Sample records for nh fl ga

  1. Rare Earth ? N = N* fs fGHZ fp nH fl

    E-Print Network [OSTI]

    Walter, Frederick M.

    Rare Earth ? #12;N to date N = N* fs fGHZ fp nH fl ·N* = 4 x 1011 ·fs = 0.2 ·fGHZ = 0.1 ·fp = 0.8 ·nH = 2 ·fl = 1.0 N = 1.3 x 1010 #12;The Goldilocks Effect Earth is "Just Right" Yes, life on Earth has adapted to Earth, but ... Earth has just the right mass to be ·Tectonically-active ·Retain

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

    E-Print Network [OSTI]

    Anderson, Timothy J.

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

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

    SciTech Connect (OSTI)

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

    2012-01-01T23:59:59.000Z

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

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

    E-Print Network [OSTI]

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

  5. High external quantum efficiency and fill-factor InGaN/GaN heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Lang, J. R.; Hurni, C. A.; Cruz, S. C.; Matioli, E.; Speck, J. S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States); Neufeld, C. J.; Mishra, U. K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

    2011-03-28T23:59:59.000Z

    High external quantum efficiency (EQE) p-i-n heterojunction solar cells grown by NH{sub 3}-based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorption measurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By adjusting the thickness of the top p-type GaN window contact layer, it is shown that the short-wavelength (<365 nm) quantum efficiency is limited by the minority carrier diffusion length in highly Mg-doped p-GaN.

  6. Atomic layer deposition of GaN using GaCl3 and NH3 Oh Hyun Kim, Dojun Kim, and Tim Andersona

    E-Print Network [OSTI]

    Anderson, Timothy J.

    be grown at lower temperature than by CVD. As example, ALD growth of device quality GaAs, GaP, and InGaP

  7. Optical and digital GaAs technologies for signal-processing applications; Proceedings of the Meeting, Orlando, FL, Apr. 16-18, 1990

    SciTech Connect (OSTI)

    Bendett, M.P.; Butler, D.H., Jr.; Prabhakar, A.; Yang, A.; (Honeywell, Inc., Minneapolis, MN; Booz, Allen and Hamilton, Inc., Bethesda, MD; DARPA, Arlington, VA)

    1990-01-01T23:59:59.000Z

    Practical problems that need to be solved for the introduction of optical modules into processing systems are reviewed. Some papers deal with the state of the art in such key devices as Bragg cells, spatial light modulators, and fast CCDs. Issues unique to optical packaging are also highlightened. New architectures to enable real-time operations are demonstrated, and optical interconnects for parallel processors are discussed. Particular attention is given to the status and operational advantages of government-sponsored efforts to upgrade existing military systems with digital GaAs signal processors and the state of the art in computer-aided design and advanced system architectures.

  8. 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.

  9. Stochastic dynamic systems fl T. Soderstrom, 1997

    E-Print Network [OSTI]

    Flener, Pierre

    Stochastic dynamic systems Chapter 5 c fl T. S¨oderstr¨om, 1997 1 Optimal estimation ffl The conditional mean ffl Best linear estimate ffl ML estimation c fl T. S¨oderstr¨om, 1997 2 Optimal estimation criterion 2. Symmetric cond pdf c fl T. S¨oderstr¨om, 1997 3 Best linear estimate Given Ex = mx ; Ey = my E

  10. Monolithically Peltier-cooled vertical-cavity surface-emitting lasers Paul FL Berger, Niloy K. Dutta, Kent D. Choquette, Ghulam Hasnain, and Naresh Chand

    E-Print Network [OSTI]

    Monolithically Peltier-cooled vertical-cavity surface-emitting lasers Paul FL Berger, Niloy K. The thermoelectric element is the n + -GaAs substrate based on the Peltier effect. A variation of active region contact on the n + -GaAs substrate. The thermoelectric (Peltier) ef- fect of the n f -GaAs substrate can

  11. Stochastic dynamic systems fl T. Soderstrom, 1997

    E-Print Network [OSTI]

    Flener, Pierre

    Stochastic dynamic systems Chapter 2 c fl T. S¨oderstr¨om, 1997 1 Some probability theory ffl Basic facts ffl Conditional distributions ffl Complex­valued Gaussian variables c fl T. S¨oderstr¨om, 1997 2) increasing ffl limx!1 F(x) = 1 ffl lim x!\\Gamma1 F (x) = 0 c fl T. S¨oderstr¨om, 1997 3 Random variables

  12. Stochastic dynamic systems fl T. Soderstrom, 1997

    E-Print Network [OSTI]

    Flener, Pierre

    Stochastic dynamic systems Chapter 10 c fl T. S¨oderstr¨om, 1997 1 Optimal stochastic control ffl controllers c fl T. S¨oderstr¨om, 1997 2 Optimal stochastic control ­ some illustrative examples System x¨oderstr¨om, 1997 3 Optimal stochastic control ­ Deterministic system Criterion J = x 2 (N) = [ax(N \\Gamma 1) + bu

  13. Ab initio potential energy surfaces for NH,,3 -...NH,,3 -

    E-Print Network [OSTI]

    Ab initio potential energy surfaces for NH,,3 - ...­NH,,3 - ... with analytical long range Liesbeth, Poland Received 16 September 2009; accepted 7 November 2009; published online 10 December 2009; publisher error corrected 15 December 2009 We present four-dimensional ab initio potential energy surfaces

  14. FUPWG Meeting Agenda - Destin, FL | Department of Energy

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

    Destin, FL FUPWG Meeting Agenda - Destin, FL Going coastal for energy efficiency. FUPWG. April 15-16, 2008, Destin, Florida Gulf Power: A Southern Company FEMP logo April 15-16,...

  15. ARIZONA STATE UNIVERSITY STETSON UNIVERSITY Phoenix, AZ Deland, FL

    E-Print Network [OSTI]

    Wu, Shin-Tson

    English Literature English BOWLING GREEN STATE UNIVERSITY Bowling Green, OH SYRACUSE UNIVERSITY IndustrialARIZONA STATE UNIVERSITY STETSON UNIVERSITY Phoenix, AZ Deland, FL Interdisciplinary Studies Leadership FLORIDA STATE UNIVERSITY Instructional Systems Design Tallahassee, FL Interdisciplinary Studies

  16. Stochastic dynamic systems fl T. Soderstrom, 1997

    E-Print Network [OSTI]

    Flener, Pierre

    Stochastic dynamic systems Chapter 9 c fl T. S¨oderstr¨om, 1997 1 Nonlinear filtering ffl Extended(t)H(t)P(tjt \\Gamma 1) â?? x(t + 1jt) = f(t; â?? x(tjt)) F(t) = @f(t;x) @x fi fi fi x=â??x(tjt) G(t) = g(t; x)j x=â??x(tjt) P

  17. High-resolution energy-selected study of the reaction NH3+ -> NH2 ++H: Accurate thermo chemistry for the NH2/NH2+ and NH3/NH3 + systems

    SciTech Connect (OSTI)

    Song, Y.; Qian, X.M.; Lau, K.C.; Ng, C.Y.; Liu, J.B.; Chen, W.W.

    2001-03-01T23:59:59.000Z

    Employing the newly developed high-resolution pulsed field ionization-photoelectron (PFI-PE)-photoion coincidence (PFI-PEPICO) technique, we have examined the dissociation of energy-selected NH{sub 3}{sup +} to form NH{sub 2}{sup +} + H near its threshold. The breakdown curves for NH{sub 2}{sup +} and NH{sub 3}{sup +} thus obtained yield a value of 15.765 {+-} 0.001 eV for the 0 K dissociation threshold or appearance energy (AE) for NH{sub 2}{sup +} from NH{sub 3}. This value, together with the known ionization energy (IE=10.1864 {+-} 0.0001 eV) and 0 K bond dissociation energy (D{sub 0} = 4.6017 {+-} 0.0025 eV) for NH{sub 3}, allows the determination of the D{sub 0}(NH{sub 2}{sup +}-H) and IE(NH{sub 2}), which are 5.5786 {+-} 0.0010 and 11.1633 {+-} 0.0025 eV, respectively. Using the known 0 K heats of formation ({Delta}H{sup 0}{sub f0}) for NH{sub 3} and H and the AE(NH{sub 2}{sup +}), we obtain the {Delta}H{sup o}{sub f0}(NH{sub 2}{sup +}) = 302.60 {+-} 0.08 kcal/mol. The PFI-PE spectrum for NH{sub 3} exhibits a step-like feature at the 0 K AE(NH{sub 2}{sup +}), indicating that the dissociation of excited NH{sub 3} in high-n (n {ge} 100) Rydberg states at energies slightly above the dissociation threshold occurs on a time scale {le}10{sup -7} s. This step confirms the AE(NH{sub 2}{sup +}) value derived from the PFI-PEPICO measurements. Highly accurate energetic data with well-founded error limits, such as those obtained in the present and other studies using the PFI techniques, are expected to play an important role for the development of the next generation of ab initio quantum computation procedures. This experiment has stimulated a state-of-the-art ab initio quantum chemical calculation (Dixon et al., J. Chem. Phys., accepted). The comparison between theoretical predictions and the best experimental results for the NH{sub 2}/NH{sub 2}{sup +} and NH{sub 3}/NH{sub 3}{sup +} systems indicates that the accuracy of the computational scheme used is {le}0.4 kcal/mol.

  18. 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.

  19. 5, 1133111375, 2005 NH total ozone

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ACPD 5, 11331­11375, 2005 NH total ozone increase S. Dhomse et al. Title Page Abstract Introduction On the possible causes of recent increases in NH total ozone from a statistical analysis of satellite data from License. 11331 #12;ACPD 5, 11331­11375, 2005 NH total ozone increase S. Dhomse et al. Title Page Abstract

  20. Category:Miami, FL | 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 being directedAnnualProperty EditCalifornia:Power LPInformationCashtonGo Back toFL" The following 16 files

  1. Publisher's Note: "Ab initio potential energy surfaces for NH,,3 -...-NH,,3 -

    E-Print Network [OSTI]

    Publisher's Note: "Ab initio potential energy surfaces for NH,,3 - ...-NH,,3 - ... with analytical of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice, Poland Received 21 December 2009; published

  2. 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

  3. 150W.UniversityBlvd. Melbourne,FL32901

    E-Print Network [OSTI]

    Wood, Stephen L.

    150W.UniversityBlvd. Melbourne,FL32901 321-674-8000 NickAbruzzini Junior,Ocean Engineering JanelleBoisvert Junior,Ocean Engineering KatieDobek Junior, Ocean Engineering Anthony Tedeschi Junior,Ocean Engineering

  4. Geotechnical/Environmental Engineering Intern Manchester, NH

    E-Print Network [OSTI]

    Pohl, Karsten

    Geotechnical/Environmental Engineering Intern Manchester, NH POSITION DESCRIPTION The candidate will provide support for site characterization geotechnical investigations, site development, remediation include, but are not limited to: Interpreting, and presenting, environmental data; performing engineering

  5. SALT-flSH INPUSTRIES FISHERY LEAFLET 240

    E-Print Network [OSTI]

    SALT-flSH INPUSTRIES FISHERY LEAFLET 240 FISH AND WILDLIFE SERVICE UNITED STATES DEPARTMENT, Albert M. Day, Director #12;THE VENEZUKLAN SALT-FISH INDUSTRIES CONTE^fTS Part II Potential Productive and Craft 29 Development of Unused or Underutilized Species 29 Development of New Areas 35 Salt 35 Studies

  6. CPDD 2011 Annual Meeting June 22, 2011 Hollywood, FL

    E-Print Network [OSTI]

    Murphy, Susan A.

    Improve maternal and infant outcomes Conduct clinical research to generate new knowledge to improve Setting CAP Clinical Outcome ResearchNo CAP Treatment (n=100) (n=46) Clinical measure: Prenatal visits 8 4 CPDD 2011 Annual Meeting June 22, 2011 Hollywood, FL Outline 1. Complexities of the Problem 2. Clinical

  7. Lecture #5: The Language FL October 4, 2007

    E-Print Network [OSTI]

    Gifford, David K.

    ' language, that transforms the FL language back down into expres- sions in FLK. And then we can describe you won't fault me for writing it out again here. A question from the back of the room: Is he saying alpha-substitution, and expressions which are the same up to an alpha transformation of their bound

  8. Wet-Nanotechnology: fl id t NIUnanofluids at NIU

    E-Print Network [OSTI]

    Kostic, Milivoje M.

    .kostic.niu.edu 4 Mechanical Engineering NORTHERN ILLINOIS UNIVERSITY #12;One Step Nanofluid Production ImprovementOne-Step Nanofluid Production Improvement Insulated and vertically-adjustable boat- heater evaporator NIU with i fl id heater evaporatorLaboratoryLaboratory S.S. ChoiChoi J. Hull,J. Hull, and othersand others

  9. International Conference on Multiphase Flow, ICMF 2010, Tampa, FL, May 30 June 4, 2010

    E-Print Network [OSTI]

    Dabiri, John O.

    7th International Conference on Multiphase Flow, ICMF 2010, Tampa, FL, May 30 ­ June 4, 2010 Shock Conference on Multiphase Flow, ICMF 2010, Tampa, FL, May 30 ­ June 4, 2010 Us Shock speed (m s-1 ) x Spatial

  10. Measurement and Modeling of Spatial NH3 Storage Distributions...

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

    NH3 Storage Distributions in a Commercial Small Port Cu Zeolite Urea SCR Catalyst Measurement and Modeling of Spatial NH3 Storage Distributions in a Commercial Small Port Cu...

  11. Red emission from Eu-doped GaN luminescent films grown by metalorganic chemical vapor deposition

    E-Print Network [OSTI]

    Steckl, Andrew J.

    chemical vapor deposition on GaN/Al2O3 substrates. Trimethylgallium TMGa , ammonia (NH3), and europium 2 europium doping was performed utilizing a europium beta-diketonate, eu- ropium 2,2,4,4-tetramethyl-3

  12. S M Stoller Star Center-WWNA Monthly; Largo, FL

    Office of Legacy Management (LM)

    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 742EnergyOn AprilA groupTuba City, Arizona, DisposalFourthN V O 1 8B100B100WWNA Monthly; Largo, FL

  13. ,"Pittsburg, NH 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","Pittsburg, NH...

  14. 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

  15. 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

  16. Directions from MCO to Hilton University of Florida Starting from: Orlando International Airport MCO, Orlando, FL

    E-Print Network [OSTI]

    Slatton, Clint

    Directions from MCO to Hilton University of Florida Starting from: Orlando International Airport MCO, Orlando, FL Arriving at: Hilton University of Florida (1714 SW 34th St. Gainesville, FL 32607-4138) Distance: 120.4 miles Approximate Travel Time: 2 hours 29 min 1. Exit MCO on AIRPORT BLVD E - go 0.7 mi 2

  17. Studies of Rotational Energy Transfer (RET) in long-range NH3-NH3 collisions in the gas phase (*)

    E-Print Network [OSTI]

    Boyer, Edmond

    L-477 Studies of Rotational Energy Transfer (RET) in long-range NH3-NH3 collisions in the gas phase-780 Pozna0144, Poland (Refu le 2 mars 1982, accepte le 14 mai 1982) Résumé. 2014 Le champ du dipôle- polarizability, only). From the dispersional part of the total interaction energy, we extract the RET

  18. Proceedings of the US Hydrographic Conference, Tampa, FL, 25-28 Apr 2011 THE PORT OF NORFOLK PROJECT

    E-Print Network [OSTI]

    New Hampshire, University of

    Proceedings of the US Hydrographic Conference, Tampa, FL, 25-28 Apr 2011 1 THE PORT OF NORFOLK;Proceedings of the US Hydrographic Conference, Tampa, FL, 25-28 Apr 2011 2 Background Creating raster

  19. American Statistical Association Announces 2011 Award Recipients Awards ceremony to be held at Joint Statistical Meetings in Miami Beach, FL

    E-Print Network [OSTI]

    Washington at Seattle, University of

    American Statistical Association Announces 2011 Award Recipients Awards ceremony to be held at Joint Statistical Meetings in Miami Beach, FL MIAMI BEACH, FL (PRWEB) AUGUST 1, 2011 ­ The American Statistical Association (ASA), the nation's preeminent professional statistical society, today announced

  20. EPR and IR studies of [Ru(NH?)?]³+-Y and [Ru(NH?)?N?]²+-Y type zeolites

    E-Print Network [OSTI]

    Leubner, Raymond Leon

    1973-01-01T23:59:59.000Z

    EPR AND IR STUDIES OF [Ru(NH ) ] -Y 3 6 AND [Ru(NE ) N ] -Y TYPE ZEOLITES 2+ A Thesis by RAYMOND LEON LEUBNER Submitted to the Graduate College of Texas A&M University in partia1 fulfillment of the requirement for the degree of MASTER... OF SCIENCE December 1973 Major Subject: Chemistry EPR AND IR STUDIES OF [Ru(NH3) ] -Y 3+ AND [Ru(NH3) N ) -Y TYPE ZEOLITES 2+ 3&2 A Thesis by RAYMOND LEON LEUBNER Approved as to style and content by: (Chairman of Committ (Head of Department) (Memb...

  1. Jere Chase Ocean Engineering Lab, Durham, NH Directions & Parking

    E-Print Network [OSTI]

    Jere Chase Ocean Engineering Lab, Durham, NH Directions & Parking Jere Chase Ocean Engineering Lab of the University of New Hampshire. Parking is available at the Jere A. Chase Ocean Engineering Building. Directions

  2. Quasielastic neutron scattering of -NH3 and -BH3 rotational dynamics...

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

    Quasielastic neutron scattering of -NH3 and -BH3 rotational dynamics in orthorhombic ammonia borane. Quasielastic neutron scattering of -NH3 and -BH3 rotational dynamics in...

  3. Proton transfer dynamics of the reaction H3O ,,NH3 ,H2O...NH4

    E-Print Network [OSTI]

    Farrar, James M.

    , Rochester, New York 14627 Received 29 September 2003; accepted 8 October 2003 The proton transfer reaction of H3O and NH3 was studied using the crossed molecular beam technique at relative energies of 0.41, 0.81, and 1.27 eV. At all three energies, the center-of-mass flux distribution of the product ion NH4 exhibits

  4. ASME 2008 Summer Heat transfer Conference August 10-14, 2008, Jacksonville, FL., USA

    E-Print Network [OSTI]

    Bahrami, Majid

    ASME 2008 Summer Heat transfer Conference August 10-14, 2008, Jacksonville, FL., USA HT2008, University of Victoria Victoria, BC , V8W 2Y2, Canada ABSTRACT Accurate information on the temperature eld

  5. ASME Symposium on Modeling and Control Electrohydraulic Systems, Orlando, FL. November, 2000

    E-Print Network [OSTI]

    Li, Perry Y.

    ASME Symposium on Modeling and Control Electrohydraulic Systems, Orlando, FL. November, 2000 1 not present in previous models. The model has been coded in Simulink and experimentally validated. I

  6. Matematik Dnyas>, 2005 K>fl ahit Arf'> tan>ma mutluluuna erdim. ok

    E-Print Network [OSTI]

    Sertöz, Ali Sinan

    ¤in tan>m> akl>mda kal- m>fl. Önemli bir fley söyleyece¤inin ayr>m>nda olan insanlar>n tavr>yla bana do

  7. Student Disability Services 240 O'Leary Library , 61 Wilder Street Fl-2

    E-Print Network [OSTI]

    Massachusetts at Lowell, University of

    Student Disability Services 240 O'Leary Library , 61 Wilder Street Fl-2 Lowell, Massachusetts 01854 Disability Services 240 O'Leary Library, 61 Wilder Street Lowell, MA 01854 Disability@uml.edu Phone: (978

  8. DOE Zero Energy Ready Home Case Study, e2Homes, Winterpark, FL...

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

    Winter Park, FL that scored HERS 57 without PV or HERS -7 with PV. This 4,305 ft2 custom home has autoclaved aerated concrete walls, a sealed attic with R-20 spray foam, and...

  9. Complete composition tunability of InGaN nanowires using a combinatorial approach

    E-Print Network [OSTI]

    Yang, Peidong

    a horizontal, single-zone tube furnace and two independently controlled heating elements. InCl3, GaCl3 and NH3, particularly for In-rich nitride alloys, which has led to the need for increasingly high ammonia flow rates

  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. On rotational dynamics of an NH4+ ion in water

    SciTech Connect (OSTI)

    Chang, Tsun-Mei (University of Wisconsin-Parkside); Dang, Liem X. (BATTELLE (PACIFIC NW LAB))

    2003-05-15T23:59:59.000Z

    We used molecular dynamics simulations to characterize the rotational dynamics of the NH4+ ion in liquid water. The polarizable potential models were to describe the ion-water and water-water interactions. This study complements the work of Karim and Haymet (J. Chem. Phys., 93, 5961, 1990), who employed effective pir potential models. The computed rotational diffusion coefficients of the NH4+ ion in water, which were determined from the angular momentum autocorrelation function and the angular mean-square displacement, are 0.093 x 1012 rad2/s and 0.067 x 1012 rad2/s, repectively. These results are in good agreement with the 0.075 x 1012 rad2/s value determined from the nuclear magnetic resonance (NMR) spectroscopy studies of Perrin and Gipe (J. Am. Chem. Soc., 108, 1088, 1986; Science, 238, 1393, 1987).

  12. Thermal Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx...

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

    Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx Reduction. Thermal Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx Reduction. Abstract: Multiple catalytic functions...

  13. Department of Ocean and Mechanical Engineering 777 Glades Road, Boca Raton, FL 33431

    E-Print Network [OSTI]

    Fernandez, Eduardo

    Department of Ocean and Mechanical Engineering 777 Glades Road, Boca Raton, FL 33431 561.297.3430, fax 561.297.3885 SeaTech ­ The Institute for Ocean & Systems Engineering 101 North Beach Road, Dania of Ocean and Mechanical Engineering at Florida Atlantic University is pleased to announce fellowship

  14. Eddy-current interaction with an ideal crack. II. The inverse problem John FL Bowler

    E-Print Network [OSTI]

    Bowler, John R.

    Eddy-current interaction with an ideal crack. II. The inverse problem John FL Bowler The University 1994) Eddy-current inversion is the process whereby the geometry of a flaw in a metal is derived from eddy-current probe impedance measurements. The approach is based on an optimization scheme that seeks

  15. Theory of eddy current inversion Stephen:J. Nortona) and John FL Bowler

    E-Print Network [OSTI]

    Bowler, John R.

    Theory of eddy current inversion Stephen:J. Nortona) and John FL Bowler University of Surrey) The inverse eddy current problem can be described as the task of reconstructing an unknown distribution of electrical conductivity from eddy-current probe impedance measurements recorded as a function of probe

  16. DOE Zero Energy Ready Home Case Study, e2Homes, Winterpark, FL, Custom Homes

    Broader source: Energy.gov [DOE]

    Case study of a DOE Zero Energy Ready Home in Winter Park, FL that scored HERS 57 without PV or HERS -7 with PV. This 4,305 ft2 custom home has autoclaved aerated concrete walls, a sealed attic with R-20 spray foam, and ductless mini-split heat pumps.

  17. St. Petersburg, FL: Vehicle Use of Recycled Natural Gas Derived from Wastewater Biosolids

    Broader source: Energy.gov [DOE]

    Breakout Session 3A—Conversion Technologies III: Energy from Our Waste—Will we Be Rich in Fuel or Knee Deep in Trash by 2025? St. Petersburg, FL: Vehicle Use of Recycled Natural Gas Derived from Wastewater Biosolids William Eleazer, Supervising Engineer, Brown and Caldwell

  18. FL47CH15-Goldstein ARI 25 November 2014 9:45 Green Algae as Model

    E-Print Network [OSTI]

    Goldstein, Raymond E.

    FL47CH15-Goldstein ARI 25 November 2014 9:45 Green Algae as Model Organisms for Biological Fluid green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model of flagellar synchronization. Green algae are well suited to the study of such problems because of their range

  19. ANRV400-FL42-05 ARI 9 August 2009 14:52 Slip on Superhydrophobic

    E-Print Network [OSTI]

    Rothstein, Jonathan

    ANRV400-FL42-05 ARI 9 August 2009 14:52 R E V I E W S IN A D V A N CE Slip on Superhydrophobic, simulations, and theory of flow past superhydrophobic surfaces. In addition, the designs and limitations on a special class of materials called superhydrophobic surfaces that have been used recently to engineer large

  20. Characterization of the selective reduction of NO by NH/sub 3/

    SciTech Connect (OSTI)

    Lucas, D.; Brown, N.J.

    1981-04-01T23:59:59.000Z

    The selective reduction of NO by NH/sub 3/ addition has been studied in a lean-burning oil-fired laboratory combustion tunnel as a function of equivalence ratio, NH/sub 3/ injection temperature, concentration of NH/sub 3/ added, and the source of NO. Ammonia breakthrough was found to depend strongly on the NH/sub 3/ addition temperature. The total concentration of nitrogen containing species other N/sub 2/, NO, and NH/sub 3/ was measured with a variety of techniques and was found to be less than 5 ppM over the range of conditions studied.

  1. 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

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

    SciTech Connect (OSTI)

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

    1999-07-01T23:59:59.000Z

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

  3. Micromechanical resonators fabricated from lattice-matched and etch-selective GaAs/InGaP/GaAs heterostructures

    E-Print Network [OSTI]

    Micromechanical resonators fabricated from lattice-matched and etch-selective GaAs/InGaP September 2007 Utilizing lattice-matched GaAs/InGaP/GaAs heterostructures, clean micromechanical resonators are fabricated and characterized. The nearly perfect selectivity of GaAs/InGaP is demonstrated by realizing

  4. Ga nanoparticle-enhanced photoluminescence of GaAs

    SciTech Connect (OSTI)

    Kang, M.; Al-Heji, A. A.; Jeon, S.; Wu, J. H. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Lee, J.-E.; Saucer, T. W.; Zhao, L.; Sih, V. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States); Katzenstein, A. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Eckerd College, St. Petersburg, Florida 33711-4744 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-09-02T23:59:59.000Z

    We have examined the influence of surface Ga nanoparticles (NPs) on the enhancement of GaAs photoluminescence (PL) efficiency. We have utilized off-normal focused-ion-beam irradiation of GaAs surfaces to fabricate close-packed Ga NP arrays. The enhancement in PL efficiency is inversely proportional to the Ga NP diameter. The maximum PL enhancement occurs for the Ga NP diameter predicted to maximize the incident electromagnetic (EM) field enhancement. The PL enhancement is driven by the surface plasmon resonance (SPR)-induced enhancement of the incident EM field which overwhelms the SPR-induced suppression of the light emission.

  5. 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 ...

  6. 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.

  7. Array-type NH.sub.3 sensor

    DOE Patents [OSTI]

    West, David Lawrence; Montgomery, Frederick Charles; Armstrong, Timothy R; Warmack, Robert J

    2013-12-31T23:59:59.000Z

    An array-type sensor that senses NH.sub.3 includes non-Nernstian sensing elements constructed from metal and/or metal-oxide electrodes on an O.sub.2 ion conducting substrate. In one example sensor, one electrode may be made of platinum, another electrode may be made of manganese (III) oxide (Mn.sub.2O.sub.3), and another electrode may be made of tungsten trioxide (WO.sub.3). Some sensing elements may further include an electrode made of La.sub.0.6Sr.sub.0.4Co.sub.0.2Fe.sub0.8O.sub.3 and another electrode made of LaCr.sub.0.95.Mg.sub.0.05O.sub.3.

  8. Indium and impurity incorporation in InGaN films on polar, nonpolar, and semipolar GaN orientations grown by ammonia molecular beam epitaxy

    SciTech Connect (OSTI)

    Browne, David A.; Young, Erin C.; Lang, Jordan R.; Hurni, Christophe A.; Speck, James S. [Materials Department, University of California Santa Barbara, Santa Barbara, California 93106 (United States)

    2012-07-15T23:59:59.000Z

    The effects of NH{sub 3} flow, group III flux, and substrate growth temperature on indium incorporation and surface morphology have been investigated for bulk InGaN films grown by ammonia molecular beam epitaxy. The incorporation of unintentional impurity elements (H, C, O) in InGaN films was studied as a function of growth temperature for growth on polar (0001) GaN on sapphire templates, nonpolar (1010) bulk GaN, and semipolar (1122), (2021) bulk GaN substrates. Enhanced indium incorporation was observed on both (1010) and (2021) surfaces relative to c-plane, while reduced indium incorporation was observed on (1122) for co-loaded conditions. Indium incorporation was observed to increase with decreasing growth temperature for all planes, while being relatively unaffected by the group III flux rates for a 1:1 Ga:In ratio. Indium incorporation was found to increase at the expense of a decreased growth rate for higher ammonia flows; however, smooth surface morphology was consistently observed for growth on semipolar orientations. Increased concentrations of oxygen and hydrogen were observed on semipolar and nonpolar orientations with a clear trend of increased hydrogen incorporation with indium content.

  9. Carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well

    SciTech Connect (OSTI)

    Asami, T.; Nosho, H.; Tackeuchi, A. [Department of Applied Physics, Waseda University, Shinjuku, Tokyo 169-8555 (Japan); Li, L. H.; Harmand, J. C. [Laboratory for Photonics and Nanostructures-CNRS, Site Alcatel de Marcoussis, Route de Nozay, 91460 Marcoussis (France); Lu, S. L. [Suzhou Institute of Nano-tech and Nano-bionics, CAS, Dushu, Lake Higher Education Town, Ruoshui Road 398, Suzhou Industrial Park, Suzhou 215125 (China)

    2011-12-23T23:59:59.000Z

    We have investigated the carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well (QW) by time-resolved photoluminescence (PL) measurement. The sample consists of an 8-nm-thick GaIn{sub 0.36}N{sub 0.006}AsSb{sub 0.015} well, 5-nm-thick GaN{sub 0.01}AsSb{sub 0.11} intermediate barriers and 100-nm-thick GaAs barriers grown by molecular beam epitaxy on a GaAs(100) substrate. The spin relaxation time and recombination lifetime at 10 K are measured to be 228 ps and 151 ps, respectively. As a reference, we have also obtained a spin relaxation time of 125 ps and a recombination lifetime of 63 ps for GaInNAs/GaNAs/GaAs QW. This result shows that crystal quality is slightly improved by adding Sb, although these short carrier lifetimes mainly originate from a nonradiative recombination. These spin relaxation times are longer than the 36 ps spin relaxation time of InGaAs/InP QWs and shorter than the 2 ns spin relaxation time of GaInNAs/GaAs QW.

  10. NH3 generation over commercial Three-Way Catalysts and Lean-NOx...

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

    & Publications Emissions Control for Lean Gasoline Engines Emissions Control for Lean Gasoline Engines Spatiotemporal Distribution of NOx Storage: a Factor Controlling NH3 and...

  11. Heteroepitaxial growth of GaN/Si (111) junctions in ammonia-free atmosphere: Charge transport, optoelectronic, and photovoltaic properties

    SciTech Connect (OSTI)

    Saron, K. M. A.; Hashim, M. R. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, Penang 11800 (Malaysia); Allam, Nageh K. [Energy Materials Laboratory (EML), Department of Physics, School of Sciences and Engineering, The American University in Cairo, New Cairo 11835 (Egypt)

    2013-03-28T23:59:59.000Z

    We report the catalyst-free growth of gallium nitride (GaN) nanostructures on n-Si (111) substrates using physical vapor deposition via thermal evaporation of GaN powder at 1150 Degree-Sign C in the absence of NH{sub 3} gas. Scanning electron microscopy and energy dispersive x-ray analysis indicate that the growth rate of GaN nanostructures varies with deposition time. Photoluminescence spectra showed the suppression of the UV emission and the enhancement of the visible band emission with increasing the deposition time. The fabricated GaN nanostructures exhibited p-type behavior at the GaN/Si interface, which can be related to the diffusion of Ga into the Si substrate. The obtained lowest reflection and highest transmittance over a wide wavelength range (450-750 nm) indicate the high quality of the fabricated GaN films. Hall-effect measurements showed that all fabricated films have p-type behavior with decreasing electron concentration from 10{sup 21} to 10{sup 12} cm{sup -3} and increasing the electron mobility from 50 to 225 cm{sup 2}/V s with increasing the growth time. The fabricated solar cell based on the 1 h-deposited GaN nanostructures on n-Si (111) substrate showed a well-defined rectifying behavior with a rectification ratio larger than 8.32 Multiplication-Sign 10{sup 3} in dark. Upon illumination (30 mW/cm{sup 2}), the 1 h-deposited heterojunction solar cell device showed a conversion efficiency of 5.78%. The growth of GaN in the absence of NH{sub 3} gas has strong effect on the morphological, optical, and electrical properties and consequently on the efficiency of the solar cell devices made of such layers.

  12. Compositionally-graded InGaAsInGaP alloys and GaAsSb alloys for metamorphic InP on GaAs

    E-Print Network [OSTI]

    Compositionally-graded InGaAs­InGaP alloys and GaAsSb alloys for metamorphic InP on GaAs Li Yang a of tandem graded layers of InGaAs and InGaP with compositional grading of the In concentration. This tandem

  13. 8798_FL

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

    AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del(ANL-IN-03-032) -Less isNFebruaryOctober 2, AlgeriaQ1 Q2 Q3 U . S .1α,RESEARCH

  14. Hydrogen Storage Properties of New Hydrogen-Rich BH3NH3-Metal...

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

    Storage Properties of New Hydrogen-Rich BH3NH3-Metal Hydride (TiH2, ZrH2, MgH2, andor CaH2) Composite Systems. Hydrogen Storage Properties of New Hydrogen-Rich BH3NH3-Metal...

  15. DOE - Office of Legacy Management -- University of Miami - FL 0-01

    Office of Legacy Management (LM)

    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 742EnergyOn AprilA group currentBradleyTableSelling Corp -K LeDowntownUnited NuclearMiami - FL 0-01

  16. 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

  17. Polarization-engineered GaN/InGaN/GaN tunnel diodes

    E-Print Network [OSTI]

    Sriram Krishnamoorthy; Digbijoy N. Nath; Fatih Akyol; Pil Sung Park; Michele Esposto; Siddharth Rajan

    2010-08-24T23:59:59.000Z

    We report on the design and demonstration of polarization-engineered GaN/InGaN/GaN tunnel junction diodes with high current density and low tunneling turn-on voltage. Wentzel-Kramers-Brillouin (WKB) calculations were used to model and design tunnel junctions with narrow bandgap InGaN-based barrier layers. N-polar p-GaN/In0.33Ga0.67N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient zero bias tunneling turn-on with a high current density of 118 A/cm2 at a reverse bias of 1V, reaching a maximum current density up to 9.2 kA/cm2 were obtained. These results represent the highest current density reported in III-nitride tunnel junctions, and demonstrate the potential of III-nitride tunnel devices for a broad range of optoelectronic and electronic applications.

  18. 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

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

    E-Print Network [OSTI]

    Nabben, Reinhard

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

  20. OPTICAL CONSTANTS OF NH{sub 3} AND NH{sub 3}:N{sub 2} AMORPHOUS ICES IN THE NEAR-INFRARED AND MID-INFRARED REGIONS

    SciTech Connect (OSTI)

    Zanchet, Alexandre; Rodríguez-Lazcano, Yamilet; Gálvez, Óscar; Herrero, Víctor J.; Escribano, Rafael; Maté, Belén, E-mail: belen.mate@csic.es [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, E-28006 Madrid (Spain)

    2013-11-01T23:59:59.000Z

    Ammonia ice has been detected on different astrophysical media ranging from interstellar medium (ISM) particles to the surface of various icy bodies of our solar system, where nitrogen is also present. We have carried out a detailed study of amorphous NH{sub 3} ice and NH{sub 3}:N{sub 2} ice mixtures, based on infrared (IR) spectra in the mid-IR (MIR) and near-IR (NIR) regions, supported by theoretical quantum chemical calculations. Spectra of varying ice thicknesses were obtained and optical constants were calculated for amorphous NH{sub 3} at 15 K and 30 K and for a NH{sub 3}:N{sub 2} mixture at 15 K over a 500-7000 cm{sup –1} spectral range. These spectra have improved accuracy over previous data, where available. Moreover, we also obtained absolute values for the band strengths of the more prominent IR features in both spectral regions. Our results indicate that the estimated NH{sub 3} concentration in ISM ices should be scaled upward by ?30%.

  1. 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.

  2. 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

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

    SciTech Connect (OSTI)

    Möreke, Janina, E-mail: janina.moereke@bristol.ac.uk; Uren, Michael J.; Kuball, Martin [H.H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Novikov, Sergei V.; Foxon, C. Thomas [Department of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Hosseini Vajargah, Shahrzad; Wallis, David J.; Humphreys, Colin J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Haigh, Sarah J. [Super STEM Laboratory, STFC Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD (United Kingdom); School of Materials, University of Manchester, Manchester M13 9PL (United Kingdom); Al-Khalidi, Abdullah; Wasige, Edward; Thayne, Iain [School of Engineering, University of Glasgow, Rankine Bldg, Oakfield Avenue, Glasgow G12 8LT (United Kingdom)

    2014-07-07T23:59:59.000Z

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

  4. Experimental and theoretical studies of reactions of neutral vanadium and tantalum oxide clusters with NO and NH3

    E-Print Network [OSTI]

    Rocca, Jorge J.

    molecules on the respective clusters. A gas mixture of NO:NH3 9:1 is also added into the fast flow reactor oxide clusters with NO, NH3, and an NO/NH3 mixture in a fast flow reactor are investigated by time, a complete elucidation of the reaction mechanism has not been achieved, and very few, if any, gas phase

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

    E-Print Network [OSTI]

    Svane, Axel Torstein

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

  6. Cross-sectional Scanning Tunneling Microscopy and Spectroscopy of InGaP/GaAs Heterojunctions

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Cross-sectional Scanning Tunneling Microscopy and Spectroscopy of InGaP/GaAs Heterojunctions Y Abstract Compositionally abrupt InGaP/GaAs heterojunctions grown by gas-source molecular beam epitaxy have the InGaP layer show non-uniform In and Ga distribution. About 1.5 nm of transition region

  7. 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

  8. 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

  9. Beta decay of Ga-62 

    E-Print Network [OSTI]

    Hyman, BC; Iacob, VE; Azhari, A.; Gagliardi, Carl A.; Hardy, John C.; Mayes, VE; Neilson, RG; Sanchez-Vega, M.; Tang, X.; Trache, L.; Tribble, Robert E.

    2003-01-01T23:59:59.000Z

    We report a study of the beta decay of Ga-62, whose dominant branch is a superallowed 0(+)-->0(+) transition to the ground state of Zn-62. We find the total half-life to be 115.84+/-0.25 ms. This is the first time that the Ga-62 half-life has been...

  10. Influence of GaAs surface termination on GaSb/GaAs quantum dot structure and band offsets

    SciTech Connect (OSTI)

    Zech, E. S.; Chang, A. S.; Martin, A. J.; Canniff, J. C.; Millunchick, J. M. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Lin, Y. H. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

    2013-08-19T23:59:59.000Z

    We have investigated the influence of GaAs surface termination on the nanoscale structure and band offsets of GaSb/GaAs quantum dots (QDs) grown by molecular-beam epitaxy. Transmission electron microscopy reveals both coherent and semi-coherent clusters, as well as misfit dislocations, independent of surface termination. Cross-sectional scanning tunneling microscopy and spectroscopy reveal clustered GaSb QDs with type I band offsets at the GaSb/GaAs interfaces. We discuss the relative influences of strain and QD clustering on the band offsets at GaSb/GaAs interfaces.

  11. Regulatory Safety Issues in the Structural Design Criteria of ASME Section III Subsection NH and for Very High Temperatures for VHTR & GEN IV

    SciTech Connect (OSTI)

    William J. O’Donnell; Donald S. Griffin

    2007-05-07T23:59:59.000Z

    The objective of this task is to identify issues relevant to ASME Section III, Subsection NH [1], and related Code Cases that must be resolved for licensing purposes for VHTGRs (Very High Temperature Gas Reactor concepts such as those of PBMR, Areva, and GA); and to identify the material models, design criteria, and analysis methods that need to be added to the ASME Code to cover the unresolved safety issues. Subsection NH was originally developed to provide structural design criteria and limits for elevated-temperature design of Liquid Metal Fast Breeder Reactor (LMFBR) systems and some gas-cooled systems. The U.S. Nuclear Regulatory Commission (NRC) and its Advisory Committee for Reactor Safeguards (ACRS) reviewed the design limits and procedures in the process of reviewing the Clinch River Breeder Reactor (CRBR) for a construction permit in the late 1970s and early 1980s, and identified issues that needed resolution. In the years since then, the NRC and various contractors have evaluated the applicability of the ASME Code and Code Cases to high-temperature reactor designs such as the VHTGRs, and identified issues that need to be resolved to provide a regulatory basis for licensing. This Report describes: (1) NRC and ACRS safety concerns raised during the licensing process of CRBR , (2) how some of these issues are addressed by the current Subsection NH of the ASME Code; and (3) the material models, design criteria, and analysis methods that need to be added to the ASME Code and Code Cases to cover unresolved regulatory issues for very high temperature service.

  12. Characterization of Cu-SSZ-13 NH3 SCR Catalysts: an in situ FTIR...

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

    of Cu-SSZ-13 NH3 SCR Catalysts: an in situ FTIR Study. Abstract: The adsorption of CO and NO over Cu-SSZ-13 zeolite catalysts, highly active in the selective...

  13. Selective Catalytic Oxidation (SCO) of NH3 to N2 for Hot Exhaust...

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

    Oxidation (SCO) of NH3 to N2 for Hot Exhaust Treatment Investigation of a series of transition metal oxides and precious metal based catalysts for ammonia selective oxidation at...

  14. Fe/SSZ-13 as an NH3-SCR Catalyst: A Reaction Kinetics andFTIR...

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

    as an NH3-SCR Catalyst: A Reaction Kinetics and FTIRMssbauer Spectroscopic Study."Applied Catalysis. B, Environmental 164:407-419. doi:10.1016j.apcatb.2014.09.031 Authors:...

  15. Low Temperature Milling of the LiNH2 + LiH Hydrogen Storage System...

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

    Hu, JH Kwak, and Z Yang.2009."Low Temperature Milling of the LiNH2 + LiH Hydrogen Storage System."International Journal of Hydrogen Energy 34(10):4331-4339. doi:10.1016...

  16. Structures of the Kplus and NH4 Forms of Linde J

    SciTech Connect (OSTI)

    R Broach; R Kirchner

    2011-12-31T23:59:59.000Z

    The aluminosilicate zeolite Linde J has a unique topology. The structures of the K{sup +} and NH{sub 4}{sup +} forms of Linde J ([X{sub 2}(H{sub 2}O)][Si{sub 2}Al{sub 2}O{sub 8}] where X = K or NH{sub 4}) are identical except for slight cell size and positional differences due to NH{sub 4}{sup +} being larger than K{sup +} cations. The space group is P2{sub 1}2{sub 1}2{sub 1}. Cell dimensions are: K{sup +} Linde J, a = 9.4577(2) {angstrom}, b = 9.5573(2) {angstrom}, c = 9.9429(2) {angstrom}; NH{sub 4}{sup +} Linde J, a = 9.6324(4) {angstrom}, b = 9.6423(3) {angstrom}, c = 10.0230(3) {angstrom}. Zigzag 8-ring channels intersect giving a 2-D pore system.

  17. Structures of the K[superscript +] and NH[subscript 4 superscript +] forms of Linde J

    SciTech Connect (OSTI)

    Broach, Robert W.; Kirchner, Richard M. (UOP); (Manhattan C)

    2011-11-17T23:59:59.000Z

    The aluminosilicate zeolite Linde J has a unique topology. The structures of the K{sup +} and NH{sub 4}{sup +} forms of Linde J ([X{sub 2}(H{sub 2}O)][Si{sub 2}Al{sub 2}O{sub 8}] where X = K or NH{sub 4}) are identical except for slight cell size and positional differences due to NH{sub 4}{sup +} being larger than K{sup +} cations. The space group is P2{sub 1}2{sub 1}2{sub 1}. Cell dimensions are: K{sup +} Linde J, a = 9.4577(2) {angstrom}, b = 9.5573(2) {angstrom}, c = 9.9429(2) {angstrom}; NH{sub 4}{sup +} Linde J, a = 9.6324(4) {angstrom}, b = 9.6423(3) {angstrom}, c = 10.0230(3) {angstrom}. Zigzag 8-ring channels intersect giving a 2-D pore system.

  18. Breath gating of cardiac PET using 13N-NH3: An optimization

    E-Print Network [OSTI]

    was carried out using 13 N-NH3 on two dierent PET/CT scanners: a Siemens Biograph 64 and a Siemens mCT PET. In this project the breath-motion was estimated using an ane transformation on the obtained images, from which- jekt er udført ved brug af 13 N-NH3 på to skannere, henholdsvis en Siemens Biograph 64 og en Siemens m

  19. By Joseph M. Gambogi Titanium (Ti) is a lightweight metal well Springs, FL; E. I. du Pont de Nemours & Co.

    E-Print Network [OSTI]

    1 TITANIUM By Joseph M. Gambogi Titanium (Ti) is a lightweight metal well Springs, FL; E. I. du mineral strength-to-weight ratio. Titanium comprises sands deposits; and P. W. Gillibrand Co., Simi about, rutile, and producer of natural rutile. Kerr-McGee sphene. Although titanium is best known for its

  20. Direct measurement of the reactivity of NH and OH on a silicon nitride surface

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P.; Breiland, W.G. [Sandia National Labs., Albuquerque, NM (United States); Fisher, E.R. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Chemistry

    1993-12-31T23:59:59.000Z

    In order to understand and successfully model the plasma processing used in device fabrication, it is important to determine the role played by plasma-generated radicals. The authors have used the IRIS technique (Imaging of Radicals Interacting Surfaces) to obtain the reactivity of NH (X{sup 3}S{sup {minus}}) and OH (X{sup 2}P) at a silicon nitride film surface while the film is exposed to a plasma-type environment. The reactivity of NH was found to be zero both during exposure of the surface to an NH{sub 3} plasma and during active deposition of silicon nitride from a SiH{sub 4}/NH{sub 3} plasma. No NH surface reaction was detectable for any rotational states of NH and over a surface temperature range of 300--700 K. OH radicals generated in an H{sub 2}O plasma were found to have a reactivity of 0.57 on a room temperature oxidized silicon nitride surface. The OH reactivity falls to zero as the temperature of the substrate is raised.

  1. Multiple-band-edge quantum-well intermixing in the InGaAs/InGaAsP/InGaP material system

    E-Print Network [OSTI]

    Coldren, Larry A.

    Multiple-band-edge quantum-well intermixing in the InGaAs/InGaAsP/InGaP material system Erik J InGaAs/InGaAsP/InGaP material system. © 2005 American Institute of Physics. DOI: 10 of achieving QWI in such active regions.3,4 However, InGaAs/InGaAsP/InGaP-based de- vices offer numerous

  2. GaInNAs laser gain

    SciTech Connect (OSTI)

    CHOW,WENG W.; JONES,ERIC D.; MODINE,NORMAND A.; KURTZ,STEVEN R.; ALLERMAN,ANDREW A.

    2000-05-23T23:59:59.000Z

    The optical gain spectra for GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of the lasing threshold current density of GaInNAs/GaAs quantum well structures.

  3. 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 ...

  4. A Complete Survey of the Central Molecular Zone in NH3

    E-Print Network [OSTI]

    Takumi Nagayama; Toshihiro Omodaka; Toshihiro Handa; Hayati Bebe Hajra Iahak; Tsuyoshi Sawada; Takeshi Miyaji; Yasuhiro Koyama

    2007-07-06T23:59:59.000Z

    We present a map of the major part of the central molecular zone (CMZ) of simultaneous observations in the NH3 (J,K) = (1,1) and (2,2) lines using the Kagoshima 6-m telescope. The mapped area is -1.000 80 K contain 75% and 25% of the total NH3 flux, respectively. These temperatures indicate that the dense molecular gas in the CMZ is dominated by gas that is warmer than the majority of the dust present there. A comparison with the CO survey by Sawada et al. (2001) shows that the NH3 emitting region is surrounded by a high pressure region on the l-v plane. Although NH3 emission traces dense gas, it is not extended into a high pressure region. Therefore, the high pressure region is less dense and has to be hotter. This indicates that the molecular cloud complex in the Galactic center region has a ``core'' of dense and warm clouds which are traced by the NH3 emission, and an ``envelope'' of less dense and hotter gas clouds. Besides heating by ambipolar diffusion, the hot plasma gas emitting the X-ray emission may heat the hot ``envelope''.

  5. Thermal Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx Reduction

    SciTech Connect (OSTI)

    Schmieg, Steven J.; Oh, Se H.; Kim, Chang H.; Brown, David B.; Lee, Jong H.; Peden, Charles HF; Kim, Do Heui

    2012-04-30T23:59:59.000Z

    Multiple catalytic functions (NOx conversion, NO and NH3 oxidation, NH3 storage) of a commercial Cu-zeolite urea/NH3-SCR catalyst were assessed in a laboratory fixed-bed flow reactor system after differing degrees of hydrothermal aging. Catalysts were characterized by using x-ray diffraction (XRD), 27Al solid state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) / energy dispersive X-ray (EDX) spectroscopy to develop an understanding of the degradation mechanisms during catalyst aging. The catalytic reaction measurements of laboratory-aged catalysts were performed, which allows us to obtain a universal curve for predicting the degree of catalyst performance deterioration as a function of time at each aging temperature. Results show that as the aging temperature becomes higher, the zeolite structure collapses in a shorter period of time after an induction period. The decrease in SCR performance was explained by zeolite structure destruction and/or Cu agglomeration, as detected by XRD/27Al NMR and by TEM/EDX, respectively. Destruction of the zeolite structure and agglomeration of the active phase also results in a decrease in the NO/NH3 oxidation activity and the NH3 storage capacity of the catalyst. Selected laboratory aging conditions (16 h at 800oC) compare well with a 135,000 mile vehicle-aged catalyst for both performance and characterization criteria.

  6. 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

  7. Comparison of Chloroflexus aurantiacus strain J-10-fl proteomes of cells grown chemoheterotrophically and photoheterotrophically

    SciTech Connect (OSTI)

    Cao, Li; Bryant, Donald A.; Schepmoes, Athena A.; Vogl, Kajetan; Smith, Richard D.; Lipton, Mary S.; Callister, Stephen J.

    2012-01-17T23:59:59.000Z

    Chloroflexus aurantiacus J-10-fl is a thermophilic green bacterium, a filamentous anoxygenic phototroph, and the model organism of the phylum Chloroflexi. We applied high-throughput, liquid chromatography-mass spectrometry in a global quantitative proteomics investigation of C. aurantiacus cells grown under oxic (chemoorganoheterotrophically) and anoxic (photoorganoheterotrophically) redox states. Our global analysis identified 13,524 high-confidence peptides that matched to 1,286 annotated proteins, 242 of which were either uniquely identified or significantly increased in abundance under anoxic culture conditions. Fifty-three of the 242 proteins are previously characterized photosynthesis-related proteins, including chlorosome proteins, proteins involved in the bacteriochlorophyll biosynthesis, 3-hydroxypropionate (3-OHP) CO2 fixation pathway, and components of electron transport chains. The remaining 190 proteins have not previously been reported. Of these, five proteins were found to be encoded by genes from a novel operon and observed only in photoheterotrophically grown cells. These proteins candidates may prove useful in further deciphering the phototrophic physiology of C. aurantiacus and other filamentous anoxygenic phototrophs.

  8. A Review & Assessment of Current Operating Conditions Allowable Stresses in ASME Section III Subsection NH

    SciTech Connect (OSTI)

    R. W. Swindeman

    2009-12-14T23:59:59.000Z

    The current operating condition allowable stresses provided in ASME Section III, Subsection NH were reviewed for consistency with the criteria used to establish the stress allowables and with the allowable stresses provided in ASME Section II, Part D. It was found that the S{sub o} values in ASME III-NH were consistent with the S values in ASME IID for the five materials of interest. However, it was found that 0.80 S{sub r} was less than S{sub o} for some temperatures for four of the materials. Only values for alloy 800H appeared to be consistent with the criteria on which S{sub o} values are established. With the intent of undertaking a more detailed evaluation of issues related to the allowable stresses in ASME III-NH, the availabilities of databases for the five materials were reviewed and augmented databases were assembled.

  9. Composition and Interface Analysis of InGaN/GaN Multiquantum...

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

    Composition and Interface Analysis of InGaNGaN Multiquantum-Wells on GaN Substrates Using Atom Probe Tomography. Composition and Interface Analysis of InGaNGaN Multiquantum-Wells...

  10. FSU Health Compliance Record fax to 8506448958 or mail to 960 Learning Way, Tallahassee, FL 323064178 Part A--Print or type. Illegible forms will not be processed.

    E-Print Network [OSTI]

    Weston, Ken

    323064178 Part A--Print or type. Illegible forms will not be processed. STUDENT NAME, Tallahassee, FL 323064178 Part A--Print or type. Illegible forms will not be processed. STUDENT

  11. 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}.

  12. PRESSURE DEPENDENCE OF OPTICAL TRANSITIONS IN InGaN/GaN MULTIPLE QUANTUM WELLS

    E-Print Network [OSTI]

    McCluskey, Matthew

    -µm thick GaN layer deposited on a sapphire substrate, and it is capped by a 0.2-µm GaN:Mg pPRESSURE DEPENDENCE OF OPTICAL TRANSITIONS IN InGaN/GaN MULTIPLE QUANTUM WELLS W. Shan,* J.W. Ager pressure on optical transitions in InGaN/GaN multiple quantum wells (MQWs) has been studied

  13. 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

  14. InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular-beam epitaxy with a valved phosphorus cracker

    E-Print Network [OSTI]

    Woodall, Jerry M.

    InGaP/GaAs/InGaP double-heterojunction bipolar transistors grown by solid-source molecular; accepted 17 November 1995 The growth and device characterization of an InGaP/GaAs double-quality phosphorus-containing compounds.1­4 The growth of high-performance InGaP/ GaAs and InGaAs/InP single

  15. InGaP/InGaAsN/GaAs NpN double-heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P. C. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Baca, A. G. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Li, N. Y. [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States)] [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States); Xie, X. M. [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States)] [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States); Hou, H. Q. [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States)] [Emcore Photovoltaics, Emcore Corporation, Albuquerque, New Mexico 87123 (United States); Armour, E. [Emcore Corporation, Somerset, New Jersey 08873 (United States)] [Emcore Corporation, Somerset, New Jersey 08873 (United States)

    2000-04-17T23:59:59.000Z

    We have demonstrated a functional NpN double-heterojunction bipolar transistor (DHBT) using InGaAsN for the base layer. The InGaP/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs DHBT has a low V{sub ON} of 0.81 V, which is 0.13 V lower than in a InGaP/GaAs heterojunction bipolar transistor (HBT). The lower turn-on voltage is attributed to the smaller band gap (1.20 eV) of metalorganic chemical vapor deposition-grown In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} base layer. GaAs is used for the collector; thus the breakdown voltage (BV{sub CEO}) is 10 V, consistent with the BV{sub CEO} of InGaP/GaAs HBTs of comparable collector thickness and doping level. To alleviate the current blocking phenomenon caused by the larger conduction band discontinuity between InGaAsN and GaAs, a graded InGaAs layer with {delta} doping is inserted at the base-collector junction. The improved device has a peak current gain of seven with ideal current-voltage characteristics. (c) 2000 American Institute of Physics.

  16. InGaP/InGaAsN/GaAs NpN double heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Chang, P.C.; Baca, A.G.; Li, N.Y.; Xie, X.M.; Sharps, P.R.; Hou, H.Q.

    2000-01-10T23:59:59.000Z

    The authors have demonstrated a functional NpN double heterojunction bipolar transistor (DHBT) using InGaAsN for base layer. The InGaP/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}/GaAs DHBT has a low V{sub ON} of 0.81 V, which is 0.13 V lower than in a InGaP/GaAs HBT. The lower V{sub ON} is attributed to the smaller bandgap (E{sub g}=1.20eV) of MOCVD grown In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} base layer. GaAs is used for the collector; thus the BV{sub CEO} is 10 V, consistent with the BV{sub CEO} of InGaP/GaAs Hbts of comparable collector thickness and doping level. To alleviate the current blocking phenomenon caused by the larger {triangle}E{sub C} between InGaAsN and GaAs, a graded InGaAs layer with {delta}-doping is inserted at the base-collector junction. The improved device has a peak current gain of 7 with ideal IV characteristics.

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

    E-Print Network [OSTI]

    Sirenko, Andrei

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

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

    E-Print Network [OSTI]

    Tu, Charles W

    2000-01-01T23:59:59.000Z

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

  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. Superior radiation-resistant properties of InGaP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Yamaguchi, M.; Okuda, T.; Taylor, S.J.; Takamoto, T. [Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468 (Japan)] [Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468 (Japan); Ikeda, E.; Kurita, H. [Central Resource Laboratory, Japan Energy Company, Niizo-Minami, Toda, Saitama 335 (Japan)] [Central Resource Laboratory, Japan Energy Company, Niizo-Minami, Toda, Saitama 335 (Japan)

    1997-03-01T23:59:59.000Z

    The observation of minority-carrier injection-enhanced annealing of radiation damage to InGa{sub 0.5}P{sub 0.5}/GaAs tandem solar cells is reported. Radiation resistance of InGaP/GaAs tandem solar cells as is similar with GaAs-on-Ge cells have been confirmed with 1 MeV electron irradiations. Moreover, minority-carrier injection under light illumination and forward bias conditions is shown to enhance defect annealing in InGaP and to result in the recovery of InGaP/GaAs tandem solar cell properties. These results suggest that the InGaP/GaAs(/Ge) multijunction solar cells and InGaP-based devices have great potential for space applications. {copyright} {ital 1997 American Institute of Physics.}

  1. Synthesis and Characterization of Th2N2(NH) Isomorphous to Th2N3

    SciTech Connect (OSTI)

    Silva, G W Chinthaka M [ORNL; Yeamans, Charles B. [University of California, Berkeley; Hunn, John D [ORNL; Sattelberger, Alfred P [Argonne National Laboratory (ANL); Czerwinski, Ken R. [University of Nevada, Las Vegas; Weck, Dr. Phil F [University of Nevada, Las Vegas

    2012-01-01T23:59:59.000Z

    Using a new, low-temperature, fluoride-based process, thorium nitride imide of the chemical formula Th{sub 2}N{sub 2}(NH) was synthesized from thorium dioxide via an ammonium thorium fluoride intermediate. The resulting product phase was characterized by powder X-ray diffraction (XRD) analysis and was found to be crystallographically similar to Th{sub 2}N{sub 3}. Its unit cell was hexagonal with a space group of P3m{bar 1} and lattice parameters of a = b = 3.886(1) and c = 6.185(2) {angstrom}. The presence of -NH in the nitride phase was verified by Fourier transform infrared spectroscopy (FTIR). Total energy calculations performed using all-electron scalar relativistic density functional theory (DFT) showed that the hydrogen atom in the Th{sub 2}N{sub 2}(NH) prefers to bond with nitrogen atoms occupying 1a Wyckoff positions of the unit cell. Lattice fringe disruptions observed in nanoparticle areas of the nitride species by high-resolution transmission electron microscopic (HRTEM) images also displayed some evidence for the presence of -NH group. As ThO{sub 2} was identified as an impurity, possible reaction mechanisms involving its formation are discussed.

  2. Synthesis and Evaluation of Cu/SAPO-34 Catalysts for NH3-SCR...

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

    of CuSAPO-34 Catalysts for NH3-SCR 2: Solid-state Ion Exchange and One-pot Synthesis."Applied Catalysis. B, Environmental 162:501-514. doi:10.1016j.apcatb.2014.07.029 Authors:...

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

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

    Ertem, Mehmed Z. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yale Univ., New Haven, CT (United States); Kharche, Neerav [Brookhaven National Lab. (BNL), Upton, NY (United States); Batista, Victor S. [Yale Univ., New Haven, CT (United States); Hybertsen, Mark S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tully, John C. [Yale Univ., New Haven, CT (United States); Muckerman, James T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-04-03T23:59:59.000Z

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

  4. Bridging the Causeway: A Center for Healthcare Policy and Research Symposium

    E-Print Network [OSTI]

    Carmichael, Owen

    TN MS AL GA FL SC VA WV OH MI NY PA MD DE NJ CT RI MA ME VT NH AK HI FY06 CTSA Grantees (12) FY07 CTSA Grantees (12) #12;NIH and Institutions: Working together as a National Consortium Informatics

  5. STRUCTURE OF PENTAKIS (UREA) DIOXOURANIUM(VI)NITRATE LUO2 (OC (NH2)2)5 (NO3) 2

    E-Print Network [OSTI]

    Zalkin, Allan

    2011-01-01T23:59:59.000Z

    2(OC(NH 2 )2)5](N0 3 )2 by Allan Zalkin*, Helena Ruben andU0 2 (OC(NH 2)2)5](N0 3)2 by Allan Zalkin, Hel~na Ruben and

  6. Beta decay of Ga-62

    E-Print Network [OSTI]

    Hyman, BC; Iacob, VE; Azhari, A.; Gagliardi, Carl A.; Hardy, John C.; Mayes, VE; Neilson, RG; Sanchez-Vega, M.; Tang, X.; Trache, L.; Tribble, Robert E.

    2003-01-01T23:59:59.000Z

    from the ex- perimental ft value for a 01?01 b decay between analog states with the relation @3# 0556-2813/2003/68~1!/015501~6!/$20.00 68 015501- of 62Ga . Hardy, V. E. Mayes, R. G. Neilson, M. Sanchez-Vega, and R. E. Tribble y, College Station...

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

    E-Print Network [OSTI]

    Espinosa, Horacio D.

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

  8. 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 ...

  9. 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

  10. New GaInP/GaAs/GaInAs, Triple-Bandgap, Tandem Solar Cell for High-Efficiency Terrestrial Concentrator Systems

    SciTech Connect (OSTI)

    Kurtz, S.; Wanlass, M.; Kramer, C.; Young, M.; Geisz, J.; Ward, S.; Duda, A.; Moriarty, T.; Carapella, J.; Ahrenkiel, P.; Emery. K.; Jones, K.; Romero, M.; Kibbler, A.; Olson, J.; Friedman, D.; McMahon, W.; Ptak, A.

    2005-11-01T23:59:59.000Z

    GaInP/GaAs/GaInAs three-junction cells are grown in an inverted configuration on GaAs, allowing high quality growth of the lattice matched GaInP and GaAs layers before a grade is used for the 1-eV GaInAs layer. Using this approach an efficiency of 37.9% was demonstrated.

  11. InAs=InGaP=GaAs heterojunction power Schottky rectifiers

    E-Print Network [OSTI]

    Woodall, Jerry M.

    InAs=InGaP=GaAs heterojunction power Schottky rectifiers A. Chen, M. Young and J.M. Woodall A low-matched InGaP on GaAs, to make a high-temperature power rectifier. The LT molecular beam epitaxy technique enables the formation of an abrupt interface between InAs and InGaP. This heterojunction rectifier

  12. 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

  13. Role of strain in polarization switching in semipolar InGaN/GaN quantum wells

    E-Print Network [OSTI]

    Role of strain in polarization switching in semipolar InGaN/GaN quantum wells Qimin Yan,1,a Patrick November 2010 The effect of strain on the valence-band structure of 112¯2 semipolar InGaN grown on GaN D6 is calculated for GaN and InN using density functional theory with the Heyd­Scuseria­ Ernzerhof

  14. 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

  15. Fractal Inspired Models of Quark and Gluon Distributions and Longitudinal Structure Function FL(x, Q2) at small x

    E-Print Network [OSTI]

    Akbari Jahan; D. K. Choudhury

    2010-12-30T23:59:59.000Z

    In recent years, Fractal Inspired Models of quark and gluon densities at small x have been proposed. In this paper, we investigate longitudinal structure function F-L (x, Q2) within this approach. We make predictions using the QCD based approximate relation between the longitudinal structure function and the gluon density. As the Altarelli-Martinelli equation for the longitudinal structure function cannot be applied to Model I due to the presence of a singularity in the Bjorken x-space we consider Model II only. The qualitative feature of the prediction of Model II is found to be compatible with the QCD expectation.

  16. 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.

  17. 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.

  18. Strain variations in InGaAsP/InGaP superlattices studied by scanning probe microscopy

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Strain variations in InGaAsP/InGaP superlattices studied by scanning probe microscopy Huajie Chen, Kista, Sweden Abstract Strain-compensated InGaAsP/InGaP superlattices are studied in cross- section. The strain compensated InGaAsP/InGaP/InP superlattices studied here have application for light sources

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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.

  5. Planetary fluids He and NH/sub 3/ at high shock pressures and temperatures

    SciTech Connect (OSTI)

    Nellis, W.J.; Radousky, H.B.; Mitchell, A.C.; Holmes, N.C.; Ross, M.; Young, D.A.

    1985-04-01T23:59:59.000Z

    Liquid He at 4.3 K and 1 atm was shocked to 16 GPa (160 kbar) and 12,000 K and double-shocked to 56 GPa and 21,000 K. Liquid perturbation theory was used to determine an effective interatomic potential from which the equation of state of He can be obtained over a wide range of densities and temperatures in the envelopes of the outer planets. A new fast optical pyrometer and a cryogenic specimen holder for liquid NH/sub 3/ were developed to measure shock temperatures of 4400 and 3600 K at pressures of 59 and 48 GPa. These conditions correspond to those in the ice layers in Uranus and Neptune. The shock temperature data are in reasonable agreement with an equation of state by Ree based on an intermolecular potential derived from NH/sub 3/ Hugoniot data.

  6. High efficiency InGaP solar cells for InGaP/GaAs tandem cell application

    SciTech Connect (OSTI)

    Takamoto, T.; Ikeda, E.; Kurita, H.; Ohmori, M. [Japan Energy Corp., Toda, Saitama (Japan). Central Research Lab.

    1994-12-31T23:59:59.000Z

    In this paper, high conversion efficiency single junction InGaP solar cells with n-p-p{sup +} structure are presented and their application to InGaP/GaAs monolithic tandem cells is discussed. In the InGaP cells, a best conversion efficiency of 18.48% was achieved by introducing the p{sup +} peak back surface field (BSF) layer with a high carrier concentration of 2 {times} 10{sup 18} cm{sup {minus}3}, which improved both short circuit current (Isc) and open circuit voltage (Voc). However, in the case of InGaP/GaAs tandem cells, a decrease in carrier concentration of the InGaP BSF layer, which was caused by the diffusion of Zn, was found to reduce the Isc and Voc of the tandem cell. The reduction in the carrier concentration was suppressed by using a thicker BSF layer of 0.5 {micro}m, which reduced the current density in the GaAs bottom cell. An InGaP/GaAs tandem cell with 27.3% efficiency and a high Voc of 2.418 V was obtained.

  7. Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phase separation

    E-Print Network [OSTI]

    Relaxed, high-quality InP on GaAs by using InGaAs and InGaP graded buffers to avoid phaseAs was 70% of that on bulk InP at both temperatures. To achieve this, graded buffers in the InGaAs, InGaP

  8. 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

  9. 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

  10. Tracing the evolutionary stage of Bok globules: CCS and NH3

    E-Print Network [OSTI]

    Marka, C; Launhardt, R; Semenov, D A; Henning, Th

    2011-01-01T23:59:59.000Z

    We pursue the investigation of a previously proposed correlation between chemical properties and physical evolutionary stage of isolated low-mass star-forming regions. In the past, the NH3/CCS abundance ratio was suggested to be a potentially useful indicator for the evolutionary stage of cloud cores. We aim to study its applicability for isolated Bok globules. A sample of 42 Bok globules with and without signs of current star formation was searched for CCS(2-1) emission, the observations were complemented with NH3 measurements available in the literature and own observations. The abundance ratio of both molecules is discussed with respect to the evolutionary stage of the objects and in the context of chemical models. The NH3/CCS ratio could be assessed for 18 Bok globules and is found to be moderately high and roughly similar across all evolutionary stages from starless and prestellar cores towards internally heated cores harbouring protostars of Class 0, Class I or later. Bok globules with extremely high CC...

  11. 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.

  12. InGaAsN/GaAs heterojunction for multi-junction solar cells

    DOE Patents [OSTI]

    Kurtz, Steven R. (Albuquerque, NM); Allerman, Andrew A. (Albuquerque, NM); Klem, John F. (Albuquerque, NM); Jones, Eric D. (Edgewood, NM)

    2001-01-01T23:59:59.000Z

    An InGaAsN/GaAs semiconductor p-n heterojunction is disclosed for use in forming a 0.95-1.2 eV bandgap photodetector with application for use in high-efficiency multi-junction solar cells. The InGaAsN/GaAs p-n heterojunction is formed by epitaxially growing on a gallium arsenide (GaAs) or germanium (Ge) substrate an n-type indium gallium arsenide nitride (InGaAsN) layer having a semiconductor alloy composition In.sub.x Ga.sub.1-x As.sub.1-y N.sub.y with 0GaAs layer, with the InGaAsN and GaAs layers being lattice-matched to the substrate. The InGaAsN/GaAs p-n heterojunction can be epitaxially grown by either molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD). The InGaAsN/GaAs p-n heterojunction provides a high open-circuit voltage of up to 0.62 volts and an internal quantum efficiency of >70%.

  13. InGaP/GaAs and InGaAs mechanically-stacked triple-junction solar cells

    SciTech Connect (OSTI)

    Takamoto, T.; Ikeda, E.; Agui, T. [Japan Energy Corp., Toda, Saitama (Japan)] [and others

    1997-12-31T23:59:59.000Z

    Triple-junction cells with AM1.5 efficiencies of over 33% have been demonstrated. A planar type InGaP/GaAs monolithic dual-junction cell was fabricated on a semi-insulating FaAs substrate, which has high infra-red transparency. Then a dual-junction cell, with efficiency of 27--28%, was mechanically stacked on an InGaAs cell fabricated on an InP substrate. The bottom InGaAs cell showed an efficiency of 6.2% under the InGaP/GaAs cell, and a total efficiency of 33--34% was achieved for the four-terminal triple-junction cell.

  14. 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.

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

    SciTech Connect (OSTI)

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

    2011-10-17T23:59:59.000Z

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

  16. Ultra-Thin, Triple-Bandgap GaInP/GaAs/GaInAs Monolithic Tandem Solar Cells

    SciTech Connect (OSTI)

    Wanlass, M. W.; Ahrenkiel, S. P.; Albin, D. S.; Carapella, J. J.; Duda, A.; Emery, K.; Geisz, J. F.; Jones, K.; Kurtz, S.; Moriarty, T.; Romero, M. J.

    2007-02-01T23:59:59.000Z

    The performance of state-of-the-art, series-connected, lattice-matched (LM), triple-junction (TJ), III-V tandem solar cells could be improved substantially (10-12%) by replacing the Ge bottom subcell with a subcell having a bandgap of {approx}1 eV. For the last several years, research has been conducted by a number of organizations to develop {approx}1-eV, LM GaInAsN to provide such a subcell, but, so far, the approach has proven unsuccessful. Thus, the need for a high-performance, monolithically integrable, 1-eV subcell for TJ tandems has remained. In this paper, we present a new TJ tandem cell design that addresses the above-mentioned problem. Our approach involves inverted epitaxial growth to allow the monolithic integration of a lattice-mismatched (LMM) {approx}1-eV GaInAs/GaInP double-heterostructure (DH) bottom subcell with LM GaAs (middle) and GaInP (top) upper subcells. A transparent GaInP compositionally graded layer facilitates the integration of the LM and LMM components. Handle-mounted, ultra-thin device fabrication is a natural consequence of the inverted-structure approach, which results in a number of advantages, including robustness, potential low cost, improved thermal management, incorporation of back-surface reflectors, and possible reclamation/reuse of the parent crystalline substrate for further cost reduction. Our initial work has concerned GaInP/GaAs/GaInAs tandem cells grown on GaAs substrates. In this case, the 1-eV GaInAs experiences 2.2% compressive LMM with respect to the substrate. Specially designed GaInP graded layers are used to produce 1-eV subcells with performance parameters nearly equaling those of LM devices with the same bandgap (e.g., LM, 1-eV GaInAsP grown on InP). Previously, we reported preliminary ultra-thin tandem devices (0.237 cm{sup 2}) with NREL-confirmed efficiencies of 31.3% (global spectrum, one sun) (1), 29.7% (AM0 spectrum, one sun) (2), and 37.9% (low-AOD direct spectrum, 10.1 suns) (3), all at 25 C. Here, we include recent results of testing similar devices under the concentrated AMO spectrum, and also present the first demonstration of a high-efficiency, ultra-thin GaInP/GaAs/GaInAs tandem cell processed on a flexible kapton handle.

  17. 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

  18. 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

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

    E-Print Network [OSTI]

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

  20. Laboratory-measured H2SO4-H2O-NH3 ternary homogeneous nucleation rates: Initial observations

    E-Print Network [OSTI]

    Lee, Shan-Hu

    -ammonia (H2SO4-H2O-NH3) ternary homogeneous nucleation (THN), with a fast flow nucleation reactor attached. 1. Introduction [2] Nucleation is a gas-to-particle conversion process [Seinfeld and Pandis, 2006

  1. Presented in Conway, Lee, Merrimack and Plymouth, NH by the UNHCE Geospatial Outreach Program ArcGIS Workshops Spring 2013

    E-Print Network [OSTI]

    New Hampshire, University of

    , as well as, conduct geospatial analysis. Participants will learn to: symbolize GIS data; add labelsPresented in Conway, Lee, Merrimack and Plymouth, NH by the UNHCE Geospatial Outreach Program Arc

  2. Presented in Concord, Merrimack and West Lebanon, NH by the UNHCE Geospatial Outreach Program ArcGIS Workshops Fall 2012

    E-Print Network [OSTI]

    New Hampshire, University of

    , as well as, conduct geospatial analysis. Participants will learn to: symbolize GIS data; add labelsPresented in Concord, Merrimack and West Lebanon, NH by the UNHCE Geospatial Outreach Program Arc

  3. Presented in Lee and Concord, NH by the UNHCE Geospatial Outreach Program ArcGIS Workshops Winter 2013

    E-Print Network [OSTI]

    New Hampshire, University of

    .1 to produce effective maps, edit and create GIS data, as well as, conduct geospatial analysis. ParticipantsPresented in Lee and Concord, NH by the UNHCE Geospatial Outreach Program ArcGIS Workshops Winter

  4. 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.

  5. 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

  6. Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method

    E-Print Network [OSTI]

    Okamoto, Koichi

    Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method; 78.55.Cr; 78.67.De; S7.14 Carrier dynamics in GaN and InGaN/GaN SQW structures were observed by using inhomogeneity of In composition. Recently, InGaN/GaN-based light emitting diodes (LEDs) have been commercialized

  7. 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 ...

  8. Development and Industrialization of InGaN/GaN LEDs on Patterned...

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

    of InGaNGaN LEDs on Patterned Sapphire Substrates for Low Cost Emitter Architecture Development and Industrialization of InGaNGaN LEDs on Patterned Sapphire...

  9. 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 ...

  10. Siemens Pittsburgh, PA Novelis Corporation Atlanta, GA

    E-Print Network [OSTI]

    McGaughey, Alan

    Industrial Design ­ Shanghai, China Eaton Corporation ­ Pittsburgh, PA CMU, CTTEC ­ PittsburghSiemens ­ Pittsburgh, PA Novelis Corporation ­ Atlanta, GA Expense

  11. Structural transitions of ternary imide Li{sub 2}Mg(NH){sub 2} for hydrogen storage

    SciTech Connect (OSTI)

    Liang, C. [College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); State Key Laboratory of Silicon Materials, Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Gao, M. X.; Pan, H. G., E-mail: hgpan@zju.edu.cn; Liu, Y. F. [State Key Laboratory of Silicon Materials, Key Laboratory of Advanced Materials and Applications for Batteries of Zhejiang Province and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2014-08-25T23:59:59.000Z

    Phase transitions and energetic properties of Li{sub 2}Mg(NH){sub 2} with different crystal structures are investigated by experiments and first-principles calculations. The Li{sub 2}Mg(NH){sub 2} with the primitive cubic and orthorhombic structure is obtained by dynamically dehydrogenating a Mg(NH{sub 2}){sub 2}-2LiH mixture up to 280?°C under an initial vacuum and 9.0?bars H{sub 2}, respectively. It is found that the obtained orthorhombic Li{sub 2}Mg(NH){sub 2} is converted to a primitive cubic structure as the dehydrogenation temperature is further increased to 400?°C or performed by a 36?h of high-energetic ball milling. Moreover, the primitive cubic phase can be converted to an orthorhombic phase after heating at 280?°C under 9.0?bars H{sub 2} for 1?h. Thermodynamic calculations show that the orthorhombic phase is the ground state structure of Li{sub 2}Mg(NH){sub 2}. The mechanism for phase transitions of Li{sub 2}Mg(NH){sub 2} is also discussed from the angle of energy.

  12. Strain-balanced InGaN/GaN multiple quantum wells

    SciTech Connect (OSTI)

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

    2014-07-21T23:59:59.000Z

    InGaN/GaN multiple quantum well (MQW) structures suffer from a high amount of compressive strain in the InGaN wells and the accompanied piezoelectric field resulting in both a blue shift in emission and a reduction of emission intensity. We report the growth of In{sub x}Ga{sub 1?x}N/GaN “strain-balanced” multiple quantum wells (SBMQWs) grown on thick In{sub y}Ga{sub 1?y}N templates for x?>?y by metal organic chemical vapor deposition. SBMQWs consist of alternating layers of In{sub x}Ga{sub 1?x}N wells and GaN barriers under compressive and tensile stress, respectively, which have been lattice matched to a thick In{sub y}Ga{sub 1?y}N template. Growth of the In{sub y}Ga{sub 1?y}N template is also detailed in order to achieve thick, relaxed In{sub y}Ga{sub 1?y}N grown on GaN without the presence of V-grooves. When compared to conventional In{sub x}Ga{sub 1?x}N/GaN MQWs grown on GaN, the SBMQW structures exhibit longer wavelength emission and higher emission intensity for the same InN mole fraction due to a reduction in the well strain and piezoelectric field. By matching the average lattice constant of the MQW active region to the lattice constant of the In{sub y}Ga{sub 1?y}N template, essentially an infinite number of periods can be grown using the SBMQW growth method without relaxation-related effects. SBMQWs can be utilized to achieve longer wavelength emission in light emitting diodes without the use of excess indium and can be advantageous in addressing the “green gap.”.

  13. High current gain InGaN=GaN HBTs with C operating temperature

    E-Print Network [OSTI]

    Asbeck, Peter M.

    with an $20 nm low-temperature (Tg ¼ 550 C) GaN buffer layer on a (0001) sapphire substrate. The layer 1018 cmÀ3 Buffer GaN 2.5 mm ­ Substrate Sapphire ­ ­ HBT device processing began by depositing a 100 nmHigh current gain InGaN=GaN HBTs with 300 C operating temperature D.M. Keogh, P.M. Asbeck, T. Chung

  14. 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 ...

  15. Spontaneous emission in GaN/InGaN photonic crystal nanopillars

    E-Print Network [OSTI]

    Boyer, Edmond

    . Sigalas, "InGaN/GaN quantum-well heterostructure light-emitting diodes employing photonic crystal, "III-nitride blue and ultraviolet photonic crystal light emitting diodes," Appl. Phys. Lett. 84, 466, and H. Benisty, "Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

  16. GaInP/GaAs/GaInAs Monolithic Tandem Cells for High-Performance Solar Concentrators

    SciTech Connect (OSTI)

    Wanlass, M. W.; Ahrenkiel, S. P.; Albin, D. S.; Carapella, J. J.; Duda, A.; Emery, K.; Geisz, J. F.; Jones, K.; Kurtz, S.; Moriarty, T.; Romero, M. J.

    2005-08-01T23:59:59.000Z

    We present a new approach for ultra-high-performance tandem solar cells that involves inverted epitaxial growth and ultra-thin device processing. The additional degree of freedom afforded by the inverted design allows the monolithic integration of high-, and medium-bandgap, lattice-matched (LM) subcell materials with lower-bandgap, lattice-mismatched (LMM) materials in a tandem structure through the use of transparent compositionally graded layers. The current work concerns an inverted, series-connected, triple-bandgap, GaInP (LM, 1.87 eV)/GaAs (LM, 1.42 eV)/GaInAs (LMM, {approx}1 eV) device structure grown on a GaAs substrate. Ultra-thin tandem devices are fabricated by mounting the epiwafers to pre-metallized Si wafer handles and selectively removing the parent GaAs substrate. The resulting handle-mounted, ultra-thin tandem cells have a number of important advantages, including improved performance and potential reclamation/reuse of the parent substrate for epitaxial growth. Additionally, realistic performance modeling calculations suggest that terrestrial concentrator efficiencies in the range of 40-45% are possible with this new tandem cell approach. A laboratory-scale (0.24 cm2), prototype GaInP/GaAs/GaInAs tandem cell with a terrestrial concentrator efficiency of 37.9% at a low concentration ratio (10.1 suns) is described, which surpasses the previous world efficiency record of 37.3%.

  17. Influence of fuel sulfur on the selective reduction of NO by NH/sub 3/

    SciTech Connect (OSTI)

    Lucas, D.; Brown, N.J.

    1981-10-01T23:59:59.000Z

    The selective reduction of NO by NH/sub 3/ addition has been studied in a lean-burning oil fired laboratory combustion tunnel with pyridine and thiophene added to the fuel oil. Two distinct, but interrelated effects were observed. The conversion of a fixed amount of fuel nitrogen to NO in the flame increased as the fuel sulfur concentration increased. In the post-combustion gases, there was a shift in the temperature dependence of the reduction process when the sulfur combustion products were present. The extent of the NO reduction was not significantly altered, but the optimum temperature for reduction shifted to higher values as the sulfur concentration increased.

  18. Fine structure of Fe-Co-Ga and Fe-Cr-Ga alloys with low Ga content

    SciTech Connect (OSTI)

    Kleinerman, Nadezhda M., E-mail: kleinerman@imp.uran.ru; Serikov, Vadim V., E-mail: kleinerman@imp.uran.ru; Vershinin, Aleksandr V., E-mail: kleinerman@imp.uran.ru; Mushnikov, Nikolai V., E-mail: kleinerman@imp.uran.ru; Stashkova, Liudmila A., E-mail: kleinerman@imp.uran.ru [Institute of Metal Physics UB RAS, S. Kovalevskaya str. 18, 620990 Ekaterinburg (Russian Federation)

    2014-10-27T23:59:59.000Z

    Investigation of Ga influence on the structure of Fe-Cr and Fe-Co alloys was performed with the use of {sup 57}Fe Mössbauer spectroscopy and X-ray diffraction methods. In the alloys of the Fe-Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The analysis of Mössbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to enter the nearest surroundings of iron atoms, thus forming binary Fe-Ga regions (or phases)

  19. TEM Characterization of InAs/GaAs Quantum Dots Capped by a GaSb/GaAs Layer

    SciTech Connect (OSTI)

    Beltran, AM [Universidad de Cadiz, Spain; Ben, Teresa [Universidad de Cadiz, Spain; Sanchez, AM [Universidad de Cadiz, Spain; Sales Lerida, David [ORNL; Chisholm, Matthew F [ORNL; Varela del Arco, Maria [ORNL; Pennycook, Stephen J [ORNL; Galindo, Pedro [Universidad de Cadiz, Spain; Ripalda, JM [Instituto de Microelectronica de Madrid (CNM, CSIC); Molina Rubio, Sergio I [ORNL

    2008-01-01T23:59:59.000Z

    It is well known that there is intense interest in expanding the usable wavelength for electronic devices. This is one of the reasons to study new self-assembled semiconductor nanostructures. Telecommunication applications use InGaAsP/InP emitting at 1.3 and 1.55 m. Research efforts are dedicated to develop GaAs technology in order to achieve emission at the same range as InP, so GaAs could be used for optical fibre communications. Ga(As)Sb on InAs/GaAs quantum dots (QDs) is a promising nanostructure to be used in telecommunications. The introduction of antimony during or after the QDs growth is an effective solution to obtain a red shift in the emission wavelength, even at room temperature.

  20. 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

  1. Morphological and compositional variations in strain-compensated InGaAsP/InGaP superlattices

    E-Print Network [OSTI]

    Feenstra, Randall

    Morphological and compositional variations in strain- compensated InGaAsP/InGaP superlattices R of Technology, Kista, Sweden Abstract We have investigated the properties of strain-compensated InGaAsP/In- GaP superlattices, grown by metalorganic vapor phase epitaxy, with and without InP interlayers inserted in the InGaP

  2. Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1

    E-Print Network [OSTI]

    Operating Characteristics of GaAs/InGaP Self Aligned Stripe Lasers Benjamin J. Stevens1 , Kristian of GaAs based self-aligned lasers based upon a single overgrowth. A lattice matched n-doped InGaP layer were exposed to oxygen. True buried heterostructures devices utilising InGaP clad- ding layers have

  3. Microstructure and luminescent properties of novel InGaP alloys on relaxed GaAsP substrates

    E-Print Network [OSTI]

    Microstructure and luminescent properties of novel InGaP alloys on relaxed GaAsP substrates M. J of unconventional alloys of InGaP with In fraction of 0.2­0.4 grown on fully relaxed GaAsP virtual substrates demonstrate growth of extremely high quality InGaP heterostructures which hold promise for fabrication

  4. Band Offsets of InGaP/GaAs Heterojunctions by Scanning Tunneling Spectroscopy Y. Dong and R. M. Feenstra

    E-Print Network [OSTI]

    Feenstra, Randall

    1 Band Offsets of InGaP/GaAs Heterojunctions by Scanning Tunneling Spectroscopy Y. Dong and R. M Abstract Scanning tunneling microscopy and spectroscopy are used to study InGaP/GaAs heterojunctions computation of the tunnel current. Curve fitting of theory to experiment is performed. Using an InGaP band gap

  5. 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

  6. 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

  7. Embracing and Empowering Women to Serve Central Florida PO BOX 2895 Orlando FL 32802 ! wecOrlando.com ! facebook.com/wecOrlando ! scholarships@wecOrlando.com

    E-Print Network [OSTI]

    Van Stryland, Eric

    Orlando.com ! facebook.com/wecOrlando ! scholarships@wecOrlando.com 42nd ANNUAL WOMEN'S ACHIEVEMENT AWARDS EVENT Monday Orlando FL 32802 ! wecOrlando.com ! facebook.com/wecOrlando ! scholarships@wecOrlando.com All information 32802 ! wecOrlando.com ! facebook.com/wecOrlando ! scholarships@wecOrlando.com Please provide three (3

  8. Proceedings of the 1997 IEEE International Conference on Systems, Man, and Cybernetics (SMC'97) . Orlando, FL . Oct. 1215, 1997 DATA REPRESENTATION AND ORGANIZATION FOR AN INDUSTRIAL MULTISENSOR

    E-Print Network [OSTI]

    Naish, Michael D.

    INTEGRATION ARCHITECTURE Michael D. Naish and Elizabeth A. Croft Industrial Automation Laboratory Department) . Orlando, FL . Oct. 12­15, 1997 DATA REPRESENTATION AND ORGANIZATION FOR AN INDUSTRIAL MULTISENSOR@mech.ubc.ca ABSTRACT An open architecture for intelligent multisensor integra­ tion in an industrial environment

  9. 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.

  10. Michael J. Poston Atlanta, GA 30307

    E-Print Network [OSTI]

    Orlando, Thomas

    Page | 1 Michael J. Poston Atlanta, GA 30307 Michael.Poston@gatech.edu Cell: 770.561.4756 U.S. Citizen Education PhD Candidate in Chemistry Georgia Institute of Technology, Atlanta, GA August 2007 with Application to Lunar Observations," JGR ­ Planets, 118, 105, doi: 10.1002/jgre.20025. Poston, M. J

  11. 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

  12. FUPWG Meeting Agenda - Atlanta, GA | Department of Energy

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

    Atlanta, GA FUPWG Meeting Agenda - Atlanta, GA Energy on My Mind FUPWG Atlanta, GA May 3-4, 2006 Hosted by: AGL Resources Logo May 3-4, 2006 Hosted by AGL Resources Atlanta,...

  13. Simultaneous removal of H{sub 2}S and NH{sub 3} from coal gas. Final report

    SciTech Connect (OSTI)

    Gangwal, S.K.; Portzer, J.W.

    1998-05-01T23:59:59.000Z

    Hydrogen sulfide (H{sub 2}S) and ammonia (NH{sub 3}) are the primary sulfur and nitrogen contaminants released when coal is gasified. Before coal gas can be utilized in an integrated gasification combined cycle (IGCC) plant to produce electricity, these contaminants need to be removed. The objective of this research was to develop sorbent-catalysts with the ability to simultaneously remove H{sub 2}S and NH{sub 3} from coal gas. Microreactor tests with HART-49, a zinc-based sorbent-catalyst with Ni, Co, and Mo as catalyst additives, showed that this material had the potential to remove 90% NH{sub 3} and reduce H{sub 2}S to <20 ppmv at 1 atm and 550 to 700 C. HART-49 was prepared in attrition-resistant fluidizable form (HART-56) using up to 75 wt% binder. Bench-scale fluidized-bed multicycle tests were conducted with the attrition-resistant sorbent-catalyst, HART-56, at 20 atm and 550 C. The H{sub 2}S and NH{sub 3} removal performance over the first two cycles was good in the presence of 5% steam but deteriorated thereafter when steam level was increased to 15%. The results point to a complex mechanism for simultaneous H{sub 2}S and NH{sub 3} removal, potentially involving both chemisorption and catalytic decomposition of NH{sub 3}. Further research and development is needed to develop a sorbent-catalyst for simultaneous H{sub 2}S and NH{sub 3} removal at IGCC hot-gas cleanup conditions.

  14. Diffusive and rotational dynamics of condensed n-H2 confined in MCM-41

    SciTech Connect (OSTI)

    Prisk, Timothy R [ORNL; Bryan, Matthew [Indiana University; Sokol, Paul E [ORNL

    2014-01-01T23:59:59.000Z

    In this paper, we report an inelastic neutron scattering study of liquid and solid n-H2 confined within MCM-41. This is a high surface area, mesoporous silica glass with a narrow pore size distribution centered at 3.5 nm. The scattering data provides information about the diffusive and rotational dynamics of the adsorbed n-H2 at low temperatures. In the liquid state, the neutron scattering data demonstrates that only a fraction of the adsorbed o-H2 is mobile on the picosecond time scale. This mobile fraction undergoes liquid-like jump diffusion, and values for the residence time t and effective mean-squared displacement hu2i are reported as a function of pore filling. In the solid state, the rotational energy levels of adsorbed H2 are strongly perturbed from their free quantum rotor behavior in the bulk solid. The underlying orientational potential of the hindered rotors is due to the surface roughness and heterogeneity of the MCM-41 pore walls. This potential is compared to the hindering potential of other porous silicas, such as Vycor. Strong selective adsorption makes the interfacial layer rich in o-H2, leaving the inner core volume consisting of a depleted mixture of o-H2 and p-H2.

  15. 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.

  16. 56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar Cells on GaAs

    E-Print Network [OSTI]

    Haller, Gary L.

    56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar bandgap range. Index Terms--Epitaxy, GaAsP, InGaP, metamorphic. I. INTRODUCTION TODAY'S highest efficiency

  17. Defect structures in rapidly degraded InGaAsP/InGaP double-heterostructure lasers

    SciTech Connect (OSTI)

    Ueda, O.; Wakao, K.; Yamaguchi, A.; Isozumi, S.; Komiya, S.

    1985-03-01T23:59:59.000Z

    Rapidly degraded InGaAsP/InGaP double-heterostructure lasers grown on (001)-oriented GaAs substrates by liquid phase epitaxy have been investigated by photolumi

  18. Emission properties of heterostructures with a (GaAsSb-InGaAs)/GaAs bilayer quantum well

    SciTech Connect (OSTI)

    Zvonkov, B. N.; Nekorkin, S. M.; Vikhrova, O. V.; Dikareva, N. V., E-mail: dikareva@nifti.unn.ru [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)

    2013-09-15T23:59:59.000Z

    The specific features of the emission characteristics of GaAs-based heterostructures with a GaAs{sub 1-x}Sb{sub x}-In{sub y}Ga{sub 1-y}As bilayer quantum well are studied. The heterostructures are grown by metal-organic chemical vapor deposition (MOCVD). With an analysis of previously reported data on the MOCVD growth process taken into account, the temperature range (560-580 Degree-Sign C), the relation between the fluxes emitted by the sources of Group-V and -III elements ( Less-Than-Or-Equivalent-To 1), and the order of layer growth for the production of the active region of a GaAs/InGaP laser heterostructure are determined experimentally. The active region is a GaAs{sub 0.75}Sb{sub 0.25}-In{sub 0.2}Ga{sub 0.8}As bilayer quantum well. For the structure, a 1075-nm electroluminescence signal attributed to indirect transitions between the valence band of the GaAs{sub 0.75}Sb{sub 0.25} layer and the conduction band of the In{sub 0.2}Ga{sub 0.8}As layer is observed. An increase in the continuous-wave pump current yields a decrease in the 1075-nm emission intensity and initiates stable lasing at a wavelength of 1022 nm at a threshold current density of 1.4 kA cm{sup -2} at room temperature. Lasing occurs at transitions direct in coordinate space.

  19. Experimental verification of the high pressure crystal structures in NH{sub 3}BH{sub 3}

    SciTech Connect (OSTI)

    Huang, Yanping; Huang, Xiaoli; Zhao, Zhonglong; Li, Wenbo; Jiang, Shuqing; Duan, Defang; Bao, Kuo; Zhou, Qiang; Liu, Bingbing; Cui, Tian, E-mail: cuitian@jlu.edu.cn [State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012 (China)

    2014-06-28T23:59:59.000Z

    A detailed high-pressure study on NH{sub 3}BH{sub 3} has been carried out using in situ synchrotron X-ray diffraction (XRD) and Raman scattering with a diamond anvil cell up to 20 and 33 GPa, respectively. The Rietveld refinement based on the XRD pattern and analysis of Raman data indicate two first-order phase transitions from the ambient pressure I4 mm structure (?-NH{sub 3}BH{sub 3}) to a high pressure Cmc2{sub 1} phase (?-NH{sub 3}BH{sub 3}) at 2.14 GPa, and further into a monoclinic P2{sub 1} (Z = 2) phase (?-NH{sub 3}BH{sub 3}) at 9.67 GPa. Fitting the measured volumetric compression data to the third order Birch-Murnaghan equation of state reveals a bulk modulus of B{sub 0} = 9.9 ± 0.5 and 17.0 ± 3.0 GPa (with fixed B{sub 0}{sup ?} = 4) for the ?-NH{sub 3}BH{sub 3} below and above 5 GPa, respectively. Still, with the splitting of the NBH rock mode in Raman experiment, it is concluded that a second-order isostructural phase transition occurs at 5 GPa. By analyzing the dihydrogen bonding framework, the origin of the isostructural phase transition is attributed to the number of dihydrogen bondings per molecule in the Cmc2{sub 1} phase increasing from 12 to 14 at 5 GPa.

  20. Functional analysis of the NH{sub 2}-terminal hydrophobic region and BRICHOS domain of GKN1

    SciTech Connect (OSTI)

    Yoon, Jung Hwan; Choi, Yoo Jin; Choi, Won Suk; Nam, Suk Woo; Lee, Jung Young; Park, Won Sang, E-mail: wonsang@catholic.ac.kr

    2013-11-01T23:59:59.000Z

    Highlights: •NH{sub 2}-terminal and BRICHOS domain of GKN1 inhibited tumor cell growth. •NH{sub 2}-terminal and BRICHOS domain of GKN1 regulated cell cycle. •NH{sub 2}-terminal and BRICHOS domain of GKN1 inhibited epigenetic regulators. -- Abstract: Gastrokine 1 (GKN1) protects the gastric antral mucosa and promotes healing by facilitating restitution and proliferation after injury. GKN1 is down-regulated in Helicobacter pylori-infected gastric epithelial cells and loss of GKN1 expression is tightly associated with gastric carcinogenesis. However, the underlying mechanisms as a tumor suppressor are largely unknown. Presently, the hydrophobic region and BRICHOS domain of GKN1, pGKN1{sup D13N}, pGKN1{sup ?68–199}, and pGKN1{sup ?1–67,165–199} were shown to suppress gastric cancer cell growth and recapitulate GKN1 functions. As well, the hydrophobic region and BRICHOS domain of GKN1 had a synergistic anti-cancer effect with 5-FU on tumor cell growth, implying that the NH{sub 2}-terminal hydrophobic region and BRICHOS domain of GKN1 are sufficient for tumor suppression, thereby suggesting a therapeutic intervention for gastric cancer. Also, its domain inducing endogenous miR-185 directly targeted the epigenetic effectors DNMT1 and EZH2 in gastric cancer cells. Our results suggest that the NH{sub 2}-terminal hydrophobic region and BRICHOS domain of GKN1 are sufficient for its tumor suppressor activities.

  1. Preparation of hexagonal WO{sub 3} from hexagonal ammonium tungsten bronze for sensing NH{sub 3}

    SciTech Connect (OSTI)

    Szilagyi, Imre Miklos [Materials Structure and Modeling Research Group of the Hungarian Academy of Sciences, Budapest University of Technology and Economics, H-1111 Budapest, Szt. Gellert ter 4 (Hungary)], E-mail: imre.szilagyi@mail.bme.hu; Wang Lisheng; Gouma, Pelagia-Irene [Department of Materials Science and Engineering, 314 Old Engineering Building, SUNY, Stony Brook, NY 11794-2275 (United States); Balazsi, Csaba [Ceramics and Nanocomposites Laboratory, Research Institute for Technical Physics and Materials Science, H-1121 Budapest, Konkoly-Thege ut 29-33 (Hungary); Madarasz, Janos; Pokol, Gyoergy [Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, H-1111 Budapest, Szt. Gellert ter 4 (Hungary)

    2009-03-05T23:59:59.000Z

    Hexagonal tungsten oxide (h-WO{sub 3}) was prepared by annealing hexagonal ammonium tungsten bronze, (NH{sub 4}){sub 0.07}(NH{sub 3}){sub 0.04}(H{sub 2}O){sub 0.09}WO{sub 2.95}. The structure, composition and morphology of h-WO{sub 3} were studied by XRD, XPS, Raman, {sup 1}H MAS (magic angle spinning) NMR, scanning electron microscopy (SEM), and BET-N{sub 2} specific surface area measurement, while its thermal stability was investigated by in situ XRD. The h-WO{sub 3} sample was built up by 50-100 nm particles, had an average specific surface area of 8.3 m{sup 2}/g and was thermally stable up to 450 deg. C. Gas sensing tests showed that h-WO{sub 3} was sensitive to various levels (10-50 ppm) of NH{sub 3}, with the shortest response and recovery times (1.3 and 3.8 min, respectively) to 50 ppm NH{sub 3}. To this NH{sub 3} concentration, the sensor had significantly higher sensitivity than h-WO{sub 3} samples prepared by wet chemical methods.

  2. 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

  3. 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

  4. 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

  5. Improvement of breakdown voltage in InGaP/InGaAs/GaAs heterostructure MESFETs for MMICs

    SciTech Connect (OSTI)

    Koh, Inoue; Yamane, Yasuro; Shiojima, Kenji [NTT LSI Lab., Kanagawa (Japan)] [and others

    1995-12-31T23:59:59.000Z

    This paper describes the trade-off between breakdown voltage and RF performance of InGaP/InGaAs/GaAs heterostructure MESFETs for power amplifiers and oscillators in multi-function MMICs in the millimeter-wave range. The authors successfully improved both gate-drain and drain-source breakdown voltages while maintaining excellent high-frequency performance by using a double-layered gate consisting of WSiN with different nitrogen contents, and by varying epitaxial layer thickness and implantation dose.

  6. Necessity of Ga prelayers in GaAs/Ge growth using gas-source molecular beam epitaxy

    E-Print Network [OSTI]

    in a highly defective GaAs layer.as5 Recently, InGaP light-emitting diodes have been fabricated on Si using

  7. Structural and optical properties of InGaN–GaN nanowire heterostructures grown by molecular beam epitaxy

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

    Limbach, F. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Gotschke, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Stoica, T. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Calarco, R. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany); Sutter, E. [Brookhaven National Lab., Upton, NY (United States); Ciston, J. [Brookhaven National Lab., Upton, NY (United States); Cusco, R. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Artus, L. [Consell Superior d'Investigacions Cientifiques (CSIC), Barcelona (Spain); Kremling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Hofling, S. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Worschech, L. [Univ. Wurzburg, Wilhelm Conrad Rontgen Research Centre Complex Matter Systems, Wurzburg (Germany); Grutzmacher, D. [Institute of Bio- and Nanosystems (IBN-1), Research Centre Jülich GmbH and JARA-FIT Fundamentals of Future Information Technology (Germany)

    2011-01-07T23:59:59.000Z

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

  8. High-efficiency radiation-resistant InGaP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Takamoto, T. [Toyota Technological Inst., Tempaku, Nagoya (Japan); [Japan Energy Corp., Toda, Saitama (Japan); Yamaguchi, M.; Taylor, S.J. [Toyota Technological Inst., Tempaku, Nagoya (Japan); Ikeda, E.; Agui, T.; Kurita, H. [Japan Energy Corp., Toda, Saitama (Japan)

    1997-12-31T23:59:59.000Z

    A world-record efficiency of 26.9% (AM0, 28 C) has been obtained for InGaP/GaAs tandem solar cells fabricated by the MOCVD method. The radiation resistance of the InGaP/GaAs tandem solar cells has also been evaluated following 1 MeV electron irradiation. Degradation in the tandem cell performance has been confirmed to be mainly attributed to large degradation in the GaAs bottom cell, which features a highly doped base layer. Similar radiation-resistance with GaAs-on-Ge cells has been observed for the InGaP/GaAs tandem cell. However, some recovery of the tandem cell performance has been found due to minority-carrier injection under light illumination of forward bias, which causes defect annealing in InGaP cells. The optimal design of the InGaP base layer thickness for current matching at end of life (EOL) (after irradiation with 10{sup 15} electrons cm{sup {minus}2}) has been examined.

  9. Highly uniform, multi-stacked InGaAs/GaAs quantum dots embedded in a GaAs nanowire

    SciTech Connect (OSTI)

    Tatebayashi, J., E-mail: tatebaya@iis.u-tokyo.ac.jp; Ota, Y. [NanoQUINE, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Ishida, S.; Nishioka, M.; Iwamoto, S.; Arakawa, Y. [NanoQUINE, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-09-08T23:59:59.000Z

    We demonstrate a highly uniform, dense stack of In{sub 0.22}Ga{sub 0.78}As/GaAs quantum dot (QD) structures in a single GaAs nanowire (NW). The size (and hence emission energy) of individual QD is tuned by careful control of the growth conditions based on a diffusion model of morphological evolution of NWs and optical characterization. By carefully tailoring the emission energies of individual QD, dot-to-dot inhomogeneous broadening of QD stacks in a single NW can be as narrow as 9.3?meV. This method provides huge advantages over traditional QD stack using a strain-induced Stranski-Krastanow growth scheme. We show that it is possible to fabricate up to 200 uniform QDs in single GaAs NWs using this growth technique without degradation of the photoluminescence intensity.

  10. Strain induced variations in band offsets and built-in electric fields in InGaN/GaN multiple quantum wells

    E-Print Network [OSTI]

    Alpay, S. Pamir

    Strain induced variations in band offsets and built-in electric fields in InGaN/GaN multiple InxGa1-xN(InGaN)/GaN multilayers on the In composition and misfit strain. The results indicate that for non-polar m-plane configurations with ½1210InGaN//½1210GaN and ½0001InGaN//½0001GaN epitaxial

  11. Influence of fuel sulfur on the selective reduction of NO by NH/sub 3/

    SciTech Connect (OSTI)

    Lucas, D.; Brown, N.J.

    1981-01-01T23:59:59.000Z

    More intensive regulations of the emissions of nitrogen oxides from stationary combustion sources have prompted the innovation and characterization of new control technologies suitable for applications in utilities. One of the more recent and attractive abatement technologies is the Thermal DeNO/sub x/ process which has been described by Lyon and Longwell. This process removes NO by selectively reducing it with NH/sub 3/ added to the post-combustion gases containing excess oxygen. This process is thus independent of the NO formation mechanism and makes no distinction between thermal and fuel NO. The present study is concerned with characterizing the selective reduction process for light distillate oil fuel admixed with variable amounts of pyridene and thiophene in a laboratory scale combustion tunnel under a variety of experimental conditions. This paper reports on those aspects of the study concerned with the investigation of possible synergistic effects between the sulfur and selective reduction chemistry.

  12. 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.

  13. High-performance InGaP/GaAs pnp {delta}-doped heterojunction bipolar transistor

    SciTech Connect (OSTI)

    Tsai, J.-H. [National Kaohsiung Normal University, Department of Electronic Engineering (China)], E-mail: jhtsai@nknucc.nknu.edu.tw; Chiu, S.-Y.; Lour, W.-S. [National Taiwan Ocean University, Department of Electrical Engineering (China); Guo, D.-F. [Air Force Academy, Department of Electronic Engineering (China)

    2009-07-15T23:59:59.000Z

    In this article, a novel InGaP/GaAs pnp {delta}-doped heterojunction bipolar transistor is first demonstrated. Though the valence band discontinuity at InGaP/GaAs heterojunction is relatively large, the addition of a {delta}-doped sheet between two spacer layers at the emitter-base (E-B) junction effectively eliminates the potential spike and increases the confined barrier for electrons, simultaneously. Experimentally, a high current gain of 25 and a relatively low E-B offset voltage of 60 mV are achieved. The offset voltage is much smaller than the conventional InGaP/GaAs pnp HBT. The proposed device could be used for linear amplifiers and low-power complementary integrated circuit applications.

  14. 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.

  15. 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.

  16. 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.

  17. Mechanistic studies of the CVD of silicon nitride from SiF{sub 4} and NH{sub 3}

    SciTech Connect (OSTI)

    Buss, R.J.; Ho, P.

    1992-12-01T23:59:59.000Z

    An industrial process for the CVD of silicon nitride from SiF{sub 4} and NH{sub 3} was studied with a wide variety of techniques, ranging from numerical models of the coupled chemistry and fluid mechanics to experimental studies of chemical reactions. The latter includes a set of molecular beam experiments that probed the temperature and flux dependencies of the reaction of SiF{sub 4} and NH{sub 3} at the surface. These experiments showed that the CVD reactor chemistry was dominated by surface kinetics rather than gas-phase decomposition.

  18. Mechanistic studies of the CVD of silicon nitride from SiF[sub 4] and NH[sub 3

    SciTech Connect (OSTI)

    Buss, R J; Ho, P

    1992-01-01T23:59:59.000Z

    An industrial process for the CVD of silicon nitride from SiF[sub 4] and NH[sub 3] was studied with a wide variety of techniques, ranging from numerical models of the coupled chemistry and fluid mechanics to experimental studies of chemical reactions. The latter includes a set of molecular beam experiments that probed the temperature and flux dependencies of the reaction of SiF[sub 4] and NH[sub 3] at the surface. These experiments showed that the CVD reactor chemistry was dominated by surface kinetics rather than gas-phase decomposition.

  19. Dependence of the ground-state transition energy versus optical pumping in GaAsSb/InGaAs/GaAs heterostructures

    SciTech Connect (OSTI)

    Morozov, S. V.; Kryzhkov, D. I., E-mail: krizh@ipmras.ru; Aleshkin, V. Ya. [Institute for Physics of Microstructures, RAS, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Yablonsky, A. N.; Krasilnik, Z. F. [Institute for Physics of Microstructures, RAS, 603950 Nizhny Novgorod (Russian Federation); Zvonkov, B. N.; Vikhrova, O. V. [Physical-Technical Research Institute, Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation)

    2014-01-13T23:59:59.000Z

    In this work, we report on the time-resolved photoluminescence studies of a double quantum well In{sub 0.2}Ga{sub 0.8}As/GaAs{sub 0.8}Sb{sub 0.2}/GaAs heterostructure which, in contrast to the GaAsSb/GaAs structures, is expected to provide effective confinement of electrons due to additional InGaAs layer. The studies at 4.2?K have revealed a complicated nonmonotonic dependence of the ground-state transition energy on the concentration of nonequilibrium charge carriers in the quantum well. The effect observed in this work is important in terms of creating sources of radiation, including stimulated emission, on the basis of InGaAs/GaAsSb/GaAs structures.

  20. 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.

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

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

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

    2015-04-03T23:59:59.000Z

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

  2. Laser studies of the reactivity of NH(X{sup 3}{Sigma}{sup {minus}}) with the surface of silicon nitride

    SciTech Connect (OSTI)

    Fisher, E.R.; Ho, P.; Breiland, W.G.; Buss, R.J. [Sandia National Labs., Albuquerque, NM (United States)

    1992-11-26T23:59:59.000Z

    The reactivity of NH(X{sup 3}{Sigma}{sup {minus}}) with the surface of both a silicon nitride film and a depositing hydrogenated silicon nitride film has been measured to be essentially zero with an upper limit of 0.1 for substrate temperatures of 300-700 K. The reactivity was directly determined using spatially resolved laser-induced fluorescence of NH in a plasma-generated molecular beam incident on the surface. The NH adsorbs and then desorbs from the surface with a a spatial distribution consistent with a cosine angular distribution. No dependence of reactivity on rotational state of the NH was observed. 27 refs., 8 figs.

  3. InGaAsP/InGaP buried heterostructure lasers at 810 nm

    SciTech Connect (OSTI)

    Wakao, K.; Isozumi, S.; Nishi, H.; Ohsaka, S.

    1984-12-01T23:59:59.000Z

    InGaAsP/InGaP buried heterostructure lasers emitting at 810 nm have been grown on GaAs substrates using two-step liquid-phase epitaxy. A threshold current of 79 mA and an external differential quantum efficiency of 26% are obtained. Fundamental transverse mode operation up to 3 mW is achieved in the laser with the active region of 3.5 ..mu..m wide.

  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. Ohmic contacts to n-GaSb

    E-Print Network [OSTI]

    Yang, Zhengchong

    1997-01-01T23:59:59.000Z

    In recent years, the Ill-V semiconductor GaSb and its ternary alloys containing antimony have exhibited interesting electrical and optical properties for device applications which include negative resistance tunnel devices, lasers, detectors and FET...

  6. 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.

  7. H-gallosilicate (MFI) propane aromatization catalyst: Influence of Si/Ga ratio on acidity, activity and deactivation due to coking

    SciTech Connect (OSTI)

    Choudhary, V.R.; Kinage, A.K.; Sivadinarayana, C. [National Chemical Lab., Pune (India)] [and others] [National Chemical Lab., Pune (India); and others

    1996-01-01T23:59:59.000Z

    Influence of bulk Si/Ga ratio of H-gallosilicate (MFI) on its degalliation (during calcination for removal of template and deammoniation of NH{sub 4} form), acidity/acid strength distribution (measured by stepwise thermal desorption and chemisorption of pyridine at 50-400{degrees}C using GC techniques and also by acid catalyzed model reactions viz. iso-octane cracking and toluene disproportionation) and initial activity/product selectivity and catalyst deactivation in propane aromatization (at 550{degrees}C) has been investigated. Framework Si/Ga ratio was measured by {sup 29}Si MAS NMR. Information on the external acid sites is obtained by isooctane cracking. The influence of poisoning of strong acid sites (by pyridine) on acid catalyzed model reactions and the effect of deactivation on the product distribution in the propane aromatization have also been studied. 21 refs., 19 figs., 3 tabs.

  8. 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.}

  9. GaTe semiconductor for radiation detection

    DOE Patents [OSTI]

    Payne, Stephen A. (Castro Valley, CA); Burger, Arnold (Nashville, TN); Mandal, Krishna C. (Ashland, MA)

    2009-06-23T23:59:59.000Z

    GaTe semiconductor is used as a room-temperature radiation detector. GaTe has useful properties for radiation detectors: ideal bandgap, favorable mobilities, low melting point (no evaporation), non-hygroscopic nature, and availability of high-purity starting materials. The detector can be used, e.g., for detection of illicit nuclear weapons and radiological dispersed devices at ports of entry, in cities, and off shore and for determination of medical isotopes present in a patient.

  10. 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.

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

    E-Print Network [OSTI]

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

  12. Journal of Crystal Growth 298 (2007) 272275 Dislocation analysis in homoepitaxial GaInN/GaN light emitting

    E-Print Network [OSTI]

    Wetzel, Christian M.

    2007-01-01T23:59:59.000Z

    of GaInN/GaN-based light emitting diodes (LED) on quasi-bulk GaN with an atomically flat polished were much improved. The optical output power of the light emitting diode increased by more than one. Cathodoluminescence; A1. Threading dislocation density; A2. Homoepitaxial growth; B1. GaInN; B3. Light emitting diode

  13. 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

  14. InAsGaPInGaP high-temperature power Schottky rectifier and J. M. Woodall

    E-Print Network [OSTI]

    Woodall, Jerry M.

    °C. Further improvement of the thermal stability is expected to be achieved by reducing the diffusion is thought to be due to strong covalent bonding at the InAs/GaP interface. The InAs/GaP heterointerface effectively blocks impurity diffusion. Since InGaP is superior to GaP for high-power applica- tions, as shown

  15. GaAs-based self-aligned laser incorporating InGaP opto-electronic confinement layer

    E-Print Network [OSTI]

    GaAs-based self-aligned laser incorporating InGaP opto-electronic confinement layer K.M. Groom, B fabrication, is demonstrated. An n-doped InGaP layer is utilised for both electrical and optical confinement-doped InGaP current blocking layer that also provides optical confinement. This tech- nology relies

  16. 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

  17. Direct Evidence of Nanoscale Carrier Localization in InGaN/GaN Structures Grown on Si Substrates

    E-Print Network [OSTI]

    Nabben, Reinhard

    Direct Evidence of Nanoscale Carrier Localization in InGaN/GaN Structures Grown on Si Substrates: time-resolved photoluminescence, quantum dots, InGaN, Si substrate There exists a strong continuous expensive and are limited in size. Thus, heteroepitaxial growth of GaN on silicon substrates seems

  18. Inclined dislocation-pair relaxation mechanism in homoepitaxial green GaInN/GaN light-emitting diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    -emitting diodes LEDs on low-defect density bulk GaN substrate, but not in green LEDs on sapphire substrate an ideal substrate for homoepitaxial growth. Here we study the microstructural properties of green GaInN/GaN-Koehler force10 resulting from a macroscopic relaxation of strain. II. CRYSTAL GROWTH c plane bulk GaN substrate

  19. Junction Temperature Measurements and Thermal Modeling of GaInN/GaN Quantum Well Light-Emitting Diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    quantum well (QW) light-emitting diodes (LEDs) grown on sapphire and bulk GaN substrate by micro efficiency in dies grown on GaN substrates with a thermal resistance of 75 K/W. For dies on sapphire of GaN-based blue and green LEDs grown on sapphire and GaN substrates using micro-Raman spectroscopy

  20. Correlation between structural properties and optical amplification in InGaN/GaN heterostructures grown by molecular beam epitaxy

    E-Print Network [OSTI]

    Nabben, Reinhard

    . The lateral homogeneity can be drastically improved using a template of GaN grown on the sapphire substrate-grown heterostructures can drastically be reduced by using a template of MOVPE-GaN on the sapphire substrate, which leadsCorrelation between structural properties and optical amplification in InGaN/GaN heterostructures

  1. Access Management in Multi-Administration Networks S. P. Lord, N.H. Pope, and Susan Stepney

    E-Print Network [OSTI]

    Stepney, Susan

    Access Management in Multi-Administration Networks S. P. Lord, N.H. Pope, and Susan Stepney GEC of linking together networks controlled by different administrations, and allowing these administrations and representations. S. P. Lord, N. H. Pope, and Susan Stepney. Access Management in multi-administration networks

  2. Effective interactions between the N-H bond orientations in lithium imide and a proposed ground-state structure

    E-Print Network [OSTI]

    Ceder, Gerbrand

    Effective interactions between the N-H bond orientations in lithium imide and a proposed ground Received 28 February 2006; revised manuscript received 17 July 2006; published 4 October 2006 Lithium imide in the structure. By searching an effective Hamiltonian in which the energy of lithium imide is expressed

  3. Ultra-high frequency photoconductivity decay in GaAs/Ge/GaAs double heterostructure grown by molecular beam epitaxy

    SciTech Connect (OSTI)

    Hudait, M. K.; Zhu, Y. [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Johnston, S. W. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Maurya, D.; Priya, S. [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Umbel, R. [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2013-03-04T23:59:59.000Z

    GaAs/Ge/GaAs double heterostructures (DHs) were grown in-situ using two separate molecular beam epitaxy chambers. High-resolution x-ray rocking curve demonstrates a high-quality GaAs/Ge/GaAs heterostructure by observing Pendelloesung oscillations. The kinetics of the carrier recombination in Ge/GaAs DHs were investigated using photoconductivity decay measurements by the incidence excitation from the front and back side of 15 nm GaAs/100 nm Ge/0.5 {mu}m GaAs/(100)GaAs substrate structure. High-minority carrier lifetimes of 1.06-1.17 {mu}s were measured when excited from the front or from the back of the Ge epitaxial layer, suggests equivalent interface quality of GaAs/Ge and Ge/GaAs. Wavelength-dependent minority carrier recombination properties are explained by the wavelength-dependent absorption coefficient of Ge.

  4. Metastable states in InGaN/GaN MQW structures doped with Sm, Eu, and Eu + Sm

    SciTech Connect (OSTI)

    Mezdrogina, M. M., E-mail: Margaret.M@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Kozhanova, Yu. V. [St. Petersburg State Polytechnical University (Russian Federation)

    2013-04-15T23:59:59.000Z

    Measurements of the microphotoluminescence (microPL) spectra of InGaN/GaN:Sm and InGaN/GaN:Eu quantum well (QW) structures show that the action of a magnetic field gives rise to Van Vleck paramagnetism for Eu{sup 3+} and Sm{sup 3+}. The macrophotoluminescence (macroPL) spectra recorded after measuring the microPL spectra of InGaN/GaN QW structures doped with Sm or Eu + Sm at a high excitation level (>10{sup 23} photons cm{sup -2} s{sup -1}) in magnetic fields contain no QW emission lines which are present in the macroPL spectra recorded before these microPL measurements. This is indicative of the presence of photoinduced defects. Annealing of the InGaN/GaN:Sm and InGaN/GaN:(Eu + Sm) structures reduces the concentration of photoinduced defects.

  5. 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. ,

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

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu; Akyol, Fatih [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Rajan, Siddharth, E-mail: krishnamoorthy.13@osu.edu, E-mail: rajan@ece.osu.edu [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2014-10-06T23:59:59.000Z

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

  7. ccsd-00000821(version1):6Nov2003 Alloy effects in Ga1-xInxN/GaN heterostructures

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ccsd-00000821(version1):6Nov2003 Alloy effects in Ga1-xInxN/GaN heterostructures Duc-Phuong Nguyen, France We show that the large band offsets between GaN and InN and the heavy carrier effec- tive masses preclude the use of the Virtual Crystal Approximation to describe the electronic structure of Ga1-xInxN/GaN

  8. DESIGN, GROWTH, FABRICATION AND CHARACTERIZATION OF HIGH-BAND GAP InGaN/GaN SOLAR CELLS

    E-Print Network [OSTI]

    Honsberg, Christiana

    DESIGN, GROWTH, FABRICATION AND CHARACTERIZATION OF HIGH-BAND GAP InGaN/GaN SOLAR CELLS Omkar Jani1 with a band gap of 2.4 eV or greater. InxGa1-xN is one of a few alloys that can meet this key requirement. InGaN.4 eV. InGaN has the appropriate optical properties and has been well demonstrated for light

  9. 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

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

    E-Print Network [OSTI]

    Bowers, John

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

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

    E-Print Network [OSTI]

    Boyer, Edmond

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

  12. 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

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

    SciTech Connect (OSTI)

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

    2005-12-19T23:59:59.000Z

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

  14. 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 ...

  15. 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 ...

  16. High Indium Concentration InGaN/GaN Grown on Sapphire Substrate by MOCVD

    E-Print Network [OSTI]

    Hartono, Haryono

    The InGaN system provides the opportunity to fabricate light emitting devices over the whole visible and ultraviolet spectrum due to band-gap energies E[subscript g] varying between 3.42 eV for GaN and 1.89 eV for InN. ...

  17. 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 ...

  18. 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.

  19. Verification of Allowable Stresses In ASME Section III Subsection NH For Grade 91 Steel & Alloy 800H

    SciTech Connect (OSTI)

    R. W. Swindeman; M. J. Swindeman; B. W. Roberts; B. E. Thurgood; D. L. Marriott

    2007-11-30T23:59:59.000Z

    The database for the creep-rupture of 9Cr-1Mo-V (Grade 91) steel was collected and reviewed to determine if it met the needs for recommending time-dependent strength values, S{sub t}, for coverage in ASME Section III Subsection NH (ASME III-NH) to 650 C (1200 F) and 600,000 hours. The accumulated database included over 300 tests for 1% total strain, nearly 400 tests for tertiary creep, and nearly 1700 tests to rupture. Procedures for analyzing creep and rupture data for ASME III-NH were reviewed and compared to the procedures used to develop the current allowable stress values for Gr 91 for ASME II-D. The criteria in ASME III-NH for estimating S{sub t} included the average strength for 1% total strain for times to 600,000 hours, 80% of the minimum strength for tertiary creep for times to 600,000 hours, and 67% of the minimum rupture strength values for times to 600,000 hours. Time-temperature-stress parametric formulations were selected to correlate the data and make predictions of the long-time strength. It was found that the stress corresponding to 1% total strain and the initiation of tertiary creep were not the controlling criteria over the temperature-time range of concern. It was found that small adjustments to the current values in III-NH could be introduced but that the existing values were conservative and could be retained. The existing database was found to be adequate to extend the coverage to 600,000 hours for temperatures below 650 C (1200 F).

  20. Update and Improve Subsection NH –– Alternative Simplified Creep-Fatigue Design Methods

    SciTech Connect (OSTI)

    Tai Asayama

    2009-10-26T23:59:59.000Z

    This report described the results of investigation on Task 10 of DOE/ASME Materials NGNP/Generation IV Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 10 is to Update and Improve Subsection NH -- Alternative Simplified Creep-Fatigue Design Methods. Five newly proposed promising creep-fatigue evaluation methods were investigated. Those are (1) modified ductility exhaustion method, (2) strain range separation method, (3) approach for pressure vessel application, (4) hybrid method of time fraction and ductility exhaustion, and (5) simplified model test approach. The outlines of those methods are presented first, and predictability of experimental results of these methods is demonstrated using the creep-fatigue data collected in previous Tasks 3 and 5. All the methods (except the simplified model test approach which is not ready for application) predicted experimental results fairly accurately. On the other hand, predicted creep-fatigue life in long-term regions showed considerable differences among the methodologies. These differences come from the concepts each method is based on. All the new methods investigated in this report have advantages over the currently employed time fraction rule and offer technical insights that should be thought much of in the improvement of creep-fatigue evaluation procedures. The main points of the modified ductility exhaustion method, the strain range separation method, the approach for pressure vessel application and the hybrid method can be reflected in the improvement of the current time fraction rule. The simplified mode test approach would offer a whole new advantage including robustness and simplicity which are definitely attractive but this approach is yet to be validated for implementation at this point. Therefore, this report recommends the following two steps as a course of improvement of NH based on newly proposed creep-fatigue evaluation methodologies. The first step is to modify the current approach by incorporating the partial advantages the new method offer, and the second step is to replace the current method by the simplified test approach when it has become technically mature enough. The recommendations are basically in line with the work scope of the Task Force on Creep-Fatigue of the Subgroup on Elevated Temperature Design of the Standards Committee of the ASME Boiler and Pressure Vessel Committee Section III.

  1. Measurements of NH3 and CO2 with distributed-feedback diode lasers near 2.0 m in bioreactor vent gases

    E-Print Network [OSTI]

    Measurements of NH3 and CO2 with distributed-feedback diode lasers near 2.0 m in bioreactor vent K. Hanson Measurements of NH3 and CO2 were made in bioreactor vent gases with distributed3 and CO2 concentration in bioreactor vent gases that were recorded at NASA Johnson Space Center

  2. Intramolecular Hydrogen Bonding in Disubstituted Ethanes. A Comparison of NH,,,O-and OH,,,O-Hydrogen Bonding through Conformational Analysis of 4-Amino-4-oxobutanoate

    E-Print Network [OSTI]

    Goddard III, William A.

    Intramolecular Hydrogen Bonding in Disubstituted Ethanes. A Comparison of NH,,,O- and OH,,,O- Hydrogen Bonding through Conformational Analysis of 4-Amino-4-oxobutanoate (succinamate) and Monohydrogen 1 of amide NH,,,O- and carboxyl OH,,,O- hydrogen bonds were investigated via conformational analysis

  3. Gallium surface diffusion on GaAs (001) surfaces measured by crystallization dynamics of Ga droplets

    SciTech Connect (OSTI)

    Bietti, Sergio, E-mail: sergio.bietti@mater.unimib.it; Somaschini, Claudio; Esposito, Luca; Sanguinetti, Stefano [L–NESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 55, I–20125 Milano (Italy); Fedorov, Alexey [L–NESS and CNR–IFN, via Anzani 42, I-22100 Como (Italy)

    2014-09-21T23:59:59.000Z

    We present accurate measurements of Ga cation surface diffusion on GaAs surfaces. The measurement method relies on atomic force microscopy measurement of the morphology of nano–disks that evolve, under group V supply, from nanoscale group III droplets, earlier deposited on the substrate surface. The dependence of the radius of such nano-droplets on crystallization conditions gives direct access to Ga diffusion length. We found an activation energy for Ga on GaAs(001) diffusion E{sub A}=1.31±0.15 eV, a diffusivity prefactor of D{sub 0}?=?0.53(×2.1±1) cm{sup 2} s{sup ?1} that we compare with the values present in literature. The obtained results permit to better understand the fundamental physics governing the motion of group III ad–atoms on III–V crystal surfaces and the fabrication of designable nanostructures.

  4. 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.

  5. Green cubic GaInN/GaN light-emitting diode on microstructured silicon (100)

    SciTech Connect (OSTI)

    Stark, Christoph J. M.; Detchprohm, Theeradetch; Wetzel, Christian, E-mail: wetzel@ieee.org [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States) [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Future Chips Constellation, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Lee, S. C.; Brueck, S. R. J. [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States)] [Department of Electrical and Computer Engineering and Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 (United States); Jiang, Y.-B. [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2013-12-02T23:59:59.000Z

    GaInN/GaN light-emitting diodes free of piezoelectric polarization were prepared on standard electronic-grade Si(100) substrates. Micro-stripes of GaN and GaInN/GaN quantum wells in the cubic crystal structure were grown on intersecting (111) planes of microscale V-grooved Si in metal-organic vapor phase epitaxy, covering over 50% of the wafer surface area. Crystal phases were identified in electron back-scattering diffraction. A cross-sectional analysis reveals a cubic structure virtually free of line defects. Electroluminescence over 20 to 100??A is found fixed at 487?nm (peak), 516?nm (dominant). Such structures therefore should allow higher efficiency, wavelength-stable light emitters throughout the visible spectrum.

  6. 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

  7. 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

  8. Quantum confinement in GaP nanoclusters

    SciTech Connect (OSTI)

    Laurich, B.K.; Smith, D.C.; Healy, M.D.

    1994-06-01T23:59:59.000Z

    We have prepared GaP and GaAs nanoclusters from organometallic condensation reactions of E[Si(ChH{sub 3})3]3 (E = P, As) and GaCl{sub 3}. The size of the as synthesized clusters is 10 {Angstrom} to 15 {Angstrom}. Larger clusters of 20 {Angstrom} to 30 {Angstrom} size were obtained by thermal annealing of the as grown material. X-ray diffraction and transmission electron microscopy confirm the high crystalline quality. A lattice contraction of 6.7% could be seen for 10 {Angstrom} sized GaAs clusters. The clusters are nearly spherical in shape. Optical absorption spectra show a distinct line which can be assigned to the fundamental transition of the quantum confined electronic state. The measured blue shift, with respect to the GaP bulk absorption edge is 0.53 eV. As the cluster is smaller than the exciton radius, we can calculate the cluster size from this blue shift and obtain 20.2 {Angstrom}, consistent with the results from X-ray diffraction of 19.5 {Angstrom} for the same sample.

  9. 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

  10. 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.

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

    SciTech Connect (OSTI)

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

    2012-06-01T23:59:59.000Z

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

  12. GaAs photoconductive semiconductor switch

    DOE Patents [OSTI]

    Loubriel, G.M.; Baca, A.G.; Zutavern, F.J.

    1998-09-08T23:59:59.000Z

    A high gain, optically triggered, photoconductive semiconductor switch (PCSS) implemented in GaAs as a reverse-biased pin structure with a passivation layer above the intrinsic GaAs substrate in the gap between the two electrodes of the device is disclosed. The reverse-biased configuration in combination with the addition of the passivation layer greatly reduces surface current leakage that has been a problem for prior PCSS devices and enables employment of the much less expensive and more reliable DC charging systems instead of the pulsed charging systems that needed to be used with prior PCSS devices. 5 figs.

  13. GaAs photoconductive semiconductor switch

    DOE Patents [OSTI]

    Loubriel, Guillermo M. (Sandia Park, NM); Baca, Albert G. (Albuquerque, NM); Zutavern, Fred J. (Albuquerque, NM)

    1998-01-01T23:59:59.000Z

    A high gain, optically triggered, photoconductive semiconductor switch (PCSS) implemented in GaAs as a reverse-biased pin structure with a passivation layer above the intrinsic GaAs substrate in the gap between the two electrodes of the device. The reverse-biased configuration in combination with the addition of the passivation layer greatly reduces surface current leakage that has been a problem for prior PCSS devices and enables employment of the much less expensive and more reliable DC charging systems instead of the pulsed charging systems that needed to be used with prior PCSS devices.

  14. GaN: Defect and Device Issues

    SciTech Connect (OSTI)

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

    1998-11-09T23:59:59.000Z

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

  15. 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.

  16. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01T23:59:59.000Z

    High content of excess As is incorporated in GaAs grown by low-temperature molecular-beam-epitaxy (LTMBE). The excess As exists primarily as As antisite defects AsGa and a lesser extent of gallium vacancies V[sub Ga]. The neutral AsGa-related defects were measured by infrared absorption at 1[mu]m. Gallium vacancies, V[sub Ga], was investigated by slow positron annihilation. Dependence of defect contents on doping was studied by Si and Be dopants. No free carriers are generated by n-type or p-type doping up to 10[sup 19] cm[sup [minus]3] Si or Be. Raman data indicate Be occupies Ga substitutional sites but Si atom is not substitutional. Si induces more As[sub Ga] in the layer. As As[sub Ga] increases, photoquenchable As[sub Ga] decreases. Fraction of photoquenchable defects correlates to defects within 3 nearest neighbor separations disrupting the metastability. Annealing reduces neutral As[sub Ga] content around 500C, similar to irradiation damaged and plastically deformed Ga[sub As], as opposed to bulk grown GaAs in which As[sub Ga]-related defects are stable up to 1100C. The lower temperature defect removal is due to V[sub Ga] enhanced diffusion of As[sub Ga] to As precipitates. The supersaturated V[sub GA] and also decreases during annealing. Annealing kinetics for As[sub Ga]-related defects gives 2.0 [plus minus] 0.3 eV and 1.5 [plus minus] 0.3 eV migration enthalpies for the As[sub Ga] and V[sub Ga]. This represents the difference between Ga and As atoms hopping into the vacancy. The non-photoquenchable As[sub Ga]-related defects anneal with an activation energy of 1.1 [plus minus] 0.3eV. Be acceptors can be activated by 800C annealing. Temperature difference between defect annealing and Be activation formation of As[sub Ga]-Be[sub Ga] pairs. Si donors can only be partially activated.

  17. 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

  18. 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.

  19. Strain-induced fundamental optical transition in (In,Ga)As/GaP quantum dots

    SciTech Connect (OSTI)

    Robert, C., E-mail: cedric.robert@insa-rennes.fr, E-mail: cedric.robert@tyndall.ie; Pedesseau, L.; Cornet, C.; Jancu, J.-M.; Even, J.; Durand, O. [Université Européenne de Bretagne, INSA Rennes, France and CNRS, UMR 6082 Foton, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France)] [Université Européenne de Bretagne, INSA Rennes, France and CNRS, UMR 6082 Foton, 20 Avenue des Buttes de Coësmes, 35708 Rennes (France); Nestoklon, M. O. [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)] [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Pereira da Silva, K. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain) [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); Departamento de Física, Universidade Federal do Ceará, P.O. Box 6030, Fortaleza–CE, 60455-970 (Brazil); Alonso, M. I. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain)] [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); Goñi, A. R. [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain) [ICMAB-CSIC, Campus UAB, 08193 Bellaterra (Spain); ICREA, Passeig Lluís Companys 23, 08010 Barcelona (Spain); Turban, P. [Equipe de Physique des Surfaces et Interfaces, Institut de Physique de Rennes UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex (France)] [Equipe de Physique des Surfaces et Interfaces, Institut de Physique de Rennes UMR UR1-CNRS 6251, Université de Rennes 1, F-35042 Rennes Cedex (France)

    2014-01-06T23:59:59.000Z

    The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a strong influence on the confinement potentials, principally, for the conduction band states. Indeed, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a large tensile strain region, having mainly Xz character. Photoluminescence experiments under hydrostatic pressure strongly support the theoretical conclusions.

  20. 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.

  1. PMC·I'Fl.

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

    not limited to: programmed lowering of thermostat settings, placement of timers on hot water heaters, installation of solar hot water systems. installation of efficient...

  2. FL J. Smith, Jr.

    Office of Legacy Management (LM)

    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 742EnergyOn AprilA group currentBradleyTableSelling CorpNew 1325.8.Enaineer;/:4,4ct. B. Duillap

  3. RELAP5 assessment using semiscale SBLOCA test S-NH-1. International Agreement Report

    SciTech Connect (OSTI)

    Lee, E.J.; Chung, B.D.; Kim, H.J. [Korea Inst. of Nuclear Safety, Taejon (Korea, Republic of)

    1993-06-01T23:59:59.000Z

    2-inch cold leg break test S-NH-1, conducted at the 1/1705 volume scaled facility Semiscale was analyzed using RELAP5/MOD2 Cycle 36.04 and MOD3 Version 5m5. Loss of HPIS was assumed, and reactor trip occurred on a low PZR pressure signal (13.1 MPa), and pumps began an unpowered coastdown on SI signal (12.5 MPa). The system was recovered by opening ADV`s when the PCT became higher than 811 K. Accumulator was finally injected into the system when the primary system pressure was less than 4.0 MPa. The experiment was terminated when the pressure reached the LPIS actuation set point RELAP5/MOD2 analysis demonstrated its capability to predict, with a sufficient accuracy, the main phenomena occurring in the depressurization transient, both from a qualitative and quantitative points of view. Nevertheless, several differences were noted regarding the break flow rate and inventory distribution due to deficiencies in two-phase choked flow model, horizontal stratification interfacial drag, and a CCFL model. The main reason for the core to remain nearly fully covered with the liquid was the under-prediction of the break flow by the code. Several sensitivity calculations were tried using the MOD2 to improve the results by using the different options of break flow modeling (downward, homogeneous, and area increase). The break area compensating concept based on ``the integrated break flow matching`` gave the best results than downward junction and homogeneous options. And the MOD3 showed improvement in predicting a CCFL in SG and a heatup in the core.

  4. Energy absorption in Ni-Mn-Ga/ polymer composites

    E-Print Network [OSTI]

    Feuchtwanger, Jorge

    2006-01-01T23:59:59.000Z

    In recent years Ni-Mn-Ga has attracted considerable attention as a new kind of actuator material. Off-stoichiometric single crystals of Ni2MnGa can regularly exhibit 6% strain in tetragonal martensites and orthorhombic ...

  5. Degradation mechanisms of GaN high electron mobility transistors

    E-Print Network [OSTI]

    Joh, Jungwoo

    2007-01-01T23:59:59.000Z

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

  6. On strongly GA-convex functions and stochastic processes

    SciTech Connect (OSTI)

    Bekar, Nurgül Okur [Department of Statistics, Giresun University, Giresun (Turkey); Akdemir, Hande Günay; ??can, ?mdat [Department of Mathematics, Giresun University, Giresun (Turkey)

    2014-08-20T23:59:59.000Z

    In this study, we introduce strongly GA-convex functions and stochastic processes. We provide related well-known Kuhn type results and Hermite-Hadamard type inequality for strongly GA-convex functions and stochastic processes.

  7. TEM-Untersuchungen an GaN basierten Halbleiterheterostrukturen fur

    E-Print Network [OSTI]

    Schubart, Christoph

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

  8. GaN Nanopore Arrays: Fabrication and Characterization

    E-Print Network [OSTI]

    Wang, Yadong

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

  9. Study of NH stretching vibrations in small ammonia clusters by infrared spectroscopy in He droplets and ab initio calculations

    SciTech Connect (OSTI)

    Slipchenko, Mikhail N.; Sartakov, Boris G.; Vilesov, Andrey F.; Xantheas, Sotiris S.

    2007-08-09T23:59:59.000Z

    Infrared spectra of the NH stretching vibrations of (NH3)n clusters (n=2-4) have been obtained using the helium droplet isolation technique and first principles electronic structure anharmonic calculations. The measured spectra exhibit well-resolved bands, which have been assigned to the ?1, ?3, and 2?4 modes of the ammonia fragments in the clusters. The formation of a hydrogen bond in ammonia dimers leads to an increase of the infrared intensity by about a factor of four. In the larger clusters the infrared intensity per hydrogen bond is close to the one for dimers and approaches the value in the NH3 crystal. The intensity of the 2?4 overtone band in the trimer and tetramer increases by a factor of 10 relative to that in the monomer and dimer, and is comparable to the intensity of the ?1 and ?3 fundamental bands in larger clusters. This indicates the onset of the strong anharmonic coupling of the 2?4 and ?1 modes in larger clusters. The experimental assignments are compared to the ones obtained from first principles electronic structure anharmonic calculations for the dimer and trimer clusters. The anharmonic calculations were performed at the Møller-Plesset (MP2) level of electronic structure theory and were based on a second-order perturbative evaluation of rovibrational parameters and their effects on the vibrational spectra and average structures. In general there is excellent (<20 cm-1) agreement between the experimentally measured band origins for the N-H stretching frequencies and the calculated anharmonic vibrational frequencies. However, the calculations were found to overestimate the infrared intensities in clusters by about a factor of four. This work was supported by the Office of Basic Energy Sciences of the Department of Energy, in part by the Chemical Sciences program and in part by the Engineering and Geosciences Division. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  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. 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 ...

  12. 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.

  13. Quercetin 3-O-methyl ether protects FL83B cells from copper induced oxidative stress through the PI3K/Akt and MAPK/Erk pathway

    SciTech Connect (OSTI)

    Tseng, Hsiao-Ling, E-mail: lily1001224@gmail.com [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China)] [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China); Li, Chia-Jung, E-mail: 97751101@stmail.tcu.edu.tw [Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan (China)] [Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan (China); Huang, Lin-Huang, E-mail: yg1236@yahoo.com.tw [School of Medicine, Institute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan (China)] [School of Medicine, Institute of Traditional Medicine, National Yang-Ming University, Taipei, Taiwan (China); Chen, Chun-Yao, E-mail: cychen@mail.tcu.edu.tw [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China)] [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China); Tsai, Chun-Hao, E-mail: 100726105@stmail.tcu.edu.tw [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China)] [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China); Lin, Chun-Nan, E-mail: lincna@cc.kmu.edu.tw [Faculty of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan (China) [Faculty of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan (China); Department of Biological Science and Technology, School of Medicine, China Medical University, Taichung, Taiwan (China); Hsu, Hsue-Yin, E-mail: hsueyin@mail.tcu.edu.tw [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China)] [Department of Life Sciences, Tzu Chi University, Hualien, Taiwan (China)

    2012-10-01T23:59:59.000Z

    Quercetin is a bioflavonoid that exhibits several biological functions in vitro and in vivo. Quercetin 3-O-methyl ether (Q3) is a natural product reported to have pharmaceutical activities, including antioxidative and anticancer activities. However, little is known about the mechanism by which it protects cells from oxidative stress. This study was designed to investigate the mechanisms by which Q3 protects against Cu{sup 2+}-induced cytotoxicity. Exposure to Cu{sup 2+} resulted in the death of mouse liver FL83B cells, characterized by apparent apoptotic features, including DNA fragmentation and increased nuclear condensation. Q3 markedly suppressed Cu{sup 2+}-induced apoptosis and mitochondrial dysfunction, characterized by reduced mitochondrial membrane potential, caspase-3 activation, and PARP cleavage, in Cu{sup 2+}-exposed cells. The involvement of PI3K, Akt, Erk, FOXO3A, and Mn-superoxide dismutase (MnSOD) was shown to be critical to the survival of Q3-treated FL83B cells. The liver of both larval and adult zebrafish showed severe damage after exposure to Cu{sup 2+} at a concentration of 5 ?M. Hepatic damage induced by Cu{sup 2+} was reduced by cotreatment with Q3. Survival of Cu{sup 2+}-exposed larval zebrafish was significantly increased by cotreatment with 15 ?M Q3. Our results indicated that Cu{sup 2+}-induced apoptosis in FL83B cells occurred via the generation of ROS, upregulation and phosphorylation of Erk, overexpression of 14-3-3, inactivation of Akt, and the downregulation of FOXO3A and MnSOD. Hence, these results also demonstrated that Q3 plays a protective role against oxidative damage in zebrafish liver and remarked the potential of Q3 to be used as an antioxidant for hepatocytes. Highlights: ? Protective effects of Q3 on Cu{sup 2+}-induced oxidative stress in vitro and in vivo. ? Cu{sup 2+} induced apoptosis in FL83B cells via ROS and the activation of Erk. ? Q3 abolishes Cu{sup 2+}-induced apoptosis through the PI3K/Akt and MAPK/Erk pathway.

  14. Time-Resolved XAFS Spectroscopic Studies of B-H and N-H Oxidative Addition to Transition Metal Catalysts Relevant to Hydrogen Storage

    SciTech Connect (OSTI)

    Bitterwolf, Thomas E. [University of Idaho

    2014-12-09T23:59:59.000Z

    Successful catalytic dehydrogenation of aminoborane, H3NBH3, prompted questions as to the potential role of N-H oxidative addition in the mechanisms of these processes. N-H oxidative addition reactions are rare, and in all cases appear to involve initial dative bonding to the metal by the amine lone pairs followed by transfer of a proton to the basic metal. Aminoborane and its trimethylborane derivative block this mechanism and, in principle, should permit authentic N-H oxidative attrition to occur. Extensive experimental work failed to confirm this hypothesis. In all cases either B-H complexation or oxidative addition of solvent C-H bonds dominate the chemistry.

  15. 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

  16. 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

  17. 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

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

    E-Print Network [OSTI]

    Cohen, Philip I.

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

  19. 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

  20. Recent progress in InGaAsSb/GaSb TPV devices

    SciTech Connect (OSTI)

    Shellenbarger, Z.A.; Mauk, M.G.; DiNetta, L.C. [AstroPower, Inc., Newark, DE (United States); Charache, G.W. [Lockheed Martin Corp., Schenectady, NY (United States)

    1996-05-01T23:59:59.000Z

    AstroPower is developing InGaAsSb thermophotovoltaic (TPV) devices. This photovoltaic cell is a two-layer epitaxial InGaAsSb structure formed by liquid-phase epitaxy on a GaSb substrate. The (direct) bandgap of the In{sub 1{minus}x}Ga{sub x}As{sub 1{minus}y}Sb{sub y} alloy is 0.50 to 0.55 eV, depending on its exact alloy composition (x,y); and is closely lattice-matched to the GaSb substrate. The use of the quaternary alloy, as opposed to a ternary alloy--such as, for example InGaAs/InP--permits low bandgap devices optimized for 1,000 to 1,500 C thermal sources with, at the same time, near-exact lattice matching to the GaSb substrate. Lattice matching is important since even a small degree of lattice mismatch degrades device performance and reliability and increases processing complexity. Internal quantum efficiencies as high as 95% have been measured at a wavelength of 2 microns. At 1 micron wavelengths, internal quantum efficiencies of 55% have been observed. The open-circuit voltage at currents of 0.3 A/cm{sup 2} is 0.220 volts and 0.280 V for current densities of 2 A/cm{sup 2}. Fill factors of 56% have been measured at 60 mA/cm{sup 2}. However, as current density increases there is some decrease in fill factor. The results to date show that the GaSb-based quaternary compounds provide a viable and high performance energy conversion solution for thermophotovoltaic systems operating with 1,000 to 1,500 C source temperatures.

  1. 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.

  2. 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.

  3. TEM and HRXRD Analysis of LP MOVPE Grown InGaP/GaAs epilayers

    SciTech Connect (OSTI)

    Pelosi, Claudio; Bosi, Matteo; Attolini, Giovanni; Germini, Fabrizio; Frigeri, Cesare [CNR-IMEM Institute, Parco Area delle Scienze 37a, Loc Fontanini 43010 Parma (Italy); Prutskij, Tatiana [Instituto de Ciencias, BUAP, Privada 17 Norte, no. 3417, colSanMiguel Hueyotlipan, 72050 Puebla, Pue. (Mexico)

    2007-04-10T23:59:59.000Z

    The diffusion phenomena at interfaces between GaAs/InGaP layers grown by low pressure MOVPE have been studied by dark field (DF) transmission Electron Microscopy (TEM) and High resolution X-ray Diffractometry (HRXRD). By comparing the results of the two techniques a mismatched layer containing P or P and In has been evidenced. The causes of this behavior are briefly discussed.

  4. Guided Neuronal Growth on Arrays of Biofunctionalized GaAs/InGaAs Semiconductor Microtubes

    E-Print Network [OSTI]

    Cornelius S. Bausch; Aune Koitmäe; Eric Stava; Amanda Price; Pedro J. Resto; Yu Huang; David Sonnenberg; Yuliya Stark; Christian Heyn; Justin C. Williams; Erik W. Dent; Robert H. Blick

    2013-05-06T23:59:59.000Z

    We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes -- similar to myelin -- is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.

  5. InGaN/GaN quantum wells for polariton laser diodes: Role of inhomogeneous broadening

    SciTech Connect (OSTI)

    Glauser, Marlene; Mounir, Christian; Rossbach, Georg; Feltin, Eric; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas [École Polytechnique Fédérale de Lausanne (EPFL), Institute of Condensed Matter Physics, CH-1015 Lausanne (Switzerland)

    2014-06-21T23:59:59.000Z

    Contrary to the case of III-nitride based visible light-emitting diodes for which the inhomogeneous linewidth broadening characteristic of InGaN-based multiple quantum well (MQW) heterostructures does not appear as a detrimental parameter, such a broadening issue can prevent a microcavity (MC) system entering into the strong light-matter coupling regime (SCR). The impact of excitonic disorder in low indium content (x???0.1) In{sub x}Ga{sub 1–x}N/GaN MQW active regions is therefore investigated for the subsequent realization of polariton laser diodes by considering both simulations and optical characterizations. It allows deriving the requirements for such MQWs in terms of absorption, emission linewidth, and Stokes shift. Systematic absorption-like and photoluminescence (PL) spectroscopy experiments are performed on single and multiple In{sub 0.1}Ga{sub 0.9}N/GaN quantum wells (QWs). Micro-PL mappings reveal a low temperature PL linewidth of ?30?meV, compatible with SCR requirements, for single QWs for which the microscopic origin responsible for this broadening is qualitatively discussed. When stacking several InGaN/GaN QWs, a departure from such a narrow linewidth value and an increase in the Stokes shift are observed. Various possible reasons for this degradation such as inhomogeneous built-in field distribution among the QWs are then identified. An alternative solution for the MC design to achieve the SCR with the InGaN alloy is briefly discussed.

  6. Rapid Communications Strong piezoelectricity in individual GaN nanowires

    E-Print Network [OSTI]

    Espinosa, Horacio D.

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

  7. GaN Radiation Detectors for Particle Physics and

    E-Print Network [OSTI]

    Glasgow, University of

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

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

    E-Print Network [OSTI]

    California at Santa Barbara, University of

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

  9. 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.

  10. A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+

    E-Print Network [OSTI]

    McKittrick, Joanna

    A New Combustion Synthesis Method for GaN:Eu3+ and Ga2O3 :Eu3+ Luminescent Powders G. A. Hirata1 between the precursors. The preparation of Eu-doped Ga2O3 powders was achieved using a new combustion)3 and Ga(NO3)3 as the precursors and hydrazine as (non-carbonaceous) fuel. A spontaneous combustion

  11. 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

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

    E-Print Network [OSTI]

    Feenstra, Randall

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

  13. 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

  14. 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.

  15. Lattice-Mismatched GaAs/InGaAs Two-Junction Solar Cells by Direct Wafer Bonding

    SciTech Connect (OSTI)

    Tanabe, K.; Aiken, D. J.; Wanlass, M. W.; Morral, A. F.; Atwater, H. A.

    2006-01-01T23:59:59.000Z

    Direct bonded interconnect between subcells of a lattice-mismatched III-V compound multijunction cell would enable dislocation-free active regions by confining the defect network needed for lattice mismatch accommodation to tunnel junction interfaces, while metamorphic growth inevitably results in less design flexibility and lower material quality than is desirable. The first direct-bond interconnected multijunction solar cell, a two-terminal monolithic GaAs/InGaAs two-junction solar cell, is reported and demonstrates viability of direct wafer bonding for solar cell applications. The tandem cell open-circuit voltage was approximately the sum of the subcell open-circuit voltages. This achievement shows direct bonding enables us to construct lattice-mismatched III-V multijunction solar cells and is extensible to an ultrahigh efficiency InGaP/GaAs/InGaAsP/InGaAs four-junction cell by bonding a GaAs-based lattice-matched InGaP/GaAs subcell and an InP-based lattice-matched InGaAsP/InGaAs subcell. The interfacial resistance experimentally obtained for bonded GaAs/InP smaller than 0.10 Ohm-cm{sup 2} would result in a negligible decrease in overall cell efficiency of {approx}0.02%, under 1-sun illumination.

  16. X-ray diffraction analysis of InGaP/GaAs heterointerfaces grown by metalorganic chemical vapor deposition

    SciTech Connect (OSTI)

    Nittono, T.; Hyuga, F. [NTT System Electronics Laboratories 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-01 (Japan)] [NTT System Electronics Laboratories 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-01 (Japan)

    1997-03-01T23:59:59.000Z

    InGaP/GaAs heterointerfaces grown by metalorganic chemical vapor deposition have been characterized by a high-resolution x-ray diffraction analysis of multiple quantum well structures. The flow of AsH{sub 3} to InGaP surface produces an InGaAs-like interfacial layer at the GaAs-on-InGaP interface, indicating P atoms of the InGaP surface are easily replaced by As atoms. The flow of PH{sub 3} to GaAs surface, on the other hand, does not make any detectable interfacial layer, indicating that almost no As atoms of the GaAs surface are replaced by P atoms. It is also found that the flow of trimethylgallium (TMG) to the InGaP surface produces a GaP-like interfacial layer. This interfacial layer is probably formed by the reaction between TMG and excessive P atoms on the InGaP surface or residual PH{sub 3} in the growth chamber. {copyright} {ital 1997 American Institute of Physics.}

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

    E-Print Network [OSTI]

    Nabben, Reinhard

    2006-01-01T23:59:59.000Z

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

  18. Superluminescence in Green Emission GaInN/GaN Quantum Well Structures under Pulsed Laser Excitation

    E-Print Network [OSTI]

    Wetzel, Christian M.

    and bulk GaN substrates, respectively. Under intense pulsed photo excitation, we observed strong the same excitation conditions, the blue shift for the m-axis grown structure on bulk GaN substrate is less-plane sapphire substrate and along the non-polar m-axis on m-plane bulk GaN substrate. The frequently used

  19. Composition and Interface Analysis of InGaN/GaN Multiquantum-Wells on GaN Substrates Using Atom Probe Tomography

    SciTech Connect (OSTI)

    Liu, Fang; Huang, Li; Davis, Robert F.; Porter, Lisa M.; Schreiber, Daniel K.; Kuchibhatla, S. V. N. T.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Preble, Edward; Paskova, Tanya; Evans, K. R.

    2014-09-04T23:59:59.000Z

    In0.20Ga0.80N/GaN multi-quantum wells grown on [0001]-oriented GaN substrates with and without an InGaN buffer layer were characterized using three-dimensional atom probe tomography. In all samples, the upper interfaces of the QWs were slightly more diffuse than the lower interfaces. The buffer layers did not affect the roughness of the interfaces within the quantum well structure, a result attributed to planarization of the surface of the 1st GaN barrier layer which had an average root-mean-square roughness of 0.177 nm. The In and Ga distributions within the MQWs followed the expected distributions for a random alloy with no indications of In clustering.

  20. Point defect balance in epitaxial GaSb

    SciTech Connect (OSTI)

    Segercrantz, N., E-mail: natalie.segercrantz@aalto.fi; Slotte, J.; Makkonen, I.; Kujala, J.; Tuomisto, F. [Department of Applied Physics, Aalto University, P.O. Box 14100, FIN-00076 Aalto Espoo (Finland); Song, Y.; Wang, S. [Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg (Sweden); State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences 865 Changning Road, Shanghai 200050 (China)

    2014-08-25T23:59:59.000Z

    Positron annihilation spectroscopy in both conventional and coincidence Doppler broadening mode is used for studying the effect of growth conditions on the point defect balance in GaSb:Bi epitaxial layers grown by molecular beam epitaxy. Positron annihilation characteristics in GaSb are also calculated using density functional theory and compared to experimental results. We conclude that while the main positron trapping defect in bulk samples is the Ga antisite, the Ga vacancy is the most prominent trap in the samples grown by molecular beam epitaxy. The results suggest that the p–type conductivity is caused by different defects in GaSb grown with different methods.

  1. Supporting Information Surface Electric Fields of Aqueous Solutions of NH4NO3, Mg(NO3)2, NaNO3,

    E-Print Network [OSTI]

    S1 Supporting Information Surface Electric Fields of Aqueous Solutions of NH4NO3, Mg(NO3)2, NaNO3 interfaces of (a) 1.0 M and 2.0 M LiNO3, (b) 1.0 M and 1.7 M NaNO3, (c) 1.0 M and 1.6 M NH4NO3, and (d) 1.0 M water 1.0 M NaNO3 1.7 M NaNO3 c water 1.0 M NH4 NO3 1.6 M NH4 NO3 | (2) | 2 (10 3 arb.units) Wavenumber

  2. Room-temperature cw operation of InGaAsP/InGaP lasers at 727 nm grown on GaAs substrates by liquid phase epitaxy

    SciTech Connect (OSTI)

    Wakao, K.; Nishi, H.; Kusunoki, T.; Isozumi, S.; Ohsaka, S.

    1984-06-01T23:59:59.000Z

    InGaAsP/InGaP lasers emitting at 724--727 nm have been fabricated on GaAs substrates using liquid phase epitaxy. The threshold current is reduced to 8 kA/cm/sup 2/ by thinning the active layer. Room-temperature cw operation is achieved for the first time in the lasing wavelength range below 760 nm in this quaternary system.

  3. Self-assembled In0.5Ga0.5As quantum dots on GaP Yuncheng Song,a

    E-Print Network [OSTI]

    Haller, Gary L.

    SAQDs . Several groups have investigated the growth of both InP and In-rich InGaP SAQDs on GaP.7­12 Most temperature operation of vis- ible light emitting diodes LEDs using InP/GaP and InGaP/ GaP SAQDs, respectively

  4. Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J. Jahns

    E-Print Network [OSTI]

    Jahns, Jürgen

    Current crowding in GaInN / GaN LEDs grown on insulating substrates X. Guo, E. F. Schubert and J spreading in a mesa-structure GaN-based LED grown on an insulating or semi-insulating substrate. (b. Jahns Current crowding in mesa-structure GaInN/GaN light-emitting diodes (LEDs) grown on insulating

  5. 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

  6. 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

  7. 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

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

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

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

  9. 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.

  10. Influence of Ga content on the structure and anomalous Hall effect of Fe{sub 1?x}Ga{sub x} thin films on GaSb(100)

    SciTech Connect (OSTI)

    Anh Tuan, Duong; Shin, Yooleemi; Viet Cuong, Tran; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Phan, The-Long [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

    2014-05-07T23:59:59.000Z

    The Fe{sub 1?x}Ga{sub x} thin films (x?=?0.4, 0.5) have been grown on GaSb(100) substrate using molecular beam epitaxy. An epitaxial film with bcc ?-Fe crystal structure (A2) is observed in Fe{sub 0.6}Ga{sub 0.4} film, while an impure Fe{sub 3}Ga phase with DO{sub 3} structure is appeared in Fe{sub 0.5}Ga{sub 0.5} film. The saturated magnetizations at room temperature are observed to be 570?emu/cm{sup 3} and 180?emu/cm{sup 3} and the coercivities to be 170 and 364?Oe for Fe{sub 0.6}Ga{sub 0.4} and Fe{sub 0.5}Ga{sub 0.5}, respectively. A hysteresis trend in Hall resistance vs. magnetic field is observed for Fe{sub 0.5}Ga{sub 0.5} film. However, there is a weak hysteresis noticed in Fe{sub 0.4}Ga{sub 0.6} thin film.

  11. 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.

  12. Dynamics of thermalization in GaInN/GaN quantum wells grown on ammonothermal GaN

    SciTech Connect (OSTI)

    Binder, J.; Korona, K. P.; Wysmo?ek, A.; Kami?ska, M. [Faculty of Physics, University of Warsaw, ul. Hoza 69, 00-681 Warsaw (Poland); Köhler, K.; Kirste, L.; Ambacher, O. [Fraunhofer Institute for Applied Solid State Physics, Tullastr. 72, 79108 Freiburg (Germany); Zaj?c, M.; Dwili?ski, R. [AMMONO SA, Czerwonego Krzy?a 2/31, 00-377 Warsaw (Poland)

    2013-12-14T23:59:59.000Z

    In this work, we present measurements of the dynamics of photoexcited carriers in GaInN/GaN quantum wells (QWs) grown on ammonothermal GaN, especially thermalization and recombination rates. Emission properties were measured by time-resolved photoluminescence (PL) and electroluminescence spectroscopy. Due to the use of high quality homoepitaxial material, we were able to obtain very valuable data on carrier thermalization. The temperature dependence of the QW energy observed in PL shows characteristic S-shape with a step of about 10?meV. Such a behavior (related to thermalization and localization at potential fluctuations) is often reported for QWs; but in our samples, the effect is smaller than in heteroepitaxial InGaN/GaN QWs due to lower potential fluctuation in our material. Absorption properties were studied by photocurrent spectroscopy measurements. A comparison of emission and absorption spectra revealed a shift in energy of about 60?meV. Contrary to PL, the QW energy observed in absorption decreases monotonically with temperature, which can be described by a Bose-like dependence E(T)?=?E(0) ? ?/(exp(?/T) ? 1), with parameters ??=?(0.11?±?0.01) eV, ??=?(355?±?20)?K, or by a Varshni dependence with coefficients ??=?(10?±?3) × 10{sup ?4}?eV/K and ??=?(1500?±?500) K. Taking into account absorption and emission, the fluctuation amplitude (according to Eliseev theory) was ??=?14?meV. The time resolved PL revealed that in a short period (<1?ns) after excitation, the PL peaks were broadened because of the thermal distribution of carriers. We interpreted this distribution in terms of quasi-temperature (T{sub q}) of the carriers. The initial T{sub q} was of the order of 500?K. The thermalization led to a fast decrease of T{sub q}. The obtained cooling time in the QW was ?{sub C}?=?0.3?ns, which was faster than the observed recombination time ?{sub R}?=?2.2?ns (at 4?K)

  13. 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.

  14. 0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1eV)/GaInAs(0.7eV) Four-Junction Solar Cell

    SciTech Connect (OSTI)

    Friedman, D. J.; Geisz, J. F.; Norman, A. G.; Wanlass, M. W.; Kurtz, S. R.

    2006-01-01T23:59:59.000Z

    We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga{sub 0.5}In{sub 0.5} P/GaAs/Ga{sub 0.75}In{sub 0.25}As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga{sub 0.75}In{sub 0.25}As third junction is the last one grown, has demonstrated 38% efficiency, and 40% is likely in the near future. To achieve still further gains, a lower-bandgap Ga{sub x}In{sub 1-x}As fourth junction could be added to the three-junction structure for a four-junction cell whose efficiency could exceed 45% under concentration. Here, we present the initial development of the Ga{sub x}In{sub 1-x}As fourth junction. Junctions of various bandgaps ranging from 0.88 to 0.73 eV were grown, in order to study the effect of the different amounts of lattice mismatch. At a bandgap of 0.88 eV, junctions were obtained with very encouraging {approx}80% quantum efficiency, 57% fill factor, and 0.36 eV open-circuit voltage. The device performance degrades with decreasing bandgap (i.e., increasing lattice mismatch). We model the four-junction device efficiency vs. fourth junction bandgap to show that an 0.7-eV fourth-junction bandgap, while optimal if it could be achieved in practice, is not necessary; an 0.9-eV bandgap would still permit significant gains in multijunction cell efficiency while being easier to achieve than the lower-bandgap junction.

  15. Theory of Hydride-Proton Transfer (HPT) Carbonyl Reduction by [Os(III)(tpy)(Cl)(NH=CHCH3)(NSAr)

    SciTech Connect (OSTI)

    Ess, Daniel H.; Schauer, Cynthia; Meyer, Thomas J.

    2010-01-01T23:59:59.000Z

    Quantum mechanical analysis reveals that carbonyl reduction of aldehydes and ketones by the imine-based reductant cis-[Os{sup III}(tpy)(Cl)(NH?CHCH{sub 3})(NSAr)] (2), which is accessible by reduction of the analogous nitrile, occurs by hydride-proton transfer (HPT) involving both the imine and sulfilimido ligands. In carbonyl reduction, water or alcohol is necessary to significantly lower the barrier for proton shuttling between ligands. The ?N(H)SAr group activates the carbonyl group through hydrogen bonding while the ?NC(H)CH{sub 3} ligand delivers the hydride.

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

    E-Print Network [OSTI]

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

    2006-01-01T23:59:59.000Z

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

  17. Table 1 -ESTIMATED REDUCTION IN 1985 COTTON YIELDS RESULTING FROM INSECTDAMAGE TOTAL YIELD 13,622 bales INSECTS Loss in AL AZ AR CA FL GA LA MS MO NM NC OK SC TN TX VA No.

    E-Print Network [OSTI]

    Ray, David

    Average cost for all states nTotal yield for all states o Total acres for all states *Does not include BWE cost

  18. Refractive index of erbium doped GaN thin films

    SciTech Connect (OSTI)

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

    2014-08-25T23:59:59.000Z

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

  19. Effect of Temperature on GaGdO/GaN Metal Oxide Semiconductor Field Effect Transistors

    SciTech Connect (OSTI)

    Abernathy, C.R.; Baca, A.; Chu, S.N.G.; Hong, M.; Lothian, J.R.; Marcus, M.A.; Pearton, S.J.; Ren, F.; Schurman, M.J.

    1998-10-14T23:59:59.000Z

    GaGdO was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal oxide semiconductor field effect transistor (MOSFET). This is the fmt demonstration of such a device in the III-Nitride system. Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal semiconductor field effeet transistor (MESFET) fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400 C. Modeling of the effeet of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device.

  20. Graphene in ohmic contact for both n-GaN and p-GaN

    SciTech Connect (OSTI)

    Zhong, Haijian; Liu, Zhenghui; Shi, Lin; Xu, Gengzhao; Fan, Yingmin; Huang, Zengli [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Wang, Jianfeng; Ren, Guoqiang; Xu, Ke, E-mail: kxu2006@sinano.ac.cn [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-05-26T23:59:59.000Z

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I–V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.

  1. Photocapacitance study of type-II GaSb/GaAs quantum ring solar cells

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Carrington, P. J.; Krier, A. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2014-01-07T23:59:59.000Z

    In this study, the density of states associated with the localization of holes in GaSb/GaAs quantum rings are determined by the energy selective charging of the quantum ring distribution. The authors show, using conventional photocapacitance measurements, that the excess charge accumulated within the type-II nanostructures increases with increasing excitation energies for photon energies above 0.9?eV. Optical excitation between the localized hole states and the conduction band is therefore not limited to the ?(k?=?0) point, with pseudo-monochromatic light charging all states lying within the photon energy selected. The energy distribution of the quantum ring states could consequently be accurately related from the excitation dependence of the integrated photocapacitance. The resulting band of localized hole states is shown to be well described by a narrow distribution centered 407?meV above the GaAs valence band maximum.

  2. Efficiency enhancement of InGaN/GaN solar cells with nanostructures

    SciTech Connect (OSTI)

    Bai, J.; Yang, C. C.; Athanasiou, M.; Wang, T. [Department of Electronics and Electrical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2014-02-03T23:59:59.000Z

    We demonstrate InGaN/GaN multi-quantum-well solar cells with nanostructures operating at a wavelength of 520?nm. Nanostructures with a periodic nanorod or nanohole array are fabricated by means of modified nanosphere lithography. Under 1 sun air-mass 1.5 global spectrum illumination, a fill factor of 50 and an open circuit voltage of 1.9?V are achieved in spite of very high indium content in InGaN alloys usually causing degradation of crystal quality. Both the nanorod array and the nanohole array significantly improve the performance of solar cells, while a larger enhancement is observed for the nanohole array, where the conversion efficiency is enhanced by 51%.

  3. 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.

  4. GaN based nanorods for solid state lighting

    SciTech Connect (OSTI)

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

    2012-04-01T23:59:59.000Z

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

  5. 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

  6. 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

  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. Simultaneous enhancement of electron overflow reduction and hole injection promotion by tailoring the last quantum barrier in InGaN/GaN light-emitting diodes

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    the last quantum barrier in InGaN/GaN light-emitting diodes Zabu Kyaw, Zi-Hui Zhang, Wei Liu, Swee Tiam Tan injection and efficiency droop in InGaN/GaN light-emitting diodes with step-stage multiple- quantum distribution in InGaN/GaN light-emitting diodes with graded thickness quantum barriers Appl. Phys. Lett. 102

  9. 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

  10. Graded-base InGaN/GaN heterojunction bipolar light-emitting transistors B. F. Chu-Kung,a

    E-Print Network [OSTI]

    Asbeck, Peter M.

    Graded-base InGaN/GaN heterojunction bipolar light-emitting transistors B. F. Chu-Kung,a M. Feng, G; published online 25 August 2006 The authors report radiative recombination from a graded-base InGaN/GaN microwave power has been obtained from GaN field-effect transistors, very few operational GaN-based HBTs

  11. InGaN/GaN multiple-quantum-well light-emitting diodes with a grading InN composition suppressing the Auger recombination

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    InGaN/GaN multiple-quantum-well light-emitting diodes with a grading InN composition suppressing://scitation.aip.org/content/aip/journal/apl/105/3?ver=pdfcov Published by the AIP Publishing Articles you may be interested in High efficiency InGaN/GaN (2014); 10.1063/1.4867023 Effect of V-defects on the performance deterioration of InGaN/GaN multiple

  12. 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

  13. Fabry-Perot effects in InGaN/GaN heterostructures on Si-substrate C. Hums, T. Finger, T. Hempel, J. Christen, and A. Dadgara

    E-Print Network [OSTI]

    Nabben, Reinhard

    Fabry-Perot effects in InGaN/GaN heterostructures on Si-substrate C. Hums, T. Finger, T. Hempel, J spectra of InGaN/GaN heterostructures and quantum wells epitaxially grown on Si 111 substrates. This Fabry-Perot effect results from the high refractive index contrasts at the GaN/Si and the Air/InGaN interfaces

  14. 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

  15. 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

  16. On the mechanisms of InGaN electron cooler in InGaN/GaN light-emitting diodes

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    . Schubert, Q. Dai, J. K. Kim, E. F. Schubert, J. Piprek, and Y. Park, "Origin of efficiency droop in Ga. Tansu, "Current injection efficiency induced efficiency-droop in InGaN quantum well light. Van de Walle, "Indirect Auger recombination as a cause of efficiency droop in nitride light

  17. 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}.

  18. Temperature dependency of the emission properties from positioned In(Ga)As/GaAs quantum dots

    SciTech Connect (OSTI)

    Braun, T.; Schneider, C.; Maier, S.; Forchel, A.; Höfling, S.; Kamp, M. [Technische Physik, Physikalisches Institut and Wilhelm Conrad Röntgen-Research Center for Complex Material Systems, Universität Würzburg, Am Hubland, D-97074, Würzburg (Germany); Igusa, R.; Iwamoto, S.; Arakawa, Y. [University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2014-09-15T23:59:59.000Z

    In this letter we study the influence of temperature and excitation power on the emission linewidth from site-controlled InGaAs/GaAs quantum dots grown on nanoholes defined by electron beam lithography and wet chemical etching. We identify thermal electron activation as well as direct exciton loss as the dominant intensity quenching channels. Additionally, we carefully analyze the effects of optical and acoustic phonons as well as close-by defects on the emission linewidth by means of temperature and power dependent micro-photoluminescence on single quantum dots with large pitches.

  19. Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces

    SciTech Connect (OSTI)

    Kang, M.; Wu, J. H.; Chen, H. Y.; Thornton, K.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-08-12T23:59:59.000Z

    We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

  20. Wavelength limits for InGaN quantum wells on GaN

    SciTech Connect (OSTI)

    Pristovsek, Markus, E-mail: markus@pristovsek.de [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)] [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2013-06-17T23:59:59.000Z

    The emission wavelength of coherently strained InGaN quantum wells (QW) is limited by the maximum thickness before relaxation starts. For high indium contents x>40% the resulting wavelength decreases because quantum confinement dominates. For low indium content x<40% the electron hole wave function overlap (and hence radiative emission) is strongly reduced with increasing QW thickness due to the quantum confined Stark effect and imposes another limit. This results in a maximum usable emission wavelength at around 600?nm for QWs with 40%-50% indium content. Relaxed InGaN buffer layers could help to push this further, especially on non- and semi-polar orientations.

  1. Application of the ASME code in the design of the GA-4 and GA-9 casks

    SciTech Connect (OSTI)

    Mings, W.J. (USDOE Idaho Field Office, Idaho Falls, ID (United States)); Koploy, M.A. (General Atomics, San Diego, CA (United States))

    1992-01-01T23:59:59.000Z

    General Atomics (GA) is developing two spent fuel shipping casks for transport by legal weight truck (LWT). The casks are designed to the loading, environmental conditions and safety requirements defined in Title 10 of the Code of Federal Regulations, Part 71 (10CFR71). To ensure that all components of the cask meet the 10CFR71 rules, GA established structural design criteria for each component based on NRC Regulatory Guides and the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). This paper discusses the criteria used for different cask components, how they were applied and the conservatism and safety margins built into the criteria and assumption.

  2. Application of the ASME code in the design of the GA-4 and GA-9 casks

    SciTech Connect (OSTI)

    Mings, W.J. [USDOE Idaho Field Office, Idaho Falls, ID (United States); Koploy, M.A. [General Atomics, San Diego, CA (United States)

    1992-08-01T23:59:59.000Z

    General Atomics (GA) is developing two spent fuel shipping casks for transport by legal weight truck (LWT). The casks are designed to the loading, environmental conditions and safety requirements defined in Title 10 of the Code of Federal Regulations, Part 71 (10CFR71). To ensure that all components of the cask meet the 10CFR71 rules, GA established structural design criteria for each component based on NRC Regulatory Guides and the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). This paper discusses the criteria used for different cask components, how they were applied and the conservatism and safety margins built into the criteria and assumption.

  3. Two-color picosecond and continuous-wave experiments on anti-Stokes and Stokes carrier-transfer phenomena in GaAs/AlxGa1 xAs and InGaP2 /AlxGa1 xAs heterostructures

    E-Print Network [OSTI]

    Hohng, Sung Chul

    -transfer phenomena in GaAs/AlxGa1 xAs and InGaP2 /AlxGa1 xAs heterostructures S. C. Hohng, D. W. Khang, Y. H. Ahn, J evidence of the two-step absorption process in anti-Stokes photoluminescence in both GaAs/AlxGa1 xAs and InGaP

  4. Demonstration of a semipolar (10(1)over-bar(3)over-bar) InGaN/GaN green light emitting diode

    E-Print Network [OSTI]

    2005-01-01T23:59:59.000Z

    InGaN / GaN green light emitting diode R. Sharma, a? P. M.green ??525 nm? light emitting diode ?LED?. The fabricated

  5. 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.

  6. Ion-beam-induced chemical disorder in GaN

    SciTech Connect (OSTI)

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

    2009-09-08T23:59:59.000Z

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

  7. 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.

  8. O?[]O? nuclear ?-decay of ?²Ga

    E-Print Network [OSTI]

    Hyman, Bruce Carl

    1999-01-01T23:59:59.000Z

    information, MARS was focused such that only fully stripped N=Z ions were passed, with the vast majority of them being Ga. The second phase of the experiment was a I3-y coincidence experiment. At the back-end of MARS, a 1" x 1 '!4" x 3" four..., using the Weinberg-Salam model of electroweak interactions, to be [23]: A& ? d, ?= ? [41n(mz/m )+ln(m /m?)+2K+A +" ]. (16) Here mz is the mass of the Z boson, me the proton mass, mx is the low energy cutoff for the second and third terms that arise...

  9. A. Kusiak, Data Mining and Decision Making, in B.V. Dasarathy (Ed.), Proceedings of the SPIE Conference on Data Mining and Knowledge Discovery: Theory, Tools, and Technology IV, Vol. 4730, SPIE, Orlando, FL, April 2002, pp. 155-165.

    E-Print Network [OSTI]

    Kusiak, Andrew

    A. Kusiak, Data Mining and Decision Making, in B.V. Dasarathy (Ed.), Proceedings of the SPIE Conference on Data Mining and Knowledge Discovery: Theory, Tools, and Technology IV, Vol. 4730, SPIE, Orlando, FL, April 2002, pp. 155-165. Data Mining and Decision Making Andrew Kusiak Department of Mechanical

  10. Panel: Microgrid Research and Field Testing IEEE PES General Meeting, 24-28 June 2007, Tampa, FL 1 In general, a microgrid can operate in both the grid-connected

    E-Print Network [OSTI]

    Panel: Microgrid Research and Field Testing IEEE PES General Meeting, 24-28 June 2007, Tampa, FL 1 Abstract In general, a microgrid can operate in both the grid-connected mode and the islanded mode where the microgrid is interfaced to the main power system by a fast semiconductor switch called static switch, (SS

  11. JOURNAL DE PHYSIQUE Colloque C6, supplkment au no 12, Tome 37, DPcembre 1976,page C6-897 M~SSBAUERSTUDIES OF' lZ9IATOMS IMPLANTED IN a-AND fl-TIN

    E-Print Network [OSTI]

    Paris-Sud XI, Université de

    ~SSBAUERSTUDIES OF' lZ9IATOMS IMPLANTED IN a- AND fl-TIN H. DE WAARD and G. J. KEMERINK Laboratorium voor Algemene on the basis of a simple model. Implants of 1291 in /3 tin yield two line spectra identicalto those found for implants in a tin converted to /3 tin by heating. Repeated phase transitions show that the impurity

  12. Greitzer, F.L. April 2000. "Life Extension Analysis and Prognostics Architectures," Laboratory Directed Research and Development Annual Report, Fiscal Year 1999, pp. 85-88. PNNL-13203. U.S. Department of Energy. Richland, Washington.

    E-Print Network [OSTI]

    of Energy. Richland, Washington. Life-Extension Analysis and Prognostics Architectures Frank L. GreitzerGreitzer, F.L. April 2000. "Life Extension Analysis and Prognostics Architectures," Laboratory that perform sensor fusion, analysis, reporting and interpreting of results with little or no human

  13. P-type doping of GaN

    SciTech Connect (OSTI)

    Wong, R.K.

    2000-04-10T23:59:59.000Z

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

  14. 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...

  15. Surface Science Analysis of GaAs Photocathodes Following Sustained...

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

    Analysis of GaAs Photocathodes Following Sustained Electron Beam Delivery. Abstract: Degradation of the photocathode materials employed in photoinjectors represents a challenge for...

  16. Self-aligned InGaP/GaAs heterojunction bipolar transistors for microwave power application

    SciTech Connect (OSTI)

    Ren, F.; Abernathy, C.R.; Pearton, S.J.; Lothian, J.R.; Wisk, P.W.; Fullowan, T.R.; Youngkai Chen (AT and T Bell Labs., Murray Hill, NJ (United States)); Yang, L.W.; Fu, S.T.; Brozovich, R.S. (General Electric Co., Syracuse, NY (USSR))

    1993-07-01T23:59:59.000Z

    As an alternative to AlGaAs/GaAs heterojunction bipolar transistors (HBT's) for microwave applications, InGaP/ GaAs HBT's with carbon-doped base layers grown by metal organic molecular beam epitaxy (MOMBE) are demonstrated with excellent dc, RF, and microwave performance. As previously reported, with a 700-[angstrom]-thick base layer (135-[Omega]/[open square] sheet resistance), a dc current gain of 25, and cutoff frequency and maximum frequency of oscillation above 70 GHz were measured for a 2 [times] 5-[mu]m[sup 2] emitter area device. A device with 12 cells, each consisting of a 2 [times] 15-[mu] m[sup 2] emitter area device for a total emitter area of 360 [mu] m[sup 2], was power tested at 4 GHz under continuous-wave (CW) bias condition. The device delivered 0.6-W output power with 13-dB linear gain and a power-added efficiency of 50%.

  17. High efficiency InGaN/GaN light emitting diodes with asymmetric triangular multiple quantum wells

    SciTech Connect (OSTI)

    Chang, Chiao-Yun; Li, Hen; Lu, Tien-Chang, E-mail: timtclu@mail.nctu.edu.tw [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, Taiwan 300 (China)

    2014-03-03T23:59:59.000Z

    In this study, we demonstrated high efficiency InGaN/GaN light emitting diodes (LEDs) with asymmetric triangular multiple quantum wells (MQWs). Asymmetric triangular MQWs not only contribute to uniform carrier distribution in InGaN/GaN MQWs but also yield a low Auger recombination rate. In addition, asymmetric triangular MQWs with gallium face-oriented inclination band profiles can be immune from the polarization charge originating from typical c-plane InGaN/GaN quantum well structures. In the experiment, LEDs incorporated with asymmetric triangular MQWs with gallium face-oriented inclination band profiles exhibited a 60.0% external quantum efficiency at 20?mA and a 27.0% efficiency droop at 100?mA (corresponding to a current density of 69?A/cm{sup 2}), which accounted for an 11.7% efficiency improvement and a 31.1% droop reduction compared with symmetric square quantum well structure LEDs.

  18. 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.

  19. 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

  20. Radiation response of single and dual junction p{sup +}n InGaP/GaAs space solar cells

    SciTech Connect (OSTI)

    Walters, R.J.; Xapsos, M.A.; Summers, G.P. [Naval Research Lab., Washington, DC (United States); Cotal, H.L.; Messenger, S.R. [SFA, Inc., Largo, MD (United States)

    1997-12-31T23:59:59.000Z

    The radiation response of single and dual-junction p{sup +}n InGaP/GaAs solar cells is studied. The degradation mechanisms of single-junction InGaP cells are identified, and characteristic degradation curves in terms of displacement damage dose are calculated. The response of dual-junction cells is presented, and the response of each sub-cell is discussed. The cell response is compared with those of other technologies. The effect of current injection on irradiated InGaP cell is presented.

  1. DC characteristics of OMVPE-grown N-p-n InGaP/InGaAsN DHBTs

    SciTech Connect (OSTI)

    Li, N.Y.; Chang, P.C.; Baca, A.G.; Xie, X.M.; Sharps, P.R.; Hou, H.Q.

    2000-01-04T23:59:59.000Z

    The authors demonstrate, for the first time, a functional N-p-n heterojunction bipolar transistor using a novel material, InGaAsN, with a bandgap energy of 1.2eV as the p-type base layer. A 300{angstrom}-thick In{sub x}Ga{sub 1-x}As graded layer was introduced to reduce the conduction band offset at the p-type InGaAsN base and n-type GaAs collector junction. For an emitter size of 500 {mu}m{sup 2}, a peak current gain of 5.3 has been achieved.

  2. 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.

  3. 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

  4. 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.

  5. 4D Density Determination of NH Radicals in an MSE Microplasma Combining Planar Laser Induced Fluorescence and Cavity Ring-Down Spectroscopy

    SciTech Connect (OSTI)

    Visser, Martin; Schenk, Andreas; Gericke, Karl-Heinz [Technische Universitaet Braunschweig, Institut fuer Physikalische und Theoretische Chemie Hans-Sommer-Str. 10, 38106 Braunschweig (Germany)

    2010-10-13T23:59:59.000Z

    An application of microplasmas is surface modification under mild conditions and of small, well defined areas. For this, an understanding of the plasma composition is of importance. First results of our work on the production and detection of NH radicals in a capacitively coupled radio frequency (RF) microplasma are presented. A microstructured comb electrode was used to generate a glow discharge in a hydrogen/nitrogen gas mixture by applying 13.56 MHz RF voltage. The techniques of planar laser induced fluorescence (PLIF) and cavity ring-down spectroscopy (CRDS) are used for space and time resolved, quantitative detection of the NH radical in the plasma. The rotational temperature was determined to be 820 K and, the density 5.1x10{sup 12} cm{sup 3}. Also, time dependent behaviour of the NH production was observed.

  6. Unusual defect physics in CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cell absorber

    SciTech Connect (OSTI)

    Yin, Wan-Jian, E-mail: wanjian.yin@utoledo.edu; Shi, Tingting; Yan, Yanfa, E-mail: yanfa.yan@utoledo.edu [Department of Physics and Astronomy and Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606 (United States)

    2014-02-10T23:59:59.000Z

    Thin-film solar cells based on Methylammonium triiodideplumbate (CH{sub 3}NH{sub 3}PbI{sub 3}) halide perovskites have recently shown remarkable performance. First-principle calculations show that CH{sub 3}NH{sub 3}PbI{sub 3} has unusual defect physics: (i) Different from common p-type thin-film solar cell absorbers, it exhibits flexible conductivity from good p-type, intrinsic to good n-type depending on the growth conditions; (ii) Dominant intrinsic defects create only shallow levels, which partially explain the long electron-hole diffusion length and high open-circuit voltage in solar cell. The unusual defect properties can be attributed to the strong Pb lone-pair s orbital and I p orbital antibonding coupling and the high ionicity of CH{sub 3}NH{sub 3}PbI{sub 3}.

  7. Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii, R. Deblock, B. Reulet, and H. Bouchiat

    E-Print Network [OSTI]

    Shepelyansky, Dima

    Mesoscopic photovoltaic effect in GaAs/Ga1-xAlxAs Aharonov-Bohm rings L. Angers, A. Chepelianskii specific dc voltage. We have investigated this photovoltaic PV effect on GaAs/Ga1-xAlxAs Aharonov is generally done by measuring the dc induced signal sometimes called photovoltaic effect which has also given

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

    E-Print Network [OSTI]

    Feenstra, Randall

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

  9. 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

  10. 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

  11. Encapsulation of titanium (IV) silsesquioxane into the NH{sub 4}USY zeolite: Preparation, characterization and application

    SciTech Connect (OSTI)

    Ribeiro do Carmo, Devaney [Faculdade de Engenharia de Ilha Solteira (UNESP), Departamento de Fisica e Quimica, Av. Brasil Centro, 56 CEP 15385-000, Ilha Solteira, SP (Brazil)], E-mail: docarmo@dfq.feis.unesp.br; Dias Filho, Newton Luiz [Faculdade de Engenharia de Ilha Solteira (UNESP), Departamento de Fisica e Quimica, Av. Brasil Centro, 56 CEP 15385-000, Ilha Solteira, SP (Brazil); Ramos Stradiotto, Nelson [Universidade Estadual Paulista, UNESP, Instituto de Quimica PO Box, Araraquara, SP (Brazil)

    2007-10-02T23:59:59.000Z

    This work describes the encapsulation of titanium (IV) silsesquioxane into the supercavities of NH{sub 4}USY ultra stabilized zeolite, after chemical treatment. The modified zeolite was characterized by Fourier transform infrared spectra, Nuclear magnetic resonance, scanning electronic microscopy, X-ray diffraction and thermogravity. This encapsulated titanium (IV) silsesquioxane can adsorb Azure A chloride after treatment with H{sub 3}PO{sub 4}, without modifier leaching problems. In an electrochemical study, the cyclic voltammograms of the graphite paste modified electrode, shows two redox couples with formal potential (E{sup 0}') -0.1 V and 0.21 V to I and II redox couples respectively (v=700mVs{sup -1}; Britton Robinson buffer (B-R) solution, pH 3) versus SCE ascribed to a monomer and dimmer of azure. This paper shows the use of ultra stabilized zeolite in the electrochemical field as host for molecules with nanometric dimensions.

  12. 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

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

    E-Print Network [OSTI]

    Nabben, Reinhard

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

  14. Ohmic contacts to p-type GaP

    E-Print Network [OSTI]

    Jorge Estevez, Humberto Angel

    1996-01-01T23:59:59.000Z

    was measured by the Cox-Strack method. Ohmic contacts based on the Zn/Pd system were developed. The Zn(350A)/Pd(IOOA)/p-GaP and Zn(350A)/Pd(IOOA)/p-GaP gave rather high values of the contact resistivity, 3-8xl 0-4 f2CM2. An improvement in the contact...

  15. The development of integrated chemical microsensors in GaAs

    SciTech Connect (OSTI)

    CASALNUOVO,STEPHEN A.; ASON,GREGORY CHARLES; HELLER,EDWIN J.; HIETALA,VINCENT M.; BACA,ALBERT G.; HIETALA,S.L.

    1999-11-01T23:59:59.000Z

    Monolithic, integrated acoustic wave chemical microsensors are being developed on gallium arsenide (GaAs) substrates. With this approach, arrays of microsensors and the high frequency electronic components needed to operate them reside on a single substrate, increasing the range of detectable analytes, reducing overall system size, minimizing systematic errors, and simplifying assembly and packaging. GaAs is employed because it is both piezoelectric, a property required to produce the acoustic wave devices, and a semiconductor with a mature microelectronics fabrication technology. Many aspects of integrated GaAs chemical sensors have been investigated, including: surface acoustic wave (SAW) sensors; monolithic SAW delay line oscillators; GaAs application specific integrated circuits (ASIC) for sensor operation; a hybrid sensor array utilizing these ASICS; and the fully monolithic, integrated SAW array. Details of the design, fabrication, and performance of these devices are discussed. In addition, the ability to produce heteroepitaxial layers of GaAs and aluminum gallium arsenide (AlGaAs) makes possible micromachined membrane sensors with improved sensitivity compared to conventional SAW sensors. Micromachining techniques for fabricating flexural plate wave (FPW) and thickness shear mode (TSM) microsensors on thin GaAs membranes are presented and GaAs FPW delay line and TSM resonator performance is described.

  16. Ohmic contacts to p-type Ga

    E-Print Network [OSTI]

    Jorge Estevez, Humberto Angel

    1996-01-01T23:59:59.000Z

    was measured by the Cox-Strack method. Ohmic contacts based on the Zn/Pd system were developed. The Zn(350A)/Pd(IOOA)/p-GaP and Zn(350A)/Pd(IOOA)/p-GaP gave rather high values of the contact resistivity, 3-8xl 0-4 f2CM2. An improvement in the contact...

  17. Solvent extraction of Li+, H3O+ and NH4+ into nitrobenzene by using sodium dicarbollylcobaltate and calix[4]arene-bis(t-octylbenzo-18-crown-6)

    SciTech Connect (OSTI)

    Makrlik, Emanuel [Czech University of Life Sciences, Prague, Kamy´cká; Selucky, P. [Nuclear Research Institute, Rez, Czech Republic; Vanura, Petr [Institute of Chemical Technology, Prague, Czech Republic; Moyer, Bruce A [ORNL

    2013-01-01T23:59:59.000Z

    From extraction experiments and c-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+ (aq) + NaL+ (nb) , ML+ (nb) + Na+ (aq) taking place in the two-phase water nitrobenzene system (M+ = Li+, H3O+, NH+4; L = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: zH3O+ < Li+ < NH+4.

  18. Polarized x-ray spectroscopy of quaternary ferromagnetic semiconductor (Ga,Mn)(As,P)

    E-Print Network [OSTI]

    Wadley, P.

    2011-01-01T23:59:59.000Z

    quaternary diluted magnetic semiconductor (Ga,Mn)(As,P) as aIn diluted magnetic semiconductors such as (Ga,Mn)As, whichquaternary diluted magnetic semiconductors such as (Ga,Mn)(

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

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

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

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

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

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

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

    E-Print Network [OSTI]

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

    2007-01-01T23:59:59.000Z

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

  2. Imaging of InGaN inhomogeneities using visible apertureless near-field scanning optical microscope

    E-Print Network [OSTI]

    Stebounova, Larissa V.; Romanyuk, Yaroslav E.; Chen, Dongxue; Leone, Stephen R.

    2007-01-01T23:59:59.000Z

    InGaN dots deposited on a GaN substrate. 44 In that work, itGaN buffer layer is grown after the nitridation of the substrate.

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

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

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

  4. 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.

  5. Elastic properties of Pu metal and Pu-Ga alloys

    SciTech Connect (OSTI)

    Soderlind, P; Landa, A; Klepeis, J E; Suzuki, Y; Migliori, A

    2010-01-05T23:59:59.000Z

    We present elastic properties, theoretical and experimental, of Pu metal and Pu-Ga ({delta}) alloys together with ab initio equilibrium equation-of-state for these systems. For the theoretical treatment we employ density-functional theory in conjunction with spin-orbit coupling and orbital polarization for the metal and coherent-potential approximation for the alloys. Pu and Pu-Ga alloys are also investigated experimentally using resonant ultrasound spectroscopy. We show that orbital correlations become more important proceeding from {alpha} {yields} {beta} {yields} {gamma} plutonium, thus suggesting increasing f-electron correlation (localization). For the {delta}-Pu-Ga alloys we find a softening with larger Ga content, i.e., atomic volume, bulk modulus, and elastic constants, suggest a weakened chemical bonding with addition of Ga. Our measurements confirm qualitatively the theory but uncertainties remain when comparing the model with experiments.

  6. 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)].

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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.

  13. Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

    SciTech Connect (OSTI)

    Choi, Won Hyuck; Abraham, Michael; Yu, Shih-Ying [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); You, Guanjun; Liu, Jie; Wang, Li; Xu, Jian, E-mail: jianxu@engr.psu.edu [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Mohney, Suzanne E., E-mail: mohney@ems.psu.edu [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2014-07-07T23:59:59.000Z

    We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy.

  14. Evaluation of the two-photon absorption characteristics of GaSb/GaAs quantum rings

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Carrington, P. J. [Department of Electronic and Electrical Engineering, University College London, London (United Kingdom); Krier, A. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2014-07-28T23:59:59.000Z

    The optical parameters describing the sub-bandgap response of GaSb/GaAs quantum rings solar cells have been obtained from photocurrent measurements using a modulated pseudo-monochromatic light source in combination with a second, continuous photo-filling source. By controlling the charge state of the quantum rings, the photoemission cross-sections describing the two-photon sub-bandgap transitions could be determined independently. Temperature dependent photo-response measurements also revealed that the barrier for thermal hole emission from the quantum rings is significantly below the quantum ring localisation energy. The temperature dependence of the sub-bandgap photo-response of the solar cell is also described in terms of the photo- and thermal-emission characteristics of the quantum rings.

  15. Single photon emission from site-controlled InGaN/GaN quantum dots

    SciTech Connect (OSTI)

    Zhang, Lei; Hill, Tyler A.; Deng, Hui, E-mail: dengh@umich.edu [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States)] [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States); Teng, Chu-Hsiang; Lee, Leung-Kway; Ku, Pei-Cheng, E-mail: peicheng@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)] [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)

    2013-11-04T23:59:59.000Z

    Single photon emission was observed from site-controlled InGaN/GaN quantum dots. The single-photon nature of the emission was verified by the second-order correlation function up to 90?K, the highest temperature to date for site-controlled quantum dots. Micro-photoluminescence study on individual quantum dots showed linearly polarized single exciton emission with a lifetime of a few nanoseconds. The dimensions of these quantum dots were well controlled to the precision of state-of-the-art fabrication technologies, as reflected in the uniformity of their optical properties. The yield of optically active quantum dots was greater than 90%, among which 13%–25% exhibited single photon emission at 10?K.

  16. High internal and external quantum efficiency InGaN/GaN solar cells

    SciTech Connect (OSTI)

    Matioli, Elison; Neufeld, C. J.; Iza, Michael; Cruz, S. C.; Al-Heji, Ali A.; Chen, Xu; Farrell, Rober M.; Keller, Stacia; DenBaars, Steven; Mishra, U. K.; Nakamura, Shuji; Speck, J. S.; Weisbuch, Claude

    2011-01-01T23:59:59.000Z

    High internal and external quantum efficiency GaN/InGaN solar cells are demonstrated. The internal quantum efficiency was assessed through the combination of absorption and external quantum efficiency measurements. The measured internal quantum efficiency, as high as 97%, revealed an efficient conversion of absorbed photons into electrons and holes and an efficient transport of these carriers outside the device. Improved light incoupling into the solar cells was achieved by texturing the surface. A peak external quantum efficiency of 72%, a fill factor of 79%, a short-circuit current density of 1.06?mA/cm{sup 2} , and an open circuit voltage of 1.89 V were achieved under 1 sun air-mass 1.5 global spectrumillumination conditions.

  17. 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

  18. Wavelength-resolved low-frequency noise of GaInN/GaN green light emitting diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Wavelength-resolved low-frequency noise of GaInN/GaN green light emitting diodes S. L. Rumyantseva well light emitting diodes. The light intensity noise was measured as a function of wavelength within the light emitting diode spectral emission line. The spectral noise density is found to increase

  19. 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

  20. 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

  1. 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

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

    E-Print Network [OSTI]

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

  3. Electronic band-structure engineering of GaAs/AlxGa1(xAs quantum well superlattices with substructures

    E-Print Network [OSTI]

    Cao, Wenwu

    Electronic band-structure engineering of GaAs/AlxGa1(xAs quantum well superlattices investigation on the band structures of electrons in both infinite and finite semiconductor quantum well of these two materials, narrower passbands and/or broad stopbands can be obtained for electrons with energy

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

    E-Print Network [OSTI]

    Honsberg, Christiana

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

  5. 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...

  6. 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

  7. Diffusion of a Ga adatom on the GaAs(001)c(44)heterodimer surface: A first principles study

    E-Print Network [OSTI]

    Khare, Sanjay V.

    Diffusion of a Ga adatom on the GaAs(001)c(4×4)heterodimer surface: A first principles study J Diffusion barriers Reconstruction Density functional calculations The adsorption and diffusion behavior functional theory (DFT) computations in the local density approxima- tion. Structural and bonding features

  8. Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures at low fields

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures with increasing external electric field, with the radiative component exhibiting weaker field dependence. © 2009 applied electric field in Ref. 12, the electric field dependent radiative recombination in particular has

  9. 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.

  10. 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...

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

    SciTech Connect (OSTI)

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

    2010-11-29T23:59:59.000Z

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

  12. 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 ...

  13. Sputtering of Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN by electrosprayed nanodroplets

    SciTech Connect (OSTI)

    Borrajo-Pelaez, Rafael; Grustan-Gutierrez, Enric; Gamero-Castaño, Manuel, E-mail: mgameroc@uci.edu [Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697 (United States)

    2013-11-14T23:59:59.000Z

    This article presents a characterization of the damage caused by energetic beams of electrosprayed nanodroplets striking the surfaces of single-crystal semiconductors including Si, SiC, InAs, InP, Ge, GaAs, GaSb, and GaN. The sputtering yield (number of atoms ejected per projectile's molecule), sputtering rate, and surface roughness are measured as functions of the beam acceleration potential. The maximum values of the sputtering yields range between 1.9 and 2.2 for the technological important but difficult to etch SiC and GaN respectively, and 4.5 for Ge. The maximum sputtering rates for the non-optimized beam flux conditions used in our experiments vary between 409?nm/min for SiC and 2381?nm/min for GaSb. The maximum sputtering rate for GaN is 630?nm/min. Surface roughness increases modestly with acceleration voltage, staying within 2?nm and 20?nm for all beamlet acceleration potentials and materials except Si. At intermediate acceleration potentials, the surface of Si is formed by craters orders of magnitude larger than the projectiles, yielding surface roughness in excess of 60?nm. The effect of projectile dose is studied in the case of Si. This parameter is correlated with the formation of the large craters typical of Si, which suggests that the accumulation of damage following consecutive impacts plays an important role in the interaction between beamlet and target.

  14. Strain relaxation effect by nanotexturing InGaN/GaN multiple quantum well

    SciTech Connect (OSTI)

    Ramesh, V.; Kikuchi, A.; Kishino, K. [Department of Electrical and Electronics Engineering, Sophia University, Tokyo 102-8554, Japan and Nano-technology Research Center, Sophia University, Tokyo 102-8554 (Japan); CREST, JST, Saitama 332-0012 (Japan); Funato, M.; Kawakami, Y. [CREST, JST, Saitama 332-0012 (Japan); Department of Electronics Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan)

    2010-06-15T23:59:59.000Z

    The relaxation of lattice-mismatched strain by deep postetching was systematically investigated for InGaN/GaN multiple quantum wells (MQWs). A planar heterojunction wafer, which included an In{sub 0.21}Ga{sub 0.79}N (3.2 nm)/GaN (14.8 nm) MQW, was etched by inductively coupled plasma dry etching, to fabricate high-density nanopillar, nanostripe, and nanohole arrays. The etching depth was 570 nm for all nanostructures. The diameter of the nanopillars was varied from 50 to 300 nm, then the mesa stripe width of the nanostripes and the diameter of the nanoholes were varied from 100 nm to 440 nm and 50 nm to 310 nm, respectively. The effect of strain relaxation on various optical properties was investigated. For example, in an array of nanopillars with diameter 130 nm and interval 250 nm, a large blueshift in the photoluminescence (PL) emission peak from 510 nm (as-grown) to 459 nm occurred at room temperature (RT). PL internal quantum efficiency (defined by the ratio of PL integral intensity at 300 K to that at 4.2 K) was enhanced from 34% (as-grown) to 60%, and the PL decay time at 4.2 K was reduced from 22 ns (as-grown) to 4.2 ns. These results clearly indicate the reduction of lattice-mismatched strain by postetching, which enhanced strain reduction with decreasing nanopillar diameter down to a diameter of 130 nm, where the strain reduction became saturated. The dependence of RT-PL decay time on nanopillar diameter was measured, and the surface nonradiative recombination velocity was estimated to be 5.8x10{sup 2} cm/s. This relatively slow rate indicates a little etching damage.

  15. Infrared emission from the substrate of GaAs-based semiconductor lasers Mathias Ziegler,1,a

    E-Print Network [OSTI]

    Peinke, Joachim

    by metal- organic vapor phase epitaxy on a n-type GaAs substrate. The red-emitting laser employs an InGaP

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

    SciTech Connect (OSTI)

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

    2012-05-14T23:59:59.000Z

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

  17. Phase Transformations of the Ternary System (NH4)2SO4-H2SO4-H2O and the Implications for Cirrus Cloud Formation

    E-Print Network [OSTI]

    the presence of NH4 + ions in the aerosol of the upper troposphere. Low-temperature ternary phase diagrams distribution alters the cloud's radiative properties, persistence, and surface area available for heterogeneous radiation, which insulates or warms Earth, and scattering the sun's visible radiation upward, thus cooling

  18. Mixed quantum/classical investigation of the photodissociation of NH3,,A~ ... and a practical method for maintaining zero-point energy

    E-Print Network [OSTI]

    Truhlar, Donald G

    with a classical mechanical treatment of nuclear motion on coupled potential-energy surfaces. Whereas older mixedMixed quantum/classical investigation of the photodissociation of NH3,,A~ ... and a practical method for maintaining zero-point energy in classical trajectories David Bonhommeaua and Donald G

  19. Field dependent emission rates in radiation damaged GaAs

    SciTech Connect (OSTI)

    Fleming, R. M.; Myers, S. M.; Wampler, W. R.; Lang, D. V.; Seager, C. H.; Campbell, J. M. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1415 (United States)

    2014-07-07T23:59:59.000Z

    We have measured the temperature and field dependence of emission rates from five traps in electron damaged GaAs. Four of the traps have previously been identified as radiation defects. One of the traps, seen in higher doped diodes, has not been previously identified. We have fit the data to a multiphonon emission theory that allows recombination in GaAs to be characterized over a broad range of temperature and electric field. These results demonstrate an efficient method to calculate field-dependent emission rates in GaAs.

  20. Evidence of N substitution by Mn in GaN

    E-Print Network [OSTI]

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

    2012-01-01T23:59:59.000Z

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

  1. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect (OSTI)

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

    2014-05-15T23:59:59.000Z

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

  2. Optical spectroscopy of cubic GaN in nanowires

    SciTech Connect (OSTI)

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

    2010-08-23T23:59:59.000Z

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

  3. An Investigation of Ammonia Extraction from Liquid Manure Using a Gas-Permeable Membrane Pollution of air, soil and water caused by excessive ammonia (NH3) emission and deposition from animal

    E-Print Network [OSTI]

    Mukhtar, Saqib

    An Investigation of Ammonia Extraction from Liquid Manure Using a Gas-Permeable Membrane Summary Pollution of air, soil and water caused by excessive ammonia (NH3) emission and deposition from animal by extracting it from liquid manure and potentially using the recovered NH3 as fertilizer. For this purpose, lab

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

    SciTech Connect (OSTI)

    Banerjee, D.; Ganguly, S.; Saha, D., E-mail: dipankarsaha@iitb.ac.in [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai 400076 (India); Adari, R.; Sankaranarayan, S.; Kumar, A. [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India)] [Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Aldhaheri, R. W.; Hussain, M. A.; Balamesh, A. S. [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)] [Department of Electrical and Computer Engineering, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

    2013-12-09T23:59:59.000Z

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

  5. Structural and optical properties of GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells

    SciTech Connect (OSTI)

    Aleshkin, V. Ya.; Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru; Drozdov, M. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Zvonkov, B. N. [Nizhni Novgorod State University, Research Physical Technical Institute (Russian Federation); Kudryavtsev, K. E.; Tonkikh, A. A.; Yablonskiy, A. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Werner, P. [Max Planck Institute of Microstructure Physics (Germany)

    2013-05-15T23:59:59.000Z

    GaAs-based heterostructures with Ge and Ge/InGaAs quantum wells are grown by laser-assisted sputtering. Structural and optical studies of the heterostructures are carried out. A broad photoluminescence line is observed in the wavelength range from 1300 to 1650 nm. The line corresponds to indirect transitions in the momentum space of the Ge quantum wells and to transitions between the In{sub 0.28}Ga{sub 0.72}As and Ge layers, indirect in coordinate space, but direct in momentum space.

  6. Microscopic, electrical and optical studies on InGaN/GaN quantum wells based LED devices

    SciTech Connect (OSTI)

    Mutta, Geeta Rani; Venturi, Giulia; Castaldini, Antonio; Cavallini, Anna [Department of Physics and Astronomy, University of Bologna, Viale Carlo Berti Pichat 6/II, 40127 Bologna (Italy); Meneghini, Matteo; Zanoni, Enrico; Meneghesso, Gaudenzio [University of Padova, Department of Information Engineering, via Gradenigo 6/B, Padova 35131 (Italy); Zhu, Dandan; Humphreys, Colin [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom)

    2014-02-21T23:59:59.000Z

    We report here on the micro structural, electronic and optical properties of a GaN-based InGaN/GaN MQW LED grown by the MOVPE method. The present study shows that the threading dislocations present in these LED structures are terminated as V pits at the surface and have an impact on the electrical and optical activity of these devices. It has been pointed that these dislocations were of edge, screw and mixed types. EBIC maps suggest that the electrically active defects are screw and mixed dislocations and behave as nonradiative recombinant centres.

  7. Waveguide effect of GaAsSb quantum wells in a laser structure based on GaAs

    SciTech Connect (OSTI)

    Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Afonenko, A. A. [Belarussian State University (Belarus)] [Belarussian State University (Belarus); Dikareva, N. V. [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)] [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation); Dubinov, A. A., E-mail: sanya@ipm.sci-nnov.ru; Kudryavtsev, K. E.; Morozov, S. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Nekorkin, S. M. [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)] [Research Physical-Technical Institute of Nizhni Novgorod State University (Russian Federation)

    2013-11-15T23:59:59.000Z

    The waveguide effect of GaAsSb quantum wells in a semiconductor-laser structure based on GaAs is studied theoretically and experimentally. It is shown that quantum wells themselves can be used as waveguide layers in the laser structure. As the excitation-power density attains a value of 2 kW/cm{sup 2} at liquid-nitrogen temperature, superluminescence at the wavelength corresponding to the optical transition in bulk GaAs (at 835 nm) is observed.

  8. High temperature stable W and WSi{sub x} ohmic contacts on GaN and InGaN

    SciTech Connect (OSTI)

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

    1996-06-01T23:59:59.000Z

    Conventional III-V metallizations chemes such as Au/Ge/Ni, Ti/Pt/Au, and Au/Be were found to display poor thermal stability on both GaN and InGaN, with extensive reaction and contact degradation at {le}500 C. By contrast, W was found to produce low contact resistance ({rho}{sub c}{similar_to}8x10{sup -5}{Omega}cm{sup 2}) to n-GaN. Ga outdiffusion to the surface of thin (500 A) W films was found after annealing at 1,100 C, but not at 1000 C. Interfacial abruptness increased by 300A after 1,100 C annealing. In the case of WSi{sub X} (X=0.45), Ga outdiffusion was absent even at 1,100 C, but again there was interfacial broadening and some phase changes in the WSi{sub X}. On In{sub 0.5}Ga{sub 0.5}N, a minimum specific contact resistivity of 1.5 x10{sup -5}{Omega}cm{sup 2} was obtained for WSi{sub X} annealed at 700 C. These contacts retained a smooth morphology and abrupt interfaces to 800 C. Graded In{sub X}Ga{sub 1-X}N layers have been employed on GaAs/AlGaAs HBTs (heterojunction bipolar transistors), replacing conventional In{sub X}Ga{sub 1-X}As layers. R{sub C} values of 5x10{sup -7}{Omega}cm{sup 2} were obtained for nonalloyed Ti/Pt/Au on the InGaN, and the morphologies were superior to those of InGaAs contact layers. This proves to have significant advantages for fabrication of sub-micron HBTs. Devices with emitter dimensions of 2x5{mu}m{sup 2} displayed gains of 35 for a base doping level of 7x10{sup 19}cm{sup -3} and stable long-term behavior.

  9. 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.

  10. 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.

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

    E-Print Network [OSTI]

    2006-01-01T23:59:59.000Z

    m-plane In x Ga 1?x N / GaN blue light emitting diodesmea- surements. Since the blue MQW emission is polarized toS. Nakamura and G. Fasol, The Blue Laser Diode ?Springer,

  12. Paper J-07, in: V.S. Magar and M.E. Kelley (Eds.), In Situ and On-Site Bioremediation--2003. Proceedings of the Seventh International In Situ and On-Site Bioremediation Symposium (Orlando, FL; June 2003). ISBN 1-57477-139-6, published by

    E-Print Network [OSTI]

    Rockne, Karl J.

    Paper J-07, in: V.S. Magar and M.E. Kelley (Eds.), In Situ and On-Site Bioremediation--2003. Proceedings of the Seventh International In Situ and On-Site Bioremediation Symposium (Orlando, FL; June 2003

  13. Transverse acoustic actuation of Ni-Mn-Ga single crystals

    E-Print Network [OSTI]

    Simon, Jesse Matthew

    2007-01-01T23:59:59.000Z

    Two methods for the transverse acoustic actuation of {110}-cut Ni-Mn-Ga single crystals are discussed. In this actuation mode, crystals are used that have the {110}- type twinning planes parallel to the base of the crystal. ...

  14. Beta-decay branching ratios of 62Ga

    E-Print Network [OSTI]

    A. Bey; B. Blank; G. Canchel; C. Dossat; J. Giovinazzo; I. Matea; V. Elomaa; T. Eronen; U. Hager; M. Hakala; A. Jokinen; A. Kankainen; I. Moore; H. Penttila; S. Rinta-Antila; A. Saastamoinen; T. Sonoda; J. Aysto; N. Adimi; G. De France; J. C. Thomas; G. Voltolini; T. Chaventré

    2008-04-17T23:59:59.000Z

    Beta-decay branching ratios of 62Ga have been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyvaskyla. 62Ga is one of the heavier Tz = 0, 0+ -> 0+ beta-emitting nuclides used to determine the vector coupling constant of the weak interaction and the Vud quark-mixing matrix element. For part of the experimental studies presented here, the JYFLTRAP facility has been employed to prepare isotopically pure beams of 62Ga. The branching ratio obtained, BR= 99.893(24)%, for the super-allowed branch is in agreement with previous measurements and allows to determine the ft value and the universal Ft value for the super-allowed beta decay of 62Ga.

  15. GaBo{sub 3} crystal growth from flux

    SciTech Connect (OSTI)

    Rudenko, V.V. [Institute of Physics, Krasnoyarsk (Russian Federation)

    1995-03-01T23:59:59.000Z

    Synthesis of the chemical compound GaBO{sub 3} was first reported in paper, and the crystallographic determination of its structure and unit cell parameters was presented in paper. The chemical compound GaBO{sub 3} crystallizes in a calcite structure type with the hexagonal unit cell Parameters a{sub H} = 4.568 and c{sub H} = 14.18 {Angstrom}. GaBO{sub 3} crystals in the form of (111) hexagonal plates were grown from the solvent B{sub 2}O{sub 3}-Bi{sub 2}O{sub 3} by the method of sponvineous crystallization. That technique was hard to reproduce, however. We decided to grow a GaBO{sub 3} crystal as an object for possible studies of various physical properties. 8 refs., 2 figs.

  16. Evaporation-based Ge/.sup.68 Ga Separation

    DOE Patents [OSTI]

    Mirzadeh, Saed (Albuquerque, NM); Whipple, Richard E. (Los Alamos, NM); Grant, Patrick M. (Los Alamos, NM); O'Brien, Jr., Harold A. (Los Alamos, NM)

    1981-01-01T23:59:59.000Z

    Micro concentrations of .sup.68 Ga in secular equilibrium with .sup.68 Ge in strong aqueous HCl solution may readily be separated in ionic form from the .sup.68 Ge for biomedical use by evaporating the solution to dryness and then leaching the .sup.68 Ga from the container walls with dilute aqueous solutions of HCl or NaCl. The chloro-germanide produced during the evaporation may be quantitatively recovered to be used again as a source of .sup.68 Ga. If the solution is distilled to remove any oxidizing agents which may be present as impurities, the separation factor may easily exceed 10.sup.5. The separation is easily completed and the .sup.68 Ga made available in ionic form in 30 minutes or less.

  17. Electrical degradation mechanisms of RF power GaAs PHEMTs

    E-Print Network [OSTI]

    Villanueva, Anita A. (Anita Ariel), 1978-

    2007-01-01T23:59:59.000Z

    GaAs Pseudomorphic High-Electron Mobility Transistors (PHEMTs) are widely used in RF power applications. Since these devices typically operate at high power levels and under high voltage biasing, their electrical reliability ...

  18. Quantitative analysis of compositional changes in InGaAs/InGaAsP quantum wells on GaAs induced by intermixing with a low temperature grown InGaP cap layer

    SciTech Connect (OSTI)

    Hulko, O.; Thompson, D. A.; Czaban, J. A.; Simmons, J. G. [Centre for Emerging Devices and Technologies (CEDT), McMaster University, Hamilton, Ontario L8S 4L8 (Canada)

    2006-08-07T23:59:59.000Z

    Energy-dispersive x-ray spectroscopy was used to analyze quantum well intermixing between an InGaAs quantum well (QW) and InGaAsP barriers grown on GaAs induced by a low temperature, molecular beam epitaxy grown, InGaP cap. This cap layer produces an enhanced blueshift of the photoluminescence (PL) wavelength following postgrowth annealing, and degradation of the PL signal. Cross-sectional transmission electron microscopy reveals modification of the whole structure, with formation of arsenic precipitates, broadening, and subsequent disappearance of the QWs in the capped structure. Uncapped samples are relatively unchanged. Increased phosphorus observed in the QW for capped structures confirms the diffusion of phosphorus from the P-rich cap.

  19. Sandia National Laboratories: GaN-based nanowire laser

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

    GaN-based nanowire laser BES Web Highlight: Single-mode gallium nitride nanowire lasers On January 28, 2013, in EC, Energy Efficiency, Solid-State Lighting A new top-down method...

  20. Micro Raman Spectroscopy of Annealed Erbium Implanted GaN

    E-Print Network [OSTI]

    Vajpeyi, Agam P.

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

  1. 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...

  2. 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.

  3. Effects of constraints in general branched molecules: A quantitative ab initio study in HCO-L-Ala-NH2

    E-Print Network [OSTI]

    Pablo Echenique; J. L. Alonso; Ivan Calvo

    2006-12-04T23:59:59.000Z

    A general approach to the design of accurate classical potentials for protein folding is described. It includes the introduction of a meaningful statistical measure of the differences between approximations of the same potential energy, the definition of a set of Systematic and Approximately Separable and Modular Internal Coordinates (SASMIC), much convenient for the simulation of general branched molecules, and the imposition of constraints on the most rapidly oscillating degrees of freedom. All these tools are used to study the effects of constraints in the Conformational Equilibrium Distribution (CED) of the model dipeptide HCO-L-Ala-NH2. We use ab initio Quantum Mechanics calculations including electron correlation at the MP2 level to describe the system, and we measure the conformational dependence of the correcting terms to the naive CED based in the Potential Energy Surface (PES) without any simplifying assumption. These terms are related to mass-metric tensors determinants and also occur in the Fixman's compensating potential. We show that some of the corrections are non-negligible if one is interested in the whole Ramachandran space. On the other hand, if only the energetically lower region, containing the principal secondary structure elements, is assumed to be relevant, then, all correcting terms may be neglected up to peptides of considerable length. This is the first time, as far as we know, that the analysis of the conformational dependence of these correcting terms is performed in a relevant biomolecule with a realistic potential energy function.

  4. MOSE: zooming on the Meso-NH mesoscale model performances at the surface layer at ESO sites (Paranal and Armazones)

    E-Print Network [OSTI]

    Lascaux, Franck; di Arcetri, INAF / Osservatorio Astrofisico; 10.1117/12.925934

    2012-01-01T23:59:59.000Z

    In the context of the MOSE project, in this contribution we present a detailed analysis of the Meso-NH mesoscale model performances and their dependency on the model and orography horizontal resolutions in proximity of the ground. The investigated sites are Cerro Paranal (site of the ESO Very Large Telescope - VLT) and Cerro Armazones (site of the ESO European Extremely Large Telescope - E-ELT), in Chile. At both sites, data from a rich statistical sample of different nights are available - from AWS (Automated Weather Stations) and masts - giving access to wind speed, wind direction and temperature at different levels near the ground (from 2 m to 30 m above the ground). In this study we discuss the use of a very high horizontal resolution (dX=0.1 km) numerical configuration that overcomes some specific limitations put in evidence with a standard configuration with dX=0.5 km. In both sites results are very promising. The study is co-funded by ESO and INAF.

  5. Effect of Sb on the Properties of GaInP Top Cells (Presentation)

    SciTech Connect (OSTI)

    Olson, J. M.; McMahon, W. E.; Kurtz, S.

    2006-05-01T23:59:59.000Z

    The summary of this report is that: (1) Sb can be used to increase V{sub oc} of a GaInP top cell; (2) the photovoltaic quality of GaInP is relatively unaffected by the presence of Sb; and (3) Sb-doped GaInP/GaAs tandem cells show promise for achieving efficiencies over 32%.

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

    E-Print Network [OSTI]

    Feenstra, Randall

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

  7. 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

  8. 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.

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

    E-Print Network [OSTI]

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

  10. 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

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

    E-Print Network [OSTI]

    Yang, Peidong

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

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

    E-Print Network [OSTI]

    As, Donat Josef

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

  13. 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

  14. Quadrupole mass spectrometry desorption analysis of Ga adsorbate on AIN (0001)

    E-Print Network [OSTI]

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

    2006-01-01T23:59:59.000Z

    substrate temperatures similar to those used during PA-MBE growth of GaN /substrate temperature of 668– 669 ° C pre- dicted by the Ga/ GaNon GaN ?0001?. 13 At the 672± 2 ° C substrate temperature in

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

    E-Print Network [OSTI]

    Nabben, Reinhard

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

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

    E-Print Network [OSTI]

    Nabben, Reinhard

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

  17. Terahertz plasma wave resonance of two-dimensional electrons in InGaP/InGaAs/GaAs high-electron-mobility transistors

    SciTech Connect (OSTI)

    Otsuji, Taiichi; Hanabe, Mitsuhiro; Ogawara, Osamu [Kyushu Institute of Technology, Graduate School of Computer Science and Systems Engineering, 680-4 Kawazu, Iizuka, Fukuoka, 820-8502 (Japan)

    2004-09-13T23:59:59.000Z

    We have observed the frequency dependence of the plasma resonant intensity in the terahertz range for a short gate-length InGaP/InGaAs/GaAs pseudomorphic high-electron-mobility transistor. The plasma resonance excitation was performed by means of interband photoexcitation using the difference-frequency component of a photomixed laser beam. Under sufficient density of two-dimensional (2D) conduction electrons (>10{sup 12} cm{sup -2}) and a moderate modulation index (the ratio of the density of photoexcited electrons to the initial density of the 2D electrons) we clearly observed the plasma-resonant peaks at 1.9 and 5.8 THz corresponding to the fundamental and third-harmonic resonance at room temperature, which is in good agreement with theory.

  18. A one-dimensional Fickian model to predict the Ga depth profiles in three-stage Cu(In,Ga)Se{sub 2}

    SciTech Connect (OSTI)

    Rodriguez-Alvarez, H., E-mail: humberto.rodriguez@helmholtz-berlin.de [International Iberian Nanotechnology Laboratory, Avenida Mestre Jose Veiga s/n, 4715-330 Braga (Portugal); Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Mainz, R. [Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Sadewasser, S. [International Iberian Nanotechnology Laboratory, Avenida Mestre Jose Veiga s/n, 4715-330 Braga (Portugal)

    2014-05-28T23:59:59.000Z

    We present a one-dimensional Fickian model that predicts the formation of a double Ga gradient during the fabrication of Cu(In,Ga)Se{sub 2} thin films by three-stage thermal co-evaporation. The model is based on chemical reaction equations, structural data, and effective Ga diffusivities. In the model, the Cu(In,Ga)Se{sub 2} surface is depleted from Ga during the deposition of Cu-Se in the second deposition stage, leading to an accumulation of Ga near the back contact. During the third deposition stage, where In-Ga-Se is deposited at the surface, the atomic fluxes within the growing layer are inverted. This results in the formation of a double Ga gradient within the Cu(In,Ga)Se{sub 2} layer and reproduces experimentally observed Ga distributions. The final shape of the Ga depth profile strongly depends on the temperatures, times and deposition rates used. The model is used to evaluate possible paths to flatten the marked Ga depth profile that is obtained when depositing at low substrate temperatures. We conclude that inserting Ga during the second deposition stage is an effective way to achieve this.

  19. Regrowth of diluted magnetic semiconductor GaMnAs on InGaP (001) surfaces to realize freestanding micromechanical structures

    SciTech Connect (OSTI)

    Choi, Hyung Kook; Lee, Joon Sue; Cho, Sung Woon; Lee, Won Oh; Shim, Seung Bo; Park, Yun Daniel [CSCMR and FPRD Department of Physics and Astronomy, Seoul National University, NS 50, Seoul 151- 747 (Korea, Republic of)

    2007-03-15T23:59:59.000Z

    Low temperature molecular beam epitaxy regrowths of Ga{sub 1-x}Mn{sub x}As (x{approx_equal}0.04) diluted magnetic semiconductors on GaAs/In{sub 1-y}Ga{sub y}P/GaAs(001) and In{sub 1-y}Ga{sub y}P/GaAs(001) (y{approx_equal}0.51) heterostructures prepared by metal-organic chemical vapor deposition are described. The resulting Ga{sub 1-x}Mn{sub x}As properties are comparable to epitaxial films grown directly on GaAs (001) substrates from in situ reflection high-energy electron diffraction, x-ray diffraction, magnetometry, and transport measurements with magnetic ordering temperature of as-grown films to range between {approx}50 and {approx}60 K. Postgrowth low temperature annealing enhances both magnetic and transport properties. Perfect etch selectivity between Ga{sub 1-x}Mn{sub x}As/GaAs and In{sub 1-y}Ga{sub y}P is utilized to realize suspended Ga{sub 1-x}Mn{sub x}As/GaAs doubly clamped beam micromechanical freestanding structures.

  20. Anti-phase domains in cubic GaN

    SciTech Connect (OSTI)

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

    2011-12-15T23:59:59.000Z

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

  1. 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.

  2. High intensity low temperature (HILT) performance of space concentrator GaInP/GaInAs/Ge MJ SCs

    SciTech Connect (OSTI)

    Shvarts, Maxim Z., E-mail: shvarts@scell.ioffe.ru; Kalyuzhnyy, Nikolay A.; Mintairov, Sergey A.; Soluyanov, Andrei A.; Timoshina, Nailya Kh. [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya str., St.-Petersburg, 194021 (Russian Federation); Gudovskikh, Alexander S. [Saint-Petersburg Academic University - Nanotechnology Research and Education Centre RAS, St. Petersburg, 194021 (Russian Federation); Luque, Antonio [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya str., St.-Petersburg, 194021, Russia and Instituto de Energia Solar, Universidad Politecnica de Madrid, Madrid (Spain)

    2014-09-26T23:59:59.000Z

    In the work, the results of an investigation of GaInP/GaInAs/Ge MJ SCs intended for converting concentrated solar radiation, when operating at low temperatures (down to ?190 °C) are presented. A kink of the cell I-V characteristic has been observed in the region close to V{sub oc} starting from ?20°C at operation under concentrated sunlight. The causes for its occurrence have been analyzed and the reasons for formation of a built-in potential barrier for majority charge carriers at the n-GaInP/n-Ge isotype hetero-interface are discussed. The effect of charge carrier transport in n-GaInP/n-pGe heterostructures on MJ SC output characteristics at low temperatures has been studied including EL technique.

  3. 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.

  4. Reducing the efficiency droop by lateral carrier confinement in InGaN/GaN quantum-well nanorods

    E-Print Network [OSTI]

    Shi, Chentian; Yang, Fan; Park, Min Joo; Kwak, Joon Seop; Jung, Sukkoo; Choi, Yoon-Ho; Wang, Xiaoyong; Xiao, Min

    2013-01-01T23:59:59.000Z

    Efficiency droop is a major obstacle facing high-power application of InGaN/GaN quantum-well (QW) light-emitting diodes. In this letter, we report the suppression of efficiency droop induced by density-activated defect recombination in nanorod structure of a-plane InGaN/GaN QWs. In the high carrier density regime, the retained emission efficiency in a dry-etched nanorod sample is observed to be over two times higher than that in its parent QW sample. We further argue that the improvement is a combined effect of the amendment contributed by lateral carrier confinement and the deterioration made by surface trapping.

  5. A new InGaP/GaAs tunneling heterostructure-emitter bipolar transistor (T-HEBT)

    SciTech Connect (OSTI)

    Tsai, Jung-Hui, E-mail: jhtsai@nknucc.nknu.edu.tw [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China); Lee, Ching-Sung [Feng Chia University, Department of Electronic Engineering, Taiwan (China); Lour, Wen-Shiung [National Taiwan Ocean University, Department of Electrical Engineering, Taiwan (China); Ma, Yung-Chun; Ye, Sheng-Shiun [National Kaohsiung Normal University, Department of Electronic Engineering, Taiwan (China)

    2011-05-15T23:59:59.000Z

    Excellent characteristics of an InGaP/GaAs tunneling heterostructure-emitter bipolar transistor (T-HEBT) are first demonstrated. The insertion of a thin n-GaAs emitter layer between tynneling confinement and base layers effectivelty eliminates the potential spike at base-emitter junction and reduces the collector-emitter offset voltage, while the thin InGaP tunneling confinement layer is employed to reduce the transporting time across emitter region for electrons and maintain the good confinement effect for holes. Experimentally, the studied T-HEBN exhibits a maximum current gain of 285, a relatively low offset voltage of 40 mW, and a current-gain cutoff frequency of 26.4 GHz.

  6. 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.

  7. Epitaxial growth of Cu,,In,Ga...Se2 on GaAs,,110... and A. Rockett

    E-Print Network [OSTI]

    Rockett, Angus

    . INTRODUCTION The Cu(In, Ga)Se2 CIGS absorber layer in a recent record-efficiency CIGS solar cell1 has a 220.13 Commercially supplied ``epi-ready'' liquid- encapsulated Czo

  8. Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

    SciTech Connect (OSTI)

    Zhuang, Y. D.; Shields, P. A.; Allsopp, D. W. E., E-mail: d.allsopp@bath.ac.uk [Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom); Bruckbauer, J.; Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

    2014-11-07T23:59:59.000Z

    Cathodoluminescence (CL) hyperspectral imaging has been performed on GaN nanorods containing a single InGaN quantum disk (SQD) with controlled variations in excitation conditions. Two different nanorod diameters (200 and 280?nm) have been considered. Systematic changes in the CL spectra from the SQD were observed as the accelerating voltage of the electron beam and its position of incidence are varied. It is shown that the dominant optical transition in the SQD varies across the nanorod as a result of interplay between the contributions of the deformation potential and the quantum-confined Stark effect to the transition energy as consequence of radial variation in the pseudomorphic strain.

  9. 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

  10. Low temperature carrier redistribution dynamics in InGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Badcock, T. J., E-mail: Thomas.badcock@crl.toshiba.co.uk; Dawson, P.; Davies, M. J. [School of Physics and Astronomy, Photon Science Institute, Alan Turing Building, University of Manchester, Manchester M13 9PL (United Kingdom); Kappers, M. J.; Massabuau, F. C.-P.; Oehler, F.; Oliver, R. A.; Humphreys, C. J. [Department of Materials Science and Metallurgy, 27 Charles Babbage Road, University of Cambridge, Cambridge CB3 0FS (United Kingdom)

    2014-03-21T23:59:59.000Z

    We have studied the carrier recombination dynamics in an InGaN/GaN multiple quantum well structure as a function of emission energy and excitation density between temperatures of 10?K and 100?K. Under relatively low levels of excitation, the photoluminescence (PL) intensity and decay time of emission on the high energy side of the luminescence spectrum decrease strongly between 10?K and 50?K. In contrast, for emission detected on the low energy side of the spectrum, the PL intensity and decay time increase over the same temperature range. These results are consistent with a thermally activated carrier redistribution process in which the (temperature dependent) average timescale for carrier transfer into or out of a localised state depends on the energy of the given state. Thus, the transfer time out of shallow, weakly localised states is considerably shorter than the arrival time into more deeply localised states. This picture is consistent with carriers hopping between localisation sites in an uncorrelated disorder potential where the density of localised states decreases with increasing localisation depth, e.g., a exponential or Gaussian distribution resulting from random alloy disorder. Under significantly higher levels of excitation, the increased occupation fraction of the localised states results in a greater average separation distance between unoccupied localised states, causing a suppression of the spectral and dynamic signatures of the hopping transfer of carriers.

  11. Testing of ethylene propylene seals for the GA-4/GA-9 casks

    SciTech Connect (OSTI)

    Boonstra, R.H.

    1993-08-01T23:59:59.000Z

    The primary O-ring seal of the GA-4 and GA-9 casks was tested for leakage with a full-scale mockup of the cask lid and flange. Tests were performed at temperatures of ambient, {minus}41{degrees}, 121{degrees}, and 193{degrees}C. Shim plates between the lid and flange simulated gaps caused by thermal distortion. The testing used a helium mass spectrometer leak detector (MSLD). Results showed that the primary seal was leaktight for all test conditions. Helium permeation through the seal began in 13--23 minutes for the ambient tests and in 1--2 minutes for the tests at elevated temperatures. After each test several hours of the pumping were typically required to reduce the MSLD background reading to an acceptable level for the next test, indicating that the seal had become saturated with helium. To verify that the test results showed permeation and not real leakage, several response checks were conducted in which a calibrated leak source was inserted in the detector line near the seal. When the leak source was activated the detector responded within seconds.

  12. Impact of high energy particles in InGaP/InGaAs pseudomorphic HEMTs

    SciTech Connect (OSTI)

    Ohyama, H.; Hakata, T. [Kumamoto National Coll. of Technology, Nishigoshi, Kumamoto (Japan)] [Kumamoto National Coll. of Technology, Nishigoshi, Kumamoto (Japan); Simoen, E.; Claeys, C. [IMEC, Leuven (Belgium)] [IMEC, Leuven (Belgium); Kuroda, S. [Fujitsu Quantum Devices Ltd., Yamanashi (Japan)] [Fujitsu Quantum Devices Ltd., Yamanashi (Japan); Takami, Y. [Rikkyo Univ., Yokosuka, Kanagawa (Japan)] [Rikkyo Univ., Yokosuka, Kanagawa (Japan); Sunaga, H. [Takasaki JAERI, Takasaki, Gunma (Japan)] [Takasaki JAERI, Takasaki, Gunma (Japan)

    1998-12-01T23:59:59.000Z

    Irradiation damage and its recovery behavior resulting from thermal annealing in InGaP/InGaAs pseudomorphic HEMTs, subjected to a 20-MeV alpha ray and 220-MeV carbon, are studied for the first time. The drain current and effective mobility decrease after irradiation, while the threshold voltage increases in positive direction. The degradation of device performance increases with increasing fluence. The decrease of the mobility is thought to be due to the scattering of channel electrons with the induced lattice defects and also to the decrease of the electron density in the two dimensional electron gas (2DEG) region. The influence of the radiation source on the degradation and recovery is discussed by comparison with 1-MeV electron and 1-MeV fast neutron exposures with respect to the number of knock-on atoms and the nonionizing energy loss (NIEL). Isochronal thermal annealing for temperatures ranging from 75 to 300 C shows that the device performance degraded by the irradiation recovers completely.

  13. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    SciTech Connect (OSTI)

    Özduran, Mustafa [Ahi Evran Üniversitesi Fen Edebiyat Fakültesi Fizik Bölümü, K?r?ehir (Turkey); Turgut, Kemal [Yüksek Lisans Ö?rencisi, K?r?ehir (Turkey); Arikan, Nihat [Ahi Evran Üniversitesi E?itim Fakültesi ?lkö?retim Bölümü, K?r?ehir (Turkey); ?yigör, Ahmet; Candan, Abdullah [Ahi Evran Üniversitesi Merkezi Ara?t?rma Laboratuvar?, K?r?ehir (Turkey)

    2014-10-06T23:59:59.000Z

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni{sub 2}TiGa and Ni{sub 2}ScGa alloys in the cubic L2{sub 1} structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C{sub 11}, C{sub 12} and C{sub 44}. We calculated elastic constants in L2{sub 1} structure for Ni{sub 2}TiGa and Ni{sub 2}ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni{sub 2}TiGa, Ni 3d states and Sc 3d states for Ni{sub 2}ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni{sub 2}TiGa, 0.76 states/eV Cell for Ni{sub 2}ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L2{sub 1} phase is unstable since the phonon calculations have imagine modes.

  14. Reduced lattice temperature high-speed operation of pseudomorphic InGaAdGaAs field-effect transistors

    E-Print Network [OSTI]

    Kolodzey, James

    ,um GaAs buffer, 170 A Ino.zGao,sAs strained channel, 50 A undoped Ale,,,Ga,,,As undoped spacer, S dimensions of 0.25 x 200 pm and 0.5 X 200 pm with a source-drain spacing of 2 ,um. The MODFETs have gate dimensions of 0.35~ 100 pm and 0.47X 100 pm with a source-drain spacing of 1 ,um. The MISFETs have

  15. Optically Detected Extended X-Ray Absorption Fine Structure Study of InGaN/GaN Single Quantum Wells

    SciTech Connect (OSTI)

    Rigopoulos, N.; Hamilton, B.; Davies, G. J.; Towlson, B. M. [School of Electrical and Electronic Engineering, University of Manchester, Manchester M60 1QD (United Kingdom); Poolton, N. R. J. [Synchrotron Radiation Department, Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Dawson, P.; Graham, D. M. [School of Physics and Astronomy, University of Manchester, Manchester M60 1QD (United Kingdom); Kappers, M. J.; Humphreys, C. J. [Dept. of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Carlson, S. [MAX-lab, Lund University, P.O. Box 118, SE- 221 00 Lund (Sweden)

    2007-04-10T23:59:59.000Z

    We have investigated the local atomic environment of the Ga atoms in an InxGa1-xN single quantum well structure using Optically Detected Extended X-ray Absorption Fine Structure (OD-EXAFS). A comparison of the OD-EXAFS data with a theoretical model shows the technique to be site selective for this particular structure and reveals that the quantum well emission originates from regions with x=0.15.

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

    E-Print Network [OSTI]

    As, Donat Josef

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

  17. Electron Band Structure of MnGaN Dimiter Alexandrov1

    E-Print Network [OSTI]

    Dietz, Nikolaus

    to this orbital to be occupied. LCAO electron band structure of wurtzite MnxGa1-xN for points c1 and v15 ( = 1 of the wurtzite MnxGa1-xN are determined as well. INTRODUCTION The MnxGa1-xN semiconductor alloy is important model the MnGaN alloy on Mn content. Segregated Mn species in wurtzite GaN containing Mn

  18. D10.7.2: Results for GaAs photocathodes

    E-Print Network [OSTI]

    Xiang, R

    2013-01-01T23:59:59.000Z

    HZDR plans to apply bulk GaAs photocathode in SRF gun for high current electron source. Supported by this project, a preparation system for GaAs photocathode has been developed. The cathode plugs special for GaAs wafer have been modified and proofed in SRF gun real running conditions. Virgin GaAs wafer was tested in the SRF gun cavity, and the first GaAs activation was performed.

  19. 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

  20. 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