National Library of Energy BETA

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. SPECTROSCOPIC INVESTIGATION OF (NH4)2S TREATED GaSeTe FOR RADIATION DETECTOR APPLICATIONS

    SciTech Connect (OSTI)

    Nelson, A; Laurence, T; Conway, A; Behymer, E; Sturm, B; Voss, L; Nikolic, R; Payne, S; Mertiri, A; Pabst, G; Mandal, K; Burger, A

    2009-08-04

    The surface of the layered III-VI chalcogenide semiconductor GaSeTe was treated with (NH{sub 4}){sub 2}S at 60 C to modify the surface chemistry and determine the effect on transport properties. Room temperature photoluminescence (PL) measurements were used to assess the effect of the (NH{sub 4}){sub 2}S treatment on surface defect states. Evaluation of the subsequent surface chemistry was performed with high-resolution core-level photoemission measurements. Metal overlayers were deposited on the (NH{sub 4}){sub 2}S treated surfaces and the I-V characteristics were measured. The measurements were correlated to understand the effect of (NH{sub 4}){sub 2}S modification of the interfacial electronic structure with the goal of optimizing the metal/GaSeTe interface for radiation detector devices.

  3. High external quantum efficiency and fill-factor InGaN/GaN heterojunction solar cells grown by NH3-based molecular beam epitaxy

    SciTech Connect (OSTI)

    Lang, J. R.; Neufeld, C. J.; Hurni, C. A.; Cruz, S. C.; Matioli, E.; Mishra, U. K.; Speck, J. S.

    2011-04-01

    High external quantum efficiency (EQE) p-i-n heterojunction solar cellsgrown by NH3 -based molecular beam epitaxy are presented. EQE values including optical losses are greater than 50% with fill-factors over 72% when illuminated with a 1 sun AM0 spectrum. Optical absorptionmeasurements in conjunction with EQE measurements indicate an internal quantum efficiency greater than 90% for the InGaN absorbing layer. By adjusting the thickness of the top p-type GaN window contact layer, it is shown that the short-wavelength (<365 nm) quantum efficiency is limited by the minority carrier diffusion length in highly Mg-doped p-GaN.

  4. Sr. Engineer, Water Resources Univ of FL-SW FL Research & Education Center Immokalee, FL

    E-Print Network [OSTI]

    Hill, Jeffrey E.

    Sr. Engineer, Water Resources Univ of FL-SW FL Research & Education Center ­ Immokalee, FL Technical position for research, extension, and teaching of water resources (quantity and quality and implementing construction plans for water resources projects, carrying out field and laboratory experiments

  5. 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

  6. Record 1, Side B (FL1088)

    E-Print Network [OSTI]

    Whitehorn, John

    stream_source_info 1 FL 1088 B_whitehorn.pdf.txt stream_content_type text/plain stream_size 1 Content-Encoding ISO-8859-1 stream_name 1 FL 1088 B_whitehorn.pdf.txt Content-Type text/plain; charset=ISO-8859-1 ...

  7. Record 2, Side B (FL1144)

    E-Print Network [OSTI]

    Whitehorn, John

    stream_source_info 2 FL 1144 B_whitehorn.pdf.txt stream_content_type text/plain stream_size 1 Content-Encoding ISO-8859-1 stream_name 2 FL 1144 B_whitehorn.pdf.txt Content-Type text/plain; charset=ISO-8859-1 ...

  8. 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

  9. September 2011 Dear FL Beef Cattle Producers,

    E-Print Network [OSTI]

    Hill, Jeffrey E.

    September 2011 Dear FL Beef Cattle Producers, I am the veterinary entomologist for UF-IFAS and am beef cattle producers who have extensively used the Avenger insecticide ear tag on their cattle on beef cattle. However, the horn fly is expected to develop resistance to this chemical as it has most

  10. Thermomagnetic Torque in Nh

    E-Print Network [OSTI]

    Adair, Thomas W.; McClurg, G. R.

    1970-01-01

    raises the question of whether the Scott torque has the same sign as the molecular g~ factor in ammonia as it does in all other gases. The research reported here shows that NH3 is quite normal. Progress on a detailed theory for the transport... torque. The new ap- paratus' used in the present work gave no measur- able torque at zero magnetic field, and therefore no correction was needed. The ammonia was high-purity gas from the Mathe- son Gas Products Company with a stated purity of 99. 99...

  11. 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.174.143.43. Redistribution subject to AIP license or copyright; see http://jcp.aip.org/about/rights_and_permissions #12;

  12. Vision FL LLC | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page| Open Energy Information Serbia-EnhancingEt Al.,Turin,Village of Wellington,FL LLC Jump to: navigation, search Name:

  13. US SoAtl FL Site Consumption

    Gasoline and Diesel Fuel Update (EIA)

    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 Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of Natural GasAdjustments (Billion Cubic Feet) Wyoming963 1.969 1.979Coal Consumers inYear JanSales Type: Sales120NE MA SiteFL

  14. Porous GaN nanowires synthesized using thermal chemical vapor deposition

    E-Print Network [OSTI]

    Kim, Bongsoo

    nanotube-confined reaction [4], arc discharge [5], laser ablation [6], sublimation [7], pyrolysis [8O3)/ carbons with NH3 produced the large-quantity porous GaN nanowires on the iron (Fe)/nickel (Ni

  15. Apple Tree, NH Big Tree for May By Anne Krantz, NH Big Tree Team,

    E-Print Network [OSTI]

    New Hampshire, University of

    Apple Tree, NH Big Tree for May By Anne Krantz, NH Big Tree Team, UNH Cooperative Extension The explosion of apple blossoms in May transforms the most gnarled old tree into a delicate cloud of beauty (1817-1862) in his essay "The Wild Apple Tree," described the blossoms perfectly: `The flowers

  16. TRIBAL ISSUES TOPIC GROUP MEETING SUMMARY JACKSONVILLE, FL

    Office of Environmental Management (EM)

    JACKSONVILLE, FL JANUARY 20, 1999 Mr. Kevin Blackwell (USDOTFRA) updated the group on the status of the DOT response to DOE's inquiry about the tribal right to inspect rail...

  17. US Hydro 2011 Tampa, FL April 2528, 2011 1 On the Horizon

    E-Print Network [OSTI]

    New Hampshire, University of

    US Hydro 2011 Tampa, FL April 2528, 2011 1 On the Horizon: Better Bottom Detection for areas the eelgrass canopy and seafloor. #12;US Hydro 2011 Tampa, FL April 2528, 2011 2 Figure 1: Bottom detections

  18. Category:Concord, NH | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QA J-E-1 SECTION J APPENDIX ECoopButte County,Camilla, Georgia: Energy014771°,NorthCLEAN WebinarNH Jump to:

  19. Graphic: FL Dept. of Environmental Protection Please pass the Salt!!

    E-Print Network [OSTI]

    Graphic: FL Dept. of Environmental Protection Please pass the Salt!! Mangroves are a very unique protruding from the tree trunk and branches. These prop roots are special because they exclude salt from actually absorb saltwater through their roots, but have specially designed leaves with salt glands

  20. 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

  1. Walton County Coastal Storm Damage Reduction Project Walton County, FL

    E-Print Network [OSTI]

    US Army Corps of Engineers

    to reduce coastal storm damages by constructing berms and dunes along 18.8 miles of Walton County shoreline;vegetation and replacement of dune walkover structures as required. Material for the berm and duneWalton County Coastal Storm Damage Reduction Project Walton County, FL 13 December 2012 ABSTRACT

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

    E-Print Network [OSTI]

    Yener, Aylin

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

  3. nh Gi Tn Hi Ti Nguyn Thin Nhin do Trn Du Deep Horizon Gim nh bt Nhm Tng ni

    E-Print Network [OSTI]

    vàng và cá kim. Thit b dây câu vàng s vô tình bt phi nhng loài cá khác cng nh nhng cá th còn quá nh ca là thi gian ngh ngi. Các d án cng cung cp cho nhng ng dân tham gia hai loi thit b ánh bt thay th - tr

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

    E-Print Network [OSTI]

    Farrar, James M.

    Proton transfer dynamics of the reaction H3O¿ ,,NH3 ,H2O...NH4 ¿ studied using the crossed, Rochester, New York 14627 Received 29 September 2003; accepted 8 October 2003 The proton transfer reaction sharply asymmetry, and the maximum is close to the velocity and direction of the precursor ammonia beam

  5. International Conference on Advanced Ceramics and Composites, January 2007, Daytona FL, USA

    E-Print Network [OSTI]

    Yildiz, Bilge

    Proc. 31st International Conference on Advanced Ceramics and Composites, January 2007, Daytona FL design of electrodes with improved #12;Proc. 31st International Conference on Advanced Ceramics

  6. DOE - Office of Legacy Management -- Armour Fertilizer Works - FL 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouth Dakota Edgemont, South Dakota,You areFertilizer Works - FL 01

  7. File:EIA-FL-BOE.pdf | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New Pages Recent Changes AllApschem.pdf Jump to:ColoradoBOE.pdfFL-BOE.pdf Jump to: navigation,

  8. File:EIA-FL-GAS.pdf | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New Pages Recent Changes AllApschem.pdf Jump to:ColoradoBOE.pdfFL-BOE.pdf Jump to:

  9. File:EIA-FL-LIQ.pdf | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New Pages Recent Changes AllApschem.pdf Jump to:ColoradoBOE.pdfFL-BOE.pdf Jump to:LIQ.pdf Jump

  10. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouthReport for the WeldonB100 Monthly/Effluent; Largo, FL 7030-2267170

  11. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouthReport for the WeldonB100 Monthly/Effluent; Largo, FL

  12. CHARACTERIZATION OF THE SELECTIVE REDUCTION OF NO BY NH3

    E-Print Network [OSTI]

    Lucas, D.

    2014-01-01

    in this study. with coal type. limiting the NH The optimumlight oil and several types of coal, and have provided somecombustion air. Several types of coal with different sulfur

  13. L: Lifetimes of Civilizations N = N* fs fGHZ fp nH fl fJ ffEufmfifcL /T

    E-Print Network [OSTI]

    Walter, Frederick M.

    : natural resources regeneration, depletion · w: wealth production ­ consumption · C : consumption ­ Cc, depends on wealth · Consumption depends on wealth ­ Commoners consumption ceases when wealth falls below threshold ­ Elites consumption ceases when wealth falls below threshold/ #12;Handy Solutions · Vary

  14. 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

  15. 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

  16. 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 Selective Catalytic Oxidation (SCO) of NH3 to N2 for Hot Exhaust Treatment Investigation of a series of transition metal...

  17. Study of On-Board Ammonia (NH3) Generation for SCR Operation...

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

    Study of On-Board Ammonia (NH3) Generation for SCR Operation Study of On-Board Ammonia (NH3) Generation for SCR Operation The feasibility of on-board ammonia generation was...

  18. 1 -NH Coverts Project: 1995-2002 Program Evaluation The New Hampshire Coverts Project

    E-Print Network [OSTI]

    New Hampshire, University of

    1 - NH Coverts Project: 1995-2002 Program Evaluation The New Hampshire Coverts Project In Their Own, sexual orientation, or veteran's status. #12;2 - NH Coverts Project: 1995-2002 Program Evaluation of responses to open-ended question (#12) 19 #12;3 - NH Coverts Project: 1995-2002 Program Evaluation

  19. H irradiation effects on the GaAs-like Raman modes in GaAs{sub 1-x}N{sub x}/GaAs{sub 1-x}N{sub x}:H planar heterostructures

    SciTech Connect (OSTI)

    Giulotto, E. Geddo, M.; Patrini, M.; Guizzetti, G.; Felici, M.; Capizzi, M.; Polimeni, A.; Martelli, F.; Rubini, S.

    2014-12-28

    The GaAs-like longitudinal optical phonon frequency in two hydrogenated GaAs{sub 1-x}N{sub x}/GaAs{sub 1-x}N{sub x}:H microwire heterostructures—with similar N concentration, but different H dose and implantation conditions—has been investigated by micro-Raman mapping. In the case of GaAs{sub 0.991}N{sub 0.009} wires embedded in barriers where GaAs-like properties are recovered through H irradiation, the phonon frequency in the barriers undergoes a blue shift with respect to the wires. In GaAs{sub 0.992}N{sub 0.008} wires embedded in less hydrogenated barriers, the phonon frequency exhibits an opposite behavior (red shift). Strain, disorder, phonon localization effects induced by H-irradiation on the GaAs-like phonon frequency are discussed and related to different types of N-H complexes formed in the hydrogenated barriers. It is shown that the red (blue) character of the frequency shift is related to the dominant N-2H (N-3H) type of complexes. Moreover, for specific experimental conditions, an all-optical determination of the uniaxial strain field is obtained. This may improve the design of recently presented devices that exploit the correlation between uniaxial stress and the degree of polarization of photoluminescence.

  20. Effects of reactant rotational excitations on H{sub 2} + NH{sub 2} ? H + NH{sub 3} reactivity

    SciTech Connect (OSTI)

    Song, Hongwei; Guo, Hua

    2014-12-28

    Rotational mode specificity of the title reaction is examined using an initial state selected time-dependent wave packet method on an accurate ab initio based global potential energy surface. This penta-atomic reaction presents an ideal system to test several dynamical approximations, which might be useful for future quantum dynamics studies of polyatomic reactions, particularly with rotationally excited reactants. The first approximation involves a seven-dimensional (7D) model in which the two non-reactive N–H bonds are fixed at their equilibrium geometry. The second is the centrifugal sudden (CS) approximation within the 7D model. Finally, the J-shifting (JS) model is tested, again with the fixed N–H bonds. The spectator-bond approximation works very well in the energy range studied, while the centrifugal sudden and J-shifting integral cross sections (ICSs) agree satisfactorily with the coupled-channel counterparts in the low collision energy range, but deviate at the high energies. The calculated integral cross sections indicate that the rotational excitation of H{sub 2} somewhat inhibits the reaction while the rotational excitations of NH{sub 2} have little effect. These findings are compared with the predictions of the sudden vector projection model. Finally, a simple model is proposed to predict rotational mode specificity using K-averaged reaction probabilities.

  1. AlGaN/GaN-based power semiconductor switches

    E-Print Network [OSTI]

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

    2013-01-01

    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 ...

  2. Published in: Wet-Weather Flow in the Urban Watershed: Technology and Management. Edited by R. Field and D. Sullivan. CRC Press. Boca Raton, FL. 2002.

    E-Print Network [OSTI]

    Pitt, Robert E.

    . Field and D. Sullivan. CRC Press. Boca Raton, FL. 2002. SLAMM, the Source Loading and Management Model

  3. 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

  4. SAND2013-4882 C 39th IEEE Photovoltaic Specialists Conference, Tampa, FL, June 2013

    E-Print Network [OSTI]

    SAND2013-4882 C 39th IEEE Photovoltaic Specialists Conference, Tampa, FL, June 2013 Testing National Laboratories, Albuquerque, NM, 87123, USA Abstract -- Photovoltaic (PV) modules with attached designed for AC modules. Index Terms -- inverters, photovoltaic systems, power electronics, solar energy. I

  5. 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

  6. 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

  7. High quality crystalline YBa2Cu307+ films on thin silicon substrates FL Haakenaasen

    E-Print Network [OSTI]

    Golovchenko, Jene A.

    High quality crystalline YBa2Cu307+ films on thin silicon substrates FL Haakenaasen Department) films with near perfect crystallinity have been grown epitaxially on Si(100) using two intermediate good crystallinity and be quite thin ((1 m)? Relativistic electrons are sent through the crystal

  8. Freezing, melting, nonwetting, and coexistence in (KCl)32 John P. Rose and FL Stephen Berry

    E-Print Network [OSTI]

    Berry, R. Stephen

    Freezing, melting, nonwetting, and coexistence in (KCl)32 John P. Rose and FL Stephen Berry that of homogeneousclusters. The melting and freezing, nonwetting, and the complexity of the potential surfaceof (KC1)33areCl clustersexhibit simpleisomerizationdynamics, large NaCl clusters exhibit freezing/melting behavior sim- ilar

  9. INDEX TO VOLUME 54 . AcanLhuridao, surgeon fish______________________ fl8

    E-Print Network [OSTI]

    INDEX TO VOLUME 54 Page . AcanLhuridao, surgeon fish______________________ fl8 'Acipcnscr .fll~' STATE OF MICI-IlqAN WAT~;RS Ob' GREEN HAY __ 1-:14 cacrulca, SartlinopL ___________________________ 20 L:n, 1:{8 Cn.~piol(/ cas1Jia.__ ___ _ ______ ________ 60 Cating, .Jamcs P.: DETI'RMING AnE .w ATI.AN

  10. FL43CH19-Shelley ARI 10 September 2010 19:30 Flapping and Bending Bodies

    E-Print Network [OSTI]

    Shelley, Michael

    FL43CH19-Shelley ARI 10 September 2010 19:30 R E V I E W S IN A D V A N CE Flapping and Bending, flutter, flexible bodies, instability, drag reduction Abstract The flapping or bending of a flexible is important to applications such as paper processing (Watanabe et al. 2002), as well as to possible approaches

  11. International Technical Conference on Coal Utilization & Fuel Systems Clearwater (FL), USA, March 4-7, 2002

    E-Print Network [OSTI]

    Zevenhoven, Ron

    is slowly shifting its fuel consumption to renewable fuels like wood and waste-derived fuels, there still27th International Technical Conference on Coal Utilization & Fuel Systems Clearwater (FL), USA of the greenhouse gas CO2 from flue gases from fossil fuel-fired power plants and utilities may be accomplished

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

    Office of Energy Efficiency and Renewable Energy (EERE)

    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

  13. Formal Aspects of Computing (1995) 7(E): 30--65 fl 1995 BCS Formal Aspects

    E-Print Network [OSTI]

    Smith, Graeme

    1995-01-01

    Formal Aspects of Computing (1995) 7(E): 30--65 c fl 1995 BCS Formal Aspects of Computing A Fully of existing specification lan­ guages have been extended to incorporate object­oriented concepts [DKR91b, SBC, however, is only possible once a formal semantics of the incorporated object­oriented features has been

  14. Hollow-fiber gas-membrane process for removal of NH{sub 3} from solution of NH{sub 3} and CO{sub 2}

    SciTech Connect (OSTI)

    Qin, Y.; Cabral, J.M.S.; Wang, S.

    1996-07-01

    A hollow-fiber supported gas membrane process for the separation of NH{sub 3} from aqueous solutions containing both NH{sub 3} and CO{sub 2} was investigated theoretically and experimentally. A lumen laminar flow and radial diffusion model was applied to calculate the membrane wall transfer coefficient from the data stripping a single volatile component, NH{sub 3} or CO{sub 2}, from their individual aqueous solutions. Influence of the type of membranes and operating conditions on mass-transfer rate were discussed, especially the influence of the membrane transfer coefficient on the film mass-transfer coefficient in the lumen. Appropriate configurations of the hollow-fiber modules for stripping of a single component were analyzed to optimize mass transfer. To predict the stripping of NH{sub 3} from a solution containing NH{sub 3} and CO{sub 2}, a mathematical model incorporating local chemical equilibria and Nernst-Planck diffusion was developed to describe the mass transport. The models described the experimental data fairly well. The experimental results showed that the supported gas membrane process can be used to remove NH{sub 3} effectively from aqueous media containing NH{sub 3} and CO{sub 2}.

  15. Modeling Study of SCR/PGM Interactions in NH3 Slip Catalysts

    Broader source: Energy.gov [DOE]

    The focus of this research is on the optimization of NH3 slip catalyst performance by simulating the behavior of different SCR/PGM configurations.

  16. Opal Palmer Adisa. It Begins With Tears (Portsmouth, NH: Heinemann Press, 1997).

    E-Print Network [OSTI]

    Devlin, Leslie

    1997-01-01

    Opal Palmer Adisa. It Begins With Tears (Portsmouth, NH:Tears, is the first novel of Opal Palmer Adisa. She was born

  17. nh Gi Thit Hi Ti Nguyn Thin Nhin Do S C Trn Du Deepwater Horizon

    E-Print Network [OSTI]

    lên các bãi bin trng bng phng. Vt liu này cng có th nm thành di nh dài hai dm theo ng mc thy triu và di mc thy triu thuc phía Vnh Fort Pickens, thnh thong khách thm cng hay bi li ch này. Các mnh nh nha

  18. Simulation of an Ar/NH{sub 3} low pressure magnetized direct current discharge

    SciTech Connect (OSTI)

    Li Zhi [School of Science, University of Science and Technology Liaoning, Anshan 114051 (China); School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Zhao Zhen [School of Chemistry and Life Science, Anshan Normal University, Anshan 114007 (China); School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051 (China); Li Xuehui [Physiccal Science and Technical College, Dalian University, Dalian 116622 (China)

    2013-01-15

    A two-dimensional fluid model has been used to investigate the properties of plasma in an Ar/NH{sub 3} low pressure magnetized direct current discharge. We compared the simulation results with the theoretical and experimental results of the other gas discharge in which the magnetic field is considered. Results that obtained using this method are in good agreement with literature. The simulation results show that the positive ammonia ion density follows the positive argon ion density. The Ar{sub 2}{sup +} density is slightly higher than the Ar{sup +} density at 100 mTorr. The largest ammonia ion is NH{sub 3}{sup +} ion, followed by NH{sub 2}{sup +}, NH{sub 4}{sup +}, and NH{sup +} ions. The contribution of NH{sup +} ions to the density of the positive ammonia ions is marginal. The influence of pressure on the plasma discharge has been studied by simulation, and the mechanisms have been discussed. The average plasma density increases as pressure increased. The plasma density appears to be more inhomogeneous than that at the lower pressure. The ratio of charge particles changed as pressure increased. The Ar{sup +} density is slightly higher than the Ar{sub 2}{sup +} density as the pressure increased. It makes NH{sub 4}{sup +} ratio increase as pressure increased. It shows that the electron temperature drops with rising pressure by numerical calculation.

  19. Global distributions, time series and error characterization of atmospheric ammonia (NH[subscript 3]) from IASI satellite observations

    E-Print Network [OSTI]

    Van Damme, M.

    Ammonia (NH[subscript 3]) emissions in the atmosphere have increased substantially over the past decades, largely because of intensive livestock production and use of fertilizers. As a short-lived species, NH[subscript 3] ...

  20. Deep-Ultraviolet Resonance Raman Excitation Profiles of NH4NO3, PETN, TNT, HMX, and RDX

    E-Print Network [OSTI]

    Asher, Sanford A.

    Deep-Ultraviolet Resonance Raman Excitation Profiles of NH4NO3, PETN, TNT, HMX, and RDX Manash nitrate (NH4NO3), pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), nitroamine (HMX. The ultraviolet (UV) resonance Raman/differential Raman cross-sections of NH4NO3, PETN, TNT, HMX, and RDX

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

    SciTech Connect (OSTI)

    Krishnamoorthy, Sriram; Nath, Digbijoy N.; Akyol, Fatih; Park, Pil Sung; Esposto, Michele; Rajan, Siddharth [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2010-11-15

    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 calculations were used to model and design tunnel junctions with narrow band gap InGaN-based barrier layers. N-polar p-GaN/In{sub 0.33}Ga{sub 0.67}N/n-GaN heterostructure tunnel diodes were grown using molecular beam epitaxy. Efficient interband tunneling was achieved close to zero bias with a high current density of 118 A/cm{sup 2} at a reverse bias of 1 V, reaching a maximum current density up to 9.2 kA/cm{sup 2}. 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.

  2. CHARACTERIZATION STUDIES OF THE SELECTIVE REDUCTION OF NO by NH3

    E-Print Network [OSTI]

    Brown, N.J.

    2013-01-01

    and Maloney, K.L. , "NOx Reduction with Ammonia: Laboratoryand Hashizawa, K. , "Reduction of NOx in Combustion ExhaustSelective Noncatalytic Reduction of NOx with NH3," EPRI NOx

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

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

    generation over commercial Three-Way Catalysts and Lean-NOx Traps NH3 generation over commercial Three-Way Catalysts and Lean-NOx Traps Research to identify most promising...

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

    Broader source: Energy.gov [DOE]

    Research to identify most promising catalytic formulations and operation for the in-situ generation of NH3, storage on a downstream SCR catalyst, and utilized to reduce the remaining NOx

  5. 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

    2007-05-07

    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.

  6. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouth DakotaRobbins and Myers Co - OHStarTracerlabCincinnati -Miami - FL

  7. File:USDA-CE-Production-GIFmaps-FL.pdf | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New Pages RecentTempCampApplicationWorksheet 2011.pdf JumpTransmission SitingFL.pdf Jump to:

  8. S M Stoller Star Center-B100 Monthly/Effluent; 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouthReport for the WeldonB100 Monthly/Effluent; Largo, FL 7030-226

  9. GaInNAs laser gain

    SciTech Connect (OSTI)

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

    2000-05-23

    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.

  10. Volume 130, number 6 CHEMICAL PHYSICS LETTERS 24 October1986 VIBRATIONAL DEPENDENCE OF THE NH,+ (v2)+NO AND NO+(v) +NH,

    E-Print Network [OSTI]

    bending mode ( vz=O-12) causes no marked change in the charge transfer cross section, while in the reverse vibrational levels. We find that the vibrational excitation of the NH: v2 umbrella bending mode (v, = O-12 with the hope of con- firming or refuting this model. 2. Experimental In a previous paper we reported

  11. 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

    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 the radiative recombination rates across the active region. Consequently, the light output power was enhanced

  12. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservationBio-InspiredAtmosphericdevicesPPONeApril351APPLICATION OFsafer The mp483-I

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

    E-Print Network [OSTI]

    Kangude, Yamini

    2005-01-01

    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 ...

  14. Tunable far infrared laser spectroscopy of van der Waals bonds: Ar-NH sub 3

    SciTech Connect (OSTI)

    Gwo, Dz-Hung (Lawrence Berkeley Lab., CA (USA) California Univ., Berkeley, CA (USA). Dept. of Chemistry)

    1989-11-01

    Hyperfine resolved vibration-rotation-tunneling spectra of Ar--NH{sub 3} and (NH{sub 3}){sub 2}, generated in a planar supersonic jet, have been measured with the Berkeley tunable far infrared laser spectrometer. Among the seven rotationally assigned bands, one band belongs to Ar--NH{sub 3}, and the other six belong to (NH{sub 3}){sub 2}. To facilitate the intermolecular vibrational assignment for Ar--NH{sub 3}, a dynamics study aided by a permutation-inversion group theoretical treatment is performed on the rovibrational levels. The rovibrational quantum number correlation between the free internal rotor limit and the semi-rigid limit is established to provide a basic physical picture of the evolution of intermolecular vibrational component states. An anomalous vibronically allowed unique Q branch vibrational band structure is predicted to exist for a near prolate binary complex containing an inverting subunit. According to the model developed in this work, the observed band of Ar--NH{sub 3} centered at 26.470633(17) cm{sup {minus}1} can correlate only to either the fundamental dimeric stretching band for the A{sub 2} states with the NH{sub 3} inversional quantum number v{sub i} = 1, or the K{sub a} = 0 {l arrow} 0 subband of the lowest internal-rotation-inversion difference band. Although the estimated nuclear quadrupole coupling constant favors a tentative assignment in terms of the first possibility, a definitive assignment will require far infrared data and a dynamical model incorporating a potential surface.

  15. Numerical analysis of a mixture of Ar/NH{sub 3} microwave plasma chemical vapor deposition reactor

    SciTech Connect (OSTI)

    Li Zhi [School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); School of Science, University of Science and Technology Liaoning, Anshan 114051 (China); Zhao Zhen [Chemistry Department, Anshan Normal University, Anshan 114007 (China); School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051 (China); Li Xuehui [School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Physical Science and Technical College, Dalian University, Dalian 116622 (China)

    2012-06-01

    A two-dimensional fluid model has been used to investigate the properties of plasma in Ar/NH{sub 3} microwave electron cyclotron resonance discharge at low pressure. The electromagnetic field model solved by the three-dimensional Simpson method is coupled to a fluid plasma model. The finite difference method was employed to discrete the governing equations. 40 species (neutrals, radicals, ions, and electrons) are consisted in the model. In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. According to the simulation, the distribution of the densities of the considered plasma species has been showed and the mechanisms of their variations have been discussed. It is found that the main neutrals (Ar*, Ar**, NH{sub 3}{sup *}, NH, H{sub 2}, NH{sub 2}, H, and N{sub 2}) are present at high densities in Ar/NH{sub 3} microwave electron cyclotron resonance discharge when the mixing ratio of Ar/NH{sub 3} is 1:1 at 20 Pa. The density of NH is more than that of NH{sub 2} atom. And NH{sub 3}{sup +} are the most important ammonia ions. But the uniformity of the space distribution of NH{sub 3}{sup +} is lower than the other ammonia ions.

  16. 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

    2012-04-30

    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.

  17. 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; Masson, Denis; Riel, Bruno; Fafard, Simon; Jaouad, Abdelatif; Turala, Artur; Ares, Richard; Aimez, Vincent

    2010-10-14

    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}.

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

    SciTech Connect (OSTI)

    R. W. Swindeman

    2009-12-14

    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.

  19. GaAs MOEMS Technology

    SciTech Connect (OSTI)

    SPAHN, OLGA B.; GROSSETETE, GRANT D.; CICH, MICHAEL J.; TIGGES, CHRIS P.; RENO, JOHN L.; PEAKE, GREGORY M.; KLEM, JOHN F.; LEAN, JEN; FULLER, CHARLES T.; BURKHART, JEFF; BAUER, THOMAS; SULLIVAN, CHARLES T.

    2003-03-01

    Many MEMS-based components require optical monitoring techniques using optoelectronic devices for converting mechanical position information into useful electronic signals. While the constituent piece-parts of such hybrid opto-MEMS components can be separately optimized, the resulting component performance, size, ruggedness and cost are substantially compromised due to assembly and packaging limitations. GaAs MOEMS offers the possibility of monolithically integrating high-performance optoelectronics with simple mechanical structures built in very low-stress epitaxial layers with a resulting component performance determined only by GaAs microfabrication technology limitations. GaAs MOEMS implicitly integrates the capability for radiation-hardened optical communications into the MEMS sensor or actuator component, a vital step towards rugged integrated autonomous microsystems that sense, act, and communicate. This project establishes a new foundational technology that monolithically combines GaAs optoelectronics with simple mechanics. Critical process issues addressed include selectivity, electrochemical characteristics, and anisotropy of the release chemistry, and post-release drying and coating processes. Several types of devices incorporating this novel technology are demonstrated.

  20. Table I: Distribution Functions for Fuel Fractions Group 2L0 FL0 ( wL0

    E-Print Network [OSTI]

    Hallett, William L.H.

    Table I: Distribution Functions for Fuel Fractions Group 2L0 FL0 ( wL0 alcohols 55 20 0 0: Distribution fun ctions used to mod el the oil. Evaporation of Biomass Pyrolysis Oil Droplets - II W), and the composition of each of these groups is described by a gamma distribution function with mean 2L0, standard

  1. FORM CD-512 UNITED STATES DEPARTMENT OF COM MERCE CERTlFlCATlONS REGARDING DEBARMENT, SUSPENSION, INELIGIBILITY AND

    E-Print Network [OSTI]

    paid or will be connection with this commitment providing for the United paid, by or on behalfFORM CD-512 UNITED STATES DEPARTMENT OF COM MERCE (7-91) CERTlFlCATlONS REGARDING DEBARMENT to attest. Applicants should also review the instructions for certification included in the regulations

  2. Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)

    SciTech Connect (OSTI)

    Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel; Que, Christopher T.; Yamamoto, Kohji; Tani, Masahiko

    2012-12-15

    Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

  3. Formation of NH{sub 3} during the pyrolysis of a brown coal

    SciTech Connect (OSTI)

    Li, C.Z.; Pang, Y.; Li, X.G. [Monash Univ., Clayton, Victoria (Australia). Dept. of Chemical Engineering

    1998-12-31

    Emissions of oxides of nitrogen (NO, NO{sub 2} and N{sub 2}O) from power generation using coal are an important environmental problem, contributing to the formation of photochemical smog and acid rain or to the enhancement of greenhouse effects and to the enhanced depletion of stratospheric ozone. During pyrolysis, the nitrogen in coal, as a part of coal organic matter, is converted into NOx precursors (eg. NH{sub 3}, HCN, HNCO and the nitrogen in tar and char). These NOx precursors may then be converted into either NOx or N{sub 2} during subsequent combustion or gasification/combustion. The conversion efficiency of these NOx precursors into NOx depends strongly upon the type of NOx precursor. Knowledge of the formation of these NOx precursors during pyrolysis is therefore essential for the accurate predictions of NOx emissions from large scale power plants, and therefore for the development of optimum strategies for NOx reduction. Formation of NH{sub 3} during the pyrolysis of a Victorian brown coal (Loy Yang) has been studied in a novel reactor. The experimental results obtained suggest that a considerable amount of the nitrogen in the nascent char could be converted into NH{sub 3} if the char is held at high temperatures for a long period of time. The formation of NH{sub 3} from the thermal cracking of char was seen to last for more than an hour even at temperatures as high as 700--900 C. The experimental results seem to suggest that the differences in reactor geometries would account at least partially for some of the discrepancies in the literature regarding the formation of NH{sub 3} during the pyrolysis of coals. It is thought that NH{sub 3} may be formed from the hydrogenation of the N sites in the char by the active hydrogen generated from the thermal cracking of the char.

  4. Computational analysis of thin film InGaAs/GaAs quantum well solar cells with

    E-Print Network [OSTI]

    Yu, Edward T.

    Computational analysis of thin film InGaAs/GaAs quantum well solar cells with back side light, Austin, TX 78758, USA * ety@ece.utexas.edu Abstract: Simulations of thin film (~2.5 µm thick) InGaAs/GaAs. Roberts, G. Hill, and C. Calder, "Progress in quantum well solar cells," Thin Solid Films 511­512, 76

  5. GaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response

    E-Print Network [OSTI]

    Jalali. Bahram

    into existing multijunction cells either as a means to increase the current or efficiency by using low band gapGaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response R. B infrared spectral response of GaAs-based solar cells that incorporate type II GaSb quantum dots QDs formed

  6. NH13A: No-source tsunami forecasting for Alaska communities

    E-Print Network [OSTI]

    Tolkova, Elena

    NH13A: No-source tsunami forecasting for Alaska communities Dmitry Nicolsky (UAF) djnicolsky://nctr.pmel.noaa.gov/ Wave trains to Alaska: direction structure (time history) tsunami source R E S P and accurate regional tsunami forecasts · A deep-ocean detector and a coastal site can be connected

  7. 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.

    2005-11-01

    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.

  8. 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)

    2015-04-03

    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.

  9. Novel ethylenediamine-gallium phosphate containing 6-fold coordinated gallium atoms with unusual four equatorial Ga–N bonds

    SciTech Connect (OSTI)

    Torre-Fernández, Laura [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain); Espina, Aránzazu; Khainakov, Sergei A.; Amghouz, Zakariae [Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); García, José R. [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain); García-Granda, Santiago, E-mail: sgg@uniovi.es [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo (Spain)

    2014-07-01

    A novel ethylenediamine-gallium phosphate, formulated as Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, was synthesized under hydrothermal conditions. The crystal structure, including hydrogen positions, was determined using single-crystal X-ray diffraction data (monoclinic, a=9.4886(3) Å, b=6.0374(2) Å, c=10.2874(3) Å, and ?=104.226(3)°, space group Pc) and the bulk was characterized by chemical (Ga–P–C–H–N) and thermal analysis (TG–MS and DSC), including activation energy data of its thermo-oxidative degradation, powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (SS-NMR) measurements, and transmission electron microscopy (TEM, SAED/NBD, and STEM BF-EDX). The crystal structure is built up of infinite zig-zag chains running along the c-axis, formed by vertex-shared (PO{sub 4}) and (GaO{sub 2}N{sub 4}) polyhedra. The new compound is characterized by unusual four equatorial Ga–N bonds coming from two nonequivalent ethylenediamine molecules and exhibits strong blue emission at 430 nm (?{sub ex}=350 nm) in the solid state at room temperature. - Graphical abstract: Single crystals of a new ethylenediamine-gallium phosphate, Ga(H{sub 2}NCH{sub 2}CH{sub 2}NH{sub 2}){sub 2}PO{sub 4}·2H{sub 2}O, were obtained and the structural features presented. This structure is one of the scarce examples of GaPO with Ga–N bonds reported. - Highlights: • A novel ethylenediamine-gallium phosphate was hydrothermally synthesized. • The new compound is characterized by unusual four equatorial Ga–N bonds. • Void-volume analysis shows cages and channels with sizes ideally suited to accommodate small molecules. • The new compound exhibits strong blue emission.

  10. 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

  11. 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)

    2001-01-01

    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%.

  12. Band Structure of Strain-Balanced GaAsBi/GaAsN Super-lattices on GaAs

    SciTech Connect (OSTI)

    Hwang, J.; Phillips, J. D.

    2011-05-31

    GaAs alloys with dilute content of Bi and N provide a large reduction in band-gap energy with increasing alloy composition. GaAsBi/GaAsN heterojunctions have a type-II band alignment, where superlattices based on these materials offer a wide range for designing effective band-gap energy by varying superlattice period and alloy composition. The miniband structure and effective band gap for strain-balanced GaAsBi/GaAsN superlattices with effective lattice match to GaAs are calculated for alloy compositions up to 5% Bi and N using the k·p method. The effective band gap for these superlattices is found to vary between 0.89 and 1.32 eV for period thickness ranging from 10 to 100 Å. The joint density of states and optical absorption of a 40/40 Å GaAs0.96Bi0.04/GaAs0.98N0.02 superlattice are reported demonstrating a ground-state transition at 1.005 eV and first excited transition at 1.074 eV. The joint density of states is similar in magnitude to GaAs, while the optical absorption is approximately one order of magnitude lower due to the spatially indirect optical transition in the type-II structure. The GaAsBi/GaAsN system may provide a new material system with lattice match to GaAs in a spectral range of high importance for optoelectronic devices including solar cells, photodetectors, and light emitters.

  13. Magnetism and transport properties of epitaxial Fe-Ga thin films on GaAs(001)

    SciTech Connect (OSTI)

    Duong Anh Tuan; Shin, Yooleemi; Cho, Sunglae; Dang Duc Dung; Vo Thanh Son

    2012-04-01

    Epitaxial Fe-Ga thin films in disordered bcc {alpha}-Fe crystal structure (A2) have been grown on GaAs(001) by molecular beam epitaxy. The saturated magnetization (M{sub S}) decreased from 1371 to 1105 kA/m with increasing Ga concentration from 10.5 to 24.3 % at room temperature. The lattice parameter increased with the increase in Ga content because of the larger atomic radius of Ga atom than that of Fe. The increase in carrier density with Ga content caused in lower resistivity.

  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)

    2014-10-20

    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. GM Media-Sept 21, 2007 PBS, NH4Cl and KCl

    E-Print Network [OSTI]

    GM Media- Sept 21, 2007 PBS, NH4Cl and KCl Final volume(L) 1 50 mM PBS 100 mM 200 mM Ingredient keep the PBS solution at room temperature. GM Media Preparation: For each litter of GM media add, mineral, and PBS solution if you are not going to use them inside MFC. Combine them prior to make GM media

  16. AlGaAsSb/GaSb Distributed Bragg Reflectors Grown by Organometallic Vapor Phase Epitaxy

    SciTech Connect (OSTI)

    C.A. Wang; C.J. Vineis; D.R. Calawa

    2002-02-13

    The first AlGaAsSb/GaSb quarter-wave distributed Bragg reflectors grown by metallic vapor phase epitaxy are reported. The peak reflectance is 96% for a 10-period structure.

  17. Impact of electrochemical process on the degradation mechanisms of AlGaN/GaN HEMTs

    E-Print Network [OSTI]

    Gao, Feng, Ph. D. Massachusetts Institute of Technology

    2014-01-01

    AlGaN/GaN high electron mobility transistors (HEMTs) constitute a new generation of transistors with excellent electrical characteristics and great potential to replace silicon technology in the future, especially in high ...

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

    E-Print Network [OSTI]

    Espinosa, Horacio D.

    director cds murder nudity soundtrack BBC movie releases footage worth documentary film Blu-rays Blu-ray Ga

  19. 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.

    2005-08-01

    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%.

  20. 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

  1. 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 ...

  2. [(CH3)4N][(C5H5NH)0.8((CH3)3NH)0.2]U2Si9O23F4 (USH-8): An Organically Templated Open-Framework Uranium Silicate

    E-Print Network [OSTI]

    Wang, Xiqu

    -Framework Uranium Silicate Xiqu Wang, Jin Huang, and Allan J. Jacobson* Department of Chemistry, Uni pyramids we obtained also a number of open-framework uranium silicates.18,19 These new compounds were-framework uranium fluorosilicate [(CH3)4N][(C5H5NH)0.8((CH3)3NH)0.2]U2Si9O23F4 (USH- 8) that has been synthesized

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

    SciTech Connect (OSTI)

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

    2015-01-15

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

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

    Broader source: Energy.gov [DOE]

    A modified Spaci-IR technique can measure transient NH3 and NOx concentrations; data have been used to calibrate and validate an SCR model, with good agreement between experiments and simulations.

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

    SciTech Connect (OSTI)

    Liang, C.; Gao, M. X.; Pan, H. G. Liu, Y. F.

    2014-08-25

    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.

  6. Scientific Achievement Networks of highly photoresponsive crystalline GaSe

    E-Print Network [OSTI]

    Geohegan, David B.

    Scientific Achievement Networks of highly photoresponsive crystalline GaSe nanosheets a crystalline GaSe target was adjusted to directly grow networks of interconnected triangular GaSe crystalline nanosheets of ~ 200 nm size (inset shows atomic

  7. Acetic Acid (H3COOH): GaAs; Pb; Ti Hydrochloric Acid (HCl): Al; Cr; Cu; Fe2O3; Ga; GaAs; GaN; In; Fe; Pb; Ni; NiO, Ni2O3; Sn;

    E-Print Network [OSTI]

    Garmestani, Hamid

    ferrocyanide (s) KMnO4 : potassium permanganate (s) FeCl3 : ferric chloride (s) NH4SO5 : ammonium persulfate (s

  8. Development of metallization for GaAs and AlGaAs concentrator solar cells

    SciTech Connect (OSTI)

    Tobin, S.P.

    1987-04-01

    A three-layer metallization system was developed for high temperature stability on GaAs and AlGaAs solar cells. The layers are a Pt ohmic contact metal that forms thermally stable compounds with GaAs, a TiN diffusion barrier, and a gold conductor. The solar cell structure was also designed for contact stability, with the key component being a heavily doped GaAs cap layer. Reactively sputtered TiN was found to act as an excellent barrier when deposited under the proper conditions. The conditions were carefully optimized for low resistivity and low stress in the films. A low but nonzero substrate bias during sputtering was found to be important. Solar cells with sputtered metallizations of Pt/TiN/Ti/Pt/Au were found to be thermally stable up to 500/sup 0/C for 15 minutes in vacuum. At 600/sup 0/C there was catastrophic degradation of the cells due to dissociation of uncapped GaAs surfaces. Below this temperature the metallization performed as designed. The Pt and GaAs layers reacted to form a stable PtGa compound layer that gave low contact resistance. There was no penetration of Au or GaAs through the barrier layer. These results are a very encouraging first step leading to stable, reliable GaAs and AlGaAs concentrator cells.

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

    SciTech Connect (OSTI)

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Ho?fling, S.; Worschech, L.; Gru?tzmacher, D.

    2011-01-01

    InGaN/GaN nanowire (NW) heterostructures grown by plasma assisted molecular beam epitaxy were studied in comparison to their GaN and InGaN counterparts. The InGaN/GaN heterostructure NWs are composed of a GaN NW, a thin InGaN shell, and a multifaceted InGaN cap wrapping the top part of the GaN NW. High-resolution transmission electron microscopy (HRTEM) images taken from different parts of a InGaN/GaN NW show a wurtzite structure of the GaN core and the epitaxial InGaN shell around it, while additional crystallographic domains are observed whithin the InGaN cap region. Large changes in the lattice parameter along the wire, from pure GaN to higher In concentration demonstrate the successful growth of a complex InGaN/GaN NW heterostructure. Photoluminescence (PL) spectra of these heterostructure NW ensembles show rather broad and intense emission peak at 2.1 eV. However, ?-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.

  10. Ohmic contacts to n-GaSb 

    E-Print Network [OSTI]

    Yang, Zhengchong

    1997-01-01

    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...

  11. GaTe semiconductor for radiation detection

    DOE Patents [OSTI]

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

    2009-06-23

    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.

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

    E-Print Network [OSTI]

    Oehler, F.; Sutherland, D.; Zhu, T.; Emery, R.; Badcock, T. J.; Kappers, M. J.; Humphreys, C. J.; Dawson, P.; Oliver, R. A.

    2014-09-16

    interlayer. Keywords: A3 Metalorganic vapor phase epitaxy, B1 Nitrides, A1 Defects, A1 Characterization 1. Introduction Hexagonal gallium nitride (GaN) presents two stable growth directions inclined at 90? angle to the c-direction. Respectively named a... is kept constant at 20 standard litres per minute (SLM) by bal- ancing the flow rates of the carrier gas and NH3. Unless otherwise specified, the total reactor pressure is 100 Torr and H2 is used as the carrier gas. The growth temperatures quoted...

  13. The thermal decomposition of NH{sub 2}OH and subsequent reactions : ab initio transition state theory and reflected shock tube experiments.

    SciTech Connect (OSTI)

    Klippenstein, S. J.; Harding, L. B.; Ruscic, B.; Sivaramakrishnan, R.; Srinivasan, N. K.; Su, M.-C.; Michael, J. V.; Chemical Sciences and Engineering Division; Sonoma State Univ.

    2009-01-01

    Primary and secondary reactions involved in the thermal decomposition of NH{sub 2}OH are studied with a combination of shock tube experiments and transition state theory based theoretical kinetics. This coupled theory and experiment study demonstrates the utility of NH{sub 2}OH as a high temperature source of OH radicals. The reflected shock technique is employed in the determination of OH radical time profiles via multipass electronic absorption spectrometry. O-atoms are searched for with atomic resonance absorption spectrometry. The experiments provide a direct measurement of the rate coefficient, k{sub 1}, for the thermal decomposition of NH{sub 2}OH. Secondary rate measurements are obtained for the NH{sub 2} + OH (5a) and NH{sub 2}OH + OH (6a) abstraction reactions. The experimental data are obtained for temperatures in the range from 1355 to 1889 K and are well represented by the respective rate expressions: log[k/(cm{sup 3} molecule{sup -1} s{sup -1})] = (?10.12 {+-} 0.20) + (?6793 {+-} 317 K/T) (k{sub 1}); log[k/(cm{sup 3} molecule{sup -1} s{sup -1})] = (?10.00 {+-} 0.06) + (?879 {+-} 101 K/T) (k{sub 5a}); log[k/(cm{sup 3} molecule{sup -1} s{sup -1})] = (?9.75 {+-} 0.08) + (?1248 {+-} 123 K/T) (k{sub 6a}). Theoretical predictions are made for these rate coefficients as well for the reactions of NH{sub 2}OH + NH{sub 2}, NH{sub 2}OH + NH, NH + OH, NH{sub 2} + NH{sub 2}, NH{sub 2} + NH, and NH + NH, each of which could be of secondary importance in NH{sub 2}OH thermal decomposition. The theoretical analyses employ a combination of ab initio transition state theory and master equation simulations. Comparisons between theory and experiment are made where possible. Modest adjustments of predicted barrier heights (i.e., by 2 kcal/mol or less) generally yield good agreement between theory and experiment. The rate coefficients obtained here should be of utility in modeling NO{sub x} in various combustion environments.

  14. 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)

    2014-10-06

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

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

    E-Print Network [OSTI]

    Wetzel, Christian M.

    2007-01-01

    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

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

    E-Print Network [OSTI]

    Thermoelectric effects in wurtzite GaN and AlxGa1-xN alloys Weili Liua and Alexander A. Balandin have investigated theoretically the thermoelectric effects in wurtzite GaN crystals and AlxGa1-xN-based alloys may have some potential as thermoelectric materials at high temperature. It was found

  17. Selective catalytic reduction of NOx with NH3 over a Cu-SSZ-13 catalyst prepared by a solid state ion exchange method

    SciTech Connect (OSTI)

    Wang, Di; Gao, Feng; Peden, Charles HF; Li, Junhui; Kamasamudram, Krishna; Epling, William S.

    2014-06-01

    A novel solid state method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the solid state ion exchange (SSIE) process, the SSZ framework structure and surface area was maintained. In-situ DRIFTS and NH3-TPD experiments provide evidence that isolated Cu ions were successfully exchanged into the pores, which are the active centers for the NH3-SCR reaction.

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

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

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

    2015-03-12

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

  19. 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)

    2013-03-04

    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.

  20. NH3 formation and utilization in regenerationof Pt/Ba/Al2O3 NOx storage-reduction catalyst with H2

    SciTech Connect (OSTI)

    Partridge Jr, William P [ORNL; Choi, Jae-Soon [ORNL

    2009-01-01

    The nature of H2 regeneration of a model Pt/Ba/Al2O3 LNT catalyst was investigated with specific focus on intra-catalyst formation and utilization of NH3 and its role in catalyst regeneration. In-situ measurements of the transient intra-catalyst species (H2, NH3, N2, NOx) distributions at different temperatures were used to detail the reaction evolution along the catalyst axis. Comparison of the species transients identifies unique individual natures for the reductant (H2), inert product (N2) and intermediate-reductant product (NH3) which readily explain the conventional effluent species sequence as an integral effect. The data demonstrates that NH3 is created on similar timescales as the N2 product inside the catalyst, but consumed as aggressively as H2 reductant along the catalyst. This spatiotemporal NH3 behavior experimentally confirms that Intermediate-NH3 regeneration pathway is active. Analysis at 200 and 325 C indicates equivalent local NOx storage, H2 consumption and regeneration effectiveness, but differing NH3/N2 ratio, suggesting a temperature-dependence of partitioning between Direct-H2 and Intermediate-NH3 regeneration pathways. Further experimental and numerical work is needed to more clearly understand the partitioning between the possible regeneration pathways. Nevertheless, the experimental data show that intermediate NH3 plays a significant role in LNT catalyst regeneration.

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

    SciTech Connect (OSTI)

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

    2013-12-02

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

  2. A hole accelerator for InGaN/GaN light-emitting diodes

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ji, Yun; Wang, Liancheng; Zhu, Binbin; Zhang, Yiping; Lu, Shunpeng; Zhang, Xueliang; Hasanov, Namig; Sun, Xiao Wei, E-mail: EXWSUN@ntu.edu.sg, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Demir, Hilmi Volkan, E-mail: EXWSUN@ntu.edu.sg, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

    2014-10-13

    The quantum efficiency of InGaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, and this is caused by the inefficient p-type doping and the low hole mobility. The low hole mobility makes the holes less energetic, which hinders the hole injection into the multiple quantum wells (MQWs) especially when a p-type AlGaN electron blocking layer (EBL) is adopted. In this work, we report a hole accelerator to accelerate the holes so that the holes can obtain adequate kinetic energy, travel across the p-type EBL, and then enter the MQWs more efficiently and smoothly. In addition to the numerical study, the effectiveness of the hole accelerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED.

  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)

    2014-09-21

    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?=0.53(×2.1±1) cm² s?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. 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

  5. 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]

    McQuade, D. Tyler

    FSU Health Compliance Record fax to 8506448958 or mail to 960 Learning Way, Tallahassee, FL, at the discre on of health center per sonnel, medical and surgical care including examina ons, treatments to make contact will not prevent emergency treatment if necessary to preserve life or health Signature

  6. ION GNSS+ 2014 Conference, Session D5, Tampa, FL (Sep 8-12, 2014) 1/13 Inter-Sensor Validation for Improved Reliability

    E-Print Network [OSTI]

    Calgary, University of

    , MEMS sensor processing, and statistical signal processing. Dr. Gérard Lachapelle holds a CanadaION GNSS+ 2014 Conference, Session D5, Tampa, FL (Sep 8-12, 2014) 1/13 Inter-Sensor Validation for Improved Reliability of Multi-Sensor Systems Anup Dhital, Gérard Lachapelle, Jared B. Bancroft Position

  7. Zarillo, G. A., and Brehin, F. G. A. 2007. Hydrodynamic and Morphologic Modeling at Sebastian Inlet, FL. Proceedings Coastal Sediments '07 Conference, ASCE Press, Reston,

    E-Print Network [OSTI]

    US Army Corps of Engineers

    Inlet, FL. Proceedings Coastal Sediments '07 Conference, ASCE Press, Reston, VA, 1297-1310. HYDRODYNAMIC Modeling System (CMS) to investigate the morphological response to time varying forcing, sediment texture evolution of tidal inlet shoals is an important management tool, since they control sediment budgets. Inlet

  8. Melting of colloidal crystals: A Monte Carlo study James C. Zahorchak, FL Kesavamoorthy, @vb)Rob D. Coalson, and Sanford A. Asherb)

    E-Print Network [OSTI]

    Asher, Sanford A.

    Melting of colloidal crystals: A Monte Carlo study James C. Zahorchak, FL Kesavamoorthy, @vb)Rob D) Electrostatically stabilized colloidal crystals show phase transitions into liquid and gaslike states as the ionic of four colloidal crystals (two fee crystals and two bee crystals) which have also been examined

  9. GaN: Defect and Device Issues

    SciTech Connect (OSTI)

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

    1998-11-09

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

  10. Closed-loop control of a SCR system using a NOx sensor cross-sensitive to NH3

    E-Print Network [OSTI]

    for an automotive selective catalytic reduction (SCR) system, for which the feedback is based on a NOx sensor illustrate the performance of the proposed approach. Keywords: Automotive emissions; Diesel engines; NOx, a mechanism is introduced to prevent large NH3-slip that could result from misinterpretation of data produced

  11. Adapted from laboratory protocols of the Center for Freshwater Biology, University of New Hampshire, Durham, N.H. 2010

    E-Print Network [OSTI]

    New Hampshire, University of

    , Durham, N.H. 2010 UNH CFB Protocol for the Monitoring of Cyanobacteria & Microcystins in Drinking Water delivery to UNH CFB lab. 5. Freeze the sample if delivery/ drop-off time exceeds 12 hours. Analyses: a, Quantiplate-ELISA Kit, (Portland, Me) with increased sensitivity (UNH, CFB). Results will be reported as ng

  12. Role of hydrogen-bonding and its interplay with octahedral tilting in CH3NH3PbI3

    E-Print Network [OSTI]

    Lee, Jung-Hoon; Bristowe, Nicholas C.; Bristowe, Paul D.; Cheetham, Anthony K.

    2015-03-05

    First principles calculations on the hybrid perovskite CH3NH3PbI3 predict strong hydrogen-bonding which influences the structure and dynamics of the methylammonium cation and reveal its interaction with the tilting of the PbI6 octahedra...

  13. Ultralow Absorption Coefficient and Temperature Dependence of Radiative Recombination of CH3NH3PbI3 Perovskite from

    E-Print Network [OSTI]

    Perovskite from Photoluminescence Chog Barugkin, Jinjin Cong, The Duong, Shakir Rahman, Hieu T. Nguyen perovskite methylammonium lead iodide (CH3NH3PbI3) films from 675 to 1400 nm. Unlike other methods used of organic-inorganic halide perovskite- based solar cells has attracted enormous interest from the entire PV

  14. 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 by different administrations, and allowing these administrations to maintain autonomy but to use each others services. Consider also what happens if these administrations have different policies on how access should

  15. Influence of pressure on photoluminescence and electroluminescence in GaN/InGaN/AlGaN quantum wells

    E-Print Network [OSTI]

    Weinstein, Benard.A.

    recently that the temperature shifts of the photo- and electroluminescence EL peak energies in Nichia greenV/GPa for the green and blue diodes, respectively. The observed pressure coefficients are much lower than those characteristic of the energy gap in GaN ( 40 meV/GPa) or the energy gap in InN ( 33 meV/GPa). This kind

  16. Effect of sulfated CaO on NO reduction by NH{sub 3} in the presence of excess oxygen

    SciTech Connect (OSTI)

    Tianjin Li; Yuqun Zhuo; Yufeng Zhao; Changhe Chen; Xuchang Xu [Tsinghua University, Beijing (China). Key Laboratory for Thermal Science and Power Engineering of Ministry of Education

    2009-04-15

    The effect of sulfated CaO on NO reduction by NH{sub 3} in the presence of excess oxygen was investigated to evaluate the potential of simultaneous SO{sub 2} and NO removal at the temperature range of 700-850{sup o}C. The physical and chemical properties of the CaO sulfation products were analyzed to investigate the NO reduction mechanism. Experimental results showed that sulfated CaO had a catalytic effect on NO reduction by NH{sub 3} in the presence of excess O{sub 2} after the sulfation reaction entered the transition control stage. With the increase of CaO sulfation extent in this stage, the activity for NO reduction first increased and then decreased, and the selectivity of NH{sub 3} for NO reduction to N{sub 2} increased. The byproduct (NO{sub 2} and N{sub 2}O) formation during NO reduction experiments was negligible. X-ray photoelectron spectroscopy (XPS) analysis showed that neither CaSO{sub 3} nor CaS was detected, indicating that the catalytic activity of NO reduction by NH{sub 3} in the presence of excess O{sub 2} over sulfated CaO was originated from the CaSO{sub 4} product. These results revealed that simultaneous SO{sub 2} and NOx control by injecting NH{sub 3} into the dry flue gas desulfurization process for NO reduction might be achieved. 38 refs., 6 figs., 1 tab.

  17. 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

    2007-11-30

    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).

  18. InGaAs/GaAs quantum dot interdiffiusion induced by cap layer overgrowth

    SciTech Connect (OSTI)

    Jasinski, J.; Babinski, A.; Czeczott, M.; Bozek, R.

    2000-06-28

    The effect of thermal treatment during and after growth of InGaAs/GaAs quantum dot (QD) structures was studied. Transmission electron microscopy and atomic force microscopy confirmed the presence of interacting QDs, as was expected from analysis of temperature dependence of QD photoluminescence (PL) peak. The results indicate that the effect of post-growth annealing can be similar to the effect of elevated temperature of capping layer growth. Both, these thermal treatments can lead to a similar In and Ga interdiffiusion resulting in a similar blue-shift of QD PL peak.

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

    SciTech Connect (OSTI)

    Shi, Teng; Fickenscher, Melodie; Smith, Leigh; Jackson, Howard; Yarrison-Rice, Jan; Gao, Qiang; Tan, Hoe; Jagadish, Chennupati; Etheridge, Joanne; Wong, Bryan M.

    2013-12-04

    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.

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

    SciTech Connect (OSTI)

    Tai Asayama

    2009-10-26

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

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

    Limbach, F.; Gotschke, T.; Stoica, T.; Calarco, R.; Sutter, E.; Ciston, J.; Cusco, R.; Artus, L.; Kremling, S.; Ho?fling, S.; et al

    2011-01-01

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

  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. IEEE Energy2030 Atlanta, GA USA

    E-Print Network [OSTI]

    Gross, George

    of an aggregation of battery vehicles for the provision of frequency regulation ­ requiring very fast response timesIEEE Energy2030 Atlanta, GA USA 17-18 November, 2008 Design of a Conceptual Framework for the V2G in common is the batteries, which provide good storage capacity that can be effectively integrated

  4. 495 Tech Way NW Atlanta, GA 30318

    E-Print Network [OSTI]

    Li, Mo

    495 Tech Way NW Atlanta, GA 30318 404.385.0384 comments@energy.gatech.edu Copyright 2014 · Georgia concerns, low-cost, clean, secure energy solutions will be necessary to address our global energy needs and sustain our way of life. Georgia Tech Energy Innovations The Strategic Energy Institute's scientists

  5. Defect studies in low-temperature-grown GaAs

    SciTech Connect (OSTI)

    Bliss, D.E.

    1992-11-01

    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.

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

    E-Print Network [OSTI]

    it was discovered by Davydov et al.1 and con- firmed by independent studies2,3 that its band gap is small, EG InN =0 The conduction band offset at GaN/AlN interface was estimated as EQW=0.7 EG AlN -EG GaN =1918 meV. The nanoN/GaN/AlN QW. The depth of the nanogroove is calculated as E0=0.8 EG GaN -EG InxGa1-xN . The band gap of InxGa1

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

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

    epitaxial growth of indium gallium nitride (InGaN) layers capable of producing high-efficiency LEDs when combined with chip-on-board packaging techniques. The proposed...

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

    SciTech Connect (OSTI)

    Danilchenko, B. A.; Tripachko, N. A.; Belyaev, A. E.; Vitusevich, S. A. Hardtdegen, H.; Lüth, H.

    2014-02-17

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

  9. 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 ...

  10. Emission and Excitation Spectra of ZnO:Ga and ZnO:Ga,N Ceramics

    E-Print Network [OSTI]

    P. A. Rodnyi; I. V. Khodyuk; E. I. Gorokhova; S. B. Mikhrin; P. Dorenbos

    2010-09-07

    The spectral characteristics of ZnO:Ga and ZnO:Ga,N ceramics prepared by uniaxial hot pressing have been investigated. At room temperature, the edge (exciton) band at 3.12 eV dominates in the luminescence spectra of ZnO:Ga, while a wide luminescence band at 2.37 eV, which is likely to be due to zinc vacancies, is observed in the spectra of ZnO:Ga,N. Upon heating, the edge band maximum shifts to lower energies and the bandwidth increases. The extrapolated position of the edge-band maximum at zero temperature, Em(0) = 3.367 +/- 0.005 eV, is in agreement with the data for thin zinc oxide films. The luminescence excitation spectra in the range from 3 to 6.5 eV are reported and the mechanism of energy transfer to excitons and luminescence centers is considered.

  11. Composition profiling of GaAs/AlGaAs quantum dots grown by droplet epitaxy

    SciTech Connect (OSTI)

    Bocquel, J.; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Giddings, A. D.; Prosa, T. J.; Larson, D. J. [CAMECA Instruments, Inc., 5500 Nobel Drive, Madison, Wisconsin 53711 (United States); Mano, T. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-10-13

    Droplet epitaxy (DE) is a growth method which can create III-V quantum dots (QDs) whose optoelectronic properties can be accurately controlled through the crystallisation conditions. In this work, GaAs/AlGaAs DE-QDs have been analyzed with the complimentary techniques of cross-sectional scanning tunneling microscopy and atom probe tomography. Structural details and a quantitative chemical analysis of QDs of different sizes are obtained. Most QDs were found to be pure GaAs, while a small proportion exhibited high intermixing caused by a local etching process. Large QDs with a high aspect ratio were observed to have an Al-rich crown above the GaAs QD. This structure is attributed to differences in mobility of the cations during the capping phase of the DE growth.

  12. On strongly GA-convex functions and stochastic processes

    SciTech Connect (OSTI)

    Bekar, Nurgül Okur; Akdemir, Hande Günay; ??can, ?mdat

    2014-08-20

    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.

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

    E-Print Network [OSTI]

    Feuchtwanger, Jorge

    2006-01-01

    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 ...

  14. InGaAs/GaAs (110) quantum dot formation via step meandering

    SciTech Connect (OSTI)

    Diez-Merino, Laura; Tejedor, Paloma

    2011-07-01

    InGaAs (110) semiconductor quantum dots (QDs) offer very promising prospects as a material base for a new generation of high-speed spintronic devices, such as single electron transistors for quantum computing. However, the spontaneous formation of InGaAs QDs is prevented by two-dimensional (2D) layer-by-layer growth on singular GaAs (110) substrates. In this work we have studied, by using atomic force microscopy and photoluminescence spectroscopy (PL), the growth of InGaAs/GaAs QDs on GaAs (110) stepped substrates by molecular beam epitaxy (MBE), and the modification of the adatom incorporation kinetics to surface steps in the presence of chemisorbed atomic hydrogen. The as-grown QDs exhibit lateral dimensions below 100 nm and emission peaks in the 1.35-1.37 eV range. It has been found that a step meandering instability derived from the preferential attachment of In adatoms to [110]-step edges relative to [11n]-type steps plays a key role in the destabilization of 2D growth that leads to 3D mound formation on both conventional and H-terminated vicinal substrates. In the latter case, the driving force for 3D growth via step meandering is enhanced by H-induced upward mass transport in addition to the lower energy cost associated with island formation on H-terminated substrates, which results in a high density array of InGaAs/GaAs dots selectively nucleated on the terrace apices with reduced lateral dimensions and improved PL efficiency relative to those of conventional MBE-grown samples.

  15. 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)

    2014-06-16

    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.

  16. 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; Luque, Antonio

    2014-09-26

    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.

  17. 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

    2013-05-06

    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.

  18. Lateral and Vertical Transistors Using the AlGaN/GaN Heterostructure

    SciTech Connect (OSTI)

    Chowdhury, S; Mishra, UK

    2013-10-01

    Power conversion losses are endemic in all areas of electricity consumption, including motion control, lighting, air conditioning, and information technology. Si, the workhorse of the industry, has reached its material limits. Increasingly, the lateral AlGaN/GaN HEMT based on gallium nitride (GaN-on-Si) is becoming the device of choice for medium power electronics as it enables high-power conversion efficiency and reduced form factor at attractive pricing for wide market penetration. The reduced form factor enabled by high-efficiency operation at high frequency further enables significant system price reduction because of savings in bulky extensive passive elements and heat sink costs. The high-power market, however, still remains unaddressed by lateral GaN devices. The current and voltage demand for high power conversion application makes the chip area in a lateral topology so large that it becomes more difficult to manufacture. Vertical GaN devices would play a big role alongside of silicon carbide (SiC) to address the high power conversion needs. In this paper, the development, performance, and status of lateral and vertical GaN devices are discussed.

  19. GaNPAs Solar Cells Lattice-Matched To GaP: Preprint

    SciTech Connect (OSTI)

    Geisz, J. F.; Friedman, D. J.; Kurtz, S.

    2002-05-01

    This conference paper describes the III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We propose the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct band-gaps in the range of 1.5 to 2.0 eV. We demonstrate the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and discuss the prospects for the development of monolithic high-efficiency multijunction solar cells based on silicon substrates.

  20. Accurate characterization and improvement of GaAs microstrip attenuation 

    E-Print Network [OSTI]

    Carroll, James Mason

    1992-01-01

    Convergence. III. E. 6 Final Model. III. F Simulation Results for 100 um GaAs. . III. F. 1 On-GaAs Microstrip. III. I', 2 Suspended Microstrip Line . . . . 50 . . . . 51 . . . . 54 . . . . 56 . . . . 56 . . . 56 . . . . 64 64 . . . , 64 III. F. 3... Comparison Between On-GaAs and Suspcndcd Microstrip . . . 68 III. F. 4 Microstrip Inductance III. G EM Parameters in CAD Simulations . . III. H Simulation Results for 150 um GaAs. III. I Conclusions and Recommendations. IV RESEARCH ACCOMPLISHMENTS...

  1. Advanced technologies for improving high frequency performance of AlGaN/GaN high electron mobility transistors

    E-Print Network [OSTI]

    Chung, Jinwook W. (Jinwook Will)

    2008-01-01

    In this thesis, we have used a combination of physical analysis, numerical simulation and experimental work to identify and overcome some of the main challenges in AlGaN/GaN high electron mobility transistors (HEMTs) for ...

  2. 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

  3. Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3

    SciTech Connect (OSTI)

    Kwak, Ja Hun; Tonkyn, Russell G.; Kim, Do Heui; Szanyi, Janos; Peden, Charles HF

    2010-10-21

    Superior activity and selectivity of a Cu ion-exchanged SSZ-13 zeolite in the selective catalytic reduction (SCR) of NOx with NH3 were observed, in comparison to Cu-beta and Cu-ZSM-5 zeolites. Cu-SSZ-13 was not only more active in the NOx SCR reaction over the entire temperature range studied (up to 550 °C), but also more selective toward nitrogen formation, resulting in significantly lower amounts of NOx by-products (i.e., NO2 and N2O) than the other two zeolites. In addition, Cu-SSZ-13 demonstrated the highest activity and N2 formation selectivity in the oxidation of NH3. The results of this study strongly suggest that Cu-SSZ-13 is a promising candidate as a catalyst for NOx SCR with great potential in after-treatment systems for either mobile or stationary sources.

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

    SciTech Connect (OSTI)

    Lee, E.J.; Chung, B.D.; Kim, H.J.

    1993-06-01

    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.

  5. Improved device performance of InAs/GaAs quantum dot solar cells with GaP strain compensation layers

    E-Print Network [OSTI]

    Jalali. Bahram

    Improved device performance of InAs/GaAs quantum dot solar cells with GaP strain compensation Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico optical, electrical, and spectral response characteristics of three-stack InAs/GaAs quantum dot solar

  6. 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.

    2006-01-01

    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.

  7. 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.

    2007-08-09

    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.

  8. Properties of (Ga,Mn)As codoped with Li

    SciTech Connect (OSTI)

    Miyakozawa, Shohei; Chen, Lin; Matsukura, Fumihiro; Ohno, Hideo

    2014-06-02

    We grow Li codoped (Ga,Mn)As layers with nominal Mn composition up to 0.15 by molecular beam epitaxy. The layers before and after annealing are characterized by x-ray diffraction, transport, magnetization, and ferromagnetic resonance measurements. The codoping with Li reduces the lattice constant and electrical resistivity of (Ga,Mn)As after annealing. We find that (Ga,Mn)As:Li takes similar Curie temperature to that of (Ga,Mn)As, but with pronounced magnetic moments and in-plane magnetic anisotropy, indicating that the Li codoping has nontrivial effects on the magnetic properties of (Ga,Mn)As.

  9. 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.

    solar cells are triple-junction concentrator devices, with each junction efficiently col- lecting subcell in a multijunction de- vice. GaAs0.66 P0.34 single-junction solar cells with Eg = 1.83 eV were56 IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 2, NO. 1, JANUARY 2012 Metamorphic GaAsP and InGaP Solar

  10. High-temperature phase transformation and topochemical nature in ferroelastic (NH{sub 4}){sub 2}SO{sub 4}

    SciTech Connect (OSTI)

    Lee, Kwang-Sei; Oh, In-Hwan; Ko, Jae-Hyeon

    2014-04-01

    The electrical conductivity of ferroelastic ammonium sulfate (NH{sub 4}){sub 2}SO{sub 4} revealed an anomaly at around 130 °C (=403 K, T{sub P}) on heating with large and irreversible thermal hysteresis through thermal cycle. Ferroelastic domain walls and surface morphology of (NH{sub 4}){sub 2}SO{sub 4} were investigated by hot-stage polarizing microscopy. Structural phase transition from an orthorhombic ferroelastic phase to a hexagonal paraelastic phase was not identified at T{sub P} upon heating. On further heating above T{sub P}, microscopic spots appeared and grew on the crystal surface, suggesting that the high-temperature anomaly at T{sub P} was an indication of an onset of thermal decomposition controlled by topochemical factors. The increase of electrical conductivity above T{sub P} was attributed to proton migration. - Graphical abstract: Surface morphology of the (100) face of (NH{sub 4}){sub 2}SO{sub 4} on heating, showing chemical reaction at the surface. - Highlights: • We investigate the high-temperature phase transformation of ammonium sulfate. • The increasing conductivity upon heating is attributed to proton migration. • Structural phase transition from orthorhombic to hexagonal phase is not confirmed. • High-temperature anomaly is related to an onset of thermal decomposition. • The nature of the high-temperature anomaly is topochemical controlled by defects.

  11. Reactive codoping of GaAlInP compound semiconductors

    DOE Patents [OSTI]

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

    2008-02-12

    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.

  12. 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.

    2014-12-09

    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.

  13. A Pyrrolyl-based Triazolophane: A Macrocyclic Receptor With CH and NH Donor Groups That Exhibits a Preference for Pyrophosphate Anions

    SciTech Connect (OSTI)

    Sessler, Jonathan L.; Cia, Jiajia; Gong, Han-Yuan; Yang, Xiauping; Arambula, Jonathan F.; Hay, Benjamin

    2010-01-01

    A pyrrolyl-based triazolophane, incorporating CH and NH donor groups, acts as a receptor for the pyrophosphate anion in chloroform solution. It shows selectivity for this trianion, followed by HSO{sub 4}{sup -} > H{sub 2}PO{sub 4}{sup -} > Cl{sup -} > Br{sup -} (all as the corresponding tetrabutylammonium salts), with NH-anion interactions being more important than CH-anion interactions. In the solid state, the receptor binds the pyrophosphate anion in a clip-like slot via NH and CH hydrogen bonds.

  14. Three-junction solar cells comprised of a thin-film GaInP/GaAs tandem cell mechanically stacked on a Si cell

    SciTech Connect (OSTI)

    Yazawa, Y.; Tamura, K.; Watahiki, S.; Kitatani, T.; Ohtsuka, H.; Warabisako, T.

    1997-12-31

    Three-junction tandem solar cells were fabricated by mechanical stacking of a thin-film GaInP/GaAs monolithic tandem cell and a Si cell. The epitaxial lift-off (ELO) technique was used for the thinning of GaInP/GaAs tandem cells. Both spectral responses of the GaInP top cell and the GaAs middle cell in the thin-film GaInP/GaAs monolithic tandem cell were conserved. The Si cell performance has been improved by reducing the absorption loss in the GaAs substrate.

  15. Chemical beam epitaxy growth of AlGaAs/GaAs tunnel junctions using trimethyl aluminium for multijunction solar cells

    SciTech Connect (OSTI)

    Paquette, B.; DeVita, M.; Turala, A.; Kolhatkar, G.; Boucherif, A.; Jaouad, A.; Aimez, V.; Arès, R.; Wilkins, M.; Wheeldon, J. F.; Walker, A. W.; Hinzer, K.; Fafard, S.

    2013-09-27

    AlGaAs/GaAs tunnel junctions for use in high concentration multijunction solar cells were designed and grown by chemical beam epitaxy (CBE) using trimethyl aluminium (TMA) as the p-dopant source for the AlGaAs active layer. Controlled hole concentration up to 4?10{sup 20} cm{sup ?3} was achieved through variation in growth parameters. Fabricated tunnel junctions have a peak tunneling current up to 6140 A/cm{sup 2}. These are suitable for high concentration use and outperform GaAs/GaAs tunnel junctions.

  16. 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.

    2006-01-01

    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.

  17. Electron tunneling spectroscopy study of electrically active traps in AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Yang, Jie Cui, Sharon; Ma, T. P.; Hung, Ting-Hsiang; Nath, Digbijoy; Krishnamoorthy, Sriram; Rajan, Siddharth

    2013-11-25

    We investigate the energy levels of electron traps in AlGaN/GaN high electron mobility transistors by the use of electron tunneling spectroscopy. Detailed analysis of a typical spectrum, obtained in a wide gate bias range and with both bias polarities, suggests the existence of electron traps both in the bulk of AlGaN and at the AlGaN/GaN interface. The energy levels of the electron traps have been determined to lie within a 0.5?eV band below the conduction band minimum of AlGaN, and there is strong evidence suggesting that these traps contribute to Frenkel-Poole conduction through the AlGaN barrier.

  18. A InGaN/GaN quantum dot green ({lambda}=524 nm) laser

    SciTech Connect (OSTI)

    Zhang Meng; Banerjee, Animesh; Lee, Chi-Sen; Hinckley, John M.; Bhattacharya, Pallab

    2011-05-30

    The characteristics of self-organized InGaN/GaN quantum dot lasers are reported. The laser heterostructures were grown on c-plane GaN substrates by plasma-assisted molecular beam epitaxy and the laser facets were formed by focused ion beam etching with gallium. Emission above threshold is characterized by a peak at 524 nm (green) and linewidth of 0.7 nm. The lowest measured threshold current density is 1.2 kA/cm{sup 2} at 278 K. The slope and wall plug efficiencies are 0.74 W/A and {approx}1.1%, respectively, at 1.3 kA/cm{sup 2}. The value of T{sub 0}=233 K in the temperature range of 260-300 K.

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

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R.; Carrington, P. J.; Krier, A.

    2014-01-07

    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.

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

    SciTech Connect (OSTI)

    Bai, J.; Yang, C. C.; Athanasiou, M.; Wang, T.

    2014-02-03

    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%.

  1. 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)

    2014-05-26

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local 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.

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

    SciTech Connect (OSTI)

    Szanyi, Janos; Kwak, Ja Hun; Zhu, Haiyang; Peden, Charles HF

    2013-01-23

    The adsorption of CO and NO over Cu-SSZ-13 zeolite catalysts, highly active in the selective catalytic reduction of NOx with NH3, was investigated by FTIR spectroscopy, and the results obtained were compared to those collected from other Cu-ion exchanged zeolites (Y,FAU and ZSM-5). At low CO pressures at room temperature (295 K) CO form monocarbonyls exclusively on the Cu+ ions, while in the presence of gas phase CO dicarbonyls on Cu+ and adsorbed CO on Cu2+ centers form, as well. At low (cryogenic) sample temperatures tricarbonyl formation on Cu+ sites was also observed. The adsorption of NO produces IR bands that can be assigned to nitrosyls bound to both Cu+ and Cu2+ centers, and NO+ species located in charge compensating cationic positions of the chabasite framework. On the reduced Cu-SSZ-13 samples the formation of N2O was also detected. The assignment of the adsorbed NOx species was aided by adsorption experiments with isotopically labeled 15NO. The movement of Cu ions from the sterically hindered six member ring position to the more accessible cavity positions as a result of their interaction with adsorbates (NO and H2O) was clearly evidenced. Comparisons of the spectroscopy data obtained in the static transmission IR system to those collected in the flow-through diffuse reflectance cell points out that care must be taken when conclusions are drawn about the adsorptive and reactive properties of metal cation centers based on a set of data collected under well defined, specific experimental conditions. Financial support was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. This work was performed in the Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory (PNNL). The EMSL is a national scientific user facility supported by the US DOE, Office of Biological and Environmental Research. PNNL is a multi-program national laboratory operated for the US DOE by Battelle.

  3. 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.; Igusa, R.; Iwamoto, S.; Arakawa, Y.

    2014-09-15

    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.

  4. 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)

    2013-08-12

    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.

  5. Synthesis of the Long-Sought Unsubstituted Aminodiboranate Na(H3B-NH2-BH3) and Its N-Alkyl Analogs

    E-Print Network [OSTI]

    Girolami, Gregory S.

    storage materials.1-9 For example, ammonia borane, NH3 ·BH3, has an especially high gravimetric hydrogen as hydrogen storage materials.15-18 In a different context, metal complexes of amino- and amidoboranes can

  6. 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)

    2012-04-01

    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.

  7. GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates Melissa J. Archer,1,a

    E-Print Network [OSTI]

    Atwater, Harry

    GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates Melissa J. Archer,1,a Daniel C, crack-free GaInP/GaAs double junction solar cells were grown by metal organic chemical vapor deposition with the world record efficiency is a metamorphic triple junction GaInP/GaAs/Ge cell.6 Alternatively, wafer

  8. Enhanced hole transport in InGaN/GaN multiple quantum well light-emitting

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    -emitting diodes (LEDs) are considered the new generation lighting sources due to their advantages in power Society of America OCIS codes: 230.3670, 230.5590, 160.6000. Nitride-based high-power light devoted to the development of high-brightness GaN-based LEDs [3­5]. Lateral hole spreading is one

  9. High-Efficiency GaInP/GaAs Tandem Solar Cells

    SciTech Connect (OSTI)

    Bertness, K. A.; Friedman, D. J.; Kurtz, S. R.; Kibbler, A. E.; Cramer, C.; Olson, J. M.

    1996-09-01

    GaInP/GaAs tandem solar cells have achieved efficiencies between 25.7-30.2%, depending on illumination conditions. The efficiencies are the highest confirmed two-terminal values measured for any solar cell within each standard illumination category. The monolithic, series-connected design of the tandem cells allows them to be substituted for silicon or gallium arsenide cells in photovoltaic panel systems with minimal design changes. The advantages of using GaInP/GaAs tandem solar cells in space and terrestrial applications are discussed primarily in terms of the reduction in balance-of-system costs that accrues when using a higher efficiency cell. The new efficiency values represent a significant improvement over previous efficiencies for this materials system, and we identify grid design, back interface passivation, and top interface passivation as the three key factors leading to this improvement. In producing the high-efficiency cells, we have addressed nondestructive diagnostics and materials growth reproducibility as well as peak cell performance.

  10. High-efficiency GaInP/GaAs tandem solar cells

    SciTech Connect (OSTI)

    Bertness, K.A.; Friedman, D.J.; Kurtz, S.R.; Kibbler, A.E.; Kramer, C.; Olson, J.M.

    1994-12-01

    GaInP/GaAs tandem solar cells have achieved new record efficiencies, specifically 25.7% under air-mass 0 (AM0) illumination, 29.5% under AM 1.5 global (AM1.5G) illumination, and 30.2% at 140-180x concentration under AM 1.5 direct (AM1.5D) illumination. These values are the highest two-terminal efficiencies achieved by any solar cell under these illumination conditions. The monolithic, series-connected design of the tandem cells allows them to be substituted for silicon or gallium arsenide cells in photovoltaic panel systems with minimal design changes. The advantages of using GaInP/GaAs tandem solar cells in space and terrestrial applications are discussed primarily in terms of the reduction in balance-of-system costs that accrues when using a higher efficiency cell. The new efficiency values represent a significant improvement over previous efficiencies for this materials system, and we identify grid design, back interface passivation, and top interface passivation as the three key factors leading to this improvement. In producing the high-efficiency cells, we have addressed nondestructive diagnostics and materials growth reproducibility as well as peak cell performance. 31 refs.

  11. TJ Solar Cell (GaInP/GaAs/Ge Ultrahigh-Efficiency Solar Cells

    SciTech Connect (OSTI)

    Friedman, Daniel

    2002-04-17

    This talk will discuss recent developments in III-V multijunction photovoltaic technology which have led to the highest-efficiency solar cells ever demonstrated. The relationship between the materials science of III-V semiconductors and the achievement of record solar cell efficiencies will be emphasized. For instance, epitaxially-grown GAInP has been found to form a spontaneously-ordered GaP/InP (111) superlattice. This ordering affects the band gap of the material, which in turn affects the design of solar cells which incorporate GaInP. For the next generation of ultrahigh-efficiency III-V solar cells, we need a new semiconductor which is lattice-matched to GaAs, has a band gap of 1 eV, and has long minority-carrier diffusion lengths. Out of a number of candidate materials, the recently-discovered alloy GaInNAs appears to have the greatest promise. This material satisfies the first two criteria, but has to date shown very low diffusion lengths, a problem which is our current focus in the development of these next-generation cells.

  12. Multijunction GaInP/GaInAs/Ge solar cells with Bragg reflectors

    SciTech Connect (OSTI)

    Emelyanov, V. M. Kalyuzhniy, N. A.; Mintairov, S. A.; Shvarts, M. Z.; Lantratov, V. M.

    2010-12-15

    Effect of subcell parameters on the efficiency of GaInP/Ga(In)As/Ge tandem solar cells irradiated with 1-MeV electrons at fluences of up to 3 x 10{sup 15} cm{sup -2} has been theoretically studied. The optimal thicknesses of GaInP and GaInAs subcells, which provide the best photocurrent matching at various irradiation doses in solar cells with and without built-in Bragg reflectors, were determined. The dependences of the photoconverter efficiency on the fluence of 1-MeV electrons and on the time of residence in the geostationary orbit were calculated for structures optimized to the beginning and end of their service lives. It is shown that the optimization of the subcell heterostructures for a rated irradiation dose and the introduction of Bragg reflectors into the structure provide a 5% overall increase in efficiency for solar cells operating in the orbit compared with unoptimized cells having no Bragg reflector.

  13. Localized corrosion of GaAs surfaces and formation of porous GaAs

    SciTech Connect (OSTI)

    Schmuki, P.; Vitus, C.M.; Isaacs, H.S.; Fraser, J.; Graham, M.J.

    1995-12-01

    The present work deals with pitting corrosion of p- and n-type GaAs (100). Pit growth can be electrochemically initiated on both conduction types in chloride-containing solutions and leads after extended periods of time to the formation of a porous GaAs structure. In the case of p-type material, localized corrosion is only observed if a passivating film is present on the surface, otherwise -- e.g. in acidic solutions -- the material suffers from a uniform attack (electropolishing) which is independent of the anion present. In contrast, pitting corrosion of n-type material can be triggered independent of the presence of an oxide film. This is explained in terms of the different current limiting factor for the differently doped materials (oxide film in the case of the p- and a space charge layer in the case of the n-GaAs). The porous structure was characterized by SEM, EDX and AES, and consists mainly of GaAs. From scratch experiments it is clear that the pit initiation process is strongly influenced by surface defects. For n-type material, AFM investigations show that light induced roughening of the order of several hundred nm occurs under non-passivating conditions. This nm- scale roughening however does not affect the pitting process.

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

    E-Print Network [OSTI]

    2005-01-01

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

  15. Inverse spin Hall effect in Pt/(Ga,Mn)As

    SciTech Connect (OSTI)

    Nakayama, H.; Chen, L.; Chang, H. W.; Ohno, H.; Matsukura, F.

    2015-06-01

    We investigate dc voltages under ferromagnetic resonance in a Pt/(Ga,Mn)As bilayer structure. A part of the observed dc voltage is shown to originate from the inverse spin Hall effect. The sign of the inverse spin Hall voltage is the same as that in Py/Pt bilayer structure, even though the stacking order of ferromagnetic and nonmagnetic layers is opposite to each other. The spin mixing conductance at the Pt/(Ga,Mn)As interface is determined to be of the order of 10{sup 19?}m{sup ?2}, which is about ten times greater than that of (Ga,Mn)As/p-GaAs.

  16. Deep level defects in n-type GaAsBi and GaAs grown at low temperatures

    SciTech Connect (OSTI)

    Mooney, P. M.; Watkins, K. P.; Jiang, Zenan; Basile, A. F.; Lewis, R. B.; Bahrami-Yekta, V.; Masnadi-Shirazi, M.; Beaton, D. A.; Tiedje, T.

    2013-04-07

    Deep level defects in n-type GaAs{sub 1-x}Bi{sub x} having 0 < x < 0.012 and GaAs grown by molecular beam epitaxy (MBE) at substrate temperatures between 300 and 400 Degree-Sign C have been investigated by Deep Level Capacitance Spectroscopy. Incorporating Bi suppresses the formation of an electron trap with activation energy 0.40 eV, thus reducing the total trap concentration in dilute GaAsBi layers by more than a factor of 20 compared to GaAs grown under the same conditions. We find that the dominant traps in dilute GaAsBi layers are defect complexes involving As{sub Ga}, as expected for MBE growth at these temperatures.

  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)

    2014-03-03

    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. Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

    SciTech Connect (OSTI)

    Kondratenko, S. V. Vakulenko, O. V.; Mazur, Yu. I. Dorogan, V. G.; Marega, E.; Benamara, M.; Ware, M. E.; Salamo, G. J.

    2014-11-21

    The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80?K after excitation of electron-hole pairs due to interband transitions in both the InGaAs QDs and the GaAs matrix. Giant optically induced quenching of in-plane conductivity driven by recharging of EL2 centers is observed in the spectral range from 0.83?eV to 1.0?eV. Conductivity loss under photoexcitation is discussed in terms of carrier localization by analogy with carrier distribution in disordered media.

  19. Au impact on GaAs epitaxial growth on GaAs (111){sub B} substrates in molecular beam epitaxy

    SciTech Connect (OSTI)

    Liao, Zhi-Ming; Chen, Zhi-Gang; Xu, Hong-Yi; Guo, Ya-Nan; Sun, Wen; Zhang, Zhi; Yang, Lei; Lu, Zhen-Yu; Chen, Ping-Ping; Lu, Wei; Zou, Jin; Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia, Queensland 4072

    2013-02-11

    GaAs growth behaviour under the presence of Au nanoparticles on GaAs {l_brace}111{r_brace}{sub B} substrate is investigated using electron microscopy. It has been found that, during annealing, enhanced Ga surface diffusion towards Au nanoparticles leads to the GaAs epitaxial growth into {l_brace}113{r_brace}{sub B} faceted triangular pyramids under Au nanoparticles, governed by the thermodynamic growth, while during conventional GaAs growth, growth kinetics dominates, resulting in the flatted triangular pyramids at high temperature and the epitaxial nanowires growth at relatively low temperature. This study provides an insight of Au nanoparticle impact on GaAs growth, which is critical for understanding the formation mechanisms of semiconductor nanowires.

  20. [NH{sub 3}(CH{sub 2}){sub 2}NH{sub 3}][Co(SO{sub 4}){sub 2}(H{sub 2}O){sub 4}]: Chemical preparation, crystal structure, thermal decomposition and magnetic properties

    SciTech Connect (OSTI)

    Rekik, Walid; Naili, Houcine; Mhiri, Tahar [Laboratoire de l'Etat Solide, Departement de Chimie, Faculte des Sciences de Sfax, BP 802, 3018 Sfax (Tunisia); Bataille, Thierry [Sciences Chimiques de Rennes (CNRS, UMR 6226), Groupe Materiaux Inorganiques: Chimie Douce et Reactivite, Universite de Rennes I, Avenue du General Leclerc, 35042 Rennes Cedex (France)], E-mail: thierry.bataille@univ-rennes1.fr

    2008-10-02

    Cobalt ethylenediammonium bis(sulfate) tetrahydrate, [NH{sub 3}(CH{sub 2}){sub 2}NH{sub 3}][Co(SO{sub 4}){sub 2}(H{sub 2}O){sub 4}], has been synthesised by slow evaporation at room temperature. It crystallises in the triclinic system, space group P1-bar, with the unit cell parameters: a = 6.8033(2), b 7.0705(2), c = 7.2192(3) A, {alpha} = 74.909(2){sup o}, {beta} = 72.291(2){sup o}, {gamma} = 79.167(2){sup o}, Z = 1 and V = 317.16(2) A{sup 3}. The Co(II) atom is octahedrally coordinated by four water molecules and two sulfate tetrahedra leading to trimeric units [Co(SO{sub 4}){sub 2}(H{sub 2}O){sub 4}]. These units are linked to each other and to the ethylenediammonium cations through OW-H...O and N-H...O hydrogen bonds, respectively. The zero-dimensional structure is described as an alternation between cationic and anionic layers along the crystallographic b-axis. The dehydration of the precursor proceeds through three stages leading to crystalline intermediary hydrate phases and an anhydrous compound. The magnetic measurements show that the title compound is predominantly paramagnetic with weak antiferromagnetic interactions.

  1. An inverted AlGaAs/GaAs patterned-Ge tunnel junction cascade concentrator solar cell

    SciTech Connect (OSTI)

    Venkatasubramanian, R. )

    1993-01-01

    This report describes work to develop inverted-grown Al[sub 0.34]Ga[sub 0.66]As/GaAs cascades. Several significant developments are reported on as follows: (1) The AM1.5 1-sun total-area efficiency of the top Al[sub 0.34]Ga[sub 0.66]As cell for the cascade was improved from 11.3% to 13.2% (NREL measurement [total-area]). (2) The cycled'' organometallic vapor phase epitaxy growth (OMVPE) was studied in detail utilizing a combination of characterization techniques including Hall-data, photoluminescence, and secondary ion mass spectroscopy. (3) A technique called eutectic-metal-bonding (EMB) was developed by strain-free mounting of thin GaAs-AlGaAs films (based on lattice-matched growth on Ge substrates and selective plasma etching of Ge substrates) onto Si carrier substrates. Minority-carrier lifetime in an EMB GaAs double-heterostructure was measured as high as 103 nsec, the highest lifetime report for a freestanding GaAs thin film. (4) A thin-film, inverted-grown GaAs cell with a 1-sun AM1.5 active-area efficiency of 20.3% was obtained. This cell was eutectic-metal-bonded onto Si. (5) A thin-film inverted-grown, Al[sub 0.34]Ga[sub 0.66]As/GaAs cascade with AM1.5 efficiency of 19.9% and 21% at 1-sun and 7-suns, respectively, was obtained. This represents an important milestone in the development of an AlGaAs/GaAs cascade by OMVPE utilizing a tunnel interconnect and demonstrates a proof-of-concept for the inverted-growth approach.

  2. 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.

    2000-01-04

    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.

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

    E-Print Network [OSTI]

    sound velocity in GaN. The cut off wave vector is given by where NA is the Avogadro number, is the mass

  4. 154 Solutions Manual x Fluid Mechanics, Fifth Edition Solution: First, how high is the container? Well, 1 fluid oz. 1.805 in3, hence 12 fl. oz.

    E-Print Network [OSTI]

    Bahrami, Majid

    154 Solutions Manual x Fluid Mechanics, Fifth Edition Solution: First, how high is the container? Well, 1 fluid oz. 1.805 in3, hence 12 fl. oz. 21.66 in3 S(1.5 in)2h, or h | 3.06 in--It is a fat S (1.5 in)2(2.77 in) 19.6 in3 | 10.8 fluid oz. Ans. 2.139 The tank of liquid in the figure P2

  5. 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)

    2012-10-01

    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.

  6. 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)

    2013-11-04

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

  7. Regeneration of field-spent activated carbon catalysts for low-temperature selective catalytic reduction of NOx with NH3

    SciTech Connect (OSTI)

    Jeon, Jong Ki; Kim, Hyeonjoo; Park, Young-Kwon; Peden, Charles HF; Kim, Do Heui

    2011-10-15

    In the process of producing liquid crystal displays (LCD), the emitted NOx is removed over an activated carbon catalyst by using selective catalytic reduction (SCR) with NH3 at low temperature. However, the catalyst rapidly deactivates primarily due to the deposition of boron discharged from the process onto the catalyst. Therefore, this study is aimed at developing an optimal regeneration process to remove boron from field-spent carbon catalysts. The spent carbon catalysts were regenerated by washing with a surfactant followed by drying and calcination. The physicochemical properties before and after the regeneration were investigated by using elemental analysis, TG/DTG (thermogravimetric/differential thermogravimetric) analysis, N2 adsorption-desorption and NH3 TPD (temperature programmed desorption). Spent carbon catalysts demonstrated a drastic decrease in DeNOx activity mainly due to heavy deposition of boron. Boron was accumulated to depths of about 50 {mu}m inside the granule surface of the activated carbons, as evidenced by cross-sectional SEM-EDX analysis. However, catalyst activity and surface area were significantly recovered by removing boron in the regeneration process, and the highest NOx conversions were obtained after washing with a non-ionic surfactant in H2O at 70 C, followed by treatment with N2 at 550 C.

  8. Observational results of a multi-telescope campaign in search of interstellar urea [(NH{sub 2}){sub 2}CO

    SciTech Connect (OSTI)

    Remijan, Anthony J.; Snyder, Lewis E.; Kuo, Hsin-Lun; Looney, Leslie W.; Friedel, Douglas N.; McGuire, Brett A.; Golubiatnikov, G. Yu; Lovas, Frank J.; Ilyushin, V. V.; Alekseev, E. A.; Dyubko, S. F.; McCall, Benjamin J.; Hollis, Jan M.

    2014-03-10

    In this paper, we present the results of an observational search for gas phase urea [(NH{sub 2}){sub 2}CO] observed toward the Sgr B2(N-LMH) region. We show data covering urea transitions from ?100 GHz to 250 GHz from five different observational facilities: the Berkeley-Illinois-Maryland-Association (BIMA) Array, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the NRAO 12 m telescope, the IRAM 30 m telescope, and the Swedish-ESO Submillimeter Telescope (SEST). The results show that the features ascribed to urea can be reproduced across the entire observed bandwidth and all facilities by best-fit column density, temperature, and source size parameters which vary by less than a factor of two between observations merely by adjusting for telescope-specific parameters. Interferometric observations show that the emission arising from these transitions is cospatial and compact, consistent with the derived source sizes and emission from a single species. Despite this evidence, the spectral complexity of both (NH{sub 2}){sub 2}CO and of Sgr B2(N) makes the definitive identification of this molecule challenging. We present observational spectra, laboratory data, and models, and discuss our results in the context of a possible molecular detection of urea.

  9. 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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouth DakotaRobbins and Myers CoMadison -T:..) ".. _,;$,byFIleact.

  10. Istanbul,Turkey & Atlanta, GA Istanbul,Turkey

    E-Print Network [OSTI]

    Frantz, Kyle J.

    Istanbul,Turkey & Atlanta, GA Istanbul,Turkey & Atlanta, GA 2012 Media, Journalism and Business for departure to Istanbul,Turkey Day 9 Depart for Istanbul; guided cultural visit upon arrival; group dinner Day business leaders; site visits to local universities Day 18 UPS and the value of logistics inTurkey Day 19

  11. Photoeffects in WO{sub 3}/GaAs electrode

    SciTech Connect (OSTI)

    Yoon, K.H.; Lee, J.W.; Cho, Y.S.; Kang, D.H.

    1996-12-01

    Photoeffects of a {ital p}-type GaAs coated with WO{sub 3} thin film have been investigated as a function of film thickness and photoresponse transients of the WO{sub 3}/GaAs electrode were studied. Also, these results were compared to those for a single {ital p}-type GaAs electrode. The photocurrent of the WO{sub 3}/GaAs electrode depended on the film thickness of the WO{sub 3}, showing an optimum photon efficiency for specimens of 800 A thickness. This is due to the existence of an effective interface state within the band gap which reduces trapping of carriers and facilitates carrier movement. For an 800-A-thick WO{sub 3} thin film deposited {ital p}-GaAs photoelectrode, the photogenerated electrons were found to move to an electrolyte at a higher positive onset potential compared with that of single {ital p}-type GaAs, which was confirmed as a result of transient behavior. {ital I}{endash}{ital V} and {ital C}{endash}{ital V} characteristics of the WO{sub 3}/GaAs electrode were also compared with those of a single {ital p}-type GaAs electrode. {copyright} {ital 1996 American Institute of Physics.}

  12. Room temperature spin transport in undoped (110) GaAs/AlGaAs quantum wells

    SciTech Connect (OSTI)

    Yokota, Nobuhide Aoshima, Yohei; Ikeda, Kazuhiro; Kawaguchi, Hitoshi

    2014-02-17

    We are reporting on our first observation of a micrometer-order electron spin transport in a (110) GaAs/AlGaAs multiple quantum well (QW) at room temperature using a space- and time-resolved Kerr rotation technique. A 37-?m transport was observed within an electron spin lifetime of 1.2?ns at room temperature when using an in-plane electric field of 1.75?kV/cm. The spatio-temporal profiles of electron spins were well reproduced by the spin drift-diffusion equations coupled with the Poisson equation, supporting the validity of the measurement. The results suggest that (110) QWs are useful as a spin transport layer for semiconductor spintronic devices operating at room temperature.

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

    SciTech Connect (OSTI)

    Wagener, M. C.; Botha, J. R.; Carrington, P. J.; Krier, A.

    2014-07-28

    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.

  14. 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)

    2014-07-07

    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.

  15. Large linear magnetoresistance in a GaAs/AlGaAs heterostructure

    SciTech Connect (OSTI)

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

    2013-12-04

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

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

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

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

    2009-01-01

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

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

    SciTech Connect (OSTI)

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

    2010-01-05

    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.

  18. Transport properties of InGaAs/GaAs Heterostructures with {delta}-doped quantum wells

    SciTech Connect (OSTI)

    Baidus, N. V.; Vainberg, V. V.; Zvonkov, B. N.; Pylypchuk, A. S. Poroshin, V. N.; Sarbey, O. G.

    2012-05-15

    The lateral transport of electrons in single- and double-well pseudomorphic GaAs/n-InGaAs/GaAs heterostructures with quantum wells 50-100 meV deep and impurity {delta}-layers in the wells, with concentrations in the range 10{sup 11} < N{sub s} < 10{sup 12} cm{sup -2}, has been investigated. Single-well structures with a doped well at the center exhibit a nonmonotonic temperature dependence of the Hall coefficient and an increase in low-temperature electron mobility with an increase in the impurity concentration. The results obtained indicate that the impurity-band electron states play an important role in the conductivity of these structures. Involvement of the impurity band also allows to explain adequately the characteristics of the conductivity of double-well structures; in contrast to single-well structures, band bending caused by asymmetric doping is of great importance. The numerical calculations of conductivity within the model under consideration confirm these suggestions.

  19. Germanium subcells for multijunction GaInP/GaInAs/Ge solar cells

    SciTech Connect (OSTI)

    Kalyuzhnyy, N. A.; Gudovskikh, A. S.; Evstropov, V. V.; Lantratov, V. M.; Mintairov, S. A.; Timoshina, N. Kh.; Shvarts, M. Z.; Andreev, V. M.

    2010-11-15

    Photovoltaic converters based on n-GaInP/n-p-Ge heterostructures grown by the OMVPE under different conditions of formation of the p-n junction are studied. The heterostructures are intended for use as narrow-gap subcells of the GaInP/GaInAs/Ge three-junction solar cells. It is shown that, in Ge p-tn junctions, along with the diffusion mechanism, the tunneling mechanism of the current flow exists; therefore, the two-diode electrical equivalent circuit of the Ge p-n junction is used. The diode parameters are determined for both mechanisms from the analysis of both dark and 'light' current-voltage dependences. It is shown that the elimination of the component of the tunneling current allows one to increase the efficiency of the Ge subcell by {approx}1% with conversion of nonconcentrated solar radiation. The influence of the tunneling current on the efficiency of the Ge-based devices can be in practice reduced to zero at photogenerated current density of {approx}1.5 A/cm{sup 2} due to the use of the concentrated solar radiation.

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

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    ) In conventional InGaN/GaN light-emitting diodes (LEDs), thin InGaN quantum wells are usually adopted to mitigate recombination scales with the third power of the carrier density. As a result, the efficiency droop of the Auger recombination severely limits the LED performance. Here, we proposed and showed wide InGaN quantum wells

  1. 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. Jahns Current crowding in mesa-structure GaInN/GaN light-emitting diodes (LEDs) grown on insulating and a saturation of the optical output power at high injection currents. It is shown that the optical power

  2. Investigation of the effect of temperature during off-state degradation of AlGaN/GaN High Electron Mobility Transistors

    E-Print Network [OSTI]

    Florida, University of

    , creating both electron traps and increasing electron tunneling through the defect states [4Investigation of the effect of temperature during off-state degradation of AlGaN/GaN High Electron 2011 a b s t r a c t AlGaN/GaN High Electron Mobility Transistors were found to exhibit a negative

  3. 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

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

    E-Print Network [OSTI]

    Ozbay, Ekmel

    between GaN and a sapphire substrate, the dislocation scattering mechanism and the electron spillover

  5. Reliable wet-chemical cleaning of natively oxidized high-efficiency Cu(In,Ga)Se{sub 2} thin-film solar cell absorbers

    SciTech Connect (OSTI)

    Lehmann, Jascha; Lehmann, Sebastian; Lauermann, Iver; Rissom, Thorsten; Kaufmann, Christian A.; Lux-Steiner, Martha Ch.; Bär, Marcus; Sadewasser, Sascha

    2014-12-21

    Currently, Cu-containing chalcopyrite-based solar cells provide the highest conversion efficiencies among all thin-film photovoltaic (PV) technologies. They have reached efficiency values above 20%, the same performance level as multi-crystalline silicon-wafer technology that dominates the commercial PV market. Chalcopyrite thin-film heterostructures consist of a layer stack with a variety of interfaces between different materials. It is the chalcopyrite/buffer region (forming the p-n junction), which is of crucial importance and therefore frequently investigated using surface and interface science tools, such as photoelectron spectroscopy and scanning probe microscopy. To ensure comparability and validity of the results, a general preparation guide for “realistic” surfaces of polycrystalline chalcopyrite thin films is highly desirable. We present results on wet-chemical cleaning procedures of polycrystalline Cu(In{sub 1-x}Ga{sub x})Se{sub 2} thin films with an average x?=?[Ga]/([In]?+?[Ga])?=?0.29, which were exposed to ambient conditions for different times. The hence natively oxidized sample surfaces were etched in KCN- or NH{sub 3}-based aqueous solutions. By x-ray photoelectron spectroscopy, we find that the KCN treatment results in a chemical surface structure which is – apart from a slight change in surface composition – identical to a pristine as-received sample surface. Additionally, we discover a different oxidation behavior of In and Ga, in agreement with thermodynamic reference data, and we find indications for the segregation and removal of copper selenide surface phases from the polycrystalline material.

  6. Atomistic description of the electronic structure of InxGa1xAs alloys and InAsGaAs superlattices

    E-Print Network [OSTI]

    Kent, Paul

    quantum-wells15,20 (InxGa1 xAs)n /InP on InP and (InxGa1 xAs)n /GaAs on GaAs, and v GaAs-embedded InAs quantum dots.21­23 We wish to provide a uniform the- oretical description of the electronic structure-period dependence of the band offsets and interband transitions of InAs/GaAs systems on InP and GaAs substrates. DOI

  7. Improved hole distribution in InGaN/GaN light-emitting diodes with graded thickness quantum barriers

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    is 48.3%. Moreover, the light output power was enhanced from 770 mW for the ETQB LEDs to 870 m; accepted 3 June 2013; published online 19 June 2013) InGaN/GaN light-emitting diodes (LEDs) with graded , which is much smaller than that of the conventional equal-thickness quantum barriers (ETQB) LED, which

  8. Low-frequency noise in GaNAlGaN heterostructure field-effect transistors at cryogenic temperatures

    E-Print Network [OSTI]

    Pala, Nezih

    that the 1/f noise in GaN/AlGaN HFETs might be caused by electron tunneling from the channel to the traps was practically independent of the frequency of analysis. The model linking this maximum to the electron tunneling Department of Electrical, Computer, and Systems Engineering and Center for Integrated Electronics

  9. Development of GaAs/Si and GaAs/Si monolithic structures for future space solar cells

    SciTech Connect (OSTI)

    Spitzer, M.B.; Vernon, S.M.; Wolfson, R.G.; Tobin, S.P.

    1984-01-01

    The results of heteroepitaxial growth of GaAs and GaAlAs directly on Si are presented, and applications to new cell structures are suggested. The novel feature is the elimination of a Ge lattice transition region. This feature not only reduces the cost of substrate preparation, but also makes possible the fabrication of high efficiency monolithic cascade structures. All films to be discussed were grown by organometallic chemical vapor deposition at atmospheric pressure. This process yielded reproducible, large-area films of GaAs, grown directly on Si, that are tightly adherent and smooth, and are characterized by a defect density of 5 x 10(6) power/sq cm. Preliminary studies indicate that GaAlAs can also be grown in this way. A number of promising applications are suggested. Certainly these substrates are ideal for low-weight GaAs space solar ells. For very high efficiency, the absence of Ge makes the technology attractive for GaAlAs/Si monolithic cascades, in which the Si substrates would first be provided with a suitable p/n junction. An evaluation of a three bandgap cascade consisting of appropriately designed GaAlAs/GaAs/Si layers is also presented.

  10. 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

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

    E-Print Network [OSTI]

    be well suited for exploitation of long wavelength quantum dot and dilute nitride technology, resulting in single lateral mode emission from an In0.17Ga0.83As double quantum well laser. Introduction: Lasers based on the GaAs materials system offer advan- tages over their InP counterparts, such as the use

  12. Improved performance of In,,Ga...As/GaAs quantum dot solar cells via light scattering by nanoparticles

    E-Print Network [OSTI]

    Yu, Edward T.

    of QDs in the context of our work is attractive for achieving long wavelength absorption in solar cells enhancement at all infrared wave- lengths in the device photocurrent spectrum. Epitaxial layer structuresImproved performance of In,,Ga...As/GaAs quantum dot solar cells via light scattering

  13. 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

  14. SnO2 functionalized AlGaN/GaN high electron mobility transistor for hydrogen sensing applications

    E-Print Network [OSTI]

    Florida, University of

    for spacecraft and other long-term sensing applications. However, hydrogen is a dangerous gas for storage for monitoring leakage of hydrogen storage equipment and fuel tanks for spacecraft and hydrogen fuel cellSnO2 functionalized AlGaN/GaN high electron mobility transistor for hydrogen sensing applications

  15. Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductors: Electronic structure calculations 

    E-Print Network [OSTI]

    Masek, J.; Kudrnovsky, J.; Maca, F.; Sinova, Jairo; MacDonald, A. H.; Campion, R. P.; Gallagher, B. L.; Jungwirth, T.

    2007-01-01

    A remarkable progress towards functional ferromagnetic semiconductor materials for spintronics has been achieved in p-type (Ga,Mn)As. Robust hole-mediated ferromagnetism has, however, been observed also in other III-V hosts such as antimonides, Ga...

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

    E-Print Network [OSTI]

    Honsberg, Christiana

    photovoltaic efficiency of 39% at 236 suns is achieved by a triple-junction GaInP- GaInAs-Ge tandem solar cell [1]. While the achievable efficiency of triple-junction tandem solar cells is restricted to about 40% [2], modeling results show that a tandem solar cell of five junctions or greater, or an equivalent

  17. Progress toward technology transition of GaInP{sub 2}/GaAs/Ge multijunction solar cells

    SciTech Connect (OSTI)

    Keener, D.N.; Marvin, D.C.; Brinker, D.J.; Curtis, H.B.; Price, P.M.

    1997-12-31

    The objective of the joint WL/PL/NASA Multijunction Solar Cell Manufacturing Technology (ManTech) Program is to scale up high efficiency GaInP{sub 2}/GaAs/Ge multijunction solar cells to production size, quantity, and yield while limiting the production cost/Watt ($/W) to 15% over GaAs cells. Progress made by the program contractors, Spectrolab and TECSTAR, include, respectively, best cell efficiencies of 25.76% and 24.7% and establishment of 24.2% and 23.8% lot average efficiency baseline designs. The paper also presents side-by-side testing results collected by Phillips Laboratory and NASA Lewis on Phase 1 deliverable cells, which shows compliance with program objectives. Cell performance, pre- and post-radiation, and temperature coefficient results on initial production GaInP{sub 2}/GaAs/Ge solar cells will be presented.

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

    SciTech Connect (OSTI)

    Yin, Wan-Jian Shi, Tingting; Yan, Yanfa

    2014-02-10

    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}.

  19. 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)

    2010-10-13

    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.

  20. 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; Selucky, P.; Vanura, Petr; Moyer, Bruce A

    2013-01-01

    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.

  1. Microstructures and properties of CH{sub 3}NH{sub 3}PbI{sub 3?x}Cl{sub x} hybrid solar cells

    SciTech Connect (OSTI)

    Suzuki, Kohei E-mail: oku@mat.usp.ac.jp; Suzuki, Atsushi E-mail: oku@mat.usp.ac.jp; Zushi, Masahito E-mail: oku@mat.usp.ac.jp; Oku, Takeo E-mail: oku@mat.usp.ac.jp

    2015-02-27

    Halide-perovskite CH{sub 3}NH{sub 3}PbI{sub 3} was produced on mesoporous TiO{sub 2} layer by spin-coating a precursor solution of PbCl{sub 2} and CH{sub 3}NH{sub 3}I in dimethylformamide. The role of the annealing process and chlorine (Cl) doping for the perovskite-phase formation was investigated. It was found that crystallization of the perovskite materials was stimulated by the annealing process, and that longer annealing time is necessary for the Cl-doped perovskite compared with that of non-doped perovskite phase.

  2. Ferromagnetism in undoped One-dimensional GaN Nanowires

    SciTech Connect (OSTI)

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

    2014-05-15

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

  3. Characterization of Zns-GaP Naon-composites

    SciTech Connect (OSTI)

    Todd, V.

    1993-12-09

    It proved possible to produce consistent, high-quality nanocrystalline ZnS powders with grain sizes as small as 8 nm. These powders are nano-porous and are readily impregnated with GaP precursor, although inconsistently. Both crystal structure and small grain size of the ZnS can be maintained through the use of GaP. Heat treatment of the impregnated powders results in a ZnS-GaP composite structure where the grain sizes of the phases are on the order of 10--20 nm. Conventional powder processing should be able to produce optically dense ceramic compacts with improved mechanical properties and suitable IR transmission.

  4. Indium distribution at the interfaces of (Ga,In)(N,As)/GaAs quantum wells

    SciTech Connect (OSTI)

    Luna, E.; Ishikawa, F.; Batista, P. D.; Trampert, A. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, D-10117, Berlin (Germany)

    2008-04-07

    The indium distribution across (Ga,In)(N,As) quantum wells is determined by using transmission electron microscopy techniques. Inside the quantum well, the indium distribution is well described by Muraki's segregation model; however, it fails in reflecting the concentration at the interfaces. To describe them, we propose a sigmoidal law which defines the smooth variation of the indium concentration with the position and provides a systematic and quantitative characterization of the interfaces. The thermal stability of the interfaces and their interplay with segregation effects are discussed. A connection between the high thermal robustness of the interfaces and the inherent thermodynamic miscibility gap of the alloy is suggested.

  5. Local Structures and Interface Morphology of InGaAsN Thin Films Grown on GaAs

    SciTech Connect (OSTI)

    Allerman, A.A.; Chen, J.G.; Geisz, J.F.; Huang, S.; Hulbert, S.L.; Jones, E.D.; Kao, Y.H.; Kurtz, S.; Kurtz, S.R.; Olson, J.M.; Soo, Y.L.

    1999-02-23

    The compound semiconductor system InGaAsN exhibits many intriguing properties which are particularly useful for the development of innovative high efficiency thin film solar cells and long wavelength lasers. The bandgap in these semiconductors can be varied by controlling the content of N and In and the thin films can yet be lattice-matched to GaAs. In the present work, x-ray absorption fine structure (XAFS) and grazing incidence x-ray scattering (GIXS) techniques have been employed to probe the local environment surrounding both N and In atoms as well as the interface morphology of InGaAsN thin films epitaxially grown on GaAs. The soft x-ray XAFS results around nitrogen K-edge reveal that N is in the sp{sup 3} hybridized bonding configuration in InGaAsN and GaAsN, suggesting that N impurities most likely substitute for As sites in these two compounds. The results of In K-edge XAFS suggest a possible trend of a slightly larger coordination number of As nearest neighbors around In atoms in InGaAsN samples with a narrower bandgap whereas the In-As interatomic distance remains practically the same as in InAs within the experimental uncertainties. These results combined suggest that N-substitution of the As sites plays an important role of bandgap-narrowing while in the meantime counteracting the compressive strain caused by In-doping. Grazing incidence x-ray scattering (GIXS) experiments verify that InGaAsN thin films can indeed form very smooth interfaces with GaAs yielding an average interfacial roughness of 5-20{angstrom}.

  6. 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)

    2013-05-15

    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.

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

    SciTech Connect (OSTI)

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

    2013-12-09

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

  8. Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

    SciTech Connect (OSTI)

    Guo, Lei; Yang, Xuelin Cheng, Jianpeng; Sang, Ling; Xu, Fujun; Tang, Ning; Feng, Zhihong; Lv, Yuanjie; Wang, Xinqiang; Shen, B.; Ge, Weikun

    2014-12-15

    We have investigated the variation of electron velocity in AlGaN/GaN heterostructures depending on illuminating light intensity and wavelength. It is shown that the electron velocity at high electric field increases under above-band light illumination. This electron velocity enhancement is found to be related to the photo-generated cold holes which interact with hot electrons and thus accelerate the energy relaxation at high electric field. The results suggest an alternative way to improve the electron energy relaxation rate and hence the electron velocity in GaN based heterostructures.

  9. High-power InGaAs/GaAs quantum-well laser with enhanced broad spectrum of stimulated emission

    SciTech Connect (OSTI)

    Wang, Huolei; Yu, Hongyan; Zhou, Xuliang; Kan, Qiang; Yuan, Lijun; Wang, Wei; Pan, Jiaoqing, E-mail: jqpan@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China); Chen, Weixi [State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871 (China); Ding, Ying, E-mail: Ying.Ding@glasgow.ac.uk [School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom)

    2014-10-06

    We report the demonstration of an InGaAs/GaAs quantum well (QW) broadband stimulated emission laser with a structure that integrated a GaAs tunnel junction with two QW active regions. The laser exhibits ultrabroad lasing spectral coverage of ?51?nm at a center wavelength of 1060?nm with a total emission power of 790 mW, corresponding to a high average spectral power density of 15.5 mW/nm, under pulsed current conditions. Compared to traditional lasers, this laser with an asymmetric separate-confinement heterostructure shows broader lasing bandwidth and higher spectral power density.

  10. Linear and nonlinear optical properties of GaAs/Al{sub x}Ga{sub 1?x}As/GaAs/Al{sub y}Ga{sub 1?y}As multi-shell spherical quantum dot

    SciTech Connect (OSTI)

    Emre Kavruk, Ahmet E-mail: aekavruk@gmail.com; Koc, Fatih; Sahin, Mehmet E-mail: mehsahin@gmail.com

    2013-11-14

    In this work, the optical properties of GaAs/Al{sub x}Ga{sub 1?x}As/GaAs/Al{sub y}Ga{sub 1?y}As multi-shell quantum dot heterostructure have been studied as a function of Al doping concentrations for cases with and without a hydrogenic donor atom. It has been observed that the absorption coefficient strength and/or resonant absorption wavelength can be adjusted by changing the Al content of inner-barrier and/or outer-barrier regions. Besides, it has been shown that the donor atom has an important effect on the control of the electronic and optical properties of the structure. The results have been presented as a function of the Al contents of the inner-barrier x and outer-barrier y regions and probable physical reasons have been discussed.

  11. Electrical degradation mechanisms of RF power GaAs PHEMTs

    E-Print Network [OSTI]

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

    2007-01-01

    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 ...

  12. 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)

    1981-01-01

    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.

  13. 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

  14. 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

  15. 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)

    2014-03-21

    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.

  16. 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)

    2014-11-03

    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.

  17. Rabies Requirements for NH 4-H Animals Upon the recommendation of the New Hampshire State Veterinarian, all mammals shown or exhibited

    E-Print Network [OSTI]

    New Hampshire, University of

    Rabies Requirements for NH 4-H Animals Upon the recommendation of the New Hampshire State Veterinarian, all mammals shown or exhibited at New Hampshire 4-H events including fairs, shows, clinics, 4-H and fairs may have additional vaccination and health requirements as recommended by the New Hampshire State

  18. 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

  19. Detailed modeling and laser-induced fluorescence imaging of nitric oxide in a NH3-seeded non-premixed methane/air flame

    E-Print Network [OSTI]

    Bell, John B.

    non-premixed methane/air flame John B. Bell, Marcus S. Day, Joseph F. Grcar Computing Sciences-induced fluorescence imaging of nitric oxide in a NH3-seeded non-premixed methane/air flame Abstract In this paper we study the formation of NO in laminar, nitrogen diluted methane diffusion flames that are seeded

  20. 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)

    2014-11-07

    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.

  1. 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)

    2014-09-26

    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.

  2. The origin and reduction of switching noise in GaAs/AlGaAs lateral gated devices

    E-Print Network [OSTI]

    Davies, John H.

    to cryogenic temperature with all gates grounded to the substrate to protect against electrostatic effects in AlGaAs: electrons `freeze' into deep traps ­ DX centres ­ below about 150 K. The occupation of donors

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

    E-Print Network [OSTI]

    Keogh, David Martin

    2006-01-01

    assuming the material growth technology allows for all ofand a relatively immature growth technology, as well as theof the art for InGaN growth technology. Epitaxial growth of

  4. 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)

    2014-01-27

    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.

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

    E-Print Network [OSTI]

    Johnson, Derek Wade

    2014-07-31

    production is projected to consume ~100,000 wafers per year by 2015 (Yole Development, “Power GaN – 2012 Edition”), this manufacturing breakthrough represents potential savings of ~$17 million per year....

  6. Characterization of the gate oxide of an AlGaN/GaN high electron mobility transistor

    E-Print Network [OSTI]

    Florida, University of

    2011; published online 21 March 2011 A subnanometer thick interfacial oxide layer present between used to characterize a Ni/AlGaN interfacial oxide layer with subnanometer thickness. The semiconducting

  7. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    SciTech Connect (OSTI)

    Özduran, Mustafa; Turgut, Kemal; Arikan, Nihat; ?yigör, Ahmet; Candan, Abdullah

    2014-10-06

    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.

  8. Optical investigation of InAs quantum dots inserted in AlGaAs/GaAs modulation doped heterostructure

    SciTech Connect (OSTI)

    Khmissi, H.; Baira, M.; Bouzaieene, L.; Saidi, F.; Maaref, H. [Laboratoire de Micro-optoelectronique et Nanostructures, Universite de Monastir (Tunisia); Sfaxi, L. [Laboratoire de Micro-optoelectronique et Nanostructures, Universite de Monastir (Tunisia); Universite de Sousse Faculte des Sciences de Monastir, Avenue de l'Environnement 5019 Monastir (Tunisia); Bru-Chevallier, C. [Institut des Nanotechnologies de Lyon (INL), CNRS UMR-5270, INSA-LYON, 7, Avenue Jean Capelle, Bat. Blaise Pascal, 69621 Villeurbanne (France)

    2011-03-01

    Optical properties of InAs quantum dots (QDs) inserted in AlGaAs/GaAs modulation doped heterostructure are investigated. To study the effect of carrier transfer behavior on the luminescence of self-assembled quantum dots, a series of sample has been prepared using molecular beam epitaxy (Riber 32 system) in which we have varied the thickness separating the delta dopage and the InAs quantum dots layer. Photoluminescence spectra show the existence of two peaks that can be attributed to transition energies from the ground state (E{sub 1}-HH{sub 1}) and the first excited state (E{sub 2}-HH{sub 2}). Two antagonist effects have been observed, a blue shift of the emission energies result from electron transferred from the AlGaAs/GaAs heterojunction to the InAs quantum dots and a red shift caused by the quantum confined Stark effect due to the internal electric field existing In the AlGaAs/GaAs heterojunction.

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

    SciTech Connect (OSTI)

    Coerekci, S.; Oeztuerk, M. K.; Yu, Hongbo; Cakmak, M.; Oezcelik, S.; Oezbay, E.

    2013-06-15

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

  10. 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

  11. THE ROTATIONAL SPECTRUM OF ANTI-ETHYLAMINE (CH3CH2NH2) FROM 10 TO 270 GHz: A LABORATORY STUDY AND ASTRONOMICAL SEARCH IN SGR B2(N)

    E-Print Network [OSTI]

    Ziurys, Lucy M.

    AND ASTRONOMICAL SEARCH IN SGR B2(N) A. J. Apponi, M. Sun, D. T. Halfen,1 and L. M. Ziurys Departments of Chemistry identification of methylamine (CH3NH2) and ethylamine (CH3CH2NH2) in the aerogel collectors (Sandford et al. 2006

  12. DRAFT of 2015 Natural Resources Stewards Course Curriculum Overview Fridays, beginning Sept. 4, 2015 Dec. 4, 2015, 8:30 a.m. to 4:00 p.m. at NH Fish and Game Dept.

    E-Print Network [OSTI]

    and Game Dept. Session 4 9/25/15 1:00 pm - 8:00 pm Permaculture Day ­ Nottingham, NH Special session and Sustainable Design Services Session 5 10/02/15 8:30 am - 4:00 pm Permaculture Principles and Ethics & Reading the Forested Landscape ­ Society for the Protection of NH Forests permaculture principles introduced forces

  13. p-doping-free InGaN/GaN light-emitting diode driven by three-dimensional hole gas

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Tiam Tan, Swee; Kyaw, Zabu; Liu, Wei; Ji, Yun; Ju, Zhengang; Zhang, Xueliang [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore) [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Wei Sun, Xiao, E-mail: EXWSUN@ntu.edu.sg [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Department of Electronics and Electrical Engineering, South University of Science and Technology of China, Shenzhen, Guangdong 518055 (China); Volkan Demir, Hilmi, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Department of Electrical and Electronics, UNAM-Institute of Material Science and Nanotechnology, Bilkent University, Ankara TR-06800 (Turkey); Department of Physics, UNAM-Institute of Material Science and Nanotechnology, Bilkent University, Ankara TR-06800 (Turkey)

    2013-12-23

    Here, GaN/Al{sub x}Ga{sub 1-x}N heterostructures with a graded AlN composition, completely lacking external p-doping, are designed and grown using metal-organic-chemical-vapour deposition (MOCVD) system to realize three-dimensional hole gas (3DHG). The existence of the 3DHG is confirmed by capacitance-voltage measurements. Based on this design, a p-doping-free InGaN/GaN light-emitting diode (LED) driven by the 3DHG is proposed and grown using MOCVD. The electroluminescence, which is attributed to the radiative recombination of injected electrons and holes in InGaN/GaN quantum wells, is observed from the fabricated p-doping-free devices. These results suggest that the 3DHG can be an alternative hole source for InGaN/GaN LEDs besides common Mg dopants.

  14. Lasing characteristics of GaSb/GaAs self-assembled quantum dots embedded in an InGaAs quantum well

    E-Print Network [OSTI]

    Jalali. Bahram

    Center for High Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico, New Mexico 87545 Received 26 February 2007; accepted 1 June 2007; published online 28 June 2007 intriguing optoelectronic device possibilities on GaAs substrates including lasers, detectors, or solar cells

  15. 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

    2012-01-01

    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.

  16. Density Functional Studies of Stoichiometric Surfaces of Orthorhombic Hybrid Perovskite CH3NH3PbI3

    SciTech Connect (OSTI)

    Wang, Yun; Huang, Jingsong; Sumpter, Bobby G; Zhang, Haimin; Liu, Porun; Yang, Huagui; Zhao, Huijun

    2015-01-01

    Organic/inorganic hybrid perovskite materials are highly attractive for dye-sensitized solar cells as demonstrated by their rapid advances in energy conversion efficiency. In this work, the structures, energetics, and electronic properties for a range of stoichiometric surfaces of the orthorhombic perovskite CH3NH3PbI3 are theoretically studied using density functional theory. Various possible spatially and constitutionally isomeric surfaces are considered by diversifying the spatial orientations and connectivities of surface Pb-I bonds. The comparison of the surface energies for the most stable configurations identified for various surfaces shows that the stabilities of stoichiometric surfaces are mainly dictated by the coordination numbers of surface atoms, which are directly correlated with the numbers of broken bonds. Additionally, Coulombic interactions between I anions and organic countercations on the surface also contribute to the stabilization. Electronic properties are compared between the most stable (100) surface and the bulk phase, showing generally similar features except for the lifted band degeneracy and the enhanced bandgap energy for the surface. These studies on the stoichiometric surfaces serve as the first step toward gaining a fundamental understanding of the interfacial properties in the current structural design of perovskite based solar cells, in order to achieve further breakthroughs in solar conversion efficiencies.

  17. 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

    2006-12-04

    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.

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

    E-Print Network [OSTI]

    York, Robert A.

    amplifier using GaN- HEMTs-on-Sapphire. I INTRODUCTION GaN HEMTs have enormous potential for realizing high-power Traveling Wave Power Amplifier circuit (TWPA)[1][2] for realization of wideband power amplifiersWE4A-5 A 3-10 GHZLCR-matched Power Amplifier using Flip-Chip Mounted AlGaN/GaN HEMTs Jane J

  19. Intermixing of InGaAs/GaAs Quantum Well Using Multiple Cycles Annealing Cu-doped SiO2

    SciTech Connect (OSTI)

    Hongpinyo, V; Ding, Y H; Dimas, C E; Wang, Y; Ooi, B S; Qiu, W; Goddard, L L; Behymer, E M; Cole, G D; Bond, T C

    2008-06-11

    The authors investigate the effect of intermixing in InGaAs/GaAs quantum well structure using Cu-doped SiO{sub 2}. The incorporation of Cu into the silica film yields larger bandgap shift than typical impurity-free vacancy diffusion (IFVD) method at a lower activation temperature. We also observe enhancement of the photoluminescence (PL) signal from the intermixed InGaAs/GaAs quantum well structure after being cycle-annealed at 850 C.

  20. Metamorphic GaAsP buffers for growth of wide-bandgap InGaP solar cells J. Simon,1,a

    E-Print Network [OSTI]

    Haller, Gary L.

    . INTRODUCTION Triple-junction metamorphic solar cells have reached ef- ficiencies as high as 41.1% by combiningMetamorphic GaAsP buffers for growth of wide-bandgap InGaP solar cells J. Simon,1,a S. Tomasulo,1 P-yP solar cells. Tensile-strained GaAsxP1-x buffers grown on GaAs using unoptimized conditions

  1. FIRST DEMONSTRATION OF MONOLITHIC InP-BASED InAlAs/InGaAsP/InGaAs TRIPLE JUNCTION SOLAR CELLS

    E-Print Network [OSTI]

    Atwater, Harry

    FIRST DEMONSTRATION OF MONOLITHIC InP-BASED InAlAs/InGaAsP/InGaAs TRIPLE JUNCTION SOLAR CELLS RobynAlAs/InGaAsP/InGaAs triple junction solar cell grown on InP substrate. X-ray diffraction characterization shows high quality solar cell materials. Preliminary 1-sun AM1.5D testing of the triple junction solar cell shows promising

  2. Characterization of Cu(In,Ga)Se2 (CIGS) films with varying gallium ratios

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

    Claypoole, Jesse; Peace, Bernadette; Sun, Neville; Dwyer, Dan; Eisaman, Matthew D.; Haldar, Pradeep; Efstathiadis, Harry

    2015-09-05

    Cu(In1-x,Gax)Se2 (CIGS) absorber layers were deposited on molybdenum (Mo) coated soda-lime glass substrates with varying Ga content (described as Ga/(In+Ga) ratios) with respect to depth. As the responsible mechanisms for the limitation of the performance of the CIGS solar cells with high Ga contents are not well understood, the goal of this work was to investigate different properties of CIGS absorber films with Ga/(In+Ga) ratios varied between 0.29 and 0.41 (as determined by X-ray florescence spectroscopy (XRF)) in order to better understand the role that the Ga content has on film quality. The Ga grading in the CIGS layer hasmore »the effect causing a higher bandgap toward the surface and Mo contact while the band gap in the middle of the CIGS layer is lower. Also, a wider and larger Ga/(In+Ga) grading dip located deeper in the CIGS absorber layers tend to produce larger grains in the regions of the films that have lower Ga/(In+Ga) ratios. It was found that surface roughness decreases from 51.2 nm to 41.0 nm with increasing Ga/(In+Ga) ratios. However, the surface roughness generally decreases if the Ga grading occurs deeper in the absorber layer.« less

  3. Radiation damage of GaAs thin-film solar cells on Si substrates

    SciTech Connect (OSTI)

    Itoh, Y.; Yamaguchi, M.; Nishioka, T.; Yamamoto, A.

    1987-01-15

    1-MeV electron irradiation damages in GaAs thin-film solar cells on Si substrates are examined for the first time. Damage constant for minority-carrier diffusion length in GaAs heteroepitaxial films on Si substrates is found to be the same as that in GaAs homoepitaxial films on GaAs substrates. This agreement suggests that GaAs/Si has the same defect introduction rate with radiation as GaAs/GaAs. The degradation of GaAs solar cells on Si with electron irradiation is less than that of GaAs solar cells on GaAs, because in the present, GaAs films on Si substrates have lower minority-carrier diffusion length compared to GaAs films on GaAs and these films are insensitive to radiation. The p/sup +/-p/sup +/-n AlGaAs-GaAs heteroface solar cell with junction depth of about 0.3 ..mu..m is concluded to be useful for a high-efficiency and radiation-resistant solar cell fabricated on a Si substrate.

  4. Laser Gain and Threshold Properties in Compressive-Strained and Lattice-Matched GaInNAs/GaAs Quantum Wells

    SciTech Connect (OSTI)

    Chow, W.W.; Jones, E.D.; Modine, N.A.; Allerman, A.A.; Kurtz, S.R.

    1999-08-04

    The optical gain spectra for compressive-strained and lattice-matched 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 lasing threshold current density for different GAInNAs/GaAs laser structures.

  5. Metal contacts on ZnSe and GaN

    SciTech Connect (OSTI)

    Duxstad, K J [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering

    1997-05-01

    Recently, considerable interest has been focused on the development of blue light emitting materials and devices. The focus has been on GaN and ZnSe, direct band gap semiconductors with bands gaps of 3.4 and 2.6 eV, respectively. To have efficient, reliable devices it is necessary to have thermally and electrically stable Ohmic contacts. This requires knowledge of the metal-semiconductor reaction behavior. To date few studies have investigated this behavior. Much information has accumulated over the years on the behavior of metals on Si and GaAs. This thesis provides new knowledge for the more ionic wide band gap semiconductors. The initial reaction temperatures, first phases formed, and phase stability of Pt, Pd, and Ni on both semiconductors were investigated. The reactions of these metals on ZnSe and GaN are discussed in detail and correlated with predicted behavior. In addition, comparisons are made between these highly ionic semiconductors and Si and GaAs. The trends observed here should also be applicable to other II-VI and III-Nitride semiconductor systems, while the information on phase formation and stability should be useful in the development of contacts for ZnSe and GaN devices.

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

    SciTech Connect (OSTI)

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

    2014-10-07

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

  7. Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

    SciTech Connect (OSTI)

    Schmidt, Gordon Müller, Marcus; Veit, Peter; Bertram, Frank; Christen, Jürgen; Glauser, Marlene; Carlin, Jean-François; Cosendey, Gatien; Butté, Raphaël; Grandjean, Nicolas

    2014-07-21

    Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperatures, the optical and structural properties of a 62 InGaN/GaN multiple quantum well embedded in an AlInN/GaN based microcavity are investigated at the nanometer scale. We are able to spatially resolve a spectral redshift between the individual quantum wells towards the surface. Cathodoluminescence spectral linescans allow directly visualizing the critical layer thickness in the quantum well stack resulting in the onset of plastic relaxation of the strained InGaN/GaN system.

  8. Active region based on graded-gap InGaN/GaN superlattices for high-power 440- to 470-nm light-emitting diodes

    SciTech Connect (OSTI)

    Tsatsulnikov, A. F., E-mail: Andrew@beam.ioffe.ru; Lundin, W. V.; Sakharov, A. V.; Zavarin, E. E.; Usov, S. O.; Nikolaev, A. E.; Cherkashin, N. A.; Ber, B. Ya.; Kazantsev, D. Yu. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Mizerov, M. N. [Russian Academy of Sciences, Center for Microelectronics, Ioffe Physicotechnical Institute (Russian Federation); Park, Hee Seok [Samsung Electro-Mechanics Co. Ltd. (Korea, Republic of); Hytch, M.; Hue, F. [National Center for Scientific Research, Center for Material Elaboration and Structural Studies (France)

    2010-01-15

    The structural and optical properties of light-emitting diode structures with an active region based on ultrathin InGaN quantum wells limited by short-period InGaN/GaN superlattices from both sides have been investigated. The dependences of the external quantum efficiency on the active region design are analyzed. It is shown that the use of InGaN/GaN structures as limiting graded-gap short-period superlattices may significantly increase the quantum efficiency.

  9. Graphene/GaN diodes for ultraviolet and visible photodetectors

    SciTech Connect (OSTI)

    Lin, Fang; Chen, Shao-Wen; Meng, Jie; Tse, Geoffrey; Fu, Xue-Wen; Xu, Fu-Jun [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Shen, Bo; Liao, Zhi-Min, E-mail: liaozm@pku.edu.cn, E-mail: yudp@pku.edu.cn; Yu, Da-Peng, E-mail: liaozm@pku.edu.cn, E-mail: yudp@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)

    2014-08-18

    The Schottky diodes based on graphene/GaN interface are fabricated and demonstrated for the dual-wavelength photodetection of ultraviolet (UV) and green lights. The physical mechanisms of the photoelectric response of the diodes with different light wavelengths are different. For UV illumination, the photo-generated carriers lower the Schottky barrier and increase the photocurrent. For green light illumination, as the photon energy is smaller than the bandgap of GaN, the hot electrons excited in graphene via internal photoemission are responsible for the photoelectric response. Using graphene as a transparent electrode, the diodes show a ?mS photoresponse, providing an alternative route toward multi-wavelength photodetectors.

  10. Polycrystalline MBE-grown GaAs for solar cells

    SciTech Connect (OSTI)

    Friedman, D.J.; Kurtz, S.R.; Kibbler, A.E.; Al-Jassim, M.; Jones, K.; Keyes, B.; Matson, R.

    1997-02-01

    This paper will discuss initial studies of thin-film GaAs grown by molecular-beam epitaxy for use in developing a thin-film GaAs solar cell. Photocurrent and photoluminescence intensity are related to the material morphology as a function of growth conditions. Growth temperature and V/III ratio have a dramatic effect on the photocurrent. However, it seems likely that even after optimizing such growth parameters, it will be necessary to provide substrates that can provide templates to enhance grain size from the start of thin-film growth. {copyright} {ital 1997 American Institute of Physics.}

  11. Polycrystalline MBE-grown GaAs for solar cells

    SciTech Connect (OSTI)

    Friedman, D. J.; Kurtz, Sarah R.; Kibbler, A. E.; Al-Jassim, M.; Jones, K.; Keyes, B.; Matson, R.

    1997-02-15

    This paper will discuss initial studies of thin-film GaAs grown by molecular-beam epitaxy for use in developing a thin-film GaAs solar cell. Photocurrent and photoluminescence intensity are related to the material morphology as a function of growth conditions. Growth temperature and V/III ratio have a dramatic effect on the photocurrent. However, it seems likely that even after optimizing such growth parameters, it will be necessary to provide substrates that can provide templates to enhance grain size from the start of thin-film growth.

  12. Highly transparent ammonothermal bulk GaN substrates

    SciTech Connect (OSTI)

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

    2014-10-01

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

  13. A hole modulator for InGaN/GaN light-emitting diodes Zi-Hui Zhang, Zabu Kyaw, Wei Liu, Yun Ji, Liancheng Wang, Swee Tiam Tan, Xiao Wei Sun, and Hilmi Volkan

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    well on optical power of light-emitting diodes Appl. Phys. Lett. 96, 051113 (2010); 10-emitting diodes (LEDs) due to the ineffective hole injection into the InGaN/GaN multiple quantum well (MQW) active in the p-GaN layer can be enhanced. Furthermore, the hole modulator is adopted in the InGaN/GaN LEDs, which

  14. Direct Observation of Long Electron-Hole Diffusion Distance beyond 1 Micrometer in CH3NH3PbI3 Perovskite Thin Film

    E-Print Network [OSTI]

    Li, Yu; Li, Yunlong; Wang, Wei; Bian, Zuqiang; Xiao, Lixin; Wang, Shufeng; Gong, Qihuang

    2015-01-01

    In high performance perovskite based on CH3NH3PbI3, the formerly reported short charge diffusion distance is a confliction to thick working layer in solar cell devices. We carried out a study on charge diffusion in spin-coated CH3NH3PbI3 perovskite thin film by transient fluorescent spectroscopy. A thickness-dependent fluorescent lifetime was found. This effect correlates to the defects at crystal grain boundaries. By coating the film with electron or hole transfer layer, PCBM or Spiro-OMeTAD respectively, we observed the charge transfer directly through the fluorescent decay. One-dimensional diffusion model was applied to obtain long charge diffusion distances, which is ~1.3 micron for electrons and ~5.2 micron for holes. This study gives direct support to the high performance of perovskite solar cells.

  15. Strong enhancement of terahertz emission from GaAs in InAs/GaAs quantum dot structures

    SciTech Connect (OSTI)

    Estacio, Elmer; Pham, Minh Hong; Takatori, Satoru; Cadatal-Raduban, Marilou; Nakazato, Tomoharu; Shimizu, Toshihiko; Sarukura, Nobuhiko; Somintac, Armando; Defensor, Michael; Awitan, Fritz Christian B.; Jaculbia, Rafael B.; Salvador, Arnel; Garcia, Alipio

    2009-06-08

    We report on the intense terahertz emission from InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. Results reveal that the QD sample emission was as high as 70% of that of a p-type InAs wafer, the most intense semiconductor emitter to date. Excitation wavelength studies showed that the emission was due to absorption in strained undoped GaAs, and corresponds to a two order-of-magnitude enhancement. Moreover, it was found that multilayer QDs emit more strongly compared with a single layer QD sample. At present, we ascribe the intense radiation to huge strain fields at the InAs/GaAs interface.

  16. Characteristics of InGaP/InGaAs pseudomorphic high electron mobility transistors with triple delta-doped sheets

    SciTech Connect (OSTI)

    Chu, Kuei-Yi; Chiang, Meng-Hsueh Cheng, Shiou-Ying; Liu, Wen-Chau

    2012-02-15

    Fundamental and insightful characteristics of InGaP/InGaAs double channel pseudomorphic high electron mobility transistors (DCPHEMTs) with graded and uniform triple {delta}-doped sheets are coomprehensively studied and demonstrated. To gain physical insight, band diagrams, carrier densities, and direct current characteristics of devices are compared and investigated based on the 2D semiconductor simulator, Atlas. Due to uniform carrier distribution and high electron density in the double InGaAs channel, the DCPHEMT with graded triple {delta}-doped sheets exhibits better transport properties, higher and linear transconductance, and better drain current capability as compared with the uniformly triple {delta}-doped counterpart. The DCPHEMT with graded triple {delta}-doped structure is fabricated and tested, and the experimental data are found to be in good agreement with simulated results.

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

    SciTech Connect (OSTI)

    Edmunds, C.; Malis, O.; Shao, J.; Shirazi-HD, M.; Manfra, M. J.

    2014-07-14

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

  18. High-performance broadband optical coatings on InGaN/GaN solar cells for multijunction device integration

    SciTech Connect (OSTI)

    Young, N. G. Farrell, R. M.; Iza, M.; Speck, J. S.; Perl, E. E.; Keller, S.; Bowers, J. E.; Nakamura, S.; DenBaars, S. P.

    2014-04-21

    We demonstrate InGaN/GaN multiple quantum well solar cells grown by metalorganic chemical vapor deposition on a bulk (0001) substrate with high-performance broadband optical coatings to improve light absorption. A front-side anti-reflective coating and a back-side dichroic mirror were designed to minimize front surface reflections across a broad spectral range and maximize rear surface reflections only in the spectral range absorbed by the InGaN, making the cells suitable for multijunction solar cell integration. Application of optical coatings increased the peak external quantum efficiency by 56% (relative) and conversion efficiency by 37.5% (relative) under 1 sun AM0 equivalent illumination.

  19. InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

    SciTech Connect (OSTI)

    Alonso-Álvarez, D.; Thomas, T.; Führer, M.; Hylton, N. P.; Ekins-Daukes, N. J.; Lackner, D.; Philipps, S. P.; Bett, A. W.; Sodabanlu, H.; Fujii, H.; Watanabe, K.; Sugiyama, M.; Nasi, L.; Campanini, M.

    2014-08-25

    Quantum wires (QWRs) form naturally when growing strain balanced InGaAs/GaAsP multi-quantum wells (MQW) on GaAs [100] 6° misoriented substrates under the usual growth conditions. The presence of wires instead of wells could have several unexpected consequences for the performance of the MQW solar cells, both positive and negative, that need to be assessed to achieve high conversion efficiencies. In this letter, we study QWR properties from the point of view of their performance as solar cells by means of transmission electron microscopy, time resolved photoluminescence and external quantum efficiency (EQE) using polarised light. We find that these QWRs have longer lifetimes than nominally identical QWs grown on exact [100] GaAs substrates, of up to 1??s, at any level of illumination. We attribute this effect to an asymmetric carrier escape from the nanostructures leading to a strong 1D-photo-charging, keeping electrons confined along the wire and holes in the barriers. In principle, these extended lifetimes could be exploited to enhance carrier collection and reduce dark current losses. Light absorption by these QWRs is 1.6 times weaker than QWs, as revealed by EQE measurements, which emphasises the need for more layers of nanostructures or the use light trapping techniques. Contrary to what we expected, QWR show very low absorption anisotropy, only 3.5%, which was the main drawback a priori of this nanostructure. We attribute this to a reduced lateral confinement inside the wires. These results encourage further study and optimization of QWRs for high efficiency solar cells.

  20. The Origin and Coupling Mechanism of the Magnetoelectric Effect in TM Cl 2 -4SC(NH 2 ) 2 ( TM = Ni and Co)

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

    Mun, Eundeok; Wilcox, Jason; Manson, Jamie L.; Scott, Brian; Tobash, Paul; Zapf, Vivien S.

    2014-01-01

    Most research on multiferroics and magnetoelectric effects to date has focused on inorganic oxides. Molecule-based materials are a relatively new field in which to search for magnetoelectric multiferroics and to explore new coupling mechanisms between electric and magnetic order. We present magnetoelectric behavior in NiCl 2 -4SC(NH 2 ) 2 (DTN) and CoCl 2 -4SC(NH 2 ) 2 (DTC). These compounds form tetragonal structures where the transition metal ion (Ni or Co) is surrounded by four electrically polar thiourea molecules [SC(NH 2 ) 2 ]. By tracking the magnetic and electric properties of these compounds as a function ofmore »magnetic field, we gain insights into the coupling mechanism by observing that, in DTN, the electric polarization tracks the magnetic ordering, whereas in DTC it does not. For DTN, all electrically polar thiourea molecules tilt in the same direction along the c -axis, breaking spatial-inversion symmetry, whereas, for DTC, two thiourea molecules tilt up and two tilt down with respect to c -axis, perfectly canceling the net electrical polarization. Thus, the magnetoelectric coupling mechanism in DTN is likely a magnetostrictive adjustment of the thiourea molecule orientation in response to magnetic order. « less

  1. Modeling of plasma chemistry in an atmospheric pressure Ar/NH{sub 3} cylindrical dielectric barrier discharge described using the one-dimensional fluid model

    SciTech Connect (OSTI)

    Li Zhi [School of Science, University of Science and Technology Liaoning, Anshan 114051 (China); School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Zhao Zhen [School of Chemistry and Life Science, Anshan Normal University, Anshan 114007 (China); School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051 (China); Li Xuehui [Physical Science and Technical College, Dalian University, Dalian 116622 (China)

    2013-01-15

    The keynote of our research is to study the gas phase chemistry in an atmospheric pressure Ar/NH{sub 3} cylindrical dielectric barrier discharge, which is very important to produce the iron-nitride magnetic fluid. For this purpose, a home-made one dimensional fluid model with the Scharfetter-Gummel method has been developed. The equations solved are the particle balances, assuming a drift-diffusion approximation for the fluxes, and the electron energy equation. The self-consistent electric field is obtained by the simultaneous solution of Poisson's equation. The simulations were carried out for the different ammonia concentrations (2%, 3.5%, and 7%), at a voltage of 1 kV, and a driving frequency of 20 kHz. It concluded that the major ion products of Ar are Ar{sup +} and Ar{sub 2}{sup +}. Ar{sup +} is the most important positive ions, followed by Ar{sub 2}{sup +}. It is shown that the NH{sup +} density is smaller than that of the other ammonia ions. The density of NH{sub 4}{sup +} is more than that of the other ammonia ions when the ammonia concentration increased. The diffuse mode can be established after the discharge was ignited, and the mode changes to filamentary mode with an increase in ammonia concentration.

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

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

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

    2015-04-01

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

  3. Electrically pumped single-photon emission at room temperature from a single InGaN/GaN quantum dot

    SciTech Connect (OSTI)

    Deshpande, Saniya; Frost, Thomas; Hazari, Arnab; Bhattacharya, Pallab, E-mail: pkb@eecs.umich.edu [Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109 (United States)

    2014-10-06

    We demonstrate a semiconductor quantum dot based electrically pumped single-photon source operating at room temperature. Single photons emitted in the red spectral range from single In{sub 0.4}Ga{sub 0.6}N/GaN quantum dots exhibit a second-order correlation value g{sup (2)}(0) of 0.29, and fast recombination lifetime ?1.3 ±0.3 ns at room temperature. The single-photon source can be driven at an excitation repetition rate of 200?MHz.

  4. 1.9 kV AlGaN/GaN Lateral Schottky Barrier Diodes on Silicon

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

    Zhu, Mingda; Song, Bo; Qi, Meng; Hu, Zongyang; Nomoto, Kazuki; Yan, Xiaodong; Cao, Yu; Johnson, Wayne; Kohn, Erhard; Jena, Debdeep; et al

    2015-02-16

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

  5. Theory of weak localization in ferromagnetic (Ga,Mn)As 

    E-Print Network [OSTI]

    Garate, Ion; Sinova, Jairo; Jungwirth, T.; MacDonald, A. H.

    2009-01-01

    We study quantum interference corrections to the conductivity in (Ga,Mn)As ferromagnetic semiconductors using a model with disordered valence-band holes coupled to localized Mn moments through a p-d kinetic-exchange interaction. We find that at Mn...

  6. Low-temperature magnetization of (Ga,Mn) As semiconductors 

    E-Print Network [OSTI]

    Jungwirth, T.; Masek, J.; Wang, KY; Edmonds, KW; Sawicki, M.; Polini, M.; Sinova, Jairo; MacDonald, AH; Campion, RP; Zhao, LX; Farley, NRS; Johal, TK; van der Laan, G.; Foxon, CT; Gallagher, BL.

    2006-01-01

    the semiphenomenological virtual crystal model the valence band holes experience a mean-field hMF =JpdNMn?S , and the band Hamiltonian can then be written as H? MF=H? KL?B?+hMFs?z, where H? KL?B? is the B-dependent six- band Kohn-Luttinger Hamiltonian of the GaAs host...

  7. Ohmic contacts for high-temperature GaP devices 

    E-Print Network [OSTI]

    Van der Hoeven, Willem Bernard

    1981-01-01

    in Table II, heat treatments have also been made by laser. One of the earliest papers that describe laser annealing to obtain ohmic contacts to GaP appeared in 1974 (20] . In this paper, Pounds, Saifi, and Hahm reported to have obtained ohmic contacts...

  8. High-quality InP on GaAs

    E-Print Network [OSTI]

    Quitoriano, Nathaniel Joseph

    2006-01-01

    In addition to traditional telecommunication applications, devices based on InP have received increased attention for high-performance electronics. InP growth on GaAs is motivated by the fact that InP wafers are smaller, ...

  9. Nanoscale GaAs metalsemiconductormetal photodetectors fabricated using nanoimprint lithography

    E-Print Network [OSTI]

    ­V) characteristics of the contacts are very sensi- tive to the surface states and defects. In this letter, we report mold with interdigited fin- gers was first created on a silicon substrate. Next, a layer of polymethylmethancrylate PMMA was spun on a semi- insulating SI GaAs substrate. Before imprinting, both the mold

  10. Properties of H, O and C in GaN

    SciTech Connect (OSTI)

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

    1996-04-01

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

  11. Luminescence properties of defects in GaN

    SciTech Connect (OSTI)

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

    2005-03-15

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

  12. Testing a GaAs cathode in SRF gun

    SciTech Connect (OSTI)

    Wang, E.; Kewisch, J.; Ben-Zvi, I.; Burrill, A.; Rao, T.; Wu, Q.; Holmes, D.

    2011-03-28

    RF electron guns with a strained superlattice GaAs cathode are expected to generate polarized electron beams of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface and lower cathode temperature. We plan to install a bulk GaAs:Cs in a SRF gun to evaluate the performance of both the gun and the cathode in this environment. The status of this project is: In our 1.3 GHz 1/2 cell SRF gun, the vacuum can be maintained at nearly 10{sup -12} Torr because of cryo-pumping at 2K. With conventional activation of bulk GaAs, we obtained a QE of 10% at 532 nm, with lifetime of more than 3 days in the preparation chamber and have shown that it can survive in transport from the preparation chamber to the gun. The beam line has been assembled and we are exploring the best conditions for baking the cathode under vacuum. We report here the progress of our test of the GaAs cathode in the SRF gun. Future particle accelerators, such as eRHIC and the ILC require high-brightness, high-current polarized electrons. Strained superlattice GaAs:Cs has been shown to be an efficient cathode for producing polarized electrons. Activation of GaAs with Cs,O(F) lowers the electron affinity and makes it energetically possible for all the electrons, excited into the conduction band that drift or diffuse to the emission surface, to escape into the vacuum. Presently, all operating polarized electron sources, such as the CEBAF, are DC guns. In these devices, the excellent ultra-high vacuum extends the lifetime of the cathode. However, the low field gradient on the photocathode's emission surface of the DC guns limits the beam quality. The higher accelerating gradients, possible in the RF guns, generate a far better beam. Until recently, most RF guns operated at room temperature, limiting the vacuum to {approx}10{sup -9} Torr. This destroys the GaAs's NEA surface. The SRF guns combine the excellent vacuum conditions of DC guns and the high accelerating gradient of the RF guns, potentially offering a long lived cathode with very low emittance. Testing this concept requires preparation of the cathode, transportation to the SRF gun and evaluation of the performance of the cathode and the gun at cryogenic temperatures. In our work at BNL, we successfully activated the bulk GaAs in the preparation chamber. The highest quantum efficient was 10% at 532 nm that fell to 0.5% after 100 hours. We explored three different ways to activate the GaAs. We verified that the GaAs photocathode remains stable for 30 hours in a 10{sup -11} Torr vacuum. Passing the photocathode through the low 10{sup -9} Torr transfer section in several seconds caused the QE to drop to 0.8%. The photocathode with 0.8% QE can be tested for the SRF gun. The gun and beam pipe were prepared and assembled. After baking at 200 C baking, the vacuum of the gun and beam pipe can sustain a low 10{sup -11} Torr at room temperature. The final test to extract electrons from the gun is ongoing. In this paper, we discuss our progress with this SRF gun and the results of the photocathode in preparation chamber and in magnet transfer line.

  13. Quaternary InGaAsSb Thermophotovoltaic Diodes

    SciTech Connect (OSTI)

    MW Dashiell; JF Beausang; H Ehsani; GJ Nichols; DM Depoy; LR Danielson; P Talamo; KD Rahner; EJ Brown; SR Burger; PM Foruspring; WF Topper; PF Baldasaro; CA Wang; R Huang; M Connors; G Turner; Z Shellenbarger; G Taylor; J Li; R Martinelli; D Donetski; S Anikeev; G Belenky; S Luryi

    2006-03-09

    In{sub x}Ga{sub 1-x}As{sub y}Sb{sub 1-y} thermophotovoltaic (TPV) diodes were grown lattice-matched to GaSb substrates by Metal Organic Vapor Phase Epitaxy (MOVPE) in the bandgap range of E{sub G} = 0.5 to 0.6eV. InGaAsSb TPV diodes, utilizing front-surface spectral control filters, are measured with thermal-to-electric conversion efficiency and power density of {eta}{sub TPV} = 19.7% and PD =0.58 W/cm{sup 2} respectively for a radiator temperature of T{sub radiator} = 950 C, diode temperature of T{sub diode} = 27 C, and diode bandgap of E{sub G} = 0.53eV. Practical limits to TPV energy conversion efficiency are established using measured recombination coefficients and optical properties of front surface spectral control filters, which for 0.53eV InGaAsSb TPV energy conversion is {eta}{sub TPV} = 28% and PD = 0.85W/cm{sup 2} at the above operating temperatures. The most severe performance limits are imposed by (1) diode open-circuit voltage (VOC) limits due to intrinsic Auger recombination and (2) parasitic photon absorption in the inactive regions of the module. Experimentally, the diode V{sub OC} is 15% below the practical limit imposed by intrinsic Auger recombination processes. Analysis of InGaAsSb diode electrical performance vs. diode architecture indicate that the V{sub OC} and thus efficiency is limited by extrinsic recombination processes such as through bulk defects.

  14. Remarkably reduced efficiency droop by using staircase thin InGaN quantum barriers in InGaN based blue light emitting diodes

    SciTech Connect (OSTI)

    Zhou, Kun; Ikeda, Masao, E-mail: mikeda2013@sinano.ac.cn, E-mail: jpliu2010@sinano.ac.cn; Liu, Jianping, E-mail: mikeda2013@sinano.ac.cn, E-mail: jpliu2010@sinano.ac.cn; Zhang, Shuming; Li, Deyao; Zhang, Liqun; Yang, Hui [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou (China); Key Laboratory of Nanodevices and Applications, Chinese Academy of Sciences, Suzhou (China); Cai, Jin; Wang, Hui; Wang, H. B. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou (China); Key Laboratory of Nanodevices and Applications, Chinese Academy of Sciences, Suzhou (China); Suzhou Nanojoin Photonics Co., Ltd., Suzhou (China)

    2014-10-27

    The efficiency droop of InGaN/GaN(InGaN) multiple quantum well (MQW) light emitting diodes (LEDs) with thin quantum barriers (QB) is studied. With thin GaN QB (3?nm–6?nm thickness), the efficiency droop is not improved, which indicates that hole transport cannot be significantly enhanced by the thin GaN QBs. On the contrary, the efficiency droop was remarkably reduced by using a InGaN staircase QB (InGaN SC-QB) MQWs structure where InGaN SC-QBs lower the transport energy barrier of holes. The efficiency droop ratio was as low as 3.3% up to 200?A/cm{sup 2} for the InGaN SC-QB LED. By using monitoring QW with longer wavelength we observe a much uniform carrier distribution in the InGaN SC-QB LEDs, which reveals the mechanism of improvement in the efficiency droop.

  15. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub2}.

    SciTech Connect (OSTI)

    Peter, S. C.; Malliakas, C. D.; Nakotte, H.; Kothapilli, K.; Rayaprol, S.; Schultz, A. J.; Kanatzidis, M. G. (Materials Science Division); ( XSD); (Northwestern Univ.); (Jawaharlal Nehru Centre for Adv. Sci. Res.); (New Mexico State Univ.); (Los Alamos Nat. Lab.); (UGC-DAE Consortium for Sci. Res.)

    2012-03-01

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a = 12.2261(20) {angstrom}, b = 10.7447(20) {angstrom}, c = 8.4754(17) {angstrom} and {beta} = 110.288(30){sup o} (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge)n. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a = b = 5.9874(6) {angstrom} and c = 15.1178(19) {angstrom}. The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{alpha}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures.

  16. Nonlinear Terahertz Metamaterials via Field-Enhanced Carrier Dynamics in GaAs

    E-Print Network [OSTI]

    Fan, Kebin

    We demonstrate nonlinear metamaterial split ring resonators (SRRs) on GaAs at terahertz frequencies. For SRRs on doped GaAs films, incident terahertz radiation with peak fields of ?20–160??kV/cm drives intervalley scattering. ...

  17. Device-level thermal analysis of GaN-based electronics

    E-Print Network [OSTI]

    Bagnall, Kevin Robert

    2013-01-01

    Gallium nitride (GaN)-based microelectronics are one of the most exciting semiconductor technologies for high power density and high frequency electronics. The excellent electrical properties of GaN and its related alloys ...

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

    E-Print Network [OSTI]

    Zhou, Xiang

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

  19. Inves&ga&ng the Trade-Off between Luminous Efficacy of Radia&on

    E-Print Network [OSTI]

    California at Davis, University of

    Inves&ga&ng the Trade-Off between Luminous Efficacy of Radia&on and Color, Canada · Lorne Whitehead, Canada #12;Inves&ga&ng the Trade-Off between Luminous

  20. Characterization of NIR InGaAs imager arrays for the JDEM SNAP mission concept

    E-Print Network [OSTI]

    2006-01-01

    Characterization of NIR InGaAs imager arrays for the JDEMapplications. Keywords: NIR, InGaAs, astronomy, low-1.7um band Near Infrared (NIR) focal plane mosaic with high

  1. Atomic structure of postgrowth annealed epitaxial Fe/(001)GaAs interfaces

    E-Print Network [OSTI]

    LeBeau, James; Hu, Qi O.; Palmstrom, Christopher; Stemmer, Susanne

    2008-01-01

    line pro?le across the interface along the line indicated inHAADF images of the GaAs/Fe interface along ?a? ?11 0? GaAsindicates the location of an interface step. Arrows in ?b?

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

    SciTech Connect (OSTI)

    Bia?ek, M. Witowski, A. M.; Grynberg, M.; ?usakowski, J.; Orlita, M.; Potemski, M.; Czapkiewicz, M.; Umansky, V.

    2014-06-07

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

  3. On the redox origin of surface trapping in AlGaN/GaN high electron mobility transistors

    SciTech Connect (OSTI)

    Gao, Feng; Chen, Di; Tuller, Harry L.; Thompson, Carl V.; Palacios, Tomás

    2014-03-28

    Water-related redox couples in ambient air are identified as an important source of the surface trapping states, dynamic on-resistance, and drain current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). Through in-situ X-ray photoelectron spectroscopy (XPS), direct signature of the water-related species—hydroxyl groups (OH) was found at the AlGaN surface at room temperature. It was also found that these species, as well as the current collapse, can be thermally removed above 200?°C in vacuum conditions. An electron trapping mechanism based on the H{sub 2}O/H{sub 2} and H{sub 2}O/O{sub 2} redox couples is proposed to explain the 0.5?eV energy level commonly attributed to the surface trapping states. Finally, the role of silicon nitride passivation in successfully removing current collapse in these devices is explained by blocking the water molecules away from the AlGaN surface.

  4. High 400?°C operation temperature blue spectrum concentration solar junction in GaInN/GaN

    SciTech Connect (OSTI)

    Zhao, Liang; Detchprohm, Theeradetch; Wetzel, Christian

    2014-12-15

    Transparent wide gap junctions suitable as high temperature, high flux topping cells have been achieved in GaInN/GaN by metal-organic vapor phase epitaxy. In structures of 25 quantum wells (QWs) under AM1.5G illumination, an open circuit voltage of 2.1?V is achieved. Of the photons absorbed in the limited spectral range of <450?nm, 64.2% are converted to electrons collected at the contacts under zero bias. At a fill factor of 45%, they account for a power conversion efficiency of38.6%. Under concentration, the maximum output power density per sun increases from 0.49?mW/cm{sup 2} to 0.51?mW/cm{sup 2} at 40?suns and then falls 0.42?mW/cm{sup 2} at 150?suns. Under external heating, a maximum of 0.59?mW/cm{sup 2} is reached at 250?°C. Even at 400?°C, the device is fully operational and exceeds room temperature performance. A defect analysis suggests that significantly higher fill factors and extension into longer wavelength ranges are possible with further development. The results prove GaInN/GaN QW solar junctions a viable and rugged topping cell for concentrator photovoltaics with minimal cooling requirements. By capturing the short range spectrum, they reduce the thermal load to any conventional cells stacked behind.

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

    E-Print Network [OSTI]

    quantum wells (QW)s,1) and InAs quantum dots at 1.3 mm2) have brought about the commercialization of Ga differential quantum efficiency, T-zero and far field as a function of stripe width. # 2009 The Japan Society offer a number of advantages over their InP counterparts, namely the use of larger substrates (>3 in

  6. Highly Ordered Ga Nanodroplets on a GaAs Surface Formed by a Focused Ion Beam Qiangmin Wei,1

    E-Print Network [OSTI]

    Lu, Wei

    quantum dots by low-energy ion sputtering on a surface has been reported in several semiconductor sys quantum dots on the surface. The mechanism involves the balance between roughening and smoothing actions], Ge [10], as well as a variety of III­V compounds (GaSb [11], InP [12], and InSb [13]) can form

  7. Comparison of electrostatic and localized plasmon induced light enhancement in hybrid InGaN/GaN quantum wells

    SciTech Connect (OSTI)

    Lin, Jie; Llopis, Antonio; Krokhin, Arkadii; Neogi, Arup, E-mail: arup@unt.edu [Department of Physics, University of North Texas, Denton, Texas 76203 (United States); Pereira, Sergio [CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Watson, Ian M. [SUPA, Institute of Photonics, University of Strathclyde, Glasgow (United Kingdom)

    2014-06-16

    The light enhancement phenomena in InGaN/GaN multi-quantum wells (MQWs) infiltrated with metal nanoparticles (NPs) are studied using resonant and off-resonant localized plasmon interactions. The emission and recombination characteristics of carriers in InGaN/GaN MQW structures with inverted hexagonal pits (IHPs) are modified distinctly depending on the nature of their interaction with the metal NPs and with the pumping and emitted photons. It is observed that the emission intensity of light is significantly enhanced when the emission energy is off-resonant to the localized plasmon frequency of the metal nanoparticles. This results in enhanced emission from MQW due to Au nanoparticles and from IHPs due to Ag nanoparticles. At resonant-plasmon frequency of the Ag NPs, the emission from MQWs is quenched due to the re-absorption of the emitted photons, or due to the drift carriers from c-plane MQWs towards the NPs because of the Coulomb forces induced by the image charge effect.

  8. Molecular Dynamics Simulation of GaAs Molecular Beam Epitaxy D. A. Murdick,1

    E-Print Network [OSTI]

    Wadley, Haydn

    of Virginia, Charlottesville, Virginia 22904, USA 2 Department of Materials, University of Oxford, Oxford OX1 3PH, UK ABSTRACT The vapor deposition of epitaxial GaAs and (Ga,Mn)As thin films during far-temperature growth of Ga0.94Mn0.06As and the Mn clustering trends in as-grown films. INTRODUCTION GaAs is widely used

  9. GaN Initiative for Grid Applications (GIGA)

    SciTech Connect (OSTI)

    Turner, George

    2015-07-03

    For nearly 4 ½ years, MIT Lincoln Laboratory (MIT/LL) led a very successful, DoE-funded team effort to develop GaN-on-Si materials and devices, targeting high-voltage (>1 kV), high-power, cost-effective electronics for grid applications. This effort, called the GaN Initiative for Grid Applications (GIGA) program, was initially made up of MIT/LL, the MIT campus group of Prof. Tomas Palacios (MIT), and the industrial partner M/A Com Technology Solutions (MTS). Later in the program a 4th team member was added (IQE MA) to provide commercial-scale GaN-on-Si epitaxial materials. A basic premise of the GIGA program was that power electronics, for ubiquitous utilization -even for grid applications - should be closer in cost structure to more conventional Si-based power electronics. For a number of reasons, more established GaN-on-SiC or even SiC-based power electronics are not likely to reach theses cost structures, even in higher manufacturing volumes. An additional premise of the GIGA program was that the technical focus would be on materials and devices suitable for operating at voltages > 1 kV, even though there is also significant commercial interest in developing lower voltage (< 1 kV), cost effective GaN-on-Si devices for higher volume applications, like consumer products. Remarkable technical progress was made during the course of this program. Advances in materials included the growth of high-quality, crack-free epitaxial GaN layers on large-diameter Si substrates with thicknesses up to ~5 ?m, overcoming significant challenges in lattice mismatch and thermal expansion differences between Si and GaN in the actual epitaxial growth process. Such thick epilayers are crucial for high voltage operation of lateral geometry devices such as Schottky barrier (SB) diodes and high electron mobility transistors (HEMTs). New “Normally-Off” device architectures were demonstrated – for safe operation of power electronics circuits. The trade-offs between lateral and vertical devices were explored, with the conclusion that lateral devices are superior for fundamental thermal reasons, as well as for the demonstration of future generations of monolithic power circuits. As part of the materials and device investigations breakdown mechanisms in GaN-on-Si structures were fully characterized and effective electric field engineering was recognized as critical for achieving even higher voltage operation. Improved device contact technology was demonstrated, including the first gold-free metallizations (to enable processing in CMOS foundries) while maintaining low specific contact resistance needed for high-power operation and 5-order-of magnitude improvement in device leakage currents (essential for high power operation). In addition, initial GaN-on-Si epitaxial growth was performed on 8”/200 mm Si starting substrates.

  10. DISSERTATION ANTICIPATED PERFORMANCE OF Cu(In,Ga)Se2 SOLAR CELLS IN THE

    E-Print Network [OSTI]

    Sites, James R.

    i DISSERTATION ANTICIPATED PERFORMANCE OF Cu(In,Ga)Se2 SOLAR CELLS IN THE THIN-FILM LIMIT Submitted ENTITLED `ANTICIPATED PERFORMANCE OF Cu(In,Ga)Se2 SOLAR CELLS IN THE THIN-FILM LIMIT' BE ACCEPTED(In,Ga)Se2 SOLAR CELLS IN THE THIN-FILM LIMIT The demand for alternative sources of energy is rapidly

  11. TESLA-FEL 2007-03 Application of low cost GaAs LED as neutron

    E-Print Network [OSTI]

    neutrons in unbiased Gallium Arsenide (GaAs) Light Emitting Diodes (LED) resulted in a reduction Keywords: COTS components, Displacement damage, Electron Linear Accelerator, GaAs Light emitting diode (LED) Gallium Arsenide (GaAs) light emitting diode (LED) for the assessment of integrated neutron fluence

  12. Surface plasmon enhanced InGaN light emitter Koichi Okamoto*a

    E-Print Network [OSTI]

    Okamoto, Koichi

    is a very promising method for developing the super bright light emitting diodes (LEDs). Moreover, we foundGaN/GaN, light emitting diode, quantum well, internal quantum efficiency, solid-state light source 1. INTRODUCTION Since 1993, InGaN quantum wells (QW)-based light emitting diodes (LEDs) have been continuously

  13. Near perfect solar absorption in ultra-thin-film GaAs photonic crystals

    E-Print Network [OSTI]

    John, Sajeev

    Near perfect solar absorption in ultra-thin-film GaAs photonic crystals Sergey Eyderman,*a Alexei voltage of GaAs solar cells. The current world record for high efficiency solar cells is held by thin ultra-thin (GaAs in low-cost solar cells. However, this reduction in the volume

  14. ORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission

    E-Print Network [OSTI]

    Polman, Albert

    a non-concentrating system with limited emission angle in a thin, light trapping GaAs solar cellORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission angle Emily D Kosten1 of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38

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

    E-Print Network [OSTI]

    Feenstra, Randall

    in the growth rate of GaN on different crystallographic planes [8], pointing to a surfactant effect of Mg on Ga in these films and the carrier concentration was therefore very low [1,2]; dopant activa- tion can be achieved of Mg at GaN growth temperatures is an issue and dopant in- corporation may be rather inefficient [5

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

    SciTech Connect (OSTI)

    Cheng, Junjie; Li, Jiadong; Miao, Bin; Wu, Dongmin; Wang, Jine; Pei, Renjun; Wu, Zhengyan

    2014-08-25

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

  17. An inverted AlGaAs/GaAs patterned-Ge tunnel junction cascade concentrator solar cell. Final subcontract report, 1 January 1991--31 August 1992

    SciTech Connect (OSTI)

    Venkatasubramanian, R.

    1993-01-01

    This report describes work to develop inverted-grown Al{sub 0.34}Ga{sub 0.66}As/GaAs cascades. Several significant developments are reported on as follows: (1) The AM1.5 1-sun total-area efficiency of the top Al{sub 0.34}Ga{sub 0.66}As cell for the cascade was improved from 11.3% to 13.2% (NREL measurement [total-area]). (2) The ``cycled`` organometallic vapor phase epitaxy growth (OMVPE) was studied in detail utilizing a combination of characterization techniques including Hall-data, photoluminescence, and secondary ion mass spectroscopy. (3) A technique called eutectic-metal-bonding (EMB) was developed by strain-free mounting of thin GaAs-AlGaAs films (based on lattice-matched growth on Ge substrates and selective plasma etching of Ge substrates) onto Si carrier substrates. Minority-carrier lifetime in an EMB GaAs double-heterostructure was measured as high as 103 nsec, the highest lifetime report for a freestanding GaAs thin film. (4) A thin-film, inverted-grown GaAs cell with a 1-sun AM1.5 active-area efficiency of 20.3% was obtained. This cell was eutectic-metal-bonded onto Si. (5) A thin-film inverted-grown, Al{sub 0.34}Ga{sub 0.66}As/GaAs cascade with AM1.5 efficiency of 19.9% and 21% at 1-sun and 7-suns, respectively, was obtained. This represents an important milestone in the development of an AlGaAs/GaAs cascade by OMVPE utilizing a tunnel interconnect and demonstrates a proof-of-concept for the inverted-growth approach.

  18. Nanoscale selective area growth of thick, dense, uniform, In-rich, InGaN nanostructure arrays on GaN/sapphire template

    SciTech Connect (OSTI)

    Sundaram, S.; El Gmili, Y.; Bonanno, P. L. [CNRS, UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Puybaret, R.; Li, X.; Voss, P. L.; Ougazzaden, A. [Georgia Institute of Technology, UMI 2958 Georgia Tech - CNRS, 57070 Metz (France); Pantzas, K.; Patriarche, G. [CNRS, UPR LPN, Route de Nozay, 91460 Marcoussis (France); Orsal, G.; Salvestrini, J. P., E-mail: salvestr@metz.supelec.fr [Université de Lorraine, Supélec, LMOPS, EA4423, 57070 Metz (France); Troadec, D. [Université des Sciences et Technologies de Lille, CNRS, UMR 8520 IEMN, 59000 Lille (France); Cai, Z.-H. [Advanced Photon Source, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2014-10-28

    Uniform, dense, single-phase, 150?nm thick indium gallium nitride (InGaN) nanostructure (nanorods and nanostripes) arrays have been obtained on gallium nitride templates, by metal organic chemical vapor deposition and nanoscale selective area growth on silicon dioxide patterned masks. The 150?nm thick InGaN nanorods have a perfect hexagonal pyramid shape with relatively homogenous indium concentration up to 22%, which is almost twice as high as in planar InGaN grown in the same condition, and luminesce at 535?nm. InGaN nanostripes feature c-axis oriented InGaN in the core which is covered by InGaN grown along semi-polar facets with higher In content. Transmission electron microscope and sub micron beam X-rays diffraction investigations confirm that both InGaN nanostructures are mostly defect free and monocrystalline. The ability to grow defect-free thick InGaN nanostructures with reduced polarization and high indium incorporation offers a solution to develop high efficiency InGaN-based solar cells.

  19. Method of plasma etching GA-based compound semiconductors

    DOE Patents [OSTI]

    Qiu, Weibin; Goddard, Lynford L.

    2013-01-01

    A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl.sub.4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.

  20. Method of plasma etching Ga-based compound semiconductors

    DOE Patents [OSTI]

    Qiu, Weibin; Goddard, Lynford L.

    2012-12-25

    A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent to the process chamber. The process chamber contains a sample comprising a Ga-based compound semiconductor. The sample is in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. The method includes flowing SiCl.sub.4 gas into the chamber, flowing Ar gas into the chamber, and flowing H.sub.2 gas into the chamber. RF power is supplied independently to the source electrode and the platen. A plasma is generated based on the gases in the process chamber, and regions of a surface of the sample adjacent to one or more masked portions of the surface are etched to create a substantially smooth etched surface including features having substantially vertical walls beneath the masked portions.

  1. AlGaAs-On-Insulator Nonlinear Photonics

    E-Print Network [OSTI]

    Pu, Minhao; Semenova, Elizaveta; Yvind, Kresten

    2015-01-01

    The combination of nonlinear and integrated photonics has recently seen a surge with Kerr frequency comb generation in micro-resonators as the most significant achievement. Efficient nonlinear photonic chips have myriad applications including high speed optical signal processing, on-chip multi-wavelength lasers, metrology, molecular spectroscopy, and quantum information science. Aluminium gallium arsenide (AlGaAs) exhibits very high material nonlinearity and low nonlinear loss when operated below half its bandgap energy. However, difficulties in device processing and low device effective nonlinearity made Kerr frequency comb generation elusive. Here, we demonstrate AlGaAs-on-insulator as a nonlinear platform at telecom wavelengths. Using newly developed fabrication processes, we show high-quality-factor (Q>100,000) micro-resonators with integrated bus waveguides in a planar circuit where optical parametric oscillation is achieved with a record low threshold power of 3 mW and a frequency comb spanning 350 nm i...

  2. Formation and properties of porous GaAs

    SciTech Connect (OSTI)

    Schmuki, P.; Lockwood, D.J.; Fraser, J.W.; Graham, M.J.; Isaacs, H.S.

    1996-06-01

    Porous structures on n-type GaAs (100) can be grown electrochemically in chloride-containing solutions. Crystallographic etching of the sample is a precursor stage of the attack. Polarization curves reveal the existanece of a critical onset potential for por formation (PFP). PFP is strongly dependent on the doping level of the sample and presence of surface defects. Good agreement between PFP and breakdown voltage of the space charge layer is found. Surface analysis by EDX, AES, and XPS show that the porous structure consists mainly of GaAs and that anion uptake in the structure can only observed after attackhas been initiated. Photoluminescence measurements reveal (under certain conditions) visible light emission from the porous structure.

  3. Exploiting parameter space in MOFs: a 20-fold enhancement of phosphate-ester hydrolysis with UiO-66-NH 2

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

    Katz, Michael J.; Moon, Su-Young; Mondloch, Joseph E.; Beyzavi, M. Hassan; Stephenson, Casey J.; Hupp, Joseph T.; Farha, Omar K.

    2015-02-24

    The hydrolysis of nerve agents is of primary concern due to the severe toxicity of these agents. Using a MOF-based catalyst (UiO-66), we have previously demonstrated that the hydrolysis can occur with relatively fast half-lives of 50 minutes. However, these rates are still prohibitively slow to be efficiently utilized for some practical applications (e.g., decontamination wipes used to clean exposed clothing/skin/vehicles). We thus turned our attention to derivatives of UiO-66 in order to probe the importance of functional groups on the hydrolysis rate. Three UiO-66 derivatives were explored; UiO-66-NO2 and UiO-66-(OH)2 showed little to no change in hydrolysis rate. However,more »UiO-66-NH2 showed a 20 fold increase in hydrolysis rate over the parent UiO-66 MOF. Half-lives of 1 minute were observed with this MOF. In order to probe the role of the amino moiety, we turned our attention to UiO-67, UiO-67-NMe2 and UiO-67-NH2. In these MOFs, the amino moiety is in close proximity to the zirconium node. We observed that UiO-67-NH2 is a faster catalyst than UiO-67 and UiO-67-NMe2. We conclude that the role of the amino moiety is to act as a proton-transfer agent during the catalytic cycle and not to hydrogen bond or to form a phosphorane intermediate.« less

  4. Influence of n-type versus p-type AlGaN electron-blocking layer on InGaN/GaN multiple quantum wells light-emitting diodes

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    to be further improved in order for the high- power LEDs to penetrate into the consumer market of gen- eral to higher optical output power and external quantum efficiency, compared to the devices with p-AlGaN EBLGaN/GaN based light-emitting diodes (LEDs) possess unique advantages including high energy conversion effi

  5. The transputer based GA. SP data acquisition system

    SciTech Connect (OSTI)

    Colombo, D.; Avano, B.; DePoli, M.; Maron, G. ); Negro, A.; Parlati, G. )

    1992-04-01

    In this paper, the new data acquisition for the GA.SP detector is presented. It is a distributed system based on a network of 40 T800 and T222 transputers linked to a VME system used for histogram storage. A 100 MBit/s FDDI ring connects the system to UNIX workstations used for the experiment control, histogram display and second level data analysis.

  6. Minority-carrier properties of GaAs on silicon

    SciTech Connect (OSTI)

    Ahrenkiel, R.K.; Al-Jassim, M.M.; Dunlavy, D.J.; Jones, K.M.; Vernon, S.M.; Tobin, S.P.; Haven, V.E.

    1988-07-18

    The minority-carrier lifetimes of the heteroepitaxial system of GaAs on Si are limited by recombination at mismatch dislocations. Here we show that increasing the thickness of the buffer layer, with an additional annealing step, reduces the dislocation density by about an order of magnitude. At the same time, the minority-carrier lifetime in these double heterostructures increases more than an order of magnitude.

  7. Ohmic contacts to p-type Ga

    E-Print Network [OSTI]

    Jorge Estevez, Humberto Angel

    1996-01-01

    resistivity was achieved by developing the Si(750A)/Pd(400A)/Zn(xA)/Pd(IOOA)/p-GaP scheme. Values of the contact resistivity in the range of 3xlO-5 to 7xlO-' nCM2 were obtained. It was found that the optimum Zn layer thickness is 30 A for the Pd and Si...

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

    DOE Patents [OSTI]

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

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

  9. Continued development of metallization for GaAs concentrator cells

    SciTech Connect (OSTI)

    Tobin, S.P.

    1988-11-01

    The objective of this work was the integration of thermally stable metallizations with a high-efficiency GaAs concentrator cell process. For p-GaAs we used a Pt-TiN-Au metallization developed under a previous Sandia Contract. For n-GaAs the best results were obtained for AuGe-TiN-Au. Baseline p/n cells with a CrAu metallization achieved efficiencies of 25.4% at 200 suns. Efficiencies were about 22% at one sun. At one sun, p/n cells with high-temperature contacts were 22.2% efficient, showing that there is no efficiency penalty with the high-temperature metallization. Development efforts on n/p cells yielded high short-circuit currents and open-circuit voltages, with both conventional and high-temperature metallizations. Thermal annealing tests showed that cells with the Pt-TiN-Au metallization were more stable than those with the baseline metallization, withstanding a 15-minute anneal at 500/degree/C with negligible efficiency degradation. 22 refs., 64 figs., 54 tabs.

  10. InGaAsSb thermophotovoltaic diode physics evaluation

    SciTech Connect (OSTI)

    Charache, G.W.; Baldasaro, P.F.; Danielson, L.R. [Lockheed-Martin, Inc., Schenectady, NY (United States)] [and others

    1998-06-01

    The hotside operating temperatures for many projected thermophotovoltaic (TPV) conversion system applications are approximately 1,000 C, which sets an upper limit on the TPV diode bandgap of 0.6 eV from efficiency and power density considerations. This bandgap requirement has necessitated the development of new diode material systems, never previously considered for energy generation. To date, InGaAsSb quaternary diodes grown lattice-matched on GaSb substrates have achieved the highest performance. This report relates observed diode performance to electro-optic properties such as minority carrier lifetime, diffusion length and mobility and provides initial links to microstructural properties. This analysis has bounded potential diode performance improvements. For the 0.52 eV InGaAsSb diodes used in this analysis the measured dark current is 2 {times} 10{sup {minus}5} A/cm{sup 2}, versus a potential Auger limit 1 {times} 10{sup {minus}5} A/cm{sup 2}, a radiative limit of 2 {times} 10{sup {minus}6} A/cm{sup 2} (no photon recycling), and an absolute thermodynamic limit of 1.4 {times} 10{sup {minus}7} A/cm{sup 2}. These dark currents are equivalent to open circuit voltage gains of 20 mV (7%), 60 mV (20%) and 140 mV (45%), respectively.

  11. Ga lithography in sputtered niobium for superconductive micro and nanowires

    SciTech Connect (OSTI)

    Henry, M. David; Wolfley, Steve; Monson, Todd; Lewis, Rupert

    2014-08-18

    This work demonstrates the use of focused ion beam (FIB) implanted Ga as a lithographic mask for plasma etching of Nb films. Using a highly collimated Ga beam of a FIB, Nb is implanted 12?nm deep with a 14?nm thick Ga layer providing etch selectivity better than 15:1 with fluorine based etch chemistry. Implanted square test patterns, both 10??m by 10??m and 100??m by 100??m, demonstrate that doses above than 7.5?×?10{sup 15?}cm{sup ?2} at 30?kV provide adequate mask protection for a 205?nm thick, sputtered Nb film. The resolution of this dry lithographic technique is demonstrated by fabrication of nanowires 75?nm wide by 10??m long connected to 50??m wide contact pads. The residual resistance ratio of patterned Nb films was 3. The superconducting transition temperature (T{sub c})?=?7.7?K was measured using a magnetic properties measurement system. This nanoscale, dry lithographic technique was extended to sputtered TiN and Ta here and could be used on other fluorine etched superconductors such as NbN, NbSi, and NbTi.

  12. Preparation of Single Phase Films of CH3NH3Pb(I1-xBrx)3 with Sharp Optical Band Edges

    E-Print Network [OSTI]

    Sadhanala, Aditya; Deschler, Felix; Thomas, Tudor H; Dutton, Siân E.; Goedel, Karl C.; Hanusch, Fabian C.; Lai, May L.; Steiner, Ullrich; Bein, Thomas; Docampo, Pablo; Cahen, David; Friend, Richard H.

    2014-07-09

    ?inorganic perovskite (CH3NH3PbI3?xClx) solar cells now show photovoltaic (PV) performance1?4 approaching 18%,5,6 and high charge-carrier mobilities.7 Perovskite films have also shown promising photoluminescence quantum efficiencies (PLQEs) of more than 70% and lasing... .; Grat?zel, M.; Mhaisalkar, S.; Sum, T. C. Low-Temperature Solution- Processed Wavelength-Tunable Perovskites for Lasing. Nat. Mater. 2014, 13, 476?480. (9) Deschler, F.; Price, M.; Pathak, S.; Klintberg, L. E.; Jarausch, D.- D.; Higler, R.; Hu?ttner, S...

  13. Synthesis and Evaluation of Cu/SAPO-34 Catalysts for NH3-SCR 2: Solid-state Ion Exchange and One-pot Synthesis

    SciTech Connect (OSTI)

    Gao, Feng; Walter, Eric D.; Washton, Nancy M.; Szanyi, Janos; Peden, Charles HF

    2015-01-01

    Cu-SAPO-34 catalysts are synthesized using two methods: solid-state ion exchange (SSIE) and one-pot synthesis. SSIE is conducted by calcining SAPO-34/CuO mixtures at elevated temperatures. For the one-pot synthesis method, Cu-containing chemicals (CuO and CuSO4) are added during gel preparation. A high-temperature calcination step is also needed for this method. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies, and scanning electron microscopy (SEM). Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3-SCR) and ammonia oxidation reactions. In Cu-SAPO-34 samples formed using SSIE, Cu presents both as isolated Cu2+ ions and unreacted CuO. The former is highly active and selective in NH3-SCR, while the latter catalyzes a side reaction; notably, the non-selective oxidation of NH3 above 350 ºC. Using the one-pot method followed by a high-temperature aging treatment, it is possible to form Cu SAPO-34 samples with predominately isolated Cu2+ ions at low Cu loadings. However at much higher Cu loadings, isolated Cu2+ ions that bind weakly with the CHA framework and CuO clusters also form. These Cu moieties are very active in catalyzing non-selective NH3 oxidation above 350 ºC. Low-temperature reaction kinetics indicate that Cu-SAPO-34 samples formed using SSIE have core-shell structures where Cu is enriched in the shell layers; while Cu is more evenly distributed within the one-pot samples. Reaction kinetics also suggest that at low temperatures, the local environment next to Cu2+ ion centers plays little role on the overall catalytic properties. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle under contract number DE-AC05-76RL01830. The authors also thank Shari Li (PNNL) for surface area/pore volume measurements, and Bruce W. Arey (PNNL) for SEM measurements. Discussions with Drs. A. Yezerets, K. Kamasamudram, J.H. Li, N. Currier and J.Y. Luo from Cummins, Inc. and H.Y. Chen and H. Hess from Johnson-Matthey are greatly appreciated.

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

    SciTech Connect (OSTI)

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

    2013-12-09

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

  15. Gallium hole traps in irradiated KTiOPO{sub 4}:Ga crystals

    SciTech Connect (OSTI)

    Grachev, V.; Meyer, M.; Malovichko, G.; Hunt, A. W.

    2014-12-07

    Nominally pure and gallium doped single crystals of potassium titanyl phosphate (KTiOPO{sub 4}) have been studied by Electron Paramagnetic Resonance at low temperatures before and after irradiation. Irradiation with 20?MeV electrons performed at room temperature and liquid nitrogen temperature caused an appearance of electrons and holes. Gallium impurities act as hole traps in KTiOPO{sub 4} creating Ga{sup 4+} centers. Two different Ga{sup 4+} centers were observed, Ga1 and Ga2. The Ga1 centers are dominant in Ga-doped samples. For the Ga1 center, a superhyperfine structure with one nucleus with nuclear spin ½ was registered and attributed to the interaction of gallium electrons with a phosphorus nucleus or proton in its surrounding. In both Ga1 and Ga2 centers, Ga{sup 4+} ions substitute for Ti{sup 4+} ions, but with a preference to one of two electrically distinct crystallographic positions (site selective substitution). The Ga doping eliminates one of the shortcomings of KTP crystals—ionic conductivity of bulk crystals. However, this does not improve significantly the resistance of the crystals to electron and ?-radiation.

  16. Efficiency calculations of thin-film GaAs solar cells on Si substrates

    SciTech Connect (OSTI)

    Yamaguchi, M.; Amano, C.

    1985-11-01

    Dislocation effect upon the efficiency of single-crystal thin-film AlGaAs-GaAs heteroface solar cells on Si substrates is analyzed. Solar-cell properties are calculated based on a simple model; in the model, dislocations act as recombination centers to reduce the minority-carrier diffusion length in each layer and increase the space-charge layer recombination current. Numerical analysis is also carried out to optimize thin-film AlGaAs-GaAs heteroface solar-cell structures. The fabrication of thin-film AlGaAs-GaAs heteroface solar cells with a practical efficiency larger than 18% on Si substrates appears possible if the dislocation density in the thin-film GaAs layer is less than 10/sup 6/ cm/sup -2/.

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

    SciTech Connect (OSTI)

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

    2012-10-01

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

  18. Electron heating due to microwave photoexcitation in the high mobility GaAs/AlGaAs two dimensional electron system

    SciTech Connect (OSTI)

    Ramanayaka, A. N.; Mani, R. G.; Wegscheider, W.

    2013-12-04

    We extract the electron temperature in the microwave photo-excited high mobility GaAs/AlGaAs two dimensional electron system (2DES) by studying the influence of microwave radiation on the amplitude of Shubnikov-de Haas oscillations (SdHOs) in a regime where the cyclotron frequency, ?{sub c}, and the microwave angular frequency, ?, satisfy 2? ? ?{sub c} ? 3.5? The results indicate that increasing the incident microwave power has a weak effect on the amplitude of the SdHOs and therefore the electron temperature, in comparison to the influence of modest temperature changes on the dark-specimen SdH effect. The results indicate negligible electron heating under modest microwave photo-excitation, in good agreement with theoretical predictions.

  19. Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires

    SciTech Connect (OSTI)

    Chen, S. L.; Filippov, S.; Chen, W. M.; Buyanova, I. A.; Ishikawa, Fumitaro

    2014-12-22

    Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (?-PL) and ?-PL excitation (?-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation.

  20. Study of the one dimensional electron gas arrays confined by steps in vicinal GaN/AlGaN heterointerfaces

    SciTech Connect (OSTI)

    Li, Huijie E-mail: sh-yyang@semi.ac.cn; Zhao, Guijuan; Liu, Guipeng; Wei, Hongyuan; Jiao, Chunmei; Yang, Shaoyan E-mail: sh-yyang@semi.ac.cn; Wang, Lianshan; Zhu, Qinsheng

    2014-05-21

    One dimensional electron gas (1DEG) arrays in vicinal GaN/AlGaN heterostructures have been studied. The steps at the interface would lead to the lateral barriers and limit the electron movement perpendicular to such steps. Through a self-consistent Schrödinger-Poisson approach, the electron energy levels and wave functions were calculated. It was found that when the total electron density was increased, the lateral barriers were lowered due to the screening effects by the electrons, and the electron gas became more two-dimension like. The calculated 1DEG densities were compared to the experimental values and good agreements were found. Moreover, we found that a higher doping density is more beneficial to form 1-D like electron gas arrays.

  1. Terrestrial Concentrator PV Modules Based on GaInP/GaAs/Ge TJ Cells and Minilens Panels

    SciTech Connect (OSTI)

    Rumyantsev, V. D.; Sadchikov, N. A.; Chalov, A. E.; Ionova, E. A.; Friedman, D. J.; Glenn, G.

    2006-01-01

    This paper is a description of research activity in the field of cost-effective modules realizing the concept of very high solar concentration with small-aperture area Fresnel lenses and multijunction III-V cells. Structural simplicity and 'all-glass' design are the guiding principles of the corresponding development. The advanced concentrator modules are made with silicone Fresnel lens panels (from 8 up to 144 lenses, each lens is 4 times 4 cm{sup 2} in aperture area) with composite structure. GaInP/GaAs/Ge triple-junction cells with average efficiencies of 31.1 and 34.7% at 1000 suns were used for the modules. Conversion efficiency as high as 26.3% has been measured indoors in a test module using a newly developed large-area solar simulator.

  2. A hole accelerator for InGaN/GaN light-emitting diodes Zi-Hui Zhang, Wei Liu, Swee Tiam Tan, Yun Ji, Liancheng Wang, Binbin Zhu, Yiping Zhang, Shunpeng Lu,

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    GaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, the effectiveness of the hole ac- celerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10

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

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    to the enhanced optical output power and external quantum efficiency. Compared to the reference InGaN/GaN LEDs; accepted 29 April 2013; published online 15 May 2013) We report InGaN/GaN light-emitting diodes (LED have been devoted to boosting the optical output power and enhancing the external quantum efficiency

  4. 1EV GaN[subscript x]As[subscript 1-x-y]Sb[subscript y] material for lattice-matched III-V solar cell implementation on GaAs and Ge

    E-Print Network [OSTI]

    Yoon, Soon Fatt

    The effect of different arsenic species (As[subscript 2] or As[subscript 4]) on the quality of molecular beam epitaxy (MBE) grown GaNAsSb materials (samples A and B) and GaAs/ GaNAsSb/GaAs p+n-n+ devices (samples C and D) ...

  5. Graded InxGa1 xAs/GaAs 1.3 m wavelength light emitting diode structures grown with molecular beam epitaxy

    E-Print Network [OSTI]

    Graded InxGa1 xAs/GaAs 1.3 m wavelength light emitting diode structures grown with molecular beam 11 June 1997; accepted for publication 29 September 1997 In this study 1.1­1.3 m wavelength light at a lower cost. Such a technology could have an impact on the economic feasibility of fiber to the home

  6. Si3N4 on GaAs by direct electron cyclotron resonance plasma assisted nitridation of Si layer in Si/GaAs structure

    E-Print Network [OSTI]

    Rockett, Angus

    from XPS as a function of photoelectron takeoff angle, initially increased rapidly with nitridation either from the higher temperature or from nitridation of all of the Si, leaving the Si3N4 in direct contact with the GaAs. © 1998 American Vacuum Society. S0734-211X 98 00302-3 I. INTRODUCTION Ga

  7. AFFECTS OF MECHANICAL MILLING AND METAL OXIDE ADDITIVES ON SORPTION KINETICS OF 1:1 LiNH2/MgH2 MIXTURE

    SciTech Connect (OSTI)

    Erdy, C.; Anton, D.; Gray, J.

    2010-12-08

    The destabilized complex hydride system composed of LiNH{sub 2}:MgH{sub 2} (1:1 molar ratio) is one of the leading candidates of hydrogen storage with a reversible hydrogen storage capacity of 8.1 wt%. A low sorption enthalpy of {approx}32 kJ/mole H{sub 2} was first predicted by Alapati et al. utilizing first principle density function theory (DFT) calculations and has been subsequently confirmed empirically by Lu et al. through differential thermal analysis (DTA). This enthalpy suggests that favorable sorption kinetics should be obtainable at temperatures in the range of 160 C to 200 C. Preliminary experiments reported in the literature indicate that sorption kinetics are substantially lower than expected in this temperature range despite favorable thermodynamics. Systematic isothermal and isobaric sorption experiments were performed using a Sievert's apparatus to form a baseline data set by which to compare kinetic results over the pressure and temperature range anticipated for use of this material as a hydrogen storage media. Various material preparation methods and compositional modifications were performed in attempts to increase the kinetics while lowering the sorption temperatures. This paper outlines the results of these systematic tests and describes a number of beneficial additions which influence kinetics as well as NH{sub 3} formation.

  8. The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2}

    SciTech Connect (OSTI)

    Peter, Sebastian C. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064 (India); Malliakas, Christos D. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Nakotte, Heinze; Kothapilli, Karunakar [Physics Department, New Mexico State University, Las Cruces, NM 88003 (United States); Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC, R-5 Shed, Trombay, Mumbai 400085 (India); Schultz, Arthur J. [X-Ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.edu [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2012-03-15

    Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20) Angstrom-Sign , b=10.7447(20) Angstrom-Sign , c=8.4754(17) Angstrom-Sign and {beta}=110.288(30) Degree-Sign (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge){sub n}. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6) Angstrom-Sign and c=15.1178(19) Angstrom-Sign . The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{proportional_to}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures. - Graphical abstract: The compounds Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are obtained from reactions of Yb and Ge in excess liquid gallium. Highlights: Black-Right-Pointing-Pointer Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are two new polygallides. Black-Right-Pointing-Pointer The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was established using neutron diffraction data. Black-Right-Pointing-Pointer YbGa{sub 4}Ge{sub 2} is one of the rare polar intermetallic compounds. Black-Right-Pointing-Pointer The physical properties of Yb{sub 3}Ga{sub 7}Ge{sub 3} point to a Fermi-liquid regime at low temperature.

  9. Temporally and spatially resolved photoluminescence investigation of (112{sup ¯}2) semi-polar InGaN/GaN multiple quantum wells grown on nanorod templates

    SciTech Connect (OSTI)

    Liu, B.; Smith, R.; Athanasiou, M.; Yu, X.; Bai, J.; Wang, T.

    2014-12-29

    By means of time-resolved photoluminescence (PL) and confocal PL measurements, temporally and spatially resolved optical properties have been investigated on a number of In{sub x}Ga{sub 1?x}N/GaN multiple-quantum-well (MQW) structures with a wide range of indium content alloys from 13% to 35% on (112{sup ¯}2) semi-polar GaN with high crystal quality, obtained through overgrowth on nanorod templates. With increasing indium content, the radiative recombination lifetime initially increases as expected, but decreases if the indium content further increases to 35%, corresponding to emission in the green spectral region. The reduced radiative recombination lifetime leads to enhanced optical performance for the high indium content MQWs as a result of strong exciton localization, which is different from the behaviour of c-plane InGaN/GaN MQWs, where quantum confined Stark effect plays a dominating role in emission process.

  10. Low dimensional GaAs/air vertical microcavity lasers

    SciTech Connect (OSTI)

    Gessler, J.; Steinl, T.; Fischer, J.; Höfling, S.; Schneider, C.; Kamp, M.; Mika, A.; S?k, G.; Misiewicz, J.

    2014-02-24

    We report on the fabrication of gallium arsenide (GaAs)/air distributed Bragg reflector microresonators with indium gallium arsenide quantum wells. The structures are studied via momentum resolved photoluminescence spectroscopy which allows us to investigate a pronounced optical mode quantization of the photonic dispersion. We can extract a length parameter from these quantized states whose upper limit can be connected to the lateral physical extension of the microcavity via analytical calculations. Laser emission from our microcavity under optical pumping is observed in power dependent investigations.

  11. Distribution of bismuth atoms in epitaxial GaAsBi

    SciTech Connect (OSTI)

    Sales, David [Universidad de Cadiz, Spain; Guerreo, E. [Universidad de Cadiz, Spain; Rodrigo, J.F. [Universidad de Cadiz, Spain; Galindo, P.L. [Universidad de Cadiz, Spain; Yanez, A. [University of Cadiz, Spain; Shafi, M. [University of Nottingham, Nottingham UK; Khatab, A. [University of Nottingham, Nottingham UK; Mari, R.H. [University of Nottingham, Nottingham UK; Henini, M. [University of Nottingham, Nottingham UK; Novikov, S. [University of Nottingham, Nottingham UK; Chisholm, Matthew F [ORNL; Molina, S.I. [Universidad de Cadiz, Spain

    2011-01-01

    The distribution of Bi atoms in epitaxial GaAs{sub (1-x)}Bi{sub x} is analyzed through aberration-corrected Z-contrast images. The relation between the atomic number and the intensity of the images allows quantifying the distribution of Bi atoms in this material. A bidimensional map of Bi atoms is extracted showing areas where nanoclustering is possible and evidencing the location of Bi at As-substitutional positions in the lattice. The distribution of Bi atoms differs from a random spatial pattern of Bi atoms in the material.

  12. Structure, transport and thermal properties of UCoGa

    SciTech Connect (OSTI)

    Purwanto, A.; Robinson, R.A.; Prokes, K.

    1994-04-01

    By means of neutron powder diffraction, we find that UCoGa crystallizes in the hexagonal ZrNiAl structure and orders ferromagnetically at low temperatures with magnetic moments stacked along the c axis. The magnetic-ordering temperature is reflected in anomalies in the temperature dependencies of the electrical resistivity and the specific heat at Tc = 47 K. Furthermore, the strong anisotropy in the electrical resistivity for i {parallel} c and i {perpendicular} c indicates a significant contribution of the magnetic anisotropy to the electrical resistivity.

  13. 22209_HPC_cvr_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: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 Outreach Home RoomPreservationBio-InspiredAtmosphericdevicesPPONeApril 30,University Turbine1.0 -Systems and

  14. Enhanced Magnetism of Fe3O4 Nanoparticles with Ga Doping

    SciTech Connect (OSTI)

    Pool, V. L.; Klem, M. T.; Chorney, C. L.; Arenholz, E.; Idzerda, Y.U.

    2010-10-22

    Magnetic (Ga{sub x}Fe{sub 1-x}){sub 3}O{sub 4} nanoparticles with 5%-33% gallium doping (x = 0.05-0.33) were measured using x-ray absorption spectroscopy and x-ray magnetic circular dichroism to determine that the Ga dopant is substituting for Fe{sub 3+} as Ga{sub 3+} in the tetrahedral A-site of the spinel structure, resulting in an overall increase in the total moment of the material. Frequency-dependent alternating-current magnetic susceptibility measurements showed these particles to be weakly interacting with a reduction of the cubic anisotropy energy term with Ga concentration. The element-specific dichroism spectra show that the average Fe moment is observed to increase with Ga concentration, a result consistent with the replacement of A-site Fe by Ga.

  15. Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology

    SciTech Connect (OSTI)

    Vernon, S.M. )

    1993-04-01

    This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, [approximately] 1 [times] 10[sup 5] cm[sup [minus]5], as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 [times]10[sup 7] cm[sup [minus]2]. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

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

    SciTech Connect (OSTI)

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

    2012-11-01

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

  17. DISSERTATION DEVICE PHYSICS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS

    E-Print Network [OSTI]

    Sites, James R.

    OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS Thin-film solar cells have the potential to be an important contributor to the global energy demand by the mid-21st-century. Cu(In,Ga)Se2 (CIGS) solar cells, which haveDISSERTATION DEVICE PHYSICS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS Submitted by Markus Gloeckler

  18. Investigation of photoexcited parallel conduction in GaAs/AlGaAs heterostructures in the quantum limit 

    E-Print Network [OSTI]

    Kobiela, Pawel Stanislaw

    1986-01-01

    conduction paths, one in the 2-DEG (medium 1) and the second an another medium (like AlGaAs), the conductivity tensor can be expressed as o' = rri + ap. Further analysis can be carried out by considering two separate limits: low and high magnetic fields.... The interval between the current pulses depended on the temperature and varied from 2-3 sec. at 10 K to about 1 min. at 15 mK. For each magnetic field scan between 0 and 7. 5 T about 500 readings were taken for l&oth current directions. As mentioned before...

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

    SciTech Connect (OSTI)

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

    2013-09-15

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

  20. Low-temperature charge transport in Ga-acceptor nanowires implanted by focused-ion beams

    E-Print Network [OSTI]

    Robinson, SJ

    2008-01-01

    Low-Temperature Charge Transport in Ga-Acceptor Nanowiresare highly nonlinear at low temperatures, and a thresholdmetallic conductance at low temperatures could be achieved

  1. Vacancy defects in as-grown and neutron irradiated GaP studied by positrons

    SciTech Connect (OSTI)

    Dlubek, G.; Bruemmer, O.; Polity, A.

    1986-08-18

    Positron lifetime and Doppler-broadening measurements have been used to study vacancy defects in n-italic-type GaP. Vacancies in the P sublattice with a concentration of some 10/sup 17/ cm/sup -3/ were observed in as-grwon GaP. The vacancies disappear during annealing at 500--800 /sup 0/C. In neutron-irradiated GaP positrons are trapped by Ga vacancies which anneal out in two stages situated at 300--550 /sup 0/C and 550--700 /sup 0/C.

  2. Structural defects in GaN revealed by Transmission Electron Microscopy

    SciTech Connect (OSTI)

    Liliental-Weber, Zuzanna

    2014-04-18

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

  3. Raman scattering in InAs/AlGaAs quantum dot nanostructures E. Giulotto,1,a

    E-Print Network [OSTI]

    As upper CL UCL with the same composition of LCL, and a 10 nm thick GaAs cap layer. Buffers and LCLs were

  4. Antimonide-Based Long-Wavelength Lasers on GaAs Substrates

    SciTech Connect (OSTI)

    KLEM,JOHN F.; Blum, O.

    2000-08-17

    We have investigated the use of GaAsSb in edge-emitting laser active regions, in order to obtain lasing near 1.3 {micro}m. Single quantum well GaAsSb devices display electroluminescence at wavelengths as long as 1.34 {micro}m, but substantial blueshifts occur under high injection conditions. GaAsSb single quantum well edge emitters have been obtained which lase at 1.275 {micro}m with a room-temperature threshold current density as low as 535 A/cm{sup 2}. Modification of the basic GaAsSb/GaAs structure with the addition of InGaAs layers results in a strongly type-II band alignment which can be used to further extend the emission wavelength of these devices. Using GaAsSb/InGaAs active regions, lasers emitting at 1.17 {micro}m have been obtained with room-temperature threshold current densities of 120 A/cm{sup 2}, and devices operating at 1.29 {micro}m have displayed thresholds as low as 375 A/cm{sup 2}. Characteristic temperatures for devices employing various GaAsSb-based active regions have been measured to be 60-73 K.

  5. Interface Reactions and Electrical Characteristics of Au/GaSb Contacts

    SciTech Connect (OSTI)

    H. Ehsani; R.J. Gutmann; G.W. Charache

    2000-07-07

    The reaction of Au with GaSb occurs at a relatively low temperature (100 C). Upon annealing, a AuSb{sub 2} compound and several Au-Ga phases are produced. Phase transitions occur toward higher Ga concentration with increasing annealing temperatures. Furthermore, the depth of the contact also increases with increased annealing temperature. They found that the AuSb{sub 2} compound forms on the GaSb surface, with the compound crystal partially ordered with respect to the substrate. The transition of Schottky- to ohmic-contact behavior in Au/n-type GaSb occurs simultaneously with the formation of the AuGa compound at about a 250 C annealing temperature. This ohmic contact forms without the segregation of dopants at the metallic compound/GaSb interface. Therefore it is postulated that transition from Schottky- to ohmic-contact behavior is obtained through a series of tunneling transitions of electrons through defects in the depletion region in the Au/n-type GaSb contacts. Contact resistivities of 6-7 x 10{sup -6} {Omega}-cm{sup 2} were obtained with the annealing temperature between 300 and 350 C for 30 seconds. In Au/p-type GaSb contacts, the resistivity was independent of the annealing temperature. This suggested that the carrier transport in p-type contact dominated by thermionic emission.

  6. A comparison of the structure and localized magnetism in Ce{sub 2}PdGa{sub 12} with the heavy fermion CePdGa{sub 6}

    SciTech Connect (OSTI)

    Macaluso, Robin T. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Millican, Jasmine N. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Nakatsuji, Satoru [Department of Physics, Kyoto University, Kyoto, Japan 606-8502 (Japan); Lee, Han-Oh [Department of Physics, University of California, Davis, CA 95616 (United States); Carter, B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Moreno, Nelson O. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Fisk, Zachary [Department of Physics, University of California, Davis, CA 95616 (United States); Chan, Julia Y. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States)]. E-mail: jchan@lsu.edu

    2005-11-15

    Single crystals of Ce{sub 2}PdGa{sub 12} have been synthesized in Ga flux and characterized by X-ray diffraction. This compound crystallizes in the tetragonal P4/nbm space group, Z=2 with lattice parameters of a=6.1040(2)A and c=15.5490(6)A. It shows strongly anisotropic magnetism and orders antiferromagnetically at T{sub N}{approx}11K. A field-induced metamagnetic transition to the ferromagnetic state is observed below T{sub N}. Structure-property relationships with the related heavy-fermion antiferromagnet CePdGa{sub 6} are discussed.

  7. Origin of InGaN/GaN light-emitting diode efficiency improvements using tunnel-junction-cascaded active regions

    SciTech Connect (OSTI)

    Piprek, Joachim, E-mail: piprek@nusod.org [NUSOD Institute LLC, P.O. Box 7204, Newark, Delaware 19714 (United States)

    2014-02-03

    This Letter investigates the efficiency enhancement achieved by tunnel junction insertion into the InGaN/GaN multi-quantum well (MQW) active region of blue light emitting diodes (LEDs). The peak quantum efficiency of such LED exceeds 100%, but the maximum wall-plug efficiency (WPE) hardly changes. However, due to the increased bias, the WPE peaks at much higher input power, i.e., the WPE droop is significantly delayed, and the output power is strongly enhanced. The main physical reason for this improvement lies in the non-uniform vertical carrier distribution typically observed within InGaN MQWs.

  8. InGaP/GaAs Inverted Dual Junction Solar Cells For CPV Applications Using Metal-Backed Epitaxial Lift-Off

    SciTech Connect (OSTI)

    Bauhuis, Gerard J.; Mulder, Peter; Haverkamp, Erik J.; Schermer, John J.; Nash, Lee J.; Fulgoni, Dominic J. F.; Ballard, Ian M.; Duggan, Geoffrey

    2010-10-14

    The epitaxial lift-off (ELO) technique has been combined with inverted III-V PV cell epitaxial growth with the aim of employing thin film PV cells in HCPV systems. In a stepwise approach to the realization of an inverted triple junction on a MELO platform we have first grown a GaAs single junction PV cell to establish the basic layer release process and cell processing steps followed by the growth, fabrication and test of an inverted InGaP/GaAs dual junction structure.

  9. InGaAsN Solar Cells with 1.0eV Bandgap, Lattice Matched to GaAs

    SciTech Connect (OSTI)

    Allerman, A.A.; Banas, J.J.; Gee, J.M.; Hammons, B.E.; Jones, E.D.; Kurtz, S.R.

    1998-11-24

    The design, growth by metal-organic chemical vapor deposition, and processing of an In{sub 0.07}Ga{sub 0.93}As{sub 0.98}N{sub 0.02} solar Al, with 1.0 ev bandgap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6-0.8 pm, and solar cell internal quantum efficiencies > 70% arc obwined. Optical studies indicate that defects or impurities, from InGAsN doping and nitrogen incorporation, limit solar cell performance.

  10. Calculation of exact vibrational spectra for P{sub 2}O and CH{sub 2}NH using a phase space wavelet basis

    SciTech Connect (OSTI)

    Halverson, Thomas, E-mail: tom.halverson@ttu.edu; Poirier, Bill [Department of Chemistry and Biochemistry and Department of Physics, Texas Tech University, P.O. Box 41061, Lubbock, Texas 79409-1061 (United States)

    2014-05-28

    ‘‘Exact” quantum dynamics calculations of vibrational spectra are performed for two molecular systems of widely varying dimensionality (P{sub 2}O and CH{sub 2}NH), using a momentum-symmetrized Gaussian basis. This basis has been previously shown to defeat exponential scaling of computational cost with system dimensionality. The calculations were performed using the new “SWITCHBLADE” black-box code, which utilizes both dimensionally independent algorithms and massive parallelization to compute very large numbers of eigenstates for any fourth-order force field potential, in a single calculation. For both molecules considered here, many thousands of vibrationally excited states were computed, to at least an “intermediate” level of accuracy (tens of wavenumbers). Future modifications to increase the accuracy to “spectroscopic” levels, along with other potential future improvements of the new code, are also discussed.

  11. Qualifying composition dependent p and n self-doping in CH{sub 3}NH{sub 3}PbI{sub 3}

    SciTech Connect (OSTI)

    Wang, Qi; Shao, Yuchuan; Huang, Jinsong; Xie, Haipeng; Lyu, Lu; Liu, Xiaoliang; Gao, Yongli

    2014-10-20

    We report the observation of self-doping in perovskite. CH{sub 3}NH{sub 3}PbI{sub 3} was found to be either n- or p-doped by changing the ratio of methylammonium halide (MAI) and lead iodine (PbI{sub 2}) which are the two precursors for perovskite formation. MAI-rich and PbI{sub 2}-rich perovskite films are p and n self-doped, respectively. Thermal annealing can convert the p-type perovskite to n-type by removing MAI. The carrier concentration varied as much as six orders of magnitude. A clear correlation between doping level and device performance was also observed.

  12. A novel theoretical model for broadband blue InGaN/GaN superluminescent light emitting diodes

    SciTech Connect (OSTI)

    Moslehi Milani, N.; Mohadesi, V.; Asgari, A.

    2015-02-07

    A broadband superluminescent light emitting diode with In{sub 0.2}Ga{sub 0.8}N/GaN multiple quantum wells (MQWs) active region is investigated. The investigation is based on a theoretical model which includes the calculation of electronic states of the structure, rate equations, and the spectral radiation power. Two rate equations corresponding to MQW active region and separate confinement heterostructures layer are solved self-consistently with no-k selection wavelength dependent gain and quasi-Fermi level functions. Our results show that the superluminescence started in a current of ?120?mA (?7.5?kA/Cm{sup 2}) at 300?K. The range of peak emission wavelengths for different currents is 423–426?nm and the emission bandwidth is ?5?nm in the superluminescence regime. A maximum light output power of 7.59 mW is obtained at 600?mA and the peak modal gain as a function of current indicates logarithmic behavior. Also, the comparison of our calculated results with published experimental data is shown to be in good agreement.

  13. Improved photoluminescence of InGaAsN,,In...GaAsP quantum well by organometallic vapor phase epitaxy using growth pause annealing

    E-Print Network [OSTI]

    Gilchrist, James F.

    for Photonics, Department of Electrical Computer Engineering, University of Wisconsin­Madison, 1415 Engineering are the hydride sources of AsH3 and PH3 . The trimethyl precursors of gal- lium Ga , aluminum Al , and indium

  14. The use of short-period InGaN/GaN superlattices in blue-region light-emitting diodes

    SciTech Connect (OSTI)

    Sizov, V. S., E-mail: vsizov@mail.ioffe.ru; Tsatsulnikov, A. F.; Sakharov, A. V.; Lundin, W. V.; Zavarin, E. E.; Cherkashin, N. A. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Hytch, M. J. [National Center for Scientific Research (CNRS), Center for Material Elaboration and Structural Studies (CEMES) (France); Nikolaev, A. E. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Mintairov, A. M.; He Yan; Merz, J. L. [University of Notre Dame, EE Department (United States)

    2010-07-15

    Optical and light-emitting diode structures with an active InGaN region containing short-period InGaN/GaN superlattices are studied. It is shown that short-period superlattices are thin two-dimensional layers with a relatively low In content that contain inclusions with a high In content 1-3 nm thick. Inclusions manifest themselves from the point of view of optical properties as a nonuniform array of quantum dots involved in a residual quantum well. The use of short-period superlattices in light-emitting diode structures allows one to decrease the concentration of nonradiative centers, as well as to increase the injection of carriers in the active region due to an increase in the effective height of the AlGaN barrier, which in general leads to an increase in the quantum efficiency of light-emitting diodes.

  15. Angular dependence of light trapping in In0.3Ga0.7As/GaAs quantum-well solar cells

    E-Print Network [OSTI]

    Yu, Edward T.

    Angular dependence of light trapping in In0.3Ga0.7As/GaAs quantum-well solar cells X. H. Li,1 P. C trapping in thin-film solar cells via engineered surface morphology or device geometry, scattering,10 In this paper, we describe and demonstrate thin-film quantum-well solar cells that are grown by molecular beam

  16. Atomistic modeling and HAADF investigations of misfit and threading dislocations in GaSb/GaAs hetero-structures for applications in high electron mobility transistors

    SciTech Connect (OSTI)

    Ruterana, Pierre Wang, Yi Chen, Jun Chauvat, Marie-Pierre; El Kazzi, S.; Deplanque, L.; Wallart, X.

    2014-10-06

    A detailed investigation on the misfit and threading dislocations at GaSb/GaAs interface has been carried out using molecular dynamics simulation and quantitative electron microscopy techniques. The sources and propagation of misfit dislocations have been elucidated. The nature and formation mechanisms of the misfit dislocations as well as the role of Sb on the stability of the Lomer configuration have been explained.

  17. Ferromagnetic (Ga,Mn)As nanostructures for spintronic applications

    SciTech Connect (OSTI)

    Wosinski, Tadeusz; Andrearczyk, Tomasz; Figielski, Tadeusz; Makosa, Andrzej; Wrobel, Jerzy; Sadowski, Janusz

    2013-12-04

    Magneto-resistive, cross-like nanostructures have been designed and fabricated by electron-beam lithography patterning and chemical etching from thin epitaxial layers of the ferromagnetic semiconductor (Ga,Mn)As. The nanostructures, composed of two perpendicular nanostripes crossing in the middle of their length, represent four-terminal devices, in which an electric current can be driven through any of the two nanostripes. In these devices, a novel magneto-resistive memory effect, related to a rearrangement of magnetic domain walls in the central part of the device, has been demonstrated. It consists in that the zero-field resistance of a nanostripe depends on the direction of previously applied magnetic field. The nanostructures can thus work as two-state devices providing basic elements of nonvolatile memory cells.

  18. High-fluence Ga-implanted silicon—The effect of annealing and cover layers

    SciTech Connect (OSTI)

    Fiedler, J., E-mail: jan.fiedler@hzdr.de; Heera, V.; Hübner, R.; Voelskow, M.; Germer, S.; Schmidt, B.; Skorupa, W. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), D-01314 Dresden (Germany)

    2014-07-14

    The influence of SiO{sub 2} and SiN{sub x} cover layers on the dopant distribution as well as microstructure of high fluence Ga implanted Si after thermal processing is investigated. The annealing temperature determines the layer microstructure and the cover layers influence the obtained Ga profile. Rapid thermal annealing at temperatures up to 750?°C leads to a polycrystalline layer structure containing amorphous Ga-rich precipitates. Already after a short 20?ms flash lamp annealing, a Ga-rich interface layer is observed for implantation through the cover layers. This effect can partly be suppressed by annealing temperatures of at least 900?°C. However, in this case, Ga accumulates in larger, cone-like precipitates without disturbing the surrounding Si lattice parameters. Such a Ga-rich crystalline Si phase does not exist in the equilibrium phase diagram according to which the Ga solubility in Si is less than 0.1 at. %. The Ga-rich areas are capped with SiO{sub x} grown during annealing which only can be avoided by the usage of SiN{sub x} cover layers.

  19. Deep-level transient spectroscopy of InAs/GaAs quantum dot superlattices

    SciTech Connect (OSTI)

    Sobolev, M. M.; Nevedomskii, V. N.; Zolotareva, R. V.; Vasil'ev, A. P.; Ustinov, V. M.

    2014-02-21

    Deep level transient spectroscopy (DLTS) has been applied to study the carrier emission from states of a 10-layer system of tunnel-coupled vertically correlated quantum dots (VCQDs) in p-n InAs/GaAs heterostructures with different widths of GaAs spacers under varied reverse bias (U{sub r}) and filling voltage pulse U{sub f}.

  20. Hetero-epitaxy of perovskite oxides on GaAs(001) by molecular beam epitaxy

    SciTech Connect (OSTI)

    Liang, Y.; Kulik, J.; Eschrich, T.C.; Droopad, R.; Yu, Z.; Maniar, P. [Microelectronics and Physical Sciences Laboratory, Process and Materials Characterization Laboratory, and Microelectronics and Physical Sciences Laboratory, Motorola Inc., 2100 East Elliot Road, Tempe, Arizona 85284 (United States)

    2004-08-16

    Hetero-epitaxy of single-crystal perovskite SrTiO{sub 3} on GaAs(001) was achieved using molecular beam epitaxy. The growth was accomplished by deposition of a submonolayer of titanium on GaAs(001), followed by the co-deposition of strontium and titanium initiated at a low-temperature, low-oxygen-pressure condition. X-ray photoelectron spectroscopy showed that the Ti prelayer reacted with As and formed TiAs-like species on the As terminated GaAs(001) surface. Reflection-high-energy-electron diffraction showed that SrTiO{sub 3} grew coherently on the GaAs(001) at early stage of growth. This coherent behavior began to degrade when SrTiO{sub 3} thickness exceeded 20 A ring . Cross-sectional transmission electron microscopy revealed an abrupt interface between SrTiO{sub 3} and GaAs and good crystallinity of the SrTiO{sub 3} film. An epitaxial relationship between SrTiO{sub 3} and GaAs was further confirmed by x-ray diffraction. The success of growth of SrTiO{sub 3} on GaAs paves the way for integration of various functional perovskite oxides with GaAs.

  1. Engineering vertically aligned InAs/GaAs quantum dot structures via anion exchange

    E-Print Network [OSTI]

    Wang, Zhong L.

    of Technology, Atlanta, GA 30332-0245, USA b School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA Received 17 March 2002; accepted 16 April 2002 by D. Van Dyck Abstract P exchange; D. Stranski­Krastanov (S­K) growth Self-assemble by exploiting the Stranski­Krastanov (S

  2. High efficiency light emitting diode with anisotropically etched GaN-sapphire interface

    E-Print Network [OSTI]

    High efficiency light emitting diode with anisotropically etched GaN- sapphire interface M. H. Lo and optimization of a light-emitting diode projection micro-stereolithography three-dimensional manufacturingGaN micro-light emitting diodes Appl. Phys. Lett. 101, 231110 (2012) A bright cadmium-free, hybrid organic

  3. Activation of small alkanes in Ga-exchanged zeolites: A quantum chemical study of ethane dehydrogenation

    SciTech Connect (OSTI)

    Frash, M.V.; Santen, R.A. van

    2000-03-23

    Quantum chemical calculations on the mechanism of ethane dehydrogenation catalyzed by Ga-exchanged zeolites have been undertaken. Two forms of gallium, adsorbed dihydride gallium ion GaH{sub 2}+Z{sup {minus}} and adsorbed gallyl ion [Ga=O]{sup +}Z{sup {minus}}, were considered. It was found that GaH{sub 2}{sup +}Z{sup {minus}} is the likely active catalyst. On the contrary, [Ga=O]{sup +}Z{sup {minus}} cannot be a working catalyst in nonoxidative conditions, because regeneration of this form is very difficult. Activation of ethane by GaH{sub 2}{sup +}Z{sup {minus}} occurs via an alkyl mechanism and the gallium atom acts as an acceptor of the ethyl group. The carbenium activation of ethane, with gallium abstracting a hydride ion, is much (ca. 51 kcal/mol) more difficult. The catalytic cycle for the alkyl activation consists of three elementary steps: (1) rupture of the ethane C-H bond; (2) formation of dihydrogen from the Bronsted proton and hydrogen bound to Ga; and (3) formation of ethene from the ethyl group bound to Ga. The best estimates (MP2/6--311++G(2df,p)//B3LYP/6--31G*) for the activation energies of these three steps are 36.9, ca. 0, and 57.9 kcal/mol, respectively.

  4. Short-time hydrothermal synthesis and delamination of ion exchangeable Mg/Ga layered double hydroxides

    SciTech Connect (OSTI)

    Unal, Ugur [Department of Nano Science and Technology, Faculty of Engineering, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555 (Japan)], E-mail: ugurunal@chem.kumamoto-u.ac.jp

    2007-09-15

    The hydrothermal synthesis of magnesium-gallium layered double hydroxides (Mg/Ga LDHs) was studied under static and agitated conditions. Not only well-crystallized and large-sized Mg/Ga LDHs having hexagonal morphology were obtained but also the reaction time was comparatively decreased from 24 to 2 h by means of agitation during hydrothermal synthesis. In static conditions, mainly GaOOH and magnesite phases were formed. The elemental analysis results show that the final Mg/Ga ratio is significantly different from the initial ratio. The reason was attributed to the difference in the hydrolytic behavior of Mg{sup 2+} and Ga{sup 3+}. Furthermore, the anion exchange studies with glycine, dodecyl sulfate, ferrocyanide and ferricyanide were performed to investigate the intercalation behavior of the anions into Mg/Ga LDHs. In addition, delamination of Mg/Ga LDHs was performed in formamide for the glycine exchanged forms. Large size of nanosheets thus obtained can be utilized in the fabrication of functional thin films. - Graphical abstract: Hydrothermal synthesis under agitation resulted in highly crystalline Mg/Ga LDHs slabs in a short time. The LDHs slabs were delaminated into two-dimensional nanosize sheets.

  5. Radiation studies for GaAs in the ATLAS Inner Detector

    E-Print Network [OSTI]

    M. Rogalla; Th. Eich; N. Evans; R. Geppert; R. Goeppert; R. Irsigler; J. Ludwig; K. Runge; Th. Schmid

    1997-01-22

    We estimate the hardness factors and the equivalent 1 MeV neutron fluences for hadrons fluences expected at the GaAs positions wheels in the ATLAS Inner Detector. On this basis the degradation of the GaAs particle detectors made from different substrates as a function of years LHC operation is predicted.

  6. In-situ surface composition measurements of CuGaSe{sub 2} thin films

    SciTech Connect (OSTI)

    Fons, P.; Yamada, A.; Niki, S.; Oyanagi, H.

    1998-12-31

    Two CuGaSe{sub 2} films were grown by molecular beam epitaxy onto GaAs (001) substrates with varying Cu/Ga flux ratios under Se overpressure conditions. Growth was interrupted at predetermined times and the surface composition was measured using Auger electron spectroscopy after which growth was continued. After growth, the film composition was analyzed using voltage dependent electron microprobe spectroscopy. Film structure and morphology were also analyzed using x-ray diffraction and atomic force microscopy. The film with a Cu/Ga ratio larger than unity showed evidence of surface segregation of a second Cu-rich phase with a Cu/Se composition ratio slightly greater than unity. A second CuGaSe{sub 2} film with a Cu/Ga ratio of less than unity showed no change in surface composition with time and was also consistent with bulk composition measurements. Diffraction measurements indicated a high concentration of twins as well as the presence of domains with mixed c and a axes in the Ga-rich film. The Cu-rich films by contrast were single domain and had a narrower mosaics. High sensitivity scans along the [001] reciprocal axis did not exhibit any new peaks not attributable to either the substrate or the CuGaSe{sub 2} thin film.

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

    E-Print Network [OSTI]

    Gilchrist, James F.

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

  8. Adhesion energy in nanogap InP/InGaAs microcantilevers Jan D. Makowski,a

    E-Print Network [OSTI]

    Talghader, Joseph J.

    Adhesion energy in nanogap InP/InGaAs microcantilevers Jan D. Makowski,a Anand S. Gawarikar 2006 The adhesion energy is measured between InGaAs quantum wells that have collapsed across a 125 nm and shape of collapsed microcantilevers with optical interferometry. The adhesion energy is found to be 72

  9. A GA-based Approach for Scheduling Decomposable Data Grid Applications

    E-Print Network [OSTI]

    Weissman, Jon

    A GA-based Approach for Scheduling Decomposable Data Grid Applications Seonho Kim and Jon B data onto communication and computation resources. The proposed GA-based scheduler takes advantage, Data Grid, Job Scheduling, Genetic Algorithm, Parallel Processing Relevant technical areas: Network-Based

  10. Development of a Low Cost Insulated Foil Substrate for Cu(InGaSe)2 Photovoltaics

    SciTech Connect (OSTI)

    ERTEN ESER

    2012-01-22

    The project validated the use of stainless steel flexible substrate coated with silicone-based resin dielectric, developed by Dow Corning Corporation, for Cu(InGa)Se2 based photovoltaics. The projects driving force was the high performance of Cu(InGa)Se2 based photovoltaics coupled with potential cost reduction that could be achieved with dielectric coated SS web substrate.

  11. File:USDA-CE-Production-GIFmaps-GA.pdf | 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 on Google Bookmark EERE: Alternative Fuels Data Center Home Page on QA:QAsource History View New Pages RecentTempCampApplicationWorksheet 2011.pdf JumpTransmission SitingFL.pdf Jump

  12. Investigation of crystalline and electronic band alignment properties of GaP/Ge(111) heterostructure

    SciTech Connect (OSTI)

    Dixit, V. K.; Kumar, Shailendra; Singh, S. D.; Khamari, S. K.; Kumar, R.; Tiwari, Pragya; Sharma, T. K.; Oak, S. M. [Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Phase, D. M. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, Madhya Pradesh 452001 (India)

    2014-03-03

    Gallium phosphide (GaP) epitaxial layer and nanostructures are grown on n-Ge(111) substrates using metal organic vapour phase epitaxy. It is confirmed by high resolution x-ray diffraction measurements that the layer is highly crystalline and oriented with the coexistence of two domains, i.e., GaP(111)A and GaP(111)B, with an angle of 60° between them due to the formation of a wurtzite monolayer at the interface. The valence band offset between GaP and Ge is 0.7?±?0.1?eV as determined from the valence band onsets and from Kraut's method. A band alignment diagram for GaP/Ge/GeOx is also constructed which can be used to design monolithic optoelectronic integrated circuits.

  13. Polycrystalline GaAs solar cells on low-cost Silicon-Film{trademark} substrates

    SciTech Connect (OSTI)

    Mauk, M.G.; Feyock, B.W.; Hall, R.B.; Cavanaugh, K.D.; Cotter, J.E.

    1997-12-31

    The authors assess the potential of a low-cost, large-area Silicon-Film{trademark} sheet as a substrate for thin-film polycrystalline GaAs solar cells. Silicon-Film is a relatively inexpensive material on which large-grain (>2 mm) polycrystalline GaAs films can be formed. The GaAs epitaxial layers are grown by a simple close-spaced vapor transport (CSVT) technique using water vapor as a transport agent. A recrystallized Ge{sub 1{minus}x}Si{sub x} buffer layer between the GaAs epilayer and Silicon-Film substrate can facilitate growth of the GaAs. Selective epitaxy on patterned, oxide-masked substrates is effective in reducing thermal stress effects.

  14. MOCVD growth of GaAs solar cells on silicon substrates

    SciTech Connect (OSTI)

    Vernon, S.M.; Haven, V.E.; Geoffroy, L.M.; Sanfacon, M.M.; Mastrovito, A.L. )

    1992-12-01

    This paper reports advances in the development of solar cells made from GaAs-on-Si structures prepared by metalorganic chemical vapor deposition (MOCVD). The use of concentrator cells, operating at [similar to]200 suns, has led to the efficiency achievements of 21.3% (AM1.5D) for a GaAs-on-Si solar cell, and 27.6 (AM1.5D) for a homoepitaxial GaAs cell. The development of epitaxial multilayer dielectric mirrors (Bragg reflectors), as back-surface reflectors in thin-film GaAs cells, on both Si and GaAs substrates, is shown to lead to modest efficiency increases, over that of conventional designs.

  15. Doping of GaN{sub 1-x}As{sub x} with high As content

    SciTech Connect (OSTI)

    Levander, A.X.; Novikov, S.V.; Liliental-Weber, Z.; dos Reis, R.; Dubon, O.D.; Wu, J.; Foxon, C.T.; Yu, K.M.; Walukiewicz, W.

    2011-09-22

    Recent work has shown that GaN{sub 1-x}As{sub x} can be grown across the entire composition range by low temperature molecular beam epitaxy with intermediate compositions being amorphous, but control of the electrical properties through doping is critical for functionalizing this material. Here we report the bipolar doping of GaN{sub 1-x}As{sub x} with high As content to conductivities above 4 S/cm at room temperature using Mg or Te. The carrier type was confirmed by thermopower measurements. Doping requires an increase in Ga flux during growth resulting in a mixed phase material of polycrystalline GaAs:N embedded in amorphous GaN{sub 1-x}As{sub x}.

  16. Numerical analysis for high-efficiency GaAs solar cells fabricated on Si substrates

    SciTech Connect (OSTI)

    Yamaguchi, M.; Amano, C.; Itoh, Y.

    1989-07-15

    This paper describes some recent developments in GaAs thin-film solar cells fabricated on Si substrates by metalorganic chemical vapor deposition and numerically analyzes them.GaAs solar cells with efficiency of more than 18% are successfully fabricated on Si substrates by reducing the dislocation density. Photovoltaic properties of GaAs/Si cells are analyzed by considering the effect of nonuniform dislocation distribution on recombination properties of GaAs thin films on Si substrates. Numerical analysis shows that the effect of majority-carrier trapping must be considered. High efficiency GaAs solar cells with total-area efficiency of over 20% on Si substrates can be realized if dislocation density can be reduced to less than 5/times/10/sup 5/ cm/sup /minus/2/.

  17. Structure of duplex DNA containing the cisplatin 1,2-{Pt(NH3)2}[superscript 2]+-d(GpG) crosslink at 1.77 [Angstrom] resolution

    E-Print Network [OSTI]

    Todd, Ryan C.

    We report the 1.77-Å resolution X-ray crystal structure of a dodecamer DNA duplex with the sequence 5?-CCTCTGGTCTCC-3? that has been modified to contain a single engineered 1,2-cis-{Pt(NH3)2}2+-d(GpG) cross-link, the major ...

  18. Experimental and Theoretical EPR Study of Jahn?Teller-Active [HIPTN[subscript 3]N]MoL Complexes (L = N[subscript 2], CO, NH[subscript 3])

    E-Print Network [OSTI]

    McNaughton, Rebecca L.

    The trigonally symmetric Mo(III) coordination compounds [HIPTN[subscript 3]N]MoL (L = N[subscript 2], CO, NH[subscript 3]; [HIPTN3N]Mo = [(3,5-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript ...

  19. Ground-state energy trends in single and multilayered coupled InAs/GaAs quantum dots capped with InGaAs layers: Effects of InGaAs layer thickness and annealing temperature

    SciTech Connect (OSTI)

    Shah, S.; Ghosh, K.; Jejurikar, S.; Mishra, A.; Chakrabarti, S.

    2013-08-01

    Graphical abstract: - Highlights: • Investigation of ground state energy in single and multi-layered InAs/GaAs QD. • Strain reducing layer (InGaAs) prevents the formation of non-radiative. • Strain reducing layer (InGaAs) is responsible for high activation energy. • Significant deviation from the Varshni model, E(T) = E ? ?T{sup 2}/T + ?. - Abstract: Vertically coupled, multilayered InAs/GaAs quantum dots (QDs) covered with thin InGaAs strain-reducing layers (SRLs) are in demand for various technological applications. We investigated low temperature photoluminescence of single and multilayered structures in which the SRL thickness was varied. The SRL layer was responsible for high activation energies. Deviation of experimental data from the Varshni (1967) model, E(T) = E ? ? T{sup 2}/T + ?, suggests that the InAs-layered QDs have properties different from those in bulk material. Anomalous ground-state peak linewidths (FWHM), especially for annealed multilayer structures, were observed. A ground-state peak blue-shift with a broadened linewidth was also observed. Loss of intensity was detected in samples annealed at 800 °C. Presence of SRLs prevents formation of non-radiative centers under high temperature annealing. The results indicate the potential importance of such structures in optoelectronic applications.

  20. Scanning tunneling microscopy study of the interfacial bonding structures of Ga2O and In2O/In0.53Ga0.47As(0 0 1)

    E-Print Network [OSTI]

    Kummel, Andrew C.

    trap density [3]. Fermi level pinning can be caused by strong perturbations to the electronic structure with the electronic structure of Ga2O on In0.53Ga0.47As(0 0 1) were explored. Scanning tunneling microscopy (STMScanning tunneling microscopy study of the interfacial bonding structures of Ga2O and In2O/In0.53Ga

  1. 9/4/2014 NEWS OF THE WEIRD | Fort Myers Newspaper | News, Business, Real Estate and Arts in Fort Myers FL | Florida http://fortmyers.floridaweekly.com/news/2014-08-27/News_of_The_Weird/NEWS_OF_THE_WEIRD.html?print=1 1/3

    E-Print Network [OSTI]

    Chiao, Jung-Chih

    9/4/2014 NEWS OF THE WEIRD | Fort Myers Newspaper | News, Business, Real Estate and Arts in Fort's the story? 13 Points Mentioned #12;9/4/2014 NEWS OF THE WEIRD | Fort Myers Newspaper | News, Business, Real Estate and Arts in Fort Myers FL | Florida http://fortmyers.floridaweekly.com/news/2014-08-27/News

  2. Comparative study of field-dependent carrier dynamics and emission kinetics of InGaN/GaN light-emitting diodes grown on (11 2 2) semipolar versus (0001) polar

    E-Print Network [OSTI]

    Demir, Hilmi Volkan

    Articles you may be interested in Ultraviolet light-emitting diodes grown by plasma-assisted molecular beam light-emitting diodes prepared on ( 11 2 ¯ 2 ) -plane GaN J. Appl. Phys. 100, 113109 (2006); 10.1063/1.2382667 Demonstration of a semipolar ( 10 1 ¯ 3 ¯ ) In Ga N Ga N green light emitting diode Appl. Phys. Lett. 87, 231110

  3. Development of an IR-transparent, inverted-grown, thin-film, Al[sub 0. 34]Ga[sub 0. 66]As/GaAs cascade solar cell

    SciTech Connect (OSTI)

    Venkatasubramanian, R.; Timmons, M.L.; Sharps, P.R.; Colpitts, T.S.; Hills, J.S.; Hancock, J.; Hutchby, J.A. )

    1992-12-01

    Inverted growth and the development of associated cell processing, are likely to offer a significant degree of freedom for improving the performance of many III-V multijunction cascades and open new avenues for advanced multijunction concepts. This is especially true for the development of high-efficiency Al[sub 0.37]Ga[sub 0.63]As/GaAs cascades where the high growth temperatures required for the AlGaAs top cell growth can cause the deterioration of the tunnel junction interconnect. In the approach of inverted-grown AlGaAs/GaAs cascade cells, the AlGaAs top cell is grown first at 780 [degree]C and the GaAs tunnel junction and bottom cell are grown at 675 [degree]C. After the inverted growth, the AlGaAs/GaAs cascade structure is selectively removed from the parent substrate. The feasibility of inverted growth is demonstrated by a fully-processed, inverted-grown, thin film GaAs cell with a 1-sun AM1.5 efficiency of 20.3%. Also, an inverted-grown, thin-film, Al[sub 0.34]Ga[sub 0.66]As/GaAs cascade with AM1.5 efficiencies of 19.9% and 21% at 1-sun and 7-suns, respectively, has been obtained.

  4. 0.7-eV GaInAs Junction for a GaInP/GaAs/GaInAs(1-eV)/GaInAs(0.7-eV) Four-Junction Solar Cell: Preprint

    SciTech Connect (OSTI)

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

    2006-05-01

    We discuss recent developments in III-V multijunction solar cells, focusing on adding a fourth junction to the Ga0.5In0.5P/GaAs/Ga0.75In0.25As inverted three-junction cell. This cell, grown inverted on GaAs so that the lattice-mismatched Ga0.75In0.25As 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 GaxIn1-xAs 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 GaxIn1-xAs 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.

  5. Ammonium–cobalt–nickel phosphates, NH{sub 4}[Co{sub 1?x}Ni{sub x}PO{sub 4}]·H{sub 2}O

    SciTech Connect (OSTI)

    Torre-Fernández, Laura; Trobajo, Camino [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, Oviedo, Asturias 33006 (Spain); Pedro, Imanol de [CITIMAC, Facultad de Ciencias, Universidad de Cantabria, 39005 Santander (Spain); Alfonso, Belén F. [Departamento de Física, Universidad de Oviedo, Oviedo, Asturias 33007 (Spain); Fabelo, Oscar [Institut Laue Langevin, Grenoble, France and Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Zaragoza (Spain); Blanco, Jesús A. [Departamento de Física, Universidad de Oviedo, Oviedo, Asturias 33007 (Spain); García, José R., E-mail: jrgm@uniovi.es [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, Oviedo, Asturias 33006 (Spain); García-Granda, Santiago [Departamentos de Química Física y Analítica y Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, Oviedo, Asturias 33006 (Spain)

    2013-10-15

    The ammonium–cobalt–nickel phosphates, NH{sub 4}[Co{sub 1?x}Ni{sub x}PO{sub 4}]·H{sub 2}O (x=0.00, 0.34, 0.59, 0.70, 1.00), and the deuterated forms, ND{sub 4}[Co{sub 1?x}Ni{sub x}PO{sub 4}]·D{sub 2}O (x=0.00, 0.38, 0.48, 0.69, 0.85), have been synthesized under mild hydrothermal conditions and characterised using X-ray and neutron diffraction, chemical and thermal analysis, and magnetic measurements. Their crystal structures, including hydrogen positions, were determined by Rietveld refinement using single-crystal X-ray and neutron powder diffraction data. The space group of these orthorhombic crystals modifies as a function of their composition. The magnetic susceptibility and magnetization measurements of these ammonium–cobalt–nickel phosphates show antiferromagnetic behaviour, and the Neel temperature evolves from 5.5 K (x=0.00) up to 13.2 K (x=1.00). - Graphical abstract: We obtained single crystals for all the members of the family. In this series, although all crystals are orthorhombic, the space group changes as a function of the composition, showing how the single-crystal diffraction data is capable to manifest structural subtleties that had not been described before for this group of materials. All the investigated materials behave antiferromagnetically with ordering temperatures from 5.5 K up to 13.2 K. Display Omitted - Highlights: • The ammonium–cobalt–nickel phosphates, NH{sub 4}[Co{sub 1?x}Ni{sub x}PO{sub 4}]·H{sub 2}O (x=0.00, 0.34, 0.59, 0.70, 1.00) and the deuterated forms ND4[Co1-xNixPO4]·D{sub 2}O (x=0.00, 0.38, 0.49, 0.68, 0.85) have synthesized by hydrothermal synthesis. • The structural studies of these compounds are introduced as a function of the composition. • The magnetic studies show an antiferromagnetically behavior with ordering temperatures from 5.5 K to 13.2 K.

  6. Investigation of carbon distribution with {sup 14}C as tracer for carbon dioxide (CO{sub 2}) sequestration through NH{sub 4}HCO{sub 3} production

    SciTech Connect (OSTI)

    Zhongxian Cheng; Youhua Ma; Xin Li; Wei-Ping Pan [Western Kentucky University, Bowling Green, KY (United States). Institute for Combustion Science and Environmental Technology

    2007-12-15

    This work studies carbon fate using the {sup 14}C tracer technique in ecosystems when synthesized fertilizer is applied. The concept of aqueous ammonia solution scrubbing CO{sub 2} from flue gas is used in the fertilizer synthesis. Products after the capture are ammonium bicarbonate (ABC, NH{sub 4}HCO{sub 3}) or long-term effect ammonium bicarbonate (LEABC, NH{sub 4}HCO{sub 3}), an economic source of nitrogen fertilizer. The ABC or LEABC is used as a 'carrier' to transport CO{sub 2} from the atmosphere to the crops and soil. An indoor greenhouse was built, and wheat was chosen as the plant to study in this ecosystem. The investigated ecosystem consists of plant (wheat), soils with three different pH values (alkaline, neutral, and acidic), and three types of underground water (different Ca{sup 2+} and Mg{sup 2+} concentrations). After biological assimilation and metabolism in wheat receiving ABC or LEABC, it was found that a considerable amount (up to 10%) of the carbon source was absorbed by the wheat with increased biomass production. The majority of the unused carbon source (up to 76%) percolated into the soil as carbonates, such as environmentally benign calcium carbonate (CaCO{sub 3}). Generally speaking, alkaline soil has a higher capability to capture and store carbon. For the same soil, there is no apparent difference in carbon capturing capability between ABC and LEABC. These findings answer the question of how carbon is distributed after synthesized ABC or LEABC is applied into the ecosystem. In addition, a separate postexperiment on carbon forms that existed in the soil was made. It was found that up to 88% of the trapped carbon existed in the form of insoluble salts (i.e., CaCO{sub 3}) in alkaline soils. This indicates that alkaline soil has a greater potential for storing carbon after the use of the synthesized ABC or LEABC from exhausted CO{sub 2}. 21 refs., 6 figs., 5 tabs.

  7. Intersubband transitions in In{sub x}Ga{sub 1?x}N/In{sub y}Ga{sub 1?y}N/GaN staggered quantum wells

    SciTech Connect (OSTI)

    Y?ld?r?m, Hasan; Aslan, Bulent

    2014-04-28

    Intersubband transition energies and absorption lineshape in staggered InGaN/GaN quantum wells surrounded by GaN barriers are computed as functions of structural parameters such as well width, In concentrations, and the doping level in the well. Schrödinger and Poisson equations are solved self-consistently by taking the free and bound surface charge concentrations into account. Many-body effects, namely, depolarization and excitonic shifts are also included in the calculations. Results for transition energies, oscillator strength, and the absorption lineshape up to nonlinear regime are represented as functions of the parameters mentioned. The well width (total and constituent layers separately) and In concentration dependence of the built-in electric field are exploited to tune the intersubband transition energies.

  8. Effect of Ga content on defect states in CuIn1xGaxSe2 photovoltaic devices

    E-Print Network [OSTI]

    Rockett, Angus

    gaps for single junction solar cells expected to be around 1.4 eV.2 This corresponds to a Ga fraction x 0.6, with x Ga/(In Ga). Higher Ga material would also be useful as a component of multi-junction or graded band gap cells. However, the best devices to date contain material with x 0.2, and it is difficult

  9. High efficiency InGaAs solar cells on Si by InP layer transfer James M. Zahler

    E-Print Network [OSTI]

    Atwater, Harry

    illumination was achieved using an InGaP/GaAs/InGaAs triple-junction cell design with an In- GaAs bottom cell.1 benefit from such an InP/Si substrate.2 Additionally, a proposed four-junction solar cell, fabri- cated for bulk InP in the fabrication of such a four-junction solar cell could significantly reduce the substrate

  10. Junction temperature, spectral shift, and efficiency in GaInN-based blue and green light emitting diodes

    E-Print Network [OSTI]

    Wetzel, Christian M.

    Keywords: GaInN/GaN Light emitting diode temperature Micro-Raman Photoluminescence Electroluminescence well light emitting diode (LED) dies is analyzed by micro-Raman, photoluminescence, cathodoluminescenceJunction temperature, spectral shift, and efficiency in GaInN-based blue and green light emitting

  11. Cr-Ga-N materials for negative electrodes in Li rechargeable batteries : structure, synthesis and electrochemical performance

    E-Print Network [OSTI]

    Kim, Miso

    2007-01-01

    Electrochemical performances of two ternary compounds (Cr2GaN and Cr3GaN) in the Cr-Ga-N system as possible future anode materials for lithium rechargeable batteries were studied. Motivation for this study was dealt in ...

  12. High bandwidth-efficiency solar-blind AlGaN Schottky photodiodes with low dark current

    E-Print Network [OSTI]

    High bandwidth-efficiency solar-blind AlGaN Schottky photodiodes with low dark current T. Tut a , N.38Ga0.62N/GaN heterojunction solar-blind Schottky photodetectors with low dark current, high responsivity, and fast pulse response were demonstrated. A five-step microwave compatible fabrication process

  13. Strain relaxation of thick (11–22) semipolar InGaN layer for long wavelength nitride-based device

    SciTech Connect (OSTI)

    Kim, Jaehwan; Min, Daehong; Jang, Jongjin; Lee, Kyuseung; Chae, Sooryong; Nam, Okhyun, E-mail: ohnam@kpu.ac.kr [Advanced Photonics Research Center/LED Technology Center, Department of Nano-Optical Engineering, Korea Polytechnic University, 237, Sangidaehak-ro, Siheung-si, Gyeonggi-do 429-793 (Korea, Republic of)

    2014-10-28

    In this study, the properties of thick stress-relaxed (11–22) semipolar InGaN layers were investigated. Owing to the inclination of growth orientation, misfit dislocations (MDs) occurred at the heterointerface when the strain state of the (11–22) semipolar InGaN layers reached the critical point. We found that unlike InGaN layers based on polar and nonpolar growth orientations, the surface morphologies of the stress-relaxed (11–22) semipolar InGaN layers did not differ from each other and were similar to the morphology of the underlying GaN layer. In addition, misfit strain across the whole InGaN layer was gradually relaxed by MD formation at the heterointerface. To minimize the effect of surface roughness and defects in GaN layers on the InGaN layer, we conducted further investigation on a thick (11–22) semipolar InGaN layer grown on an epitaxial lateral overgrown GaN template. We found that the lateral indium composition across the whole stress-relaxed InGaN layer was almost uniform. Therefore, thick stress-relaxed (11–22) semipolar InGaN layers are suitable candidates for use as underlying layers in long-wavelength devices, as they can be used to control strain accumulation in the heterostructure active region without additional influence of surface roughness.

  14. Experimental and theoretical studies of band gap alignment in GaAs{sub 1?x}Bi{sub x}/GaAs quantum wells

    SciTech Connect (OSTI)

    Kudrawiec, R. Kopaczek, J.; Polak, M. P.; Scharoch, P.; Gladysiewicz, M.; Misiewicz, J.; Richards, R. D.; Bastiman, F.; David, J. P. R.

    2014-12-21

    Band gap alignment in GaAs{sub 1?x}Bi{sub x}/GaAs quantum wells (QWs) was studied experimentally by photoreflectance (PR) and theoretically, ab initio, within the density functional theory in which the supercell based calculations are combined with the alchemical mixing approximation applied to a single atom in a supercell. In PR spectra, the optical transitions related to the excited states in the QW (i.e., the transition between the second heavy-hole and the second electron subband) were clearly observed in addition to the ground state QW transition and the GaAs barrier transition. This observation is clear experimental evidence that this is a type I QW with a deep quantum confinement in the conduction and valence bands. From the comparison of PR data with calculations of optical transitions in GaAs{sub 1?x}Bi{sub x}/GaAs QW performed for various band gap alignments, the best agreement between experimental data and theoretical calculations has been found for the valence band offset of 52?±?5%. A very similar valence band offset was obtained from ab initio calculations. These calculations show that the incorporation of Bi atoms into GaAs host modifies both the conduction and the valence band. For GaAs{sub 1?x}Bi{sub x} with 0?GaAs{sub 1?x}Bi{sub x} and GaAs in the range of ?60%–40% (?40%–60%), which is in good agreement with our conclusion derived from PR measurements.

  15. Imaging ion-molecule reactions: Charge transfer and C-N bond formation in the C{sup +}+ NH{sub 3} system

    SciTech Connect (OSTI)

    Pei, Linsen; Farrar, James M. [Department of Chemistry, University of Rochester, Rochester, New York 14627 (United States)

    2012-05-28

    The velocity mapping ion imaging method is applied to the ion-molecule reactions occurring between C{sup +} and NH{sub 3}. The velocity space images are collected over the relative collision energy range from 1.5 to 3.3 eV, allowing both product kinetic energy distributions and angular distributions to be obtained from the data. The charge transfer process appears to be direct, dominated by long-range electron transfer that results in minimal deflection of the products. The product kinetic energy distributions are consistent with a process dominated by energy resonance. The kinetic energy distributions for C-N bond formation appear to scale with the total available energy, providing strong evidence that energy in the [CNH{sub 3}]{sup +} precursor to products is distributed statistically. The angular distributions for C-N bond formation show pronounced forward-backward symmetry, as expected for a complex that resembles a prolate symmetric top decaying along its symmetry axis.

  16. MOSE: a feasibility study for optical turbulence forecasts with the Meso-Nh mesoscale model to support AO facilities at ESO sites (Paranal and Armazones)

    E-Print Network [OSTI]

    Masciadri, E; 10.1117/12.925924

    2012-01-01

    We present very encouraging preliminary results obtained in the context of the MOSE project, an on-going study aiming at investigating the feasibility of the forecast of the optical turbulence and meteorological parameters (in the free atmosphere as well as in the boundary and surface layer) at Cerro Paranal (site of the Very Large Telescope - VLT) and Cerro Armazones (site of the European Extremely Large Telescope - E-ELT), both in Chile. The study employs the Meso-Nh atmospheric mesoscale model and aims at supplying a tool for optical turbulence forecasts to support the scheduling of the scientific programs and the use of AO facilities at the VLT and the E-ELT. In this study we take advantage of the huge amount of measurements performed so far at Paranal and Armazones by ESO and the TMT consortium in the context of the site selection for the E-ELT and the TMT to constraint/validate the model. A detailed analysis of the model performances in reproducing the atmospheric parameters (T, V, p, H, ...) near the g...

  17. Application of x-ray tomography to optimization of new NOx/NH3 mixed potential sensors for vehicle on-board emissions control

    SciTech Connect (OSTI)

    Nelson, Mark A; Brosha, Eric L; Mukundan, Rangachary; Garzon, Fernando H

    2009-01-01

    Mixed potential sensors for the detection of hydrocarbons, NO{sub x}, and NH{sub 3} have been previously developed at Los Alamos National Laboratory (LANL). The LANL sensors have a unique design incorporating dense ceramic-pelletlmetal-wire electrodes and porous electrolytes. The performance of current-biased sensors using an yttria-stabilized zirconia (YSZ) electrolyte and platinum and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} electrodes is reported. X-ray tomography has been applied to non-destructively examine internal structures of these sensors. NO{sub x} and hydrocarbon response of the sensors under various bias conditions is reported, and very little NO{sub x} response hysteresis was observed. The application of a 0.6 {mu}A bias to these sensors shifts the response from a hydrocarbon response to a NO{sub x} response equal for both NO and NO{sub 2} species at approximately 500 {sup o}C in air.

  18. LOW-TEMPERATURE ION TRAP STUDIES OF N{sup +}({sup 3} P{sub ja} ) + H{sub 2}(j) {yields} NH{sup +} + H

    SciTech Connect (OSTI)

    Zymak, I.; Hejduk, M.; Mulin, D.; Plasil, R.; Glosik, J.; Gerlich, D.

    2013-05-01

    Using a low-temperature 22-pole ion trap apparatus, detailed measurements for the title reaction have been performed between 10 K and 100 K in order to get some state specific information about this fundamental hydrogen abstraction process. The relative population of the two lowest H{sub 2} rotational states, j = 0 and 1, has been varied systematically. NH{sup +} formation is nearly thermo-neutral; however, to date, the energetics are not known with the accuracy required for low-temperature astrochemistry. Additional complications arise from the fact that, so far, there is no reliable theoretical or experimental information on how the reactivity of the N{sup +} ion depends on its fine-structure (FS) state {sup 3} P{sub ja} . Since in the present trapping experiment, thermalization of the initially hot FS population competes with hydrogen abstraction, the evaluation of the decay of N{sup +} ions over long storage times and at various He and H{sub 2} gas densities provides information on these processes. First assuming strict adiabatic behavior, a set of state specific rate coefficients is derived from the measured thermal rate coefficients. In addition, by recording the disappearance of the N{sup +} ions over several orders of magnitude, information on nonadiabatic transitions is extracted including FS-changing collisions.

  19. Ultra-broadband terahertz time-domain ellipsometric spectroscopy utilizing GaP and GaSe emitters and an epitaxial layer transferred photoconductive detector

    SciTech Connect (OSTI)

    Yamashita, Masatsugu, E-mail: m-yama@riken.jp; Takahashi, Hideki; Otani, Chiko [RIKEN Center for Advanced Photonics, 519-1399 Aobaaramaki, Aoba-ku, Sendai 980-0845 (Japan); Ouchi, Toshihiko [Corporate R and D Headquarters, Canon Inc., 30-2 Shimomaruko 3-Chome, Ohta-ku, Tokyo 145-8501 (Japan)

    2014-02-03

    We present a reflection-type ultra-broadband terahertz (THz) time-domain spectroscopic ellipsometry system covering the frequency range of 0.5–30 THz. GaP (110) and z-cut GaSe crystals are used as emitters to generate the THz and mid-infrared pulses, respectively, and a photoconductive antenna switch using a low-temperature grown GaAs epitaxial layer transferred on Si substrate was used as a detector. By changing the emitter between the GaP and GaSe crystals, the measurable frequency range can be easily switched from the 0.5–7.8 THz range to the 7.8–30 THz range without additional optical alignment. We demonstrated the measurement of the dielectric function in a p-type InAs wafer and the optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good agreement with that obtained by the Hall measurement.

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

    SciTech Connect (OSTI)

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

    2012-07-23

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

  1. Sulfur-mediated palladium catalyst immobilized on a GaAs surface

    SciTech Connect (OSTI)

    Shimoda, M. [Surface Physics and Structure Unit, Surface Physics Group, National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Konishi, T. [Anan National College of Technology, 265 Aoki, Minobayashi-cho, Anan, Tokushima 774-0017 (Japan); Nishiwaki, N. [School of Environmental and Engineering, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Yamashita, Y.; Yoshikawa, H. [Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

    2012-06-15

    We present a hard x-ray photoelectron spectroscopy study on the preparation process of palladium catalyst immobilized on an S-terminated GaAs(100) surface. It is revealed that Pd(II) species are reduced on the GaAs surface and yield Pd nanoparticles during the process of Pd immobilization and the subsequent heat treatment. A comparison with the results on GaAs without S-termination suggests that the reduction of Pd is promoted by hydroxy groups during the Pd immobilization and by S during the heat treatment.

  2. p-type GaN grown by phase shift epitaxy

    SciTech Connect (OSTI)

    Zhong, M.; Steckl, A. J., E-mail: a.steckl@uc.edu [Department of Electrical Engineering and Computing Systems, University of Cincinnati, Cincinnati, Ohio 45221-0030 (United States); Roberts, J. [Nitronex Corporation, Raleigh, North Carolina 27606 (United States)] [Nitronex Corporation, Raleigh, North Carolina 27606 (United States); Kong, W.; Brown, A. S. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States)] [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States)

    2014-01-06

    Phase shift epitaxy (PSE) is a periodic growth scheme, which desynchronizes host material growth process from dopant incorporation, allowing independent optimization. p-type doping of GaN with Mg by PSE is accomplished with molecular beam epitaxy by periodic shutter action (in order to iterate between Ga- and N-rich surface conditions) and by adjusting time delays between dopant and Ga shutters. Optimum PSE growth was obtained by turning on the Mg flux in the N-rich condition. This suppresses Mg self-compensation at high Mg concentration and produces fairly high hole concentrations (2.4?×?10{sup 18}?cm{sup ?3})

  3. Low Cost Production of InGaN for Next-Generation Photovoltaic Devices

    SciTech Connect (OSTI)

    Nick M. Sbrockey, Shangzhu Sun, Gary S. Tompa,

    2012-07-09

    The goal of this project is to develop a low-cost and low-energy technology for production of photovoltaic devices based on InGaN materials. This project builds on the ongoing development by Structured Materials Industries (SMI), of novel thin film deposition technology for Group III-Nitride materials, which is capable of depositing Group-III nitride materials at significantly lower costs and significantly lower energy usage compared to conventional deposition techniques. During this project, SMI demonstrated deposition of GaN and InGaN films using metalorganic sources, and demonstrated compatibility of the process with standard substrate materials and hardware components.

  4. Coherent acoustic phonon generation in GaAs{sub 1?x}Bi{sub x}

    SciTech Connect (OSTI)

    Joshya, R. S.; Kini, R. N., E-mail: rajeevkini@iisertvm.ac.in [Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), CET Campus, Thiruvananthapuram, Kerala 695016 (India); Ptak, A. J.; France, R.; Mascarenhas, A. [National Renewable Energy Laboratory (NREL), 1617 Cole Blvd., Golden, Colorado 80401 (United States)

    2014-03-03

    We have used femtosecond laser pulses to generate coherent acoustic phonons in the dilute Bismide alloy, GaAs{sub 1?x}Bi{sub x}. The observed oscillation periods match well with the oscillation periods calculated using the propagating strain pulse model. We attribute the generation process predominantly to electronic stress due to the absorption of the laser pulse at the surface of the GaAs{sub 1?x}Bi{sub x} layer. Our initial estimates suggest that the incorporation of Bi in GaAs causes an enhancement of the hydrostatic deformation potential because of the resonant state in the valence band due to isolated Bi impurities.

  5. Towards Fully Integrated High Temperature Wireless Sensors Using GaN-based HEMT Devices

    SciTech Connect (OSTI)

    Kuruganti, Phani Teja [ORNL; Islam, Syed K [ORNL; Huque, Mohammad A [ORNL

    2008-01-01

    Wireless sensors which are capable of working at extreme environments can significantly improve the efficiency and performance of industrial processes by facilitating better control systems. GaN, a widely researched wide bandgap material, has the potential to be used both as a sensing material and to fabricate control electronics, making it a prime candidate for high temperature integrated wireless sensor fabrication. In this paper we are presenting an experimental study on AlGaN/GaN HEMT's performance at higher temperature (up to 300 C). From test results, DC and microwave parameters at different temperatures were extracted.

  6. Temperature dependence of non-radiative energy transfer in hybrid structures of InGaN/GaN nanorods and F8BT films

    SciTech Connect (OSTI)

    Smith, R. M.; Liu, B.; Bai, J.; Wang, T., E-mail: t.wang@sheffield.ac.uk [Department of Electrical and Electronic Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2014-10-27

    Hybrid organic/inorganic white light emitting structures have been fabricated based on a combination of high efficiency InGaN/GaN multiple quantum well (MQW) nanorod arrays and a yellow emitting co-polymer F8BT, leading to a minimised separation between them in order to achieve high efficiency non-radiative energy transfer (NRET). The NRET efficiency has been found 6.7 times higher at room temperature than at 7?K. This is attributed to the existence of strong exciton localization the InGaN MQWs, which can undergo thermally activated delocalization at high temperatures. The enhanced NRET efficiency is not only due to the delocalized MQW excitons, but also enhanced by the increased exciton diffusion at higher temperatures. This behaviour highlights the potential for high efficiency NRET in down-conversion hybrid white light emitting diodes operating at room temperature.

  7. Polarization self-screening in [0001] oriented InGaN/GaN light-emitting diodes for improving the electron injection efficiency

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Zhang, Xueliang; Wang, Liancheng; Kyaw, Zabu; Wei Sun, Xiao, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Volkan Demir, Hilmi, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

    2014-06-23

    InGaN/GaN light-emitting diodes (LEDs) grown along the [0001] orientation inherit very strong polarization induced electric fields. This results in a reduced effective conduction band barrier height for the p-type AlGaN electron blocking layer (EBL) and makes the electron blocking effect relatively ineffective and the electron injection efficiency drops. Here, we show the concept of polarization self-screening for improving the electron injection efficiency. In this work, the proposed polarization self-screening effect was studied and proven through growing a p-type EBL with AlN composition partially graded along the [0001] orientation, which induces the bulk polarization charges. These bulk polarization charges are utilized to effectively self-screen the positive polarization induced interface charges located at the interface between the EBL and the last quantum barrier when designed properly. Using this approach, the electron leakage is suppressed and the LED performance is enhanced significantly.

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

    SciTech Connect (OSTI)

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

    2014-11-03

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

  9. Bias dependence and correlation of the cathodoluminescence and electron beam induced current from an InGaN/GaN light emitting diode

    SciTech Connect (OSTI)

    Wallace, M. J.; Edwards, P. R.; Martin, R. W. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Kappers, M. J.; Oehler, F.; Oliver, R. A.; Humphreys, C. J. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Hopkins, M. A.; Sivaraya, S.; Allsopp, D. W. E. [Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom)

    2014-07-21

    Micron-scale mapping has been employed to study a contacted InGaN/GaN LED using combined electroluminescence (EL), cathodoluminescence (CL), and electron beam induced current (EBIC). Correlations between parameters, such as the EBIC and CL intensity, were studied as a function of applied bias. The CL and EBIC maps reveal small areas, 2–10??m in size, which have increased nonradiative recombination rate and/or a lower conductivity. The CL emission from these spots is blue shifted, by 30–40?meV. Increasing the reverse bias causes the size of the spots to decrease, due to competition between in-plane diffusion and drift in the growth direction. EL mapping shows large bright areas (?100??m) which also have increased EBIC, indicating domains of increased conductivity in the p and/or n-GaN.

  10. Current flow and potential efficiency of solar cells based on GaAs and GaSb p-n junctions

    SciTech Connect (OSTI)

    Andreev, V. M.; Evstropov, V. V.; Kalinovsky, V. S. Lantratov, V. M.; Khvostikov, V. P.

    2009-05-15

    Dependence of the efficiency of single-junction and multijunction solar cells on the mechanisms of current flow in photoactive p-n junctions, specifically on the form of the dark current-voltage characteristic J-V, has been studied. The resistanceless J-V{sub j} characteristic (with the series resistance disregarded) of a multijunction solar cell has the same shape as the characteristic of a single-junction cell: both feature a set of exponential portions. This made it possible to develop a unified analytical method for calculating the efficiency of singlejunction and multijunction solar cells. The equation relating the efficiency to the photogenerated current at each portion of the J-V{sub j} characteristic is derived. For p-n junctions in GaAs and GaSb, the following characteristics were measured: the dark J-V characteristic, the dependence of the open-circuit voltage on the illumination intensity P-V{sub OC}, and the dependence of the luminescence intensity on the forward current L-J. Calculated dependences of potential efficiency (under idealized condition for equality to unity of external quantum yield) on the photogenerated current for single-junction GaAs and GaSb solar cells and a GaAs/GaSb tandem are plotted. The form of these dependences corresponds to the shape of J-V{sub j} characteristics: there are the diffusion- and recombination-related portions; in some cases, the tunneling-trapping portion is also observed. At low degrees of concentration of solar radiation (C < 10), an appreciable contribution to photogenerated current is made by recombination component. It is an increase in this component in the case of irradiation with 6.78-MeV protons or 1-MeV electrons that brings about a decrease in the efficiency of conversion of unconcentrated solar radiation.

  11. Atomic imaging of atomic layer deposition oxide nucleation with trimethylaluminum on As-rich InGaAs(001) 2 4 vs Ga/In-rich InGaAs(001) 4 2

    E-Print Network [OSTI]

    Kummel, Andrew C.

    Atomic imaging of atomic layer deposition oxide nucleation with trimethylaluminum on As-rich In atomic layer deposition Appl. Phys. Lett. 104, 042904 (2014); 10.1063/1.4863440 Effective passivation of In0.2Ga0.8As by HfO2 surpassing Al2O3 via in-situ atomic layer deposition Appl. Phys. Lett. 101

  12. How much better are InGaN/GaN nanodisks than quantum wells—Oscillator strength enhancement and changes in optical properties

    SciTech Connect (OSTI)

    Zhang, Lei; Hill, Tyler A.; Deng, Hui E-mail: peicheng@umich.edu; Lee, Leung-Kway; Teng, Chu-Hsiang; Ku, Pei-Cheng E-mail: peicheng@umich.edu

    2014-02-03

    We show over 100-fold enhancement of the exciton oscillator strength as the diameter of an InGaN nanodisk in a GaN nanopillar is reduced from a few micrometers to less than 40?nm, corresponding to the quantum dot limit. The enhancement results from significant strain relaxation in nanodisks less than 100?nm in diameter. Meanwhile, the radiative decay rate is only improved by 10 folds due to strong reduction of the local density of photon states in small nanodisks. Further increase in the radiative decay rate can be achieved by engineering the local density of photon states, such as adding a dielectric coating.

  13. Terahertz waveguide spectroscopy of two-dimensional plasmons in GaAs

    E-Print Network [OSTI]

    Harris, C. Thomas (Charles Thomas)

    2010-01-01

    The electrical characteristics of high-mobility, two-dimensional electron gas (2DEG) systems, such as GaAs quantum wells, have been well-studied at low frequencies and in extreme conditions of high magnetic fields and ...

  14. Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors 

    E-Print Network [OSTI]

    Jungwirth, T.; Wang, KY; Masek, J.; Edmonds, KW; Konig, J.; Sinova, Jairo; Polini, M.; Goncharuk, NA; MacDonald, AH; Sawicki, M.; Rushforth, AW; Campion, RP; Zhao, LX; Foxon, CT; Gallagher, BL.

    2005-01-01

    We report on a comprehensive combined experimental and theoretical study of Curie temperature trends in (Ga,Mn)As ferromagnetic semiconductors. Broad agreement between theoretical expectations and measured data allows us to conclude that T-c in high...

  15. Precision of a Low-Cost InGaAs Detector for Near Infrared Photometry

    E-Print Network [OSTI]

    Simcoe, Robert A.

    We have designed, constructed, and tested an InGaAs near-infrared camera to explore whether low-cost detectors can make small (?1 m) telescopes capable of precise (photometry of relatively bright targets. ...

  16. Near-infrared InGaAs detectors for background-limited imaging and photometry

    E-Print Network [OSTI]

    Sullivan, Peter W.

    Originally designed for night-vision equipment, InGaAs detectors are beginning to achieve background-limited performance in broadband imaging from the ground. The lower cost of these detectors can enable multi-band ...

  17. GaN/Cu[subscript 2]O Heterojunctions for Photovoltaic Applications

    E-Print Network [OSTI]

    Hering, K.P.

    Several growth methods were employed to investigate the photovoltaic behavior of GaN/Cu[subscript 2]O heterojunctions by depositing cuprous oxide thin films on top of gallium nitride templates. The templates consist of a ...

  18. Sandia Energy - Optical performance of top-down fabricated InGaN...

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

    performance of top-down fabricated InGaNGaN nanorod light emitting diode arrays" in Optics Express. This paper details the development of a two-step top-down process for...

  19. Understanding and development of combined acoustic and magnetic actuation of Ni?MnGa single crystals

    E-Print Network [OSTI]

    Techapiesancharoenkij, Ratchatee, 1979-

    2007-01-01

    Ni-Mn-Ga based ferromagnetic shape memory alloys (FSMAs) have emerged as a promising new class of active materials capable of producing a large (several %) magnetic-field-induced strain (MFIS). FSMAs still have several ...

  20. MULTIPLE-WINDOW SPECTROMETRY FOR $sup 67$Ga. Ross, D A; McClain...

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

    FOR sup 67Ga. Ross, D A; McClain, W J; East, J K; Bell, P R N26110* --Instrumentation--Radiation Detection Instruments-- General Detectors & Monitors; N28530 --Life...

  1. High-efficiency GaAs/Ge monolithic tandem solar cells

    SciTech Connect (OSTI)

    Tobin, S.P.; Vernon, S.M.; Bajgar, C.; Haven, V.E.; Geoffroy, L.M.; Lillington, D.R.

    1988-05-01

    High photovoltaic efficiency and light weight are important criteria for spacecraft power applications. Present GaAs cells are approaching their efficiency limits, but are not efficient or light enough for future needs. The authors have investigated tandem cells of GaAs grown by MOCVD on thin Ge to address both higher efficiency and reduced weight. GaAs/Ge monolithic tandem cells of 4-cm/sup 2/ area have been produced with independently verified efficiencies up to 21.7 percent (AMO, one sun, 25/sup 0/C, total area). Under AM1.5 Global conditions, efficiencies are up to 24.3 percent. These are the highest one-sun efficiencies reported for GaAs/Ge cells, and the highest efficiency for a two-terminal monolithic tandem cell.

  2. High Voltage GaN-on-Si Field-Effect Transistors for Switching Applications

    E-Print Network [OSTI]

    Chen, Xu

    2015-01-01

    efficient GaN HEMT boost converter with 300-W output power29 Figure 3.13. Half-bridge boost converterin a half-bridge boost converter circuit shown in figure

  3. Deeply-scaled GaN high electron mobility transistors for RF applications

    E-Print Network [OSTI]

    Lee, Dong Seup

    2014-01-01

    Due to the unique combination of large critical breakdown field and high electron velocity, GaN-based high electron mobility transistors (HEMTs) have great potential for next generation high power RF amplifiers. The ...

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

    E-Print Network [OSTI]

    Chung, Jinwook W. (Jinwook Will)

    2011-01-01

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

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

    SciTech Connect (OSTI)

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

    2011-12-05

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

  6. Probing the structure of the N=Z=31 nucleus {sub 31}{sup 62}Ga

    SciTech Connect (OSTI)

    Vincent, S. M.; Regan, P. H.; Gelletly, W.; Pearson, C. J. [Department of Physics, University of Surrey, Guildford GU2 5XH (United Kingdom); Warner, D. D.; Simpson, J. [CCLRC Daresbury Laboratory, Warrington, WA4 4AD (United Kingdom); Bark, R.; Saitoh, T. [Niels Bohr Institute Tandem Accelerator Laboratory, Risoe, DK-4000, Roskilde (Denmark); Blumenthal, D.; Carpenter, M. P.; Davids, C. N.; Henderson, D. J.; Janssens, R. V. F.; Lister, C. J.; Nisius, D.; Seweryniak, D. [Argonne National Laboratory, 9700 South Cass Ave, Illinois 60439 (United States); O'Leary, C. D. [School of Sciences, Staffordshire University, Stoke-on-Trent, ST4 2DE (United Kingdom); Schwartz, J. [Argonne National Laboratory, 9700 South Cass Ave, Illinois 60439 (United States); A. W. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06511 (United States); Toermaenen, S. [Niels Bohr Institute Tandem Accelerator Laboratory, Risoe, DK-4000, Roskilde (Denmark); Department of Physics, University of Jyvaekylae, Jyvaekylae (Finland)

    1998-12-21

    The decay scheme of the N=Z odd-odd nucleus, {sup 62}Ga has been deduced for the first time using the reactions {sup 40}Ca({sup 24}Mg,pn){sup 62}Ga and {sup 40}Ca({sup 28}Si,{alpha}pn){sup 62}Ga at beam energies of 65 MeV and 88 MeV respectively. Transitions from excited states in {sup 62}Ga were identified using the PEX apparatus at the Niels Bohr Institute Tandem Accelerator Laboratory. Gamma ray angular correlation data collected using the AYEBALL array at the Argonne National Laboratory are consistent with a cascade of stretched E2 transitions which decay from a spin 1{sup +} bandhead via a pure magnetic dipole decay, directly linking a proposed T=0 structure with the T=1, J{sup {pi}}=0{sup +} ground state.

  7. Stimulated emission in GaN-based laser diodes far below the threshold region

    E-Print Network [OSTI]

    2014-01-01

    forward current of light-emitting diodes,” J. Appl. Phys.superluminescent light-emitting diodes based on GaN,” Appl.superluminescent light emitting diode structures,” J. Appl.

  8. Low-temperature charge transport in Ga-acceptor nanowires implanted by focused-ion beams

    E-Print Network [OSTI]

    Robinson, SJ

    2008-01-01

    3 ) through an 11-nm oxide layer. 10 The beam density duringemission images of the oxide layers, and they are typicallyJVD) 23 over the 11-nm oxide layer of the Ga-implanted

  9. Mechanism of lateral ordering of InP dots grown on InGaP layers

    SciTech Connect (OSTI)

    Bortoleto, J.R.R.; Gutierrez, H.R.; Cotta, M.A.; Bettini, J.

    2005-07-04

    The mechanisms leading to the spontaneous formation of a two-dimensional array of InP/InGaP dots grown by chemical-beam epitaxy are discussed. Samples where the InGaP buffer layer was grown at different conditions were characterized by transmission electron microscopy. Our results indicate that a periodic strain field related to lateral two-dimensional compositional modulation in the InGaP buffer layer determines the dot nucleation positions during InP growth. Although the periodic strain field in the InGaP is large enough to align the InP dots, both their shape and optical properties are effectively unaltered. This result shows that compositional modulation can be used as a tool for in situ dot positioning.

  10. Tuning of Spin Dependent Reflection at Ferromagnet/GaAs Interfaces

    E-Print Network [OSTI]

    Li, Yan

    2010-01-01

    In this mix, graphene is a zero gap semiconductor and spinsemiconductors have been realized on GaAs [24, 32], Si [33-35], Graphene [graphene has also been realized. 1.3.1 Spin injection into semiconductors

  11. Growth of GaMnAs under near-stoichiometric conditions

    SciTech Connect (OSTI)

    Avrutin, V.; Humienik, D.; Frank, S.; Koeder, A.; Schoch, W.; Limmer, W.; Sauer, R.; Waag, A. [Abteilung Halbleiterphysik, Universitaet Ulm, D-89069 Ulm (Germany); Institut fuer Halbleitertechnik, Technische Universitaet (TU) Braunschweig, Hans-Sommer-Strasse 66, D38103 Braunschweig (Germany)

    2005-07-15

    We studied the effect of the V/III flux ratio and substrate temperature on magnetotransport properties and lattice parameters of Ga{sub 0.96}Mn{sub 0.04}As grown by molecular-beam epitaxy. For all the substrate temperatures, the conductivities and Curie temperatures of the layers were found to increase as the V/III flux ratio approaches 1. A Curie temperature as high as 95 K was achieved for the Ga{sub 0.96}Mn{sub 0.04}As samples grown at 240 deg. C and a V/III ratio of about 1.5. The lattice parameter of Ga{sub 0.96}Mn{sub 0.04}As increased with decreasing V/III ratio and/or increasing growth temperature. Possible reasons for the effect of the V/III ratio on the magnetotransport properties and lattice parameter of GaMnAs are discussed.

  12. Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers

    SciTech Connect (OSTI)

    Yastrubchak, O., E-mail: yastrub@hektor.umcs.lublin.pl [Institute of Physics, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Institute of Semiconductor Physics, National Academy of Sciences, 41 pr. Nauki, 03028 Kyiv (Ukraine); Sadowski, J. [MAX-IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Gluba, L.; ?uk, J.; Kulik, M. [Institute of Physics, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Domagala, J. Z.; Andrearczyk, T.; Wosinski, T. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Rawski, M. [Analytical Laboratory, Maria Curie-Sklodowska University in Lublin, Pl. M. Curie-Sk?odowskiej 3, 20-031 Lublin (Poland)

    2014-08-18

    Impact of Bi incorporation into (Ga,Mn)As layers on their electronic- and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition.

  13. Computational Thermodynamics of CoNiGa High Temperature Shape Memory Alloys 

    E-Print Network [OSTI]

    Chari, Arpita

    2012-10-19

    Shape Memory Alloys (SMAs) are advanced materials with interesting properties such as pseudoelasticity (PE) and the shape memory effect (SME). Recently, the CoNiGa system has emerged as the basis for very promising High ...

  14. Structure and magnetic properties of Ce?(Ni/Al/Ga)??-A...

    Office of Scientific and Technical Information (OSTI)

    Ce(NiAlGa)-A new phase with the LaAl structure type Janka, Oliver Univ. of California, Davis, CA (United States); Westfalische Wilhelms-Universitat, Munster...

  15. Anisotropic intermediate valence in Yb2M3Ga9 (M = Rh, Ir)

    SciTech Connect (OSTI)

    Christianson, A.D.; Lawrence, J.M.; Lobos, A.M.; Aligia, A.A.; Bauer, E.D.; Moreno, N.O.; Booth, C.H.; Goremychkin, E.A.; Sarrao, J.L.; Thompson, J.D.; Batista, C.D.; Trouw, F.R.; Hehlen, M.P.

    2005-04-26

    The intermediate valence compounds Yb{sub 2}M{sub 3}Ga{sub 9} (M = Rh, Ir) exhibit an anisotropic magnetic susceptibility. We report measurements of the temperature dependence of the 4f occupation number, n{sub f}(T), for Yb{sub 2}M{sub 3}Ga{sub 9} as well as the magnetic inelastic neutron scattering spectrum S{sub mag}({Delta}E) at 12 and 300 K for Yb{sub 2}Rh{sub 3}Ga{sub 9}. Both n{sub f}(T) and S{sub mag}({Delta}E) were calculated for the Anderson impurity model with crystal field terms within an approach based on the non-crossing approximation. These results corroborate the importance of crystal field effects in these materials; they also suggest that Anderson lattice effects are important to the physics of Yb{sub 2}M{sub 3}Ga{sub 9}.

  16. Ferromagnetic transition temperature enhancement in (Ga,Mn)As semiconductors by carbon codoping 

    E-Print Network [OSTI]

    Jungwirth, T.; Masek, J.; Sinova, Jairo; MacDonald, AH.

    2003-01-01

    We present a theoretical study of (Ga,Mn)(As,C) diluted magnetic semiconductors with high C acceptor density that combines insights from phenomenological model and microscopic approaches. A tight-binding coherent-potential approximation is used...

  17. Microsecond carrier lifetimes in InGaAsP quantum wells emitting J. M. Smitha)

    E-Print Network [OSTI]

    Buller, Gerald S.

    - times are also desirable in InGaAsP photovoltaics, for the development of high efficiency multijunction solar cells which make maximum use of the solar spectrum. A large amount of work has been carried out

  18. GaInNAs Junctions for Next-Generation Concentrators: Progress and Prospects

    SciTech Connect (OSTI)

    Friedman, D. J.; Ptak, A. J.; Kurtz, S. R.; Geisz, J. F.; Kiehl, J.

    2005-08-01

    We discuss progress in the development of GaInNAs junctions for application in next-generation multijunction concentrator cells. A significant development is the demonstration of near-100% internal quantum efficiencies in junctions grown by molecular-beam epitaxy. Testing at high currents validates the compatibility of these devices with concentrator operation. The efficiencies of several next-generation multijunction structures incorporating these state-of-the-art GaInNAs junctions are projected.

  19. Gallium Pnictides of the Alkaline Earth Metals, Synthesized by Means of the Flux Method: Crystal Structures and Properties of CaGa[subscript 2]Pn[subscript 2], SrGa[subscript 2]As[subscript 2], Ba[subscript 2]Ga[subscript 5]As[subscript 5], and Ba[subscript 4]Ga[subscript 5]Pn[subscript 8] (Pn = P or As)

    SciTech Connect (OSTI)

    He, Hua; Stearrett, Ryan; Nowak, Edmund R.; Bobev, Svilen

    2014-05-28

    The focus of this paper is on the structural characterization of the new Zintl phases CaGa{sub 2}P{sub 2}, CaGa{sub 2}As{sub 2}, SrGa{sub 2}As{sub 2}, and Ba{sub 2}Ga{sub 5}As{sub 5}, and the solid solution (Ba{sub 0.85(1)}Sr{sub 0.15}){sub 2}Ga{sub 5}As{sub 5}, all of which were synthesized from molten metal fluxes.CaGa{sub 2}P{sub 2}, CaGa{sub 2}As{sub 2}, and SrGa{sub 2}As{sub 2} have layered structures with polyanionic layers made of ethane-like Ga{sub 2}P6 and Ga{sub 2}As6 motifs fused through common edges; the polyanionic substructure in Ba{sub 2}Ga{sub 5}As{sub 5} consists of condensed Ga{sub 2}As6 units and GaAs{sub 4} tetrahedra. Ba{sub 4}Ga{sub 5}P{sub 8} and Ba{sub 4}Ga{sub 5}As{sub 8}, another pair of new compounds with channel-like 3D structures, were also synthesized from metal fluxes, and their structures were established from single-crystal X-ray and synchrotron powder diffraction. They are based on GaP{sub 4} and GaAs{sub 4} tetrahedra, with parts of their structures being heavily disordered. The electronic structures computed with the linear muffin-tin orbital (LMTO) method are discussed as well, alongside the thermopower and the electrical conductivity, measured on single crystals of Ba{sub 2}Ga{sub 5}As{sub 5} and the solid solution (Ba{sub 0.85(1)}Sr{sub 0.15}){sub 2} Ga{sub 5}As{sub 5}. They demonstrate that such an approach would be an effective way to fine-tune the transport properties.

  20. GaNPAs Solar Cells that Can Be Lattice-Matched to Silicon

    SciTech Connect (OSTI)

    Geisz, J. F.; Friedman, D. J.; McMahon, W. E.; Ptak, A. J.; Kibbler, A. E.; Olson, J. M.; Kurtz, S.; Kramer, C.; Young, M.; Duda, A.; Reedy, R. C.; Keyes, B. M.; Dippo, P.; Metzger, W. K.

    2003-05-01

    III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We have proposed the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct bandgaps in the range of 1.5 to 2.0 eV. We have demonstrated the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and shown improvements in material quality by reducing carbon and hydrogen impurities through optimization of growth conditions. We have achieved quantum efficiencies (QE) in these cells as high as 60% and PL lifetimes as high as 3.0 ns.

  1. 1-MeV-Electron Irradiation of GaInAsN Cells: Preprint

    SciTech Connect (OSTI)

    Kurtz, S.; King, R. R.; Edmondson, K. M.; Friedman, D. J.; Karam, N. H.

    2002-05-01

    This conference paper describes the GaInAsN cells that are measured to retain 933% and 894% of their original efficiency after exposure to 5 X 1014 and 1 X 1015 cm-2 1-MeV electrons, respectively. The rate of degradation is not correlated with the performance at beginning of life (BOL). The depletion width remains essentially unchanged, increasing by< 1%. Temperature-coefficient data for GaInAsN cells are also presented. These numbers are used to project the efficiency of GaInAsN-containing multijunction cells. The GaInAsN junction is not currently predicted to increase the efficiencies of the multijunction cells. Nevertheless, GaInAsN-containing multijunction cell efficiencies are predicted to be comparable to those of the conventional structures, and even small improvements in the GaInAsN cell may lead to higher multijunction cell efficiencies, especially for high-radiation applications and when cell operating temperature is low.

  2. Realizing InGaN monolithic solar-photoelectrochemical cells for artificial photosynthesis

    SciTech Connect (OSTI)

    Dahal, R.; Pantha, B. N.; 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)

    2014-04-07

    InGaN alloys are very promising for solar water splitting because they have direct bandgaps that cover almost the whole solar spectrum. The demonstration of direct solar-to-fuel conversion without external bias with the sunlight being the only energy input would pave the way for realizing photoelectrochemical (PEC) production of hydrogen by using InGaN. A monolithic solar-PEC cell based on InGaN/GaN multiple quantum wells capable to directly generate hydrogen gas under zero bias via solar water splitting is reported. Under the irradiation by a simulated sunlight (1-sun with 100 mW/cm{sup 2}), a 1.5% solar-to-fuel conversion efficiency has been achieved under zero bias, setting a fresh benchmark of employing III-nitrides for artificial photosynthesis. Time dependent hydrogen gas production photocurrent measured over a prolonged period (measured for 7 days) revealed an excellent chemical stability of InGaN in aqueous solution of hydrobromic acid. The results provide insights into the architecture design of using InGaN for artificial photosynthesis to provide usable clean fuel (hydrogen gas) with the sunlight being the only energy input.

  3. Effect of arsenic on the optical properties of GaSb-based type II quantum wells with quaternary GaInAsSb layers

    SciTech Connect (OSTI)

    Janiak, F. Motyka, M.; S?k, G.; Dyksik, M.; Ryczko, K.; Misiewicz, J.; Weih, R.; Höfling, S.; Kamp, M.; Patriarche, G.

    2013-12-14

    Optical properties of molecular beam epitaxially grown type II “W” shaped GaSb/AlSb/InAs/GaIn(As)Sb/InAs/AlSb/GaSb quantum wells (QWs) designed for the active region of interband cascade lasers have been investigated. Temperature dependence of Fourier-transformed photoluminescence and photoreflectance was employed to probe the effects of addition of arsenic into the original ternary valence band well of GaInSb. It is revealed that adding arsenic provides an additional degree of freedom in terms of band alignment and strain tailoring and allows enhancing the oscillator strength of the active type II transition. On the other hand, however, arsenic incorporation apparently also affects the structural and optical material quality via generating carrier trapping states at the interfaces, which can deteriorate the radiative efficiency. These have been evidenced in several spectroscopic features and are also confirmed by cross-sectional transmission electron microscopy images. While arsenic incorporation into type II QWs is a powerful heterostructure engineering tool for optoelectronic devices, a compromise has to be found between ideal band structure properties and high quality morphological properties.

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

    SciTech Connect (OSTI)

    Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tan, Swee Tiam; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Sun, Xiao Wei, E-mail: EXWSUN@ntu.edu.sg, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Demir, Hilmi Volkan, E-mail: EXWSUN@ntu.edu.sg, E-mail: VOLKAN@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

    2014-07-21

    In conventional InGaN/GaN light-emitting diodes (LEDs), thin InGaN quantum wells are usually adopted to mitigate the quantum confined Stark effect (QCSE), caused due to strong polarization induced electric field, through spatially confining electrons and holes in small recombination volumes. However, this inevitably increases the carrier density in quantum wells, which in turn aggravates the Auger recombination, since the Auger recombination scales with the third power of the carrier density. As a result, the efficiency droop of the Auger recombination severely limits the LED performance. Here, we proposed and showed wide InGaN quantum wells with the InN composition linearly grading along the growth orientation in LED structures suppressing the Auger recombination and the QCSE simultaneously. Theoretically, the physical mechanisms behind the Auger recombination suppression are also revealed. The proposed LED structure has experimentally demonstrated significant improvement in optical output power and efficiency droop, proving to be an effective solution to this important problem of Auger recombination.

  5. NH Coverts Project Advisory Committee Meeting Notes, April 3, 2015 NH Fish & Game, Concord, NH

    E-Print Network [OSTI]

    New Hampshire, University of

    Members Present: Peter Beblowski, Antrim Karen Bennett, UNH Coop. Extension Cynthia Bruss, Springfield integrating wildlife-friendly agriculture into the list of `land management' options. Upcoming 2015 Workshop #12;- Cynthia pointed out the need for a presentation in the state on reptiles (particularly, snakes

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

    SciTech Connect (OSTI)

    Bairamis, A.; Zervos, Ch.; Georgakilas, A.; Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G.

    2014-09-15

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

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

    DOE Patents [OSTI]

    Zhang, Yu; Sun, Qian; Han, Jung

    2015-12-08

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

  8. Negative band gap bowing in epitaxial InAsGaAs alloys and predicted band offsets of the strained binaries and alloys on various substrates

    E-Print Network [OSTI]

    Hart, Gus

    As , alloy superlattices or quantum wells (InxGa1 xAs)p / InP q , and GaAs-embedded InAs quantum dots strained on InP or GaAs. We predict that while Ec(x) bows downward for relaxed bulk alloys, it bows upward constituents, bulk alloys InxGa1 xAs, epitaxial alloys that are coherently grown on a substrate InP or Ga

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

    SciTech Connect (OSTI)

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

    2014-06-16

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

  10. Observation of strongly enhanced inverse spin Hall voltage in Fe{sub 3}Si/GaAs structures

    SciTech Connect (OSTI)

    Hung, H. Y.; Kwo, J., E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw, E-mail: leesf@phys.sinica.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chiang, T. H. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Syu, B. Z.; Fanchiang, Y. T.; Hong, M., E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw, E-mail: leesf@phys.sinica.edu.tw [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Lin, J. G. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan (China); Lee, S. F., E-mail: raynien@phys.nthu.edu.tw, E-mail: mhong@phys.ntu.edu.tw, E-mail: leesf@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Taipei 115, Taiwan (China)

    2014-10-13

    We performed spin pumping experiment on high quality, epitaxial Fe{sub 3}Si/GaAs structures grown by molecular beam epitaxy. By tailoring the thickness and doping (n, p) level of the conducting GaAs epi-layer, thermal heating common of ferromagnetic metal/semiconductor heterostructure was removed effectively. A large inverse spin Hall Effect (ISHE) voltage up to 49.2??V was observed for Fe{sub 3}Si/p-GaAs. Smaller ISHE voltage (V{sub ISHE}) by a factor of ?0.4 was obtained for Fe{sub 3}Si/n-GaAs, as scaled with its resistivity. By taking into account of the “self-induced” ISHE apparently observed in our samples, the minimum value of spin Hall angle ?{sub ISHE} for n-GaAs and p-GaAs was estimated to be 1.9 × 10{sup ?4} and 2.8 × 10{sup ?5}, respectively.

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

    SciTech Connect (OSTI)

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

    2014-07-14

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

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

    SciTech Connect (OSTI)

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

    2009-07-01

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

  13. Semi-automated lab-on-a-chip for dispensing GA-68 radiotracers

    SciTech Connect (OSTI)

    Weinberg, Irving

    2014-03-12

    We solved a technical problem that is hindering American progress in molecular medicine, and restricting US citizens from receiving optimal diagnostic care. Specifically, the project deals with a mother/daughter generator of positron-emitting radiotracers (Ge-68/Ga-68). These generator systems are approved in Europe but cannot be used in the USA, because of safety issues related to possible breakthrough of long-lived Ge-68 (mother) atoms. Europeans have demonstrated abilities of Ga-68-labeled radiotracers to image cancer foci with high sensitivity and specificity, and to use such methods to effectively plan therapy.The USA Food and Drug Administration (FDA) and Nuclear Regulatory Commission (NRC) have taken the position that every patient administration of Ga-68 should be preceded by an assay demonstrated that Ge-68 breakthrough is within acceptable limits. Breakthrough of parent elements is a sensitive subject at the FDA, as evidenced by the recent recall of Rb-82 generators due to inadvertent administrations of Sr-82. Commercially, there is no acceptable rapid method for assaying breakthrough of Ge-68 prior to each human administration. The gamma emissions of daughter Ga-68 have higher energies than the parent Ge-68, so that the shielding assays typically employed for Mo-99/Tc-99m generators cannot be applied to Ga-68 generators. The half-life of Ga-68 is 68 minutes, so that the standard 10-half-life delay (used to assess breakthrough in Sr-82/Rb-82 generators) cannot be applied to Ga-68 generators. As a result of the aforementioned regulatory requirements, Ga-68 generators are sold in the USA for animal use only.The American clinical community’s inability to utilize Ga-68 generators impairs abilities to treat patients domestically, and puts the USA at a disadvantage in developing exportable products. The proposed DOE project aimed to take advantage of recent technological advances developed for lab-on-a-chip (LOC) applications. Based on our experiences constructing such devices, the proposed microfluidics-based approach could provide cost-effective validation of breakthrough compliance in minutes.

  14. Photoelectrochemical water splitting and hydrogen generation by a spontaneously formed InGaN nanowall network

    SciTech Connect (OSTI)

    Alvi, N. H., E-mail: nhalvi@isom.upm.es, E-mail: r.noetzel@isom.upm.es; Soto Rodriguez, P. E. D.; Kumar, Praveen; Gómez, V. J.; Aseev, P.; Nötzel, R., E-mail: nhalvi@isom.upm.es, E-mail: r.noetzel@isom.upm.es [ISOM Institute for Systems Based on Optoelectronics and Microtechnology, ETSI Telecomunicación, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Alvi, A. H. [Department of Physics, Government College University, Faisalabad (Pakistan); Alvi, M. A. [Department of Chemistry, Government College University, Faisalabad (Pakistan); Willander, M. [Department of Science and Technology (ITN), Campus Norrköping, Linköping University, 60174 Norrköping (Sweden)

    2014-06-02

    We investigate photoelectrochemical water splitting by a spontaneously formed In-rich InGaN nanowall network, combining the material of choice with the advantages of surface texturing for light harvesting by light scattering. The current density for the InGaN-nanowalls-photoelectrode at zero voltage versus the Ag/AgCl reference electrode is 3.4?mA cm{sup ?2} with an incident-photon-to-current-conversion efficiency (IPCE) of 16% under 350?nm laser illumination with 0.075?W·cm{sup ?2} power density. In comparison, the current density for a planar InGaN-layer-photoelectrode is 2?mA cm{sup ?2} with IPCE of 9% at zero voltage versus the Ag/AgCl reference electrode. The H{sub 2} generation rates at zero externally applied voltage versus the Pt counter electrode per illuminated area are 2.8 and 1.61??mol·h{sup ?1}·cm{sup ?2} for the InGaN nanowalls and InGaN layer, respectively, revealing ?57% enhancement for the nanowalls.

  15. Structure and scintillation yield of Ce-doped Al–Ga substituted yttrium garnet

    SciTech Connect (OSTI)

    Sidletskiy, Oleg; Kononets, Valerii; Lebbou, Kheirreddine; Neicheva, Svetlana; Voloshina, Olesya; Bondar, Valerii; Baumer, Vyacheslav; Belikov, Konstantin; Gektin, Alexander; Grinyov, Boris; Joubert, Marie-France

    2012-11-15

    Highlights: ? Range of Y{sub 3}(Al{sub 1?x}Ga{sub x}){sub 5}O{sub 12}:Ce solid solution crystals are grown from melt by the Czochralski method. ? Light yield of mixed crystals reaches 130% of the YAG:Ce value at x ? 0.4. ? ?1% of antisite defects is formed in YGG:Ce, but no evidence of this is obtained for the rest of crystals. -- Abstract: Structure and scintillation yield of Y{sub 3}(Al{sub 1?x}Ga{sub x}){sub 5}O{sub 12}:Ce solid solution crystals are studied. Crystals are grown from melt by the Czochralski method. Distribution of host cations in crystal lattice is determined. Quantity of antisite defects in crystals is evaluated using XRD and atomic emission spectroscopy data. Trend of light output at Al/Ga substitution in Y{sub 3}(Al{sub 1?x}Ga{sub x}){sub 5}O{sub 12}:Ce is determined for the first time. Light output in mixed crystals reaches 130% comparative to Ce-doped yttrium–aluminum garnet. Luminescence properties at Al/Ga substitution are evaluated.

  16. Lattice-registered growth of GaSb on Si (211) with molecular beam epitaxy

    SciTech Connect (OSTI)

    Hosseini Vajargah, S.; Botton, G. A.; Ghanad-Tavakoli, S.; Preston, J. S.; Kleiman, R. N.

    2012-11-01

    A GaSb film was grown on a Si(211) substrate using molecular beam epitaxy indicating full lattice relaxation as well as full lattice registration and dislocation-free growth in the plane perpendicular to the [01 - 1]-direction. Heteroepitaxy of GaSb on a Si(211) substrate is dominated by numerous first order and multiple higher order micro-twins. The atomic-resolved structural study of GaSb films by high-angle annular dark-field scanning transmission electron microscopy reveals that slight tilt, along with twinning, favors the lattice registry to Si(211) substrates. Preferential bonding of impinging Ga and Sb atoms at the interface due to two distinctive bonding sites on the Si(211) surface enables growth that is sublattice-ordered and free of anti-phase boundaries. The role of the substrate orientation on the strain distribution of GaSb epilayers is further elucidated by investigating the local change in the lattice parameter using the geometric phase analysis method and hence effectiveness of the lattice tilting in reducing the interfacial strain was confirmed further.

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

    SciTech Connect (OSTI)

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

    2013-01-28

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

  18. GaAs Blocked-Impurity-Band Detectors for Far-Infrared Astronomy

    SciTech Connect (OSTI)

    Cardozo, Benjamin Lewin

    2004-12-21

    High-purity and doped GaAs films have been grown by Liquid-phase epitaxy (LPE) for development of a blocked impurity band (BIB) detector for far-infrared radiation. The film growth process developed has resulted in the capability to grow GaAs with a net active impurity concentration below 1 x 10{sup 13} cm{sup -3}, ideal for the blocking layer of the BIB detector. The growth of n-type LPE GaAs films with donor concentrations below the metal-insulator transition, as required for the absorbing layer of a BIB detector, has been achieved. The control of the donor concentration, however, was found to be insufficient for detector production. The growth by LPE of a high-purity film onto a commercially grown vapor-phase epitaxial (VPE) n-type GaAs doped absorbing layer resulted in a BIB device that showed a significant reduction in the low-temperature dark current compared to the absorbing layer only. Extended optical response was not detected, most likely due to the high compensation of the commercially grown GaAs absorbing layer, which restricts the depletion width of the device.

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

    E-Print Network [OSTI]

    Nabben, Reinhard

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

  20. Finite element simulations of compositionally graded InGaN solar cells G.F. Brown a,b,n

    E-Print Network [OSTI]

    Wu, Junqiao

    for cheap multi-junction solar cells [4]. Previous simulations have shown that double-junction InxGa1ÀxFinite element simulations of compositionally graded InGaN solar cells G.F. Brown a,b,n , J.W. Ager conversion efficiency of compositionally graded InxGa1ÀxN solar cells was simulated using a finite element