile X and X{sup +} with localized and interface-pressed AX{sup ?} states.

  20. First-principles study of compensation mechanisms in negatively charged LaGaO3/MgAl2O4 interfaces

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

    Rébola, Alejandro; Fong, Dillon D.; Eastman, Jeffrey A.; Ö?üt, Serdar; Zapol, Peter

    2013-06-01T23:59:59.000Z

    Thin film oxide heterostructures with a bound charge at the interface require electrical compensation, which can involve redistribution of mobile charge carriers. We explore a model LaGaO3(001)//MgAl2O4(001) heterostructure with nominally negatively charged interfaces using first-principles methods and a Poisson-Boltzmann equation. We find that charge compensation by oxygen vacancies with quadratically decaying concentration away from the interface is more favorable than electronic redistribution. These vacancies have a potential to enhance ionic conductivity along the interfaces.

  1. Direct modulation and active mode locking of ultrahigh-speed GaAlAs lasers at frequencies up to 18 GHz

    SciTech Connect (OSTI)

    Lau, K.Y.; Yariv, A.

    1985-02-15T23:59:59.000Z

    It is demonstrate that an ultrahigh speed window buried heterostucture GaAlAs laser fabricated on a semi-insulating substrate can be used as a narrowband signal transmitter in the Ku band frequency range (12-20 GHz). The modulation efficiency can be increased over a limited bandwidth by a weak optical feedback. A stronger optical feedback enables one to actively mode lock the laser diode at a very high repetition rate up to 17.5 GHz, producing pulses approx. 12 ps long.

  2. Reduction of the spectral linewidth of semiconductor lasers with quantum wire effects: Spectral properties of GaAlAs double heterostructure lasers in high magnetic fields

    SciTech Connect (OSTI)

    Arakawa, Y.; Vahala, K.; Yariv, A.; Lau, K.

    1986-02-10T23:59:59.000Z

    The spectral linewidth of a GaAlAs double heterostructure laser placed in a high magnetic field is measured at 190 K. It is found that the power-dependent spectral linewidth is reduced by a factor of 0.6 in a magnetic field of 19 T. This reduction is believed to result mainly from the reduction of the linewidth enhancement factor ..alpha.. due to a quasi-one-dimensional electronic system formed by the high magnetic field (i.e., by quantum wire effects).

  3. Enhanced modulation bandwidth of GaAlAs double heterostructure lasers in high magnetic fields: Dynamic response with quantum wire effects

    SciTech Connect (OSTI)

    Arakawa, Y.; Vahala, K.; Yariv, A.; Lau, K.

    1985-12-01T23:59:59.000Z

    The modulation bandwidth of GaAlAs double heterostructure (DH) lasers in high magnetic fields is measured. We found that the modulation bandwidth is enhanced by 1.4 x with a magnetic field of 20 T. This improvement is believed to result from the increase of the differential gain due to two-dimensional carrier confinement effects in the high magnetic field (quantum wire effects). A comparison of the experimental results with a theoretical analysis indicates that the intraband relaxation time tau/sub in/ of the measured DH laser in the range of 0.1 to 0.2 ps.

  4. InGaN/GaN light-emitting diode with a polarization tunnel junction Zi-Hui Zhang, Swee Tiam Tan, Zabu Kyaw, Yun Ji, Wei Liu et al.

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    InGaN/GaN light-emitting diode with a polarization tunnel junction Zi-Hui Zhang, Swee Tiam Tan of AIP content is subject to the terms at: http://apl.aip.org/about/rights_and_permissions #12;InGaN/GaN; accepted 29 April 2013; published online 15 May 2013) We report InGaN/GaN light-emitting diodes (LED

  5. Transport in GaAs/Al{sub x}Ga{sub 1-x}As superlattices with narrow forbidden minibands: Low-frequency negative differential conductivity and current oscillations

    SciTech Connect (OSTI)

    Andronov, A. A., E-mail: andron@ipm.sci-nnov.ru; Dodin, E. P.; Zinchenko, D. I.; Nozdrin, Yu. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2009-02-15T23:59:59.000Z

    Current-voltage characteristics have been measured and low-frequency current instabilities have been studied for GaAs/Al{sub x}Ga{sub 1-x}As superlattices with narrow forbidden minibands. At relatively low electric fields, a saw-like structure for current-voltage characteristics with alternating portions of positive and negative differential conductivity and spontaneous generation of low-frequency current oscillations with a complex frequency spectrum (varying from discrete to continuous) are observed. It is shown that the observed specific features of electron transport are caused by the spatial-temporal dynamics of electric-field domains (dipoles and monopoles). The effects of the bifurcation, hysteresis, and multistability of current-voltage characteristics are also observed. At high fields, regular features are observed and identified in the current-voltage characteristics; these features are caused by resonance tunneling of electrons between the levels of the Wannier-Stark ladders belonging to quantum wells separated by several periods.

  6. Thickness Effect of Al-Doped ZnO Window Layer on Damp Heat Stability of CuInGaSe2 Solar Cells: Preprint

    SciTech Connect (OSTI)

    Pern, F. J.; Mansfield, L.; DeHart, C.; Glick, S. H.; Yan, F.; Noufi, R.

    2011-07-01T23:59:59.000Z

    We investigated the damp heat (DH) stability of CuInGaSe2 (CIGS) solar cells as a function of thickness of the Al-doped ZnO (AZO) window layer from the 'standard' 0.12 ?m to a modest 0.50 ?m over an underlying 0.10-?m intrinsic ZnO buffer layer. The CIGS cells were prepared with external electrical contact using fine Au wire to the tiny 'standard' Ni/Al (0.05 ?m/3 ?m) metal grid contact pads. Bare cell coupons and sample sets encapsulated in a specially designed, Al-frame test structure with an opening for moisture ingress control using a TPT backsheet were exposed to DH at 85oC and 85% relative humidity, and characterized by current-voltage (I-V), quantum efficiency (QE), and (electrochemical) impedance spectroscopy (ECIS). The results show that bare cells exhibited rapid degradation within 50-100 h, accompanied by film wrinkling and delamination and corrosion of Mo and AlNi grid, regardless of AZO thickness. In contrast, the encapsulated cells did not show film wrinkling, delamination, and Mo corrosion after 168 h DH exposure; but the trend of efficiency degradation rate showed a weak correlation to the AZO thickness.

  7. Free-standing AlxGa1-xAs heterostructures by gas-phase etching of germanium

    E-Print Network [OSTI]

    As compounds encompassing low aluminum content AlGaAs, InGaAs, InGaP, etc. , typi- cally, a sacrificial Al

  8. Effect of quantum well non-uniformities on lasing threshold, linewidth, and lateral near field filamentation in violet (Al,In)GaN laser diodes

    SciTech Connect (OSTI)

    Jeschke, J.; Zeimer, U.; Redaelli, L.; Einfeldt, S.; Weyers, M. [Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin (Germany); Kneissl, M. [Ferdinand-Braun-Institut, Leibniz-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin (Germany); Institute of Solid State Physics, Technical University of Berlin, 10623 Belin (Germany)

    2014-10-27T23:59:59.000Z

    The lateral near field patterns and filamentation effects of gain guided broad area (Al,In)GaN-based laser diodes emitting around 415?nm have been investigated. Diodes from the same laser bar, which are close to each other, show nearly the same number and widths of filaments. Comparison of different bars, which are from the same wafer but further apart from each other, reveals that a higher number of filaments correlates with a higher laser threshold and broader spectral linewidth. Cathodoluminescence mappings at 80?K show strong variations of the quantum well band gap and hence of the emission wavelength for the bars with strong filamentation. These observations confirm previous theoretical predictions stating that large band gap fluctuations increase the threshold current and spectral linewidth. Furthermore, filamentation is enhanced as well because of a reduction of the carrier diffusion length.

  9. Simulation and characterization of millimeter-wave InAlN/GaN high electron mobility transistors using Lombardi mobility model

    SciTech Connect (OSTI)

    Du, Jiangfeng, E-mail: jfdu@uestc.edu.cn; Yan, Hui; Yin, Chenggong; Yu, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Feng, Zhihong; Dun, Shaobo [Science and Technology of ASIC Lab, Hebei Semiconductor Research Institute, Shijiazhuang 050051 (China)

    2014-04-28T23:59:59.000Z

    A gate length of 0.2??m InAlN/GaN high electron mobility transistor on SiC substrate is obtained with a maximum current gain cutoff frequency (f{sub T}) of 65.8?GHz and a maximum power gain cutoff frequency (f{sub max}) of 143.6?GHz. Lombardi model, which takes interface roughness scattering into consideration, has been introduced to model the transconductance (g{sub m}) degradation. The simulated g{sub m} and f{sub T} with Lombardi model are 69% and 58% lower than the ones without considering interface roughness scattering, respectively. Further analysis show experimental g{sub m}, gate capacitance (C{sub g}), and f{sub T} are consistent with results based on Lombardi model.

  10. ,"Sumas, WA Natural Gas Pipeline Imports From Canada (MMcf)"

    U.S. Energy Information Administration (EIA) Indexed Site

    Imports From Canada (MMcf)" ,"Click worksheet name or tab at bottom for data" ,"Worksheet Name","Description"," Of Series","Frequency","Latest Data for" ,"Data 1","Sumas, WA...

  11. BayWa Group | Open Energy Information

    Open Energy Info (EERE)

    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: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are beingZealand Jump to:EzfeedflagBiomass Conversions IncBay County, Florida: Energy ResourcesBayWa Group Jump to:

  12. Low trap states in in situ SiN{sub x}/AlN/GaN metal-insulator-semiconductor structures grown by metal-organic chemical vapor deposition

    SciTech Connect (OSTI)

    Lu, Xing; Ma, Jun; Jiang, Huaxing; Liu, Chao; Lau, Kei May, E-mail: eekmlau@ust.hk [Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2014-09-08T23:59:59.000Z

    We report the use of SiN{sub x} grown in situ by metal-organic chemical vapor deposition as the gate dielectric for AlN/GaN metal-insulator-semiconductor (MIS) structures. Two kinds of trap states with different time constants were identified and characterized. In particular, the SiN{sub x}/AlN interface exhibits remarkably low trap state densities in the range of 10{sup 11}–10{sup 12?}cm{sup ?2}eV{sup ?1}. Transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the in situ SiN{sub x} layer can provide excellent passivation without causing chemical degradation to the AlN surface. These results imply the great potential of in situ SiN{sub x} as an effective gate dielectric for AlN/GaN MIS devices.

  13. Advance Patent Waiver W(A)2010-028 | Department of Energy

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

    W(A)2010-028 More Documents & Publications Advance Patent Waiver W(A)2009-028 Novel Materials for High Efficiency Direct Methanol Fuel Cells Advance Patent Waiver W(A)2008-019...

  14. Advance Patent Waiver W(A)2012-003 | Department of Energy

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

    Waiver W(A)2012-003 More Documents & Publications Advance Patent Waiver W(A)2013-019 Class Patent Waiver W(C)2012-003 WA02048EATONCORPORATIONWaviverofPatentRightsUnderA...

  15. waTer economics. environmenTand Policy

    E-Print Network [OSTI]

    Botea, Adi

    41 cenTre for waTer economics. environmenTand Policy "Men and nature must work hand in hand and public policy insights for the supply, demand, management, and governance of water CWEEP pronounced `sweep' as in to survey so as to obtain a whole and continuous view of the world #12;42 waTer is a cri

  16. A Resistive-Gate InAlAs/InGaAs/InP2DEG CCD D.V. Rossi, A.-N. Chengl, H.H. Wiederl, and E.R. Fossurn2

    E-Print Network [OSTI]

    Fossum, Eric R.

    GaAs cap layer and recess of the InAlAs layer was performed using the AuGeNi contacts as a mask and H2S04:H thermal annealing at 4OO0C for 15 sec under a forming gas ambient, and the subsequent removal of the In

  17. 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.

  18. WA_03_011_ROCKWELL_AUTOMATION_Waiver_of_Patent_Rights_Under_...

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

    3011ROCKWELLAUTOMATIONWaiverofPatentRightsUnder.pdf WA03011ROCKWELLAUTOMATIONWaiverofPatentRightsUnder.pdf WA03011ROCKWELLAUTOMATIONWaiverofPatentRights...

  19. WA_04_007_OSHKOSH_TRUCK_CORP_Waiver_of_Patent_Rights_Under_N...

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

    WaiverofPatentRightsUnderN.pdf More Documents & Publications WA03011ROCKWELLAUTOMATIONWaiverofPatentRightsUnder.pdf WA04008GENERALMOTORSCORPWaiverofPatentRi...

  20. WA_04_074_EATON_CORPORATION_Waiver_of_Domestic_and_Foreign_I...

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

    74EATONCORPORATIONWaiverofDomesticandForeignI.pdf WA04074EATONCORPORATIONWaiverofDomesticandForeignI.pdf WA04074EATONCORPORATIONWaiverofDomesticandForeig...

  1. WA_02_048_EATON_CORPORATION_Waviver_of_Patent_Rights_Under_A...

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

    48EATONCORPORATIONWaviverofPatentRightsUnderA.pdf WA02048EATONCORPORATIONWaviverofPatentRightsUnderA.pdf WA02048EATONCORPORATIONWaviverofPatentRightsUnde...

  2. WA_1994_017_GOLDEN_TECHNOLOGIES_COMPANY_Waiver_of_Domestic_a...

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

    for An Advance Waiver of Domestic and Foreign Rights. January 10, 1995 WA1994011EATONCORPORATIONWaiverofDomesticandForeign.pdf WA1994014GOLDENTECHNOLOGIESCOMPA...

  3. WA_04_059_EATON_CORPORATION_Waiver_of_Patent_Rights_Under_a_...

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

    59EATONCORPORATIONWaiverofPatentRightsUndera.pdf WA04059EATONCORPORATIONWaiverofPatentRightsUndera.pdf WA04059EATONCORPORATIONWaiverofPatentRightsUnder...

  4. WA_99_012_AIR_PRODUCTS_Waiver_of_Patent_Rights_Under_AN_NVO_...

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

    2AIRPRODUCTSWaiverofPatentRightsUnderANNVO.pdf WA99012AIRPRODUCTSWaiverofPatentRightsUnderANNVO.pdf WA99012AIRPRODUCTSWaiverofPatentRightsUnderANNV...

  5. WA_00_001_PRAXAIR_INC_Waiver_of_Domestic_and_Foreign_Inventi...

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

    01PRAXAIRINCWaiverofDomesticandForeignInventi.pdf WA00001PRAXAIRINCWaiverofDomesticandForeignInventi.pdf WA00001PRAXAIRINCWaiverofDomesticandForeignInve...

  6. WA_04_079_PRAXAIR_INC_Waiver_of_Patent_Rights_Under_a_Subcon...

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

    04079PRAXAIRINCWaiverofPatentRightsUnderaSubcon.pdf WA04079PRAXAIRINCWaiverofPatentRightsUnderaSubcon.pdf WA04079PRAXAIRINCWaiverofPatentRightsUndera...

  7. WA_02_055_PRAXAIR_Waiver_of_Domestic_and_Foreign_Patent_Righ...

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

    2055PRAXAIRWaiverofDomesticandForeignPatentRigh.pdf WA02055PRAXAIRWaiverofDomesticandForeignPatentRigh.pdf WA02055PRAXAIRWaiverofDomesticandForeignPaten...

  8. WA_03_024_PRAXAIR_Waiver_of_Domestic_and_Foreign_Invention_R...

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

    24PRAXAIRWaiverofDomesticandForeignInventionR.pdf WA03024PRAXAIRWaiverofDomesticandForeignInventionR.pdf WA03024PRAXAIRWaiverofDomesticandForeignInventio...

  9. WA_00_018_PRAXAIR_Waive_of_Domestic_and_Foreign_Invention_Ri...

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

    18PRAXAIRWaiveofDomesticandForeignInventionRi.pdf WA00018PRAXAIRWaiveofDomesticandForeignInventionRi.pdf WA00018PRAXAIRWaiveofDomesticandForeignInvention...

  10. WA_01_039_PRAXAIR_INC_Waiver_of_Domestic_and_Foreign_Patent_...

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

    1039PRAXAIRINCWaiverofDomesticandForeignPatent.pdf WA01039PRAXAIRINCWaiverofDomesticandForeignPatent.pdf WA01039PRAXAIRINCWaiverofDomesticandForeignP...

  11. High performance 70 nm In0.8GaP/In0.4AlAs/In0.35GaAs Metamorphic HEMT With Pd Schottky Contacts

    E-Print Network [OSTI]

    Seo, Kwang Seok

    contacts, due to low diffusivity with InGaP of Pd as well as its high SBH [9], the distance between Schottky contact due to its low diffusion of Pd to InGaP. The fabricated 70 nm MHEMT's with Pd Schottky

  12. Materials Science and Engineering B59 (1999) 319322 Microcalorimetric absorption spectroscopy in GaNAlGaN

    E-Print Network [OSTI]

    Nabben, Reinhard

    1999-01-01T23:59:59.000Z

    Microcalorimetric measurements of small absorption coefficients have been performed on thin GaN­AlGaN quantum wells in GaN­AlGaN quantum wells Axel Go¨ldner a, *, Axel Hoffmann a , Bernard Gil b , Pierre Lefebvre b at the energy of the GaN buffer and at the energy of the thick AlGaN barrier layers, we could also readily

  13. Comparison of the properties of AlGaInN light-emitting diode chips of vertical and flip-chip design using silicon as the a submount

    SciTech Connect (OSTI)

    Markov, L. K., E-mail: l.markov@mail.ioffe.ru; Smirnova, I. P.; Pavlyuchenko, A. S. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Kukushkin, M. V.; Vasil'eva, E. D. [ZAO Innovation 'Tetis' (Russian Federation); Chernyakov, A. E. [Russian Academy of Sciences, Science-and-Technology Microelectronics Center (Russian Federation); Usikov, A. S. [De Core Nanosemiconductors Ltd. (India)

    2013-03-15T23:59:59.000Z

    Vertical and flip-chip light-emitting diode (LED) chips are compared from the viewpoint of the behavior of current spreading in the active region and the distribution of local temperatures and thermal resistances of chips. AlGaInN LED chips of vertical design are fabricated using Si as a submount and LED flipchips were fabricated with the removal of a sapphire substrate. The latter are also mounted on a Si submount. The active regions of both chips are identical and are about 1 mm{sup 2} in size. It is shown that both the emittance of the crystal surface in the visible range and the distribution of local temperatures estimated from radiation in the infrared region are more uniform in crystals of vertical design. Heat removal from flip-chips is insufficient in regions of the n contact, which do not possess good thermal contact with the submount. As a result, the total thermal resistances between the p-n junction and the submount both for the vertical chips and for flip-chips are approximately 1 K/W. The total area of the flip-chips exceeds that of the vertical design chips by a factor of 1.4.

  14. Distribution of cations in wurtzitic InxGa1-xN and InxAl1-xN alloys: Consequences for energetics and quasiparticle electronic structures

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

    de Carvalho, Luiz Cláudio; Schleife, André; Furthmüller, Jürgen; Bechstedt, Friedhelm

    2012-03-01T23:59:59.000Z

    The ternary, isostructural, wurtzite-derived group-III mononitride alloys InxGa1-xN andInxAl1-xN are reexamined within a cluster expansion approach. Using density functional theory together with the AM05 exchange-correlation functional, the total energies and the optimized atomic geometries of all 22 clusters classes of the cluster expansion for each material system are calculated. The computationally demanding calculation of the corresponding quasiparticle electronic structures is achieved for all cluster classes by means of a recently developed scheme to approximately solve the quasiparticle equation based on the HSE06 hybrid functional and the G?W? approach. Using two different alloy statistics, the configurational averages for the lattice parameters,more »the mixing enthalpies, and the bulk moduli are calculated. The composition-dependent electronic structures of the alloys are discussed based on configurationally averaged electronic states, band gaps, and densities of states. Ordered cluster arrangements are found to be energetically rather unfavorable, however, they possess the smallest energy gaps and, hence, contribute to light emission. The influence of the alloy statistics on the composition dependencies and the corresponding bowing parameters of the band gaps is found to be significant and should, hence, lead to different signatures in the optical-absorption or -emission spectra.« less

  15. Distribution of cations in wurtzitic InxGa1-xN and InxAl1-xN alloys: Consequences for energetics and quasiparticle electronic structures

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

    de Carvalho, Luiz Cláudio; Schleife, André; Furthmüller, Jürgen; Bechstedt, Friedhelm

    2012-03-01T23:59:59.000Z

    The ternary, isostructural, wurtzite-derived group-III mononitride alloys InxGa1-xN andInxAl1-xN are reexamined within a cluster expansion approach. Using density functional theory together with the AM05 exchange-correlation functional, the total energies and the optimized atomic geometries of all 22 clusters classes of the cluster expansion for each material system are calculated. The computationally demanding calculation of the corresponding quasiparticle electronic structures is achieved for all cluster classes by means of a recently developed scheme to approximately solve the quasiparticle equation based on the HSE06 hybrid functional and the G?W? approach. Using two different alloy statistics, the configurational averages for the lattice parameters, the mixing enthalpies, and the bulk moduli are calculated. The composition-dependent electronic structures of the alloys are discussed based on configurationally averaged electronic states, band gaps, and densities of states. Ordered cluster arrangements are found to be energetically rather unfavorable, however, they possess the smallest energy gaps and, hence, contribute to light emission. The influence of the alloy statistics on the composition dependencies and the corresponding bowing parameters of the band gaps is found to be significant and should, hence, lead to different signatures in the optical-absorption or -emission spectra.

  16. Epitaxial growth of 100-?m thick M-type hexaferrite crystals on wide bandgap semiconductor GaN/Al{sub 2}O{sub 3} substrates

    SciTech Connect (OSTI)

    Hu, Bolin; Su, Zhijuan; Bennett, Steve; Chen, Yajie, E-mail: y.chen@neu.edu; Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits and Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

    2014-05-07T23:59:59.000Z

    Thick barium hexaferrite BaFe{sub 12}O{sub 19} (BaM) films having thicknesses of ?100??m were epitaxially grown on GaN/Al{sub 2}O{sub 3} substrates from a molten-salt solution by vaporizing the solvent. X-ray diffraction measurement verified the growth of BaM (001) textured growth of thick films. Saturation magnetization, 4?M{sub s}, was measured for as-grown films to be 4.6 ± 0.2 kG and ferromagnetic resonance measurements revealed a microwave linewidth of ?100?Oe at X-band. Scanning electron microscopy indicated clear hexagonal crystals distributed on the semiconductor substrate. These results demonstrate feasibility of growing M-type hexaferrite crystal films on wide bandgap semiconductor substrates by using a simple powder melting method. It also presents a potential pathway for the integration of ferrite microwave passive devices with active semiconductor circuit elements creating system-on-a-wafer architectures.

  17. Tunable THz plasmon resonances in InGaAs/InP HEMT R. E. Peale*a

    E-Print Network [OSTI]

    Peale, Robert E.

    , high ns, and small m*. A variety of materials systems such as GaAs/AlGaAs [3], InGaP/InGaAs/GaAs [4

  18. 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

  19. Si and Si/P implants in In{sub 0.5}Ga{sub 0.5}P and In{sub 0.5}Al{sub 0.5}P

    SciTech Connect (OSTI)

    Zolper, J.C.; Chui, H.C. [Sandia National Laboratories, P. O. Box 5800, Albuquerque, New Mexico 87185-0603 (United States)] [Sandia National Laboratories, P. O. Box 5800, Albuquerque, New Mexico 87185-0603 (United States)

    1996-06-01T23:59:59.000Z

    Si and Si/P ion implantation doping of In{sub 0.5}Ga{sub 0.5}P and In{sub 0.5}Al{sub 0.5}P has been studied for several Si and P doses at energies of 90 and 100 keV, respectively. For single Si implants in InGaP a maximum Hall sheet electron concentration of 1.33{times}10{sup 13} cm{sup {minus}2} is achieved for a Si dose of 5{times}10{sup 13} cm{sup {minus}2}. When an optimum dose (2.5{times}10{sup 13} cm{sup {minus}2}) P coimplant is performed this electron concentration is increased by 65{percent}. The same dose Si implants in InAlP show a maximum effective activation of 3.9{percent} with no P coimplantation and 5.2{percent} with a P-implant dose 1.5 times the silicon dose. The apparent donor ionization energies are estimated from variable temperature Hall measurements to be 2{endash}5 meV for InGaP and {approximately}80 meV for InAlP. The deeper level in InAlP is attributed to the DX level found in the Al-containing material. The reduction in sheet resistance associated with the use of Si/P coimplantation in InGaP containing heterostructures should contribute to significant performance enhancements in HFETs and lasers. {copyright} {ital 1996 American Institute of Physics.}

  20. Effect of ball milling and post-annealing on magnetic properties of Ni49.8Mn28.5Ga21.7 alloy powders

    E-Print Network [OSTI]

    Zheng, Yufeng

    , The University of Western Australia, Crawley WA6009, Australia c Department of Advanced Materials mechanical energy absorption [8,9]. Ni­Mn­Ga powders have been prepared by various methods, including spark

  1. Computer Science & Engineering Box 352350 Seattle, WA 98195-2350

    E-Print Network [OSTI]

    Borenstein, Elhanan

    Seattle, WA Permit #62Jeff Heer will join us from Stanford University, where he is a faculty member, a Presidential Early Career Award for Scientists and Engineers, the IJCAI Computers and Thought Award

  2. First principles study of the structural, elastic, electronic and phonon properties of CdX{sub 2}O{sub 4} (X=Al, Ga, In) spinel-type oxides

    SciTech Connect (OSTI)

    Candan, Abdullah [Central Research and Practice Laboratory (AH?LAB), Ahi Evran University, 40100 K?r?ehir (Turkey); U?ur, Gökay [Department of Physics, Faculty of Science, Gazi University, 06500 Ankara (Turkey)

    2014-10-06T23:59:59.000Z

    We have performed ab-initio calculations of the structural, electronic, elastic and dynamical properties for the spinel compounds CdX{sub 2}O{sub 4} (X=Al, Ga, In) using the plane wave pseudo-potential method within the generalized gradient approximation (GGA). The calculated lattice parameters, elastic constants for these compounds are in good agreement with the previous calculated values. The computed direct band gaps of CdAl{sub 2}O{sub 4}, CdGa{sub 2}O{sub 4} and CdIn{sub 2}O{sub 4} are 2.90 eV, 1.92 eV and 1.16 eV, respectively. The lattice vibrations were calculated by direct method. The calculated phonon dispersion curves show that all compounds are dynamically stable in the spinel structure.

  3. 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

  4. GaSb molecular beam epitaxial growth on p-InP(001) and passivation with in situ deposited Al{sub 2}O{sub 3} gate oxide

    SciTech Connect (OSTI)

    Merckling, C.; Brammertz, G.; Hoffmann, T. Y.; Caymax, M.; Dekoster, J. [Interuniversity Microelectronics Center (IMEC vzw), Kapeldreef 75, 3001, Leuven (Belgium); Sun, X. [Katholieke Universiteit Leuven, Celestijnelaan 200D, 3001, Leuven (Belgium); Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520-8284 (United States); Alian, A.; Heyns, M. [Interuniversity Microelectronics Center (IMEC vzw), Kapeldreef 75, 3001, Leuven (Belgium); Katholieke Universiteit Leuven, Celestijnelaan 200D, 3001, Leuven (Belgium); Afanas'ev, V. V. [Katholieke Universiteit Leuven, Celestijnelaan 200D, 3001, Leuven (Belgium)

    2011-04-01T23:59:59.000Z

    The integration of high carrier mobility materials into future CMOS generations is presently being studied in order to increase drive current capability and to decrease power consumption in future generation CMOS devices. If III-V materials are the candidates of choice for n-type channel devices, antimonide-based semiconductors present high hole mobility and could be used for p-type channel devices. In this work we first demonstrate the heteroepitaxy of fully relaxed GaSb epilayers on InP(001) substrates. In a second part, the properties of the Al{sub 2}O{sub 3}/GaSb interface have been studied by in situ deposition of an Al{sub 2}O{sub 3} high-{kappa} gate dielectric. The interface is abrupt without any substantial interfacial layer, and is characterized by high conduction and valence band offsets. Finally, MOS capacitors show well-behaved C-V with relatively low D{sub it} along the bandgap, these results point out an efficient electrical passivation of the Al{sub 2}O{sub 3}/GaSb interface.

  5. Electronic structure and bonding in garnet crystals Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12}, Gd{sub 3}Sc{sub 2}Al{sub 3}O{sub 12}, and Gd{sub 3}Ga{sub 3}O{sub 12} compared to Y{sub 3}Al{sub 3}O{sub 12}

    SciTech Connect (OSTI)

    Xu, Yong-Nian [Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States)] [Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); Ching, W. Y. [Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States)] [Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States); Brickeen, B. K. [Allied Signal FM and T, Kansas City, Missouri 64141 (United States)] [Allied Signal FM and T, Kansas City, Missouri 64141 (United States)

    2000-01-15T23:59:59.000Z

    The electronic structure and bonding of Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12} (GSGG), Gd{sub 3}Sc{sub 2}Al{sub 3}O{sub 12} (GSAG), and Gd{sub 3}Ga{sub 5}O{sub 12} (GGG) crystals with a garnet structure are studied by means of first-principles local-density calculations. The results are compared with a similar calculation on yttrium aluminum garnet [Y{sub 3}Al{sub 5}O{sub 12} (YAG)]. The calculated equilibrium volumes of the three crystals are close to the measured volumes with a slight overestimation for GGG. GGG also has a smaller bulk modulus than the other three crystals. The calculated density of states and their atomic and orbital decompositions are presented and contrasted. All four crystals show very similar band structures and interatomic bonding. However, it is found that in GSGG and GSAG crystals, the Sc atom at the octahedral site shows a higher covalent character and an increased bond order in comparison to Ga or Al at the same site. This result may provide some insight into the significant difference in the radiation hardness of Cr{sup 3+}:Nd{sup 3+}:GSGG as compared to Nd{sup 3+}:YAG. (c) 2000 The American Physical Society.

  6. PHYSICAL REVIEW B 85, 045319 (2012) Photoluminescence from In0.5Ga0.5As/GaP quantum dots coupled to photonic crystal cavities

    E-Print Network [OSTI]

    Vuckovic, Jelena

    2012-01-01T23:59:59.000Z

    in materials systems, including InP/InGaP,6­9 InP/GaP,10,11 InP/AlGaInP,12,13 GaInP/GaP,14 InAs/GaP,15 and Al have been observed only in the InP/InGaP and InP/AlGaInP systems. GaP-based materials, by contrastP compared to InGaP is preferable for on-chip frequency downconversion to telecom wavelengths. Recently,17

  7. Elastomeric Nanoparticle Composites Covalently Bound to Al2O3/GaAs Hyon Min Song, Peide D. Ye,, and Albena Ivanisevic*,,|

    E-Print Network [OSTI]

    Ye, Peide "Peter"

    . The mechanical properties of the surface-bound nanocomposites were tested using nanoindentation experiments include block copolymer-functionalized silicate,17 GaAs-PMMA (poly- (methyl methacrylate)) hybrids,18

  8. The crystal and magnetic structures of LaCa{sub 2}Fe{sub 3-x}M{sub x}O{sub 8} (M=Al, Ga, In)

    SciTech Connect (OSTI)

    Goossens, D.J., E-mail: goossens@rsc.anu.edu.au [Research School of Chemistry, Australian National University, Canberra 0200 (Australia); Henderson, L.S.F.; Trevena, S. [School of Engineering, Australian National University, Canberra 0200 (Australia)] [School of Engineering, Australian National University, Canberra 0200 (Australia); Hudspeth, J.M. [Research School of Physics and Engineering, Australian National University, Canberra 0200 (Australia)] [Research School of Physics and Engineering, Australian National University, Canberra 0200 (Australia); Avdeev, M.; Hester, J.R. [The Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia)] [The Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia)

    2012-12-15T23:59:59.000Z

    LaCa{sub 2}Fe{sub 3}O{sub 8} (A{sub 3}B{sub 3}O{sub 8}) is an example of a layered structure in that it consists of pairs of octahedral, perovskite-like layers alternating with a single tetrahedral layer. This work explores the doping of non-magnetic group 13 elements, M=Al, Ga and In, onto the B-site of LaCa{sub 2}Fe{sub 3-x}M{sub x}O{sub 8} as a function of x. The structural and magnetic effects are examined using a combination of neutron and X-ray diffraction. Solubility limits are established. It is found that for M=Ga the solubility limit occurs between x=1.0 and x=1.25, for the synthesis conditions used, while there is evidence for low (x<0.25) but non-zero substitution of Al. Structural refinements at x=1 suggest that Ga prefers neither the tetrahedral nor octahedral sites. The magnetic structure of LaCa{sub 2}Fe{sub 2}GaO{sub 8} has been examined using neutron diffraction at 3.2 K and room temperature. At low temperature the staggered moment per Fe{sup 3+} is 3.8(1){mu}{sub B} in LaCa{sub 2}Fe{sub 3}O{sub 8} and 4.8(1){mu}{sub B} in LaCa{sub 2}Fe{sub 2}GaO{sub 8}. The magnetic space group (P{sub 2b}2{sub 1} Prime ma Prime ) and moment direction (along c) does not appear to change with Ga substitution. - Graphical abstract: Solubility limits for group 13 elements in LaCa{sub 2}Fe{sub 3}O{sub 8}. Highlights: Black-Right-Pointing-Pointer Solubility limits for group 13 elements in LaCa{sub 2}Fe{sub 3}O{sub 8} are determined. Black-Right-Pointing-Pointer Evolution of the magnetic structure with temperature and doping is explored using neutron scattering. Black-Right-Pointing-Pointer The magnetic space group is quoted as P{sub 2b}2{sub 1}'ma' and the staggered moments are obtained for LaCa{sub 2}Fe{sub 3}O{sub 8} and LaCa{sub 2}Fe{sub 2}GaO{sub 8}.

  9. Excitonic properties of strained wurtzite and zinc-blende GaNAlxGa1xN quantum dots

    E-Print Network [OSTI]

    Fonoberov, Vladimir

    Excitonic properties of strained wurtzite and zinc-blende GaNÕAlxGa1ÀxN quantum dots Vladimir A 2003 We investigate exciton states theoretically in strained GaN/AlN quantum dots with wurtzite WZ of GaN QDs.1­8 Molecu- lar beam epitaxial growth in the Stranski­Krastanov mode of wurtzite WZ Ga

  10. Structural and band alignment properties of Al{sub 2}O{sub 3} on epitaxial Ge grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Patra, P. K. [Department of Biomedical Engineering and Department of Mechanical Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States); Ma, A. W. K. [Department of Chemical and Biomolecular Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Aphale, A.; Macwan, I. [Department of Electrical and Computer Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States)

    2013-04-07T23:59:59.000Z

    Structural and band alignment properties of atomic layer Al{sub 2}O{sub 3} oxide film deposited on crystallographically oriented epitaxial Ge grown in-situ on (100), (110), and (111)A GaAs substrates using two separate molecular beam epitaxy chambers were investigated using cross-sectional transmission microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). High-resolution triple axis x-ray measurement demonstrated pseudomorphic and high-quality Ge epitaxial layer on crystallographically oriented GaAs substrates. The cross-sectional TEM exhibited a sharp interface between the Ge epilayer and each orientation of the GaAs substrate as well as the Al{sub 2}O{sub 3} film and the Ge epilayer. The extracted valence band offset, {Delta}E{sub v}, values of Al{sub 2}O{sub 3} relative to (100), (110), and (111) Ge orientations using XPS measurement were 3.17 eV, 3.34 eV, and 3.10 eV, respectively. Using XPS data, variations in {Delta}E{sub v} related to the crystallographic orientation were {Delta}E{sub V}(110)Ge>{Delta}E{sub V}(100)Ge{>=}{Delta}E{sub V}(111)Ge and the conduction band offset, {Delta}E{sub c}, related to the crystallographic orientation was {Delta}E{sub c}(111)Ge>{Delta}E{sub c}(110)Ge>{Delta}E{sub c}(100)Ge using the measured {Delta}E{sub v}, bandgap of Al{sub 2}O{sub 3} in each orientation, and well-known Ge bandgap of 0.67 eV. These band offset parameters are important for future application of Ge-based p- and n-channel metal-oxide field-effect transistor design.

  11. Sub-250?nm low-threshold deep-ultraviolet AlGaN-based heterostructure laser employing HfO{sub 2}/SiO{sub 2} dielectric mirrors

    SciTech Connect (OSTI)

    Kao, Tsung-Ting; Liu, Yuh-Shiuan; Mahbub Satter, Md.; Li, Xiao-Hang; Lochner, Zachary; Douglas Yoder, P.; Detchprohm, Theeradetch; Dupuis, Russell D.; Shen, Shyh-Chiang, E-mail: shyh.shen@ece.gatech.edu; Ryou, Jae-Hyun [School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Dr. NW, Atlanta, Georgia 30332-0250 (United States)] [School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Dr. NW, Atlanta, Georgia 30332-0250 (United States); Fischer, Alec M.; Wei, Yong; Xie, Hongen; Ponce, Fernando A. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)] [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2013-11-18T23:59:59.000Z

    We report a sub-250-nm, optically pumped, deep-ultraviolet laser using an Al{sub x}Ga{sub 1?x}N-based multi-quantum-well structure grown on a bulk Al-polar c-plane AlN substrate. TE-polarization-dominant lasing action was observed at room temperature with a threshold pumping power density of 250?kW/cm{sup 2}. After employing high-reflectivity SiO{sub 2}/HfO{sub 2} dielectric mirrors on both facets, the threshold pumping power density was further reduced to 180?kW/cm{sup 2}. The internal loss and threshold modal gain can be calculated as 2?cm{sup ?1} and 10.9?cm{sup ?1}, respectively.

  12. RAPID/Roadmap/6-WA-b | Open Energy Information

    Open Energy Info (EERE)

    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: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov YouKizildere I GeothermalPotentialBiopowerSolidGenerationMethodInformatione < RAPID‎ |gWA-eID-baa <baWA-b <

  13. RAPID/Roadmap/6-WA-d | Open Energy Information

    Open Energy Info (EERE)

    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: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov YouKizildere I GeothermalPotentialBiopowerSolidGenerationMethodInformatione < RAPID‎ |gWA-eID-baa <baWA-b <d

  14. In0.6Ga0.4AsGaAs quantum-dot infrared photodetector with operating temperature up to 260 K

    E-Print Network [OSTI]

    Florida, University of

    the large band gap material such as AlGaAs or InGaP as blocking barrier to reduce the device dark current 100 K by us- ing a large band gap material such as AlGaAs or InGaP as the blocking barrier to reduce temperature up to 260 K without using the wide band gap AlGaAs or InGaP current blocking bar- rier. The sample

  15. WA_00_013_GENECOR_INTERNATIONAL_Waiver_of_US_Competitiveness...

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

    WaiverofUSCompetitiveness.pdf More Documents & Publications U.S. Biofuels Industry: Mind the Gap Advance Patent Waiver W(A)2008-045 WA01008NOVOZYMEBIOTECHWaiverofDomesti...

  16. Advance Patent Waiver W(A)2009-039 | Department of Energy

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

    Advance Patent Waiver W(A)2010-007 Advance Patent Waiver W(A)2012-034 Stabilized Lithium Metal Powder, Enabling Material and Revolutionary Technology for High Energy Li-ion...

  17. 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

  18. Self-cleaning and surface recovery with arsine pretreatment in ex situ atomic-layer-deposition of Al2O3 on GaAs

    E-Print Network [OSTI]

    /Thomas Swan close-coupled showerhead cold-wall MOCVD system. The buffer epilayers of GaAs were grown on 2 in for these interfaces. In addition, when designing an in situ MOCVD process, the typical TMA/H2O is incompatible

  19. EIS-0397: Lyle Falls Fish Passage Project, WA

    Broader source: Energy.gov [DOE]

    This EIS analyzes BPA's decision to modify funding to the existing Lyle Falls Fishway on the lower Klickitat River in Klickitat County, WA. The proposed project would help BPA meet its off-site mitigation responsibilities for anadromous fish affected by the development of the Federal Columbia River Power System and increase overall fish production in the Columbia Basin.

  20. NAME: Eelgrass Restoration in Puget Sound LOCATION: Puget Sound, WA

    E-Print Network [OSTI]

    US Army Corps of Engineers

    NAME: Eelgrass Restoration in Puget Sound LOCATION: Puget Sound, WA ACRES: 3,700 acres of subtidal restoration efforts and to contribute to the Puget Sound Partnership's Action Agenda recovery goal of 20% more within the Puget Sound region of the Salish Sea: the Nisqually, Elwha, and Skokomish Rivers. These major

  1. carleton universityottaWa, canaDa international

    E-Print Network [OSTI]

    Dawson, Jeff W.

    carleton universityottaWa, canaDa international aDmissions 2014 #12;Carleton University provides high-quality education to students from Canada and around the world. We offer a wide range of programs and be a part of this extraordinary university! Wonderful country The United Nations consistently ranks Canada

  2. UID-GaN doping1016 cm-3 2 m 5 m2 m

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    2 µm Drain Silicon UID-GaN ­ doping1016 cm-3 1.1 µm 2 µm GateSource 2 µm 5 µm2 µm AirAir Al0.25GaN ­ doping1015 cm-3 30 nm Drain Silicon UID-GaN P-GaNSource AirAir AlxGaN Drain Silicon UID-GaN GateSource AirAir AlxGaN Gate (a) (b) (c) Drain Silicon UID-GaN P-GaNSource AirAir AlxGaN Gate (d) P-GaN P-GaN 30

  3. Near ultraviolet emission from nonpolar cubic AlxGa1-xN/GaN quantum wells

    E-Print Network [OSTI]

    As, Donat Josef

    molecular beam epitaxy on free standing 3C-SiC 001 substrates. During growth of Al0.15Ga0.85N/GaN quantum growth of the quantum structures an 800 nm thick GaN buffer layer was deposited on the 3C-SiC substrate. The buffer and the c-AlGaN/GaN quantum wells were grown at a substrate temperature of 720 °C. The layers were

  4. Compositional dependence of the luminescence of In{sub 0.49}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.51}P alloys near the direct{endash}indirect band-gap crossover

    SciTech Connect (OSTI)

    Nelson, J.S.; Jones, E.D. [Semiconductor Materials and Device Sciences Department, 1113, MS-0601, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Semiconductor Materials and Device Sciences Department, 1113, MS-0601, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Myers, S.M.; Follstaedt, D.M. [Semiconductor Nanostructure Physics Department, 1112, MS-1414, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Semiconductor Nanostructure Physics Department, 1112, MS-1414, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Hjalmarson, H.P. [Compound Semiconductor Technology Department, 1322, MS-0603, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Compound Semiconductor Technology Department, 1322, MS-0603, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Schirber, J.E. [Solid State Sciences Department, 1100, MS-1437, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Solid State Sciences Department, 1100, MS-1437, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Schneider, R.P. [Semiconductor Materials Department, 1311, MS-0603, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Semiconductor Materials Department, 1311, MS-0603, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Fouquet, J.E.; Robbins, V.M.; Carey, K.W. [Hewlett Packard Laboratories, 3500 Deer Creek Road, Palo Alto, California 94303 (United States)] [Hewlett Packard Laboratories, 3500 Deer Creek Road, Palo Alto, California 94303 (United States)

    1996-06-01T23:59:59.000Z

    A number of complementary experimental characterization tools and theoretical band structure methods were used to determine unambiguously the band-edge luminescence as a function of Al concentration, and to place an upper limit on the short-wavelength emission of InAlGaP alloys lattice matched to GaAs. In particular, the direct-to-indirect band-gap crossing has been determined by analyzing a series of metalorganic vapor-phase-epitaxy-grown In{sub 0.49}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.51}P alloys lattice matched to GaAs with double-crystal x-ray analysis, Rutherford backscattering spectroscopy, pressure- and temperature-dependent photoluminescence, and transmission electron microscopy. The experimental measurements are compared to first-principles plane-wave pseudopotential band structure calculations for the ternary end points, InGaP and InAlP. The maximum room temperature direct band gap is found to be 2.24 eV, corresponding to an Al composition of {ital y}=0.52{plus_minus}0.02, in good agreement with the theoretical prediction of 0.58{plus_minus}0.05. {copyright} {ital 1996 The American Physical Society.}

  5. Electrical and structural characteristics of metamorphic In{sub 0.38}Al{sub 0.62}As/In{sub 0.37}Ga{sub 0.63}As/In{sub 0.38}Al{sub 0.62}As HEMT nanoheterostructures

    SciTech Connect (OSTI)

    Galiev, G. B., E-mail: s_s_e_r_p@mail.ru; Klimov, E. A.; Klochkov, A. N.; Maltsev, P. P.; Pushkarev, S. S. [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation)] [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation); Zhigalina, O. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)] [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Imamov, R. M., E-mail: imamov@ns.crys.ras.ru [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation); Kuskova, A. N.; Khmelenin, D. N. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)] [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2013-11-15T23:59:59.000Z

    The influence of the metamorphic buffer design and epitaxial growth conditions on the electrical and structural characteristics of metamorphic In{sub 0.38}Al{sub 0.62}As/In{sub 0.37}Ga{sub 0.63}As/In{sub 0.38}Al{sub 0.62}As high electron mobility transistor (MHEMT) nanoheterostructures has been investigated. The samples were grown on GaAs(100) substrates by molecular beam epitaxy. The active regions of the nanoheterostructures are identical, while the metamorphic buffer In{sub x}Al{sub 1-x}As is formed with a linear or stepwise (by {Delta}{sub x} = 0.05) increase in the indium content over depth. It is found that MHEMT nanoheterostructures with a step metamorphic buffer have fewer defects and possess higher values of two-dimensional electron gas mobility at T = 77 K. The structures of the active region and metamorphic buffer have been thoroughly studied by transmission electron microscopy. It is shown that the relaxation of metamorphic buffer in the heterostructures under consideration is accompanied by the formation of structural defects of the following types: dislocations, microtwins, stacking faults, and wurtzite phase inclusions several nanometers in size.

  6. Green light emission by InGaN/GaN multiple-quantum-well microdisks

    SciTech Connect (OSTI)

    Hsu, Yu-Chi; Lo, Ikai, E-mail: ikailo@mail.phys.nsysu.edu.tw; Shih, Cheng-Hung; Pang, Wen-Yuan; Hu, Chia-Hsuan; Wang, Ying-Chieh; Tsai, Cheng-Da; Chou, Mitch M. C. [Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China)] [Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China); Hsu, Gary Z. L. [United Crystal Corporation, No. 243-3, Wenshan 36061, Miaoli, Taiwan (China)] [United Crystal Corporation, No. 243-3, Wenshan 36061, Miaoli, Taiwan (China)

    2014-03-10T23:59:59.000Z

    The high-quality In{sub x}Ga{sub 1?x}N/GaN multiple quantum wells were grown on GaN microdisks with ?-LiAlO{sub 2} substrate by using low-temperature two-step technique of plasma-assisted molecular beam epitaxy. We demonstrated that the hexagonal GaN microdisk can be used as a strain-free substrate to grow the advanced In{sub x}Ga{sub 1?x}N/GaN quantum wells for the optoelectronic applications. We showed that the green light of 566-nm wavelength (2.192?eV) emitted from the In{sub x}Ga{sub 1?x}N/GaN quantum wells was tremendously enhanced in an order of amplitude higher than the UV light of 367-nm wavelength (3.383?eV) from GaN.

  7. Distributed bragg reflector using AIGaN/GaN

    DOE Patents [OSTI]

    Waldrip, Karen E.; Lee, Stephen R.; Han, Jung

    2004-08-10T23:59:59.000Z

    A supported distributed Bragg reflector or superlattice structure formed from a substrate, a nucleation layer deposited on the substrate, and an interlayer deposited on the nucleation layer, followed by deposition of (Al,Ga,B)N layers or multiple pairs of (Al,Ga,B)N/(Al,Ga,B)N layers, where the interlayer is a material selected from AlN, Al.sub.x Ga.sub.1-x N, and AlBN with a thickness of approximately 20 to 1000 angstroms. The interlayer functions to reduce or eliminate the initial tensile growth stress, thereby reducing cracking in the structure. Multiple interlayers utilized in an AlGaN/GaN DBR structure can eliminate cracking and produce a structure with a reflectivity value greater than 0.99.

  8. Vibrational analysis of the elpasolites Cs{sub 2}NaAlF{sub 6} and Cs{sub 2}NaGaF{sub 6} doped with Cr{sup 3+} ions by fluorescence spectroscopy.

    SciTech Connect (OSTI)

    Bordallo, H. N.; Sosman, L. P.; Tavares, A. D., Jr.; da Fonseca, R. J. M.

    1999-09-07T23:59:59.000Z

    Interest in 3d transition metal impurities in ionic crystals has increased due to their important role in the laser activity of these materials. Moreover, recent advances in tunable solid-state lasers and high-power semiconductor laser diode arrays have generated a strong interest in investigating new compounds that emit in the visible and near-infrared spectral regions. In particular, many optical studies have been devoted to Cr{sup 3+}-doped fluoride crystals as a consequence of the high quality of some Cr{sup 3+}-based laser materials. In the present investigation, the low temperature emission spectra of Cr{sup 3+} ions in the hexagonal elpasolites Cs{sub 2}NaAlF{sub 6} and Cs{sub 2}NaGaF{sub 6} have been measured. Each compound has two crystallographically inequivalent octahedral sites for the Al{sup 3+} and Ga{sup 3+} ions that can be occupied by Cr{sup 3+} ions. For both materials, the luminescence spectrum presents two zero-phonon lines accompanied by a well-defined vibrational structure. The different peaks of the emission broadband are described in terms of phonons of the lattice and normal modes of the octahedral complex [CrF{sub 6}]{sup 3{minus}}. A detailed analysis of the vibrational structure observed leads to the conclusion that the {sup 2}E and {sup 4}T{sub 2} excited states of the [CrF{sub 6}]{sup 3{minus}} ions are displaced along the e{sub g}, a{sub 1g} and probably the t{sub 2g} coordinates.

  9. IEEE MTT-S 2001 International Microwave Symposium Digest, Vol. 3 pp. 1713-1716 185 GHz Monolithic Amplifier in InGaAs/InAlAs

    E-Print Network [OSTI]

    Rodwell, Mark J. W.

    , and automotive radar. Monolithic amplifiers in this frequency range have previously been demonstrated in In in these technologies have exhibited large small signal gains. Weinreb et al [1] have reported a six-stage amplifier]. Larger ICs include 66 GHz master-slave flip flops [9] and 18 GHz delta-sigma ADCs [10]. Here, we report

  10. WA_1993_022_NORTON_COMPANY_Waiver_of_Domestic_and_Foreign_Ri...

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

    Golden Technologies Company, Inc. Request for An Advance Waiver of Domestic and Foreign Rights. January 10, 1995 WA1994011EATONCORPORATIONWaiverofDomesticandForeign...

  11. Climate Action Champions: Seattle, WA | Department of Energy

    Energy Savers [EERE]

    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: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov You are being directed offOCHCO OverviewAttachments4 Chairs Meeting - AprilEvents CleanSeattle, WA Climate Action

  12. RAPID/Roadmap/5-WA-a | Open Energy Information

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    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: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov YouKizildere I GeothermalPotentialBiopowerSolidGenerationMethodInformatione < RAPID‎ |gWA-e < RAPID‎

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    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: Alternative Fuels Data Center Home Page onYou are now leaving Energy.gov You are now leaving Energy.gov YouKizildere I GeothermalPotentialBiopowerSolidGenerationMethodInformatione < RAPID‎ |gWA-eID-b <ai <bb <

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  1. RAPID/Roadmap/4-WA-a | Open Energy Information

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  4. 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

  5. Synthesis and structural characterization of the ternary Zintl phases AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As)

    SciTech Connect (OSTI)

    He, Hua; Tyson, Chauntae; Saito, Maia [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen, E-mail: bobev@udel.edu [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

    2012-04-15T23:59:59.000Z

    Ten new ternary phosphides and arsenides with empirical formulae AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) have been synthesized using molten Ga, Al, and Pb fluxes. They have been structurally characterized by single-crystal and powder X-ray diffraction to form with two different structures-Ca{sub 3}Al{sub 2}P{sub 4}, Sr{sub 3}Al{sub 2}As{sub 4}, Eu{sub 3}Al{sub 2}P{sub 4}, Eu{sub 3}Al{sub 2}As{sub 4}, Ca{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}As{sub 4}, and Eu{sub 3}Ga{sub 2}As{sub 4} crystallize with the Ca{sub 3}Al{sub 2}As{sub 4} structure type (space group C2/c, Z=4); Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt the Na{sub 3}Fe{sub 2}S{sub 4} structure type (space group Pnma, Z=4). The polyanions in both structures are made up of TrPn{sub 4} tetrahedra, which share common corners and edges to form {sup 2}{sub {infinity}}[TrPn{sub 2}]{sub 3-} layers in the phases with the Ca{sub 3}Al{sub 2}As{sub 4} structure, and {sup 1}{sub {infinity}}[TrPn{sub 2}]{sub 3-} chains in Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} with the Na{sub 3}Fe{sub 2}S{sub 4} structure type. The valence electron count for all of these compounds follows the Zintl-Klemm rules. Electronic band structure calculations confirm them to be semiconductors. - Graphical abstract: AE{sub 3}Al{sub 2}Pn{sub 4} and AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) crystallize in two different structures-Ca{sub 3}Al{sub 2}P{sub 4}, Sr{sub 3}Al{sub 2}As{sub 4}, Eu{sub 3}Al{sub 2}P{sub 4}, Eu{sub 3}Al{sub 2}As{sub 4}, Ca{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}P{sub 4}, Sr{sub 3}Ga{sub 2}As{sub 4}, and Eu{sub 3}Ga{sub 2}As{sub 4}, are isotypic with the previously reported Ca{sub 3}Al{sub 2}As{sub 4} (space group C2/c (No. 15)), while Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt a different structure known for Na{sub 3}Fe{sub 2}S{sub 4} (space group Pnma (No. 62). The polyanions in both structures are made up of TrPn{sub 4} tetrahedra, which by sharing common corners and edges, form {sup 2}{sub {infinity}}[TrPn{sub 2}]{sub 3-}layers in the former and {sup 1}{sub {infinity}}[TrPn{sub 2}]{sub 3-} chains in Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4}. Highlights: Black-Right-Pointing-Pointer AE{sub 3}Ga{sub 2}Pn{sub 4} (AE=Ca, Sr, Ba, Eu; Pn=P, As) are new ternary pnictides. Black-Right-Pointing-Pointer Ba{sub 3}Al{sub 2}P{sub 4} and Ba{sub 3}Al{sub 2}As{sub 4} adopt the Na{sub 3}Fe{sub 2}S{sub 4} structure type. Black-Right-Pointing-Pointer The Sr- and Ca-compounds crystallize with the Ca{sub 3}Al{sub 2}As{sub 4} structure type. Black-Right-Pointing-Pointer The valence electron count for all title compounds follows the Zintl-Klemm rules.

  6. 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.

  7. Phase-locking of an InP/InGaP/InGaAs resonant tunneling diode relaxation oscillator by direct optical injection

    E-Print Network [OSTI]

    Eisenstein, Gadi

    Phase-locking of an InP/InGaP/InGaAs resonant tunneling diode relaxation oscillator by direct relaxation oscillator is demonstrated. The diode is an Al-free InP/InGaP/InGaAs structure in the InP/InGaAs/InGaP aluminum-free material system, following the work of Cohen and Ritter [6

  8. Polarized emission lines from A-and B-type excitonic complexes in single InGaN/GaN quantum dots

    E-Print Network [OSTI]

    Nabben, Reinhard

    Polarized emission lines from A- and B-type excitonic complexes in single InGaN/GaN quantum dots M Cathodoluminescence measurements on single InGaN/GaN quantum dots QDs are reported. Complex spectra with up to five spectral region have been realized based on InGaN structures.1 Single-photon emission from GaN/AlN quantum

  9. Over 30{percent} efficient InGaP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Takamoto, T.; Ikeda, E.; Kurita, H. [Central Research Laboratory, Japan Energy Corporation, 3-17-35 Niizo-Minami, Toda, Saitama 335 (Japan)] [Central Research Laboratory, Japan Energy Corporation, 3-17-35 Niizo-Minami, Toda, Saitama 335 (Japan); Ohmori, M. [Japan Energy Research Center Company, Ltd., 1-11-9 Azabudai, Minato-ku, Tokyo 106 (Japan)] [Japan Energy Research Center Company, Ltd., 1-11-9 Azabudai, Minato-ku, Tokyo 106 (Japan)

    1997-01-01T23:59:59.000Z

    A two-terminal monolithic InGaP/GaAs tandem solar cell with a new efficiency record of 30.28{percent} is realized with a practical large area of 4 cm{sup 2} under one-sun air-mass 1.5 global illumination. We report improvements of the tandem cell performance by introducing a double-hetero (hereafter DH) structure InGaP tunnel junction, in which the InGaP layers are surrounded by high band gap AlInP barriers. The DH structure by AlInP barriers increase the peak current of InGaP tunnel junction. The AlInP barrier directly below the InGaP top cell, which takes the part of a back surface field (hereafter BSF) layer, is found to be considerably effective in reflecting minority carriers in the top cell. The AlInP BSF layer does not only form a high potential barrier but also prevents the diffusion of zinc from a high doped tunnel junction toward the top cell during epitaxial growth. Furthermore, an InGaP tunnel junction reduces the absorption loss, which exists in a GaAs tunnel junction, and increases the photogenerated current in the GaAs bottom cell. {copyright} {ital 1997 American Institute of Physics.}

  10. Distribution of cations in wurtzitic InxGa1-xN and InxAl1-xN alloys: Consequences for energetics and quasiparticle electronic structures

    SciTech Connect (OSTI)

    de Carvalho, Luiz Cláudio; Schleife, André; Furthmüller, Jürgen; Bechstedt, Friedhelm

    2012-03-01T23:59:59.000Z

    The ternary, isostructural, wurtzite-derived group-III mononitride alloys InxGa1-xN andInxAl1-xN are reexamined within a cluster expansion approach. Using density functional theory together with the AM05 exchange-correlation functional, the total energies and the optimized atomic geometries of all 22 clusters classes of the cluster expansion for each material system are calculated. The computationally demanding calculation of the corresponding quasiparticle electronic structures is achieved for all cluster classes by means of a recently developed scheme to approximately solve the quasiparticle equation based on the HSE06 hybrid functional and the G?W? approach. Using two different alloy statistics, the configurational averages for the lattice parameters, the mixing enthalpies, and the bulk moduli are calculated. The composition-dependent electronic structures of the alloys are discussed based on configurationally averaged electronic states, band gaps, and densities of states. Ordered cluster arrangements are found to be energetically rather unfavorable, however, they possess the smallest energy gaps and, hence, contribute to light emission. The influence of the alloy statistics on the composition dependencies and the corresponding bowing parameters of the band gaps is found to be significant and should, hence, lead to different signatures in the optical-absorption or -emission spectra.

  11. The structure of GaAs/Si(211) heteroepitaxial layers

    SciTech Connect (OSTI)

    Liliental-Weber, Z.; Weber, E.R.; Washburn, J.; Liu, T.Y.; Kroemer, H.

    1985-05-01T23:59:59.000Z

    Gallium arsenide films grown on (211)Si by molecular-beam epitaxy have been investigated using transmission electron microscopy. The main defects observed in the alloy were of misfit dislocations, stacking faults, and microtwin lamellas. Silicon surface preparation was found to play an important role on the density of defects formed at the Si/GaAs interface. Two different types of strained-layer superlattices, InGaAs/InGaP and InGaAs/GaAs, were applied either directly to the Si substrate, to a graded layer (GaP-InGaP), or to a GaAs buffer layer to stop the defect propagation into the GaAs films. Applying InGaAs/GaAs instead of InGaAs/InGaP was found to be more effective in blocking defect propagation. In all cases of strained-layer superlattices investigated, dislocation propagation was stopped primarily at the top interface between the superlattice package and GaAs. Graded layers and unstrained AlGaAs/GaAs superlattices did not significantly block dislocations propagating from the interface with Si. Growing of a 50 nm GaAs buffer layer at 505/sup 0/C followed by 10 strained-layer superlattices of InGaAs/GaAs (5 nm each) resulted in the lowest dislocation density in the GaAs layer (approx.5 x 10/sup 7//cm/sup 2/) among the structures investigated. This value is comparable to the recently reported density of dislocations in the GaAs layers grown on (100)Si substrates. Applying three sets of the same strained layers decreased the density of dislocations an additional approx.2 to 3 times.

  12. Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current-

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current- spreading experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN

  13. Review of radiation damage in GaN-based materials and devices

    SciTech Connect (OSTI)

    Pearton, Stephen J.; Deist, Richard [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32606 (United States)] [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32606 (United States); Ren, Fan; Liu, Lu [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)] [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States); Polyakov, Alexander Y. [Institute of Rare Metals, Moscow, 119017, B. Tolmachevsky, 5 (Russian Federation)] [Institute of Rare Metals, Moscow, 119017, B. Tolmachevsky, 5 (Russian Federation); Kim, Jihyun [Department of Chemical and Biological Engineering, Korea University, Anam-dong, Sungbuk-gu, Seoul, 136-713 (Korea, Republic of)] [Department of Chemical and Biological Engineering, Korea University, Anam-dong, Sungbuk-gu, Seoul, 136-713 (Korea, Republic of)

    2013-09-15T23:59:59.000Z

    A review of the effects of proton, neutron, ?-ray, and electron irradiation on GaN materials and devices is presented. Neutron irradiation tends to create disordered regions in the GaN, while the damage from the other forms of radiation is more typically point defects. In all cases, the damaged region contains carrier traps that reduce the mobility and conductivity of the GaN and at high enough doses, a significant degradation of device performance. GaN is several orders of magnitude more resistant to radiation damage than GaAs of similar doping concentrations. In terms of heterostructures, preliminary data suggests that the radiation hardness decreases in the order AlN/GaN > AlGaN/GaN > InAlN/GaN, consistent with the average bond strengths in the Al-based materials.

  14. DOE Zero Energy Ready Home Case Study: TC Legend Homes, Bellingham, WA

    Broader source: Energy.gov [DOE]

    Case study of a DOE Zero Energy Ready home in Bellingham, WA, that achieves HERS 43 without PV or HERS 13 with 3.2 kW of PV.

  15. Advance Patent Waiver W(A)2010-007 | Department of Energy

    Office of Environmental Management (EM)

    0-007 Advance Patent Waiver W(A)2010-007 This document waives certain patent rights the Department of Energy (DOE) has to inventions conceived or first actually reduced to practice...

  16. Thermoelectric figure of merit of (In0.53Ga0.47As)0.8(In0.52Al0.48As)0.2 III-V semiconductor alloys Je-Hyeong Bahk,1 Zhixi Bian,2 Mona Zebarjadi,2 Joshua M. O. Zide,3 Hong Lu,1,4 Dongyan Xu,5 Joseph P. Feser,5

    E-Print Network [OSTI]

    Thermoelectric figure of merit of (In0.53Ga0.47As)0.8(In0.52Al0.48As)0.2 III-V semiconductor alloys manuscript received 15 April 2010; published 10 June 2010 The thermoelectric figure of merit is measured, 73.50.Lw, 73.61.Ey I. INTRODUCTION Seeking a better thermoelectric material for efficient thermal

  17. Vertical design of cubic GaN-based high electron mobility transistors R. Granzner,1,a)

    E-Print Network [OSTI]

    As, Donat Josef

    Vertical design of cubic GaN-based high electron mobility transistors R. Granzner,1,a) E. Tschumak 2011; accepted 24 October 2011; published online 1 December 2011) Cubic (zinc blende) AlGaN=GaN heterostructures for application in GaN-based high electron mobility transistors are investigated theoretically

  18. 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

  19. GA-AL-SC | Department of Energy

    Office of Environmental Management (EM)

    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 3,625 1,006 492 742 33 1112011 Strategic2 OPAM Flash2011-12 OPAM RevisedFunding Opportunities1 - TheD, Title

  20. VARIABLE-ANGLE SPECTROSCOPIC ELLIPSOMETRY OF InAlP NATIVE OXIDE GATE DIELECTRIC LAYERS

    E-Print Network [OSTI]

    AlP-ox, In0.49Ga0.51P (InGaP), and InAlP have been determined by VASE measurements using a photon energy of the Optical Constants of InAlP-ox, InAlP, InGaP.......... 12 3.1 OverviewAlP and InGaP Optical Constants....................................... 26 Chapter 4: Characterizing

  1. Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices

    SciTech Connect (OSTI)

    Wang, C.A.; Choi, H.K.; Turner, G.W.; Spears, D.L.; Manfra, M.J. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

    1997-05-01T23:59:59.000Z

    The materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for lattice-matched thermophotovoltaic (TPV) devices is reported. Epilayers with cutoff wavelength 2--2.4 {micro}m at room temperature and lattice-matched to GaSb substrates were grown by both low-pressure organometallic vapor phase epitaxy and molecular beam epitaxy. These layers exhibit high optical and structural quality. For demonstrating lattice-matched thermophotovoltaic devices, p- and n-type doping studies were performed. Several TPV device structures were investigated, with variations in the base/emitter thicknesses and the incorporation of a high bandgap GaSb or AlGaAsSb window layer. Significant improvement in the external quantum efficiency is observed for devices with an AlGaAsSb window layer compared to those without one.

  2. InGaN/GaN single-quantum-well microdisks

    SciTech Connect (OSTI)

    Hsu, Yu-Chi; Lo, Ikai; Shih, Cheng-Hung; Pang, Wen-Yuan; Hu, Chia-Hsuan; Wang, Ying-Chieh; Chou, Mitch M. C. [Department of Physics, Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan (China)

    2012-06-11T23:59:59.000Z

    We have grown In{sub x}Ga{sub 1-x}N/GaN quantum wells atop GaN microdisk with {gamma}-LiAlO{sub 2} substrate by using plasma-assisted molecular beam epitaxy. The structural and optical properties of the samples were analyzed by transmission electron microscopy, x-ray diffraction, cathodoluminescence, and photoluminescence measurements. Based on the measured results, we obtained the indium concentration of the In{sub x}Ga{sub 1-x}N/GaN single quantum well to be x = 0.25 with a band-gap energy of 2.31 eV, which is consistent with the bowing effect of bulk In{sub x}Ga{sub 1-x}N: E{sub g}(x) = [3.42 - x * 2.65 - x * (1 - x) * 2.4] eV.

  3. Advance Patent Waiver W(A)2005-032

    Broader source: Energy.gov [DOE]

    This is a request by HONEYWELL INTERNATIONAL, INC for a DOE waiver of domestic and foreign patent rights under agreement DE-FC36-02AL67624.

  4. Corrosion-induced degradation of GaAs PHEMTs under operation in high humidity conditions

    E-Print Network [OSTI]

    Hisaka, Takayuki

    We have comprehensively investigated the degradation mechanism of AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors (PHEMTs) under operation in high humidity conditions. PHEMTs degradation under high humidity ...

  5. 16-12-12Web Archiv e (naf wa.org)-Hosted By Hurricane Electric -Resurrection Of Ex... 1/3naf wa.org/.../11052-resurrection-of -extinct-enzy mes-rev eals-ev olutionary -strategy -f or-the-inv enti...

    E-Print Network [OSTI]

    16-12-12Web Archiv e (naf wa.org)-Hosted By Hurricane Electric - Resurrection Of Ex... 1/3naf wa Archiv e (naf wa.org)-Hosted By Hurricane Electric - Resurrection Of Ex... naf wa.org/.../11052

  6. 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

  7. Characteristics of Novel InGaAsN Double Heterojunction Bipolar Transistors

    SciTech Connect (OSTI)

    LI,N.Y.; CHANG,PING-CHIH; BACA,ALBERT G.; LAROCHE,J.R.; REN,F.; ARMOUR,E.; SHARPS,P.R.; HOU,H.Q.

    2000-08-01T23:59:59.000Z

    The authors demonstrate, for the first time, both functional Pnp AlGaAs/InGaAsN/GaAs (Pnp InGaAsN) and Npn InGaP/InGaAsN/GaAs (Npn InGaAsN) double heterojunction bipolar transistors (DHBTs) using a 1.2 eV In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} as the base layer for low-power electronic applications. The Pnp InGaAsN DHBT has a peak current gain ({beta}) of 25 and a low turn-on voltage (V{sub ON}) of 0.79 V. This low V{sub ON} is {approximately} 0.25 V lower than in a comparable Pnp AlGAAs/GaAs HBT. For the Npn InGaAsN DHBT, it has a low V{sub ON} of 0.81 V, which is 0.13 V lower than in an InGaP/GaAs HBT. A peak {beta} of 7 with nearly ideal I-V characteristics has been demonstrated. Since GaAs is used as the collector of both Npn and Pnp InGaAsN DHBTs, the emitter-collector breakdown voltage (BV{sub CEO}) are 10 and 12 V, respectively, consistent with the BV{sub CEO} of Npn InGaP/GaAs and Pnp AlGaAs/GaAs HBTs of comparable collector thickness and doping level. All these results demonstrate the potential of InGaAsN DHBTs as an alternative for application in low-power electronics.

  8. ONION (Allium cepa, 47 cultivars) B.K. Schroeder, Washington State University (WSU), Pullman, Enterobacter bulb decay; Enterobacter cloacae WA 99164; T.D. Waters, WSU Franklin Co. Extension, Pasco WA

    E-Print Network [OSTI]

    Schroeder, Brenda K.

    , Enterobacter bulb decay; Enterobacter cloacae WA 99164; T.D. Waters, WSU Franklin Co. Extension, Pasco WA 99301 in storage in Washington State, 2008-2009. An onion bulb storage trial was completed to survey 47 storage to Enterobacter cloacae, causal agent of Enterobacter bulb decay. Seeds of each cultivar were planted near Pasco

  9. ONION (Allium cepa, 55 cultivars) B.K. Schroeder, Washington State University (WSU), Pullman, Enterobacter bulb decay; Enterobacter cloacae WA 99164; T. Waters, WSU Franklin Co. Extension, Pasco WA

    E-Print Network [OSTI]

    Schroeder, Brenda K.

    , Enterobacter bulb decay; Enterobacter cloacae WA 99164; T. Waters, WSU Franklin Co. Extension, Pasco WA 99301 for resistance to Enterobacter cloacae in storage, 2007-2008. An onion bulb storage trial was completed to survey for resistance to Enterobacter cloacae, causal agent of Enterobacter bulb decay. Seeds of each cultivar were

  10. On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N- GaN built-in junctions in the n-GaN layer for InGaN/GaN: N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN

  11. 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

  12. p-doping-free InGaN/GaN light-emitting diode driven by three-dimensional hole gas

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Tiam Tan, Swee; Kyaw, Zabu; Liu, Wei; Ji, Yun; Ju, Zhengang; Zhang, Xueliang [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore) [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Wei Sun, Xiao, E-mail: EXWSUN@ntu.edu.sg [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Department of Electronics and Electrical Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Volkan Demir, Hilmi, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Department of Electrical and Electronics, UNAM-Institute of Material Science and Nanotechnology, Bilkent University, Ankara TR-06800 (Turkey); Department of Physics, UNAM-Institute of Material Science and Nanotechnology, Bilkent University, Ankara TR-06800 (Turkey)

    2013-12-23T23:59:59.000Z

    Here, GaN/Al{sub x}Ga{sub 1-x}N heterostructures with a graded AlN composition, completely lacking external p-doping, are designed and grown using metal-organic-chemical-vapour deposition (MOCVD) system to realize three-dimensional hole gas (3DHG). The existence of the 3DHG is confirmed by capacitance-voltage measurements. Based on this design, a p-doping-free InGaN/GaN light-emitting diode (LED) driven by the 3DHG is proposed and grown using MOCVD. The electroluminescence, which is attributed to the radiative recombination of injected electrons and holes in InGaN/GaN quantum wells, is observed from the fabricated p-doping-free devices. These results suggest that the 3DHG can be an alternative hole source for InGaN/GaN LEDs besides common Mg dopants.

  13. Collector-up light-emitting charge injection transistors in n-lnGaAs/lnAIAs/ plllnGaAs and n-lnGaAs/lnP/p-InGaAs heterostructures

    E-Print Network [OSTI]

    Luryi, Serge

    Collector-up light-emitting charge injection transistors in n-lnGaAs/lnAIAs/ plllnGaAs and n (Received 23 November 1992; accepted for publication 4 March 1993) The realization of collector-up light for the collector stripe definition. Electrons, injected over the wide-gap heterostructure barrier (InAlAs or In

  14. Electronic structure of the Si(111):GaSe van der Waals-like surface termination

    E-Print Network [OSTI]

    Olmstead, Marjorie

    in the energy range h = 12 - 170 eV supplied by the BESSY and ALS synchrotron light sources. The Si(111):Ga

  15. Catastrophic degradation of InGaAsP/InGaP double-heterostructure lasers grown on (001) GaAs substrates by liquid-phase epitaxy

    SciTech Connect (OSTI)

    Ueda, O.; Wakao, K.; Komiya, S.; Yamaguchi, A.; Isozumi, S.; Umebu, I.

    1985-12-01T23:59:59.000Z

    Catastrophically degraded InGaAsP/InGaP double-heterostructure lasers grown on (001) GaAs substrates by liquid-phase epitaxy, emitting at 727 and 810 nm are investigated by photoluminescence topography, scanning electron microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The degradation is mainly due to catastrophic optical damage at the facet, i.e., development of <110> dark-line defects from the facet, and rarely due to catastrophic optical damage at some defects, i.e., development of <110> dark-line defects from the defects inside the stripe region. These <110> dark-line defects correspond to complicated dislocation networks connected with dark knots, and are quite similar to those observed in catastrophically degraded GaAlAs/GaAs double-heterostructure lasers. The degradation characteristics of the InGaAsP/InGaP double-heterostructure lasers are rather similar to those in GaAlAs/GaAs double-heterostructure lasers concerning the catastrophic degradation.

  16. als erstmanifestation einer: Topics by E-print Network

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

    durch Photoeffekt mit zirkular polarisiertem Licht an einem GaAs-Kristall erzeugt Pir. Als Lichtquelle wird ein Lasersystem verwendet, das linear polarisiertes Licht...

  17. als instrument einer: Topics by E-print Network

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

    durch Photoeffekt mit zirkular polarisiertem Licht an einem GaAs-Kristall erzeugt Pir. Als Lichtquelle wird ein Lasersystem verwendet, das linear polarisiertes Licht...

  18. als folge einer: Topics by E-print Network

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

    durch Photoeffekt mit zirkular polarisiertem Licht an einem GaAs-Kristall erzeugt Pir. Als Lichtquelle wird ein Lasersystem verwendet, das linear polarisiertes Licht...

  19. als ursache einer: Topics by E-print Network

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

    durch Photoeffekt mit zirkular polarisiertem Licht an einem GaAs-Kristall erzeugt Pir. Als Lichtquelle wird ein Lasersystem verwendet, das linear polarisiertes Licht...

  20. als knstler und: Topics by E-print Network

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

    Verbindungen mit Lithium 18 2.1.3 Elektrolyte Hoffmann, Rolf 5 Wachstum und Realstruktur von epitaktischen (Al,Ga)N-Schichten. Open Access...

  1. als geschichtliches und: Topics by E-print Network

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

    Verbindungen mit Lithium 18 2.1.3 Elektrolyte Hoffmann, Rolf 5 Wachstum und Realstruktur von epitaktischen (Al,Ga)N-Schichten. Open Access...

  2. Modeling transport of disposed dredged material from placement sites in Grays Harbor, WA

    E-Print Network [OSTI]

    US Army Corps of Engineers

    Modeling transport of disposed dredged material from placement sites in Grays Harbor, WA E- to mid- term dredge material management strategies for the Federal Navigation Project at Grays Harbor dredging quantities. However, the most heavily used dredged material placement sites lie in proximity

  3. U.S. NUclear WaSte techNical revieW Board

    E-Print Network [OSTI]

    technical context as important decisions are made on managing the nation's spent nuclear fuel and high, packaging, and transporting spent nuclear fuel and high-level radioactive waste is presented. The technicalU.S. NUclear WaSte techNical revieW Board Report to The U.S. Congress and The Secretary

  4. An International Pellet Ablation Database L.R. Baylor, A. Geraud*, W.A. Houlberg,

    E-Print Network [OSTI]

    An International Pellet Ablation Database L.R. Baylor, A. Geraud*, W.A. Houlberg, D. Frigione+, M of an international pellet ablation database (IPADBASE) that has been assembled to enable studies of pellet ablation theories that are used to describe the physics of an ablating fuel pellet in a tokamak plasma. The database

  5. Electrical impedance tomography and Calderon's Department of Mathematics, University of Washington, Seattle, WA 98195, USA

    E-Print Network [OSTI]

    Uhlmann, Gunther

    Electrical impedance tomography and Calder´on's problem G Uhlmann Department of Mathematics, University of Washington, Seattle, WA 98195, USA E-mail: gunther@math.washington.edu Abstract. We survey mathematical developments in the inverse method of Electrical Impedance Tomography which consists

  6. Proceedings of the Western Protective Relay Conference, Spokane, WA, 2006 New wide-area algorithms for

    E-Print Network [OSTI]

    - 1 - Proceedings of the Western Protective Relay Conference, Spokane, WA, 2006 New wide (for N-1 contingency) or with the help of Special Protection Schemes (SPS) or Remedial Action Schemes of the relay actions that may have resulted in the angle stability phenomenon. The concept of a real

  7. General Disposal Authority for State Government Information The State Records Office of WA

    E-Print Network [OSTI]

    Tobar, Michael

    ) consolidates and amends the GDAs for Administrative Records, Human Resource Management Records, and Financial and Record Categories covered 4 of 170 Reference Activity / Record Category Page 16 CHEQUE MANAGEMENT 37 17General Disposal Authority for State Government Information The State Records Office of WA

  8. 7900 SE 28th Street, Suite 200 Mercer, Island, WA 98040-2970

    E-Print Network [OSTI]

    7900 SE 28th Street, Suite 200 Mercer, Island, WA 98040-2970 v 206.236.7200 f 206.236.3019 www Administration. The Joint Proposal is a comprehensive settlement that will bring to an end the long costs, when the responsibility for reaching agreements with IPPs, is dispersed directly to the load

  9. Comment on the future of the Bonneville Power Administration Jim G. Likes, Thurston County, WA

    E-Print Network [OSTI]

    Comment on the future of the Bonneville Power Administration Jim G. Likes, Thurston County, WA Bonneville is a regional agency that markets federal hydropower and augments its power supply with market, everyday citizens, to pay illegally inflated power costs. Because of this, Bonneville should have the legal

  10. Natural Data Mining Techniques J. N. Kok and W.A. Kosters

    E-Print Network [OSTI]

    Kosters, Walter

    , enrichment of data (for example using external data bases), coding, data mining and reporting. In data support for their operations. A usual problem in the #12;eld of data mining is that the combinationNatural Data Mining Techniques J. N. Kok and W.A. Kosters Leiden Institute of Advanced Computer

  11. Segregation of In to dislocations in InGaN

    E-Print Network [OSTI]

    Horton, Matthew K.; Rhode, Sneha; Sahonta, Suman-Lata; Kappers, Menno J.; Haigh, Sarah J.; Pennycook, Timothy J.; Humphreys, Colin J.; Dusane, Rajiv O.; Moram, Michelle A.

    2015-01-16T23:59:59.000Z

    .; Fischer, A. J.; Thaler, G.; Banas, M. A. Effect of dislocation density on efficiency droop in GaInN?GaN light-emitting diodes. Applied Physics Letters 2007, 91, 231114 DOI: 10.1063/1.2822442. (3) Schubert, M. F.; Xu, J.; Kim, J. K.; Schubert, E. F.; Kim... , M. H.; Yoon, S.; Lee, S. M.; Sone, C.; Sakong, T.; Park, Y. Polarization-matched GaInN?AlGaInN multi-quantum-well light-emitting diodes with reduced efficiency droop. Applied Physics Letters 2008, 93, 041102 DOI: 10.1063/1.2963029. (4) Hsu, J. W. P...

  12. 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 ...

  13. 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.

  14. 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.

  15. 4D-Polytopes and Their Dual Polytopes of the Coxeter Group $W(A_{4})$ Represented by Quaternions

    E-Print Network [OSTI]

    Mehmet Koca; Nazife Ozdes Koca; Mudhahir Al-Ajmi

    2011-02-06T23:59:59.000Z

    4-dimensional $A_{4}$ polytopes and their dual polytopes have been constructed as the orbits of the Coxeter-Weyl group $W(A_{4})$ where the group elements and the vertices of the polytopes are represented by quaternions. Projection of an arbitrary $W(A_{4})$ orbit into three dimensions is made using the subgroup $W(A_{3})$. A generalization of the Catalan solids for 3D polyhedra has been developed and dual polytopes of the uniform $A_{4}$ polytopes have been constructed.

  16. Carrier capture dynamics of single InGaAs/GaAs quantum-dot layers

    SciTech Connect (OSTI)

    Chauhan, K. N.; Riffe, D. M.; Everett, E. A.; Kim, D. J.; Yang, H. [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States)] [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States); Shen, F. K. [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)] [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)

    2013-05-28T23:59:59.000Z

    Using 800 nm, 25-fs pulses from a mode locked Ti:Al{sub 2}O{sub 3} laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In{sub 0.4}Ga{sub 0.6}As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140 fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated with initial InGaAs thickness and annealing temperature. With increasing excited carrier density, the capture rate decreases; this slowing of the dynamics is attributed to Pauli state blocking within the InGaAs quantum layer.

  17. Testing Buda-Lund hydro model on particle correlations and spectra in NA44, WA93 and WA98 heavy ion experiments

    E-Print Network [OSTI]

    A. Ster; T. Csorgo; B. Lorstad

    1998-09-28T23:59:59.000Z

    Analytic and numerical approximations to a hydrodynamical model describing longitudinally expanding, cylindrically symmetric, finite systems are fitted to preliminary NA44 data measured in 200 AGeV central $S + Pb$ reactions. The model describes the measured spectra and HBT radii of pions, kaons and protons, simultaneously. The source is characterized by a central freeze-out temperature of T_0 = 154 +/- 8 +/- 11 MeV, a "surface" temperature of T_r = 107 +/- 28 +/- 18 MeV and by a well-developed transverse flow, = 0.53 +/- 0.17 +/- 0.11. The transverse geometrical radius and the mean freeze-out time are found to be R_G = 5.4 +/- 0.9 +/- 0.7 fm and tau_0 = 5.1 +/- 0.3 +/- 0.3 fm/c, respectively. Fits to preliminary WA93 200 AGeV S + Au and WA98 158 AGeV Pb + Pb data dominated by pions indicate similar model parameters. The absolute normalization of the measured particle spectra together with the experimental determination of both the statistical and the systematic errors were needed to obtain successful fits.

  18. Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

    SciTech Connect (OSTI)

    Schmidt, Gordon, E-mail: Gordon.Schmidt@ovgu.de; Müller, Marcus; Veit, Peter; Bertram, Frank; Christen, Jürgen [Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, 39106 Magdeburg (Germany); Glauser, Marlene; Carlin, Jean-François; Cosendey, Gatien; Butté, Raphaël; Grandjean, Nicolas [Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

    2014-07-21T23:59:59.000Z

    Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperatures, the optical and structural properties of a 62 InGaN/GaN multiple quantum well embedded in an AlInN/GaN based microcavity are investigated at the nanometer scale. We are able to spatially resolve a spectral redshift between the individual quantum wells towards the surface. Cathodoluminescence spectral linescans allow directly visualizing the critical layer thickness in the quantum well stack resulting in the onset of plastic relaxation of the strained InGaN/GaN system.

  19. 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

  20. 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