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1

Petersburg | Open Energy Information  

Open Energy Info (EERE)

Petersburg Petersburg Jump to: navigation, search Name Petersburg Facility Petersburg Sector Wind energy Facility Type Commercial Scale Wind Facility Status In Service Owner Gestamp Wind Developer Third Planet Wind Power Energy Purchaser Omaha Public Power District Location Oakdale NE Coordinates 41.90342692°, -98.0025959° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":41.90342692,"lon":-98.0025959,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

2

St. Petersburg, FL: Vehicle Use of Recycled Natural Gas Derived...  

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

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

3

NEDERLANDS INSTITUUT IN SINT-PETERSBURG Algemene informatie  

E-Print Network [OSTI]

:00 - 18:00 Postadres Kaloezjsky pereoelok 3 St.Petersburg Rusland P.O. Box 109 53101 Lappeenranta Finland

van Rooij, Robert

4

ANNUAL WINTER SCHOOLANNUAL WINTER SCHOOL Petersburg Nuclear Physics Institute  

E-Print Network [OSTI]

ANNUAL WINTER SCHOOLANNUAL WINTER SCHOOL Petersburg Nuclear Physics Institute National Research February ­ 1 March, 2014 Petersburg Nuclear Physics Institute (PNPI) conducts the XLVIII Annual Winter Physics · Theoretical Physics School · School on Nuclear Reactor Physics · Accelerator Physics School

Titov, Anatoly

5

Minnkota Power Cooperative Wind Turbine (Petersburg) | Open Energy  

Open Energy Info (EERE)

Petersburg) Petersburg) Jump to: navigation, search Name Minnkota Power Cooperative Wind Turbine (Petersburg) Facility Minnkota Power Cooperative Wind Turbine (Petersburg) Sector Wind energy Facility Type Commercial Scale Wind Facility Status In Service Owner Minnkota Power Cooperative Developer Minnkota Power Cooperative Energy Purchaser Minnkota Power Cooperative Location East of Petersburg ND Coordinates 48.008793°, -97.930931° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":48.008793,"lon":-97.930931,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

6

City of Petersburg, Alaska (Utility Company) | Open Energy Information  

Open Energy Info (EERE)

Petersburg Petersburg Place Alaska Utility Id 14856 Utility Location Yes Ownership M NERC Location AK Operates Generating Plant Yes Activity Generation Yes Activity Distribution Yes References EIA Form EIA-861 Final Data File for 2010 - File1_a[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Utility Rate Schedules Grid-background.png Harbor Residential Residential Residential Average Rates Residential: $0.1000/kWh Commercial: $0.1160/kWh Industrial: $0.1060/kWh References ↑ "EIA Form EIA-861 Final Data File for 2010 - File1_a" Retrieved from "http://en.openei.org/w/index.php?title=City_of_Petersburg,_Alaska_(Utility_Company)&oldid=410106" Categories:

7

10 th IMEKO TC7 International Symposium June 30--July 2, 2004, SaintPetersburg, Russia  

E-Print Network [OSTI]

10 th IMEKO TC7 International Symposium June 30--July 2, 2004, Saint­Petersburg, Russia GROUP Science, Arizona State University, Tempe, USA 4 State Technical Univ. of St. Petersburg, Russia Abstract

Kreinovich, Vladik

8

IMEKO TC7 International Symposium June 30July 2, 2004, Saint-Petersburg, Russia  

E-Print Network [OSTI]

10th IMEKO TC7 International Symposium June 30­July 2, 2004, Saint-Petersburg, Russia GROUP State University, Tempe, USA 4 State Technical Univ. of St. Petersburg, Russia Abstract. When describing

Kreinovich, Vladik

9

Proceedings of 4th Fire Behavior and Fuels Conference, July 1 4, 2013, St. Petersburg, Russia  

E-Print Network [OSTI]

Proceedings of 4th Fire Behavior and Fuels Conference, July 1 ­ 4, 2013, St. Petersburg, Russia Fire Behavior and Fuels Conference, July 1 ­ 4, 2013, St. Petersburg, Russia Published

10

IMEKO TC7 International Symposium June 30July 2, 2004, Saint-Petersburg, Russia  

E-Print Network [OSTI]

10th IMEKO TC7 International Symposium June 30­July 2, 2004, Saint-Petersburg, Russia PROBABILITIES Computer Science, University of Texas, El Paso, USA 2 State Technical Univ. of St. Petersburg, Russia 3

Kreinovich, Vladik

11

th IMEKO TC7 International Symposium June 30--July 2, 2004, SaintPetersburg, Russia  

E-Print Network [OSTI]

10 th IMEKO TC7 International Symposium June 30--July 2, 2004, Saint­Petersburg, Russia. Petersburg, Russia 3 Applied Biomathematics, 100 North Country Road, Setauket, NY 11733, USA 4 University

Kreinovich, Vladik

12

European Congress on Social Insects St. Petersburg, Russia, 2227 August 2005  

E-Print Network [OSTI]

3rd European Congress on Social Insects St. Petersburg, Russia, 22­27 August 2005 PROCEEDINGS #12, Russia, 22­27 August 2005 PROCEEDINGS Edited by Vladilen E. Kipyatkov St. Petersburg 2005 #12;3 Table

Rasmont, Pierre

13

Proceedings of EUROCRYPT '06 (May 28June 1, 2006, Saint Petersburg, Russia)  

E-Print Network [OSTI]

Proceedings of EUROCRYPT '06 (May 28­June 1, 2006, Saint Petersburg, Russia) S. Vaudenay (Ed.), vol

Nguyen, Phong Q.

14

Proc. of 2nd Intern. Workshop "New Models of Business: Managerial Aspects and Enabling Technology", St. Petersburg State University, St. Petersburg, Russia, June 26-28, 2002, 212-220  

E-Print Network [OSTI]

", St. Petersburg State University, St. Petersburg, Russia, June 26-28, 2002, 212-220 Algebraic Modeling. Petersburg State University, Russia Abstract An algebraic approach to the modeling and performance evaluation, Petrodvorets, St. Petersburg, 198504 Russia, e-mail: Nikolai.Krivulin@pobox.spbu.ru. 3 The work is partially

Krivulin, Nikolai K.

15

Petersburg County, Virginia: Energy Resources | Open Energy Information  

Open Energy Info (EERE)

Petersburg County, Virginia: Energy Resources Petersburg County, Virginia: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 37.2071175°, -77.3898602° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":37.2071175,"lon":-77.3898602,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

16

Proceedings of 4th Fire Behavior and Fuels Conference, July 1-4, 2013, St. Petersburg, Russia  

E-Print Network [OSTI]

Proceedings of 4th Fire Behavior and Fuels Conference, July 1-4, 2013, St. Petersburg, Russia and 513 #12;Proceedings of 4th Fire Behavior and Fuels Conference, July 1-4, 2013, St. Petersburg, Russia

17

For Immediate Release --Wednesday, June 26, 2013 Canada Day in St. Petersburg, Russia: U of L computer  

E-Print Network [OSTI]

. Petersburg, Russia: U of L computer programming team celebrates at prestigious Collegiate Programming Contest (ICPC) World Finals in St. Petersburg, Russia challenge In addition to sending a team to Russia, Mathematics and Computer

Seldin, Jonathan P.

18

IAEA FEC Saint Petersburg, Russia, 13-18 October 2014, O. Motojima The ITER Project Construction Status  

E-Print Network [OSTI]

IAEA FEC Saint Petersburg, Russia, 13-18 October 2014, O. Motojima Slide 1/14 OM14755 The ITER Project Construction Status IAEA FEC 13 to 18 October, 2014 Saint Petersburg, Russia Osamu Motojima President Barroso (11 July 2014) #12;IAEA FEC Saint Petersburg, Russia, 13-18 October 2014, O. Motojima

19

The founding of St Petersburg in the context of The Royal Society's relationship with Russia  

Science Journals Connector (OSTI)

...The Royal Society's relationship with Russia J. H. Appleby 16 Pine Close, Upton Road...in 1712, the Society's contacts with Russia developed in many different ways. St Petersburg|Russia|The Royal Society| THE FOUNDING OF ST...

2003-01-01T23:59:59.000Z

20

Proceedings of 4th Fire Behavior and Fuels Conference, July 1-4, 2013, St. Petersburg, Russia  

E-Print Network [OSTI]

Proceedings of 4th Fire Behavior and Fuels Conference, July 1-4, 2013, St. Petersburg, Russia, Russia F USDA Forest Service, Rocky Mountain Research Station 5775 W US Highway 10 Missoula MT 59808 G;Proceedings of 4th Fire Behavior and Fuels Conference, July 1-4, 2013, St. Petersburg, Russia Published

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

ITPA Joint Meeting on Control, St. Petersburg, Russia, 14/07/2003 R. A. Pitts, Centre de Recherches en Physique des Plasmas Some requirements and possibilities for the  

E-Print Network [OSTI]

ITPA Joint Meeting on Control, St. Petersburg, Russia, 14/07/2003 R. A. Pitts, Centre de Recherches de Recherches en Physique des Plasmas #12;ITPA Joint Meeting on Control, St. Petersburg, Russia, 14, St. Petersburg, Russia, 14/07/2003 R. A. Pitts, Centre de Recherches en Physique des Plasmas

22

RUSSIAN JOURNAL OF EARTH SCIENCES, VOL. 11, ES4004, doi:10.2205/2010ES000437, 2010 Tropospheric NO2 trend over St. Petersburg (Russia)  

E-Print Network [OSTI]

trend over St. Petersburg (Russia) as measured from space D. V. Ionov1 Received 23 March 2010; accepted possible trend over the city of St. Petersburg in Russia. The time series of the monthly NO2 columns; tropospheric pollution. Citation: Ionov, D. V. (2010), Tropospheric NO2 trend over St. Petersburg (Russia

23

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

Broader source: Energy.gov [DOE]

Breakout Session 3AConversion Technologies III: Energy from Our WasteWill 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

24

Managerial threats and prospects in Russian firms: the case of St. Petersburg 1999??2005  

Science Journals Connector (OSTI)

If management in firms of the concrete region focuses on innovation development, the economy of this region will have chances to become the innovation economy. What are the chances in this respect of St. Petersburg in the North-West Russia? In order to answer this question we have investigated managerial practices in local enterprises during two time periods 1999??2000 (N = 982) and 2004??2005 (N = 633). Our research has revealed: strategies employed by industrial firms is already under an insuperable influence of the modern global information society. The innovation economy has already started to form in the region.

Raimo Blom; Harri Melin; Alfred Sarno; Irina Sarno

2008-01-01T23:59:59.000Z

25

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

SciTech Connect (OSTI)

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

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

1997-08-01T23:59:59.000Z

26

ITER pioneers receive prestigious Russian energy prize of June in Saint Petersburg, three pioneers of the international fusion project  

E-Print Network [OSTI]

Vladimir Putin, president of the Russian Federation. The laureates -- the Russian academician Evgeniy speech during the prize ceremony, President Putin said: "I will emphasize that as one of the world Putin in Saint Petersburg earlier today. Evgeniy Velikhov is one of the founders of the ITER project

27

George Sips, O-1.3A 30th EPS, St Petersburg, Russia, 7-11 July 2003 1 Improved H-mode Identity Experiments  

E-Print Network [OSTI]

George Sips, O-1.3A 30th EPS, St Petersburg, Russia, 7-11 July 2003 1 Improved H-mode Identity, Russia, 7-11 July 2003 2 Motivation 10 (400 s.) 0.851.0/1.83 Q/nGWH98(y,2)/Nq95 Requirements for ITER,edge for divertor lifetime. #12;George Sips, O-1.3A 30th EPS, St Petersburg, Russia, 7-11 July 2003 3 Motivation

28

7th Int. Symp. "Nanostructures: Physics and Technology" LOED.04 St Petersburg, Russia, June 1418, 1999  

E-Print Network [OSTI]

­18, 1999 © 1999 Ioffe Institute Surface-mode lasing from optically pumped InGaN/GaN heterostructures A. V-dimensionalarraysofshort-wavelengthsemiconductorlasersimportant for high-density high-speed optical storage applications. At the same time, fabrication of such devices of the importance of the feedback in the system resulting in appearance of lasing modes was given. In this work we

Nabben, Reinhard

29

Pain is associated with risky drinking over time among HIV-infected persons in St. Petersburg, Russia  

Science Journals Connector (OSTI)

AbstractBackground Pain is highly prevalent among persons with HIV. Alcohol may be used to self-medicate pain. This study examined the association between pain and risky alcohol use over time in a cohort of HIV-infected Russian drinkers. Methods This secondary analysis utilized longitudinal data from a randomized trial of a behavioral intervention. Subjects included HIV-infected adults who reported past 6-month risky drinking and unprotected sex and were recruited from HIV and addiction treatment sites in St. Petersburg, Russia. The main independent variable was pain that at least moderately interfered with daily living. The primary outcome was past month risky drinking amounts based on NIAAA guidelines. General estimating equations (GEE) logistic regression models were used to calculate odds ratios and 95% confidence intervals for the association between pain and risky drinking over time (i.e., baseline, 6 and 12 months), adjusting for potential confounders. Results Baseline characteristics of participants (n=699) were mean age of 30 (SD 5) years, 41% female, and 22% <9th grade education. Nearly one quarter (24%) had a CD4 cell count <200cells/?l, and only 17% were on antiretroviral therapy. Nearly half (46%) reported at least moderate pain interference in the past month and 81% were drinking risky amounts. In adjusted longitudinal GEE models, pain was significantly associated with greater odds of reporting past month risky drinking (AOR=1.34, 95% CI: 1.051.71, p value=0.02). Conclusions Among a cohort of HIV-infected Russian drinkers, pain that at least moderately interfered with daily living was associated with higher odds of reporting risky drinking amounts over time.

Judith I. Tsui; Debbie M. Cheng; Sharon M. Coleman; Marlene C. Lira; Elena Blokhina; Carly Bridden; Evgeny Krupitsky; Jeffrey H. Samet

2014-01-01T23:59:59.000Z

30

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

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

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

31

GaN High Power Devices  

SciTech Connect (OSTI)

A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers, GaN/AlGaN heterojunction bipolar transistors, GaN heterostructure and metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

PEARTON,S.J.; REN,F.; ZHANG,A.P.; DANG,G.; CAO,X.A.; LEE,K.P.; CHO,H.; GILA,B.P.; JOHNSON,J.W.; MONIER,C.; ABERNATHY,C.R.; HAN,JUNG; BACA,ALBERT G.; CHYI,J.-I.; LEE,C.-M.; NEE,T.-E.; CHUO,C.-C.; CHI,G.C.; CHU,S.N.G.

2000-07-17T23:59:59.000Z

32

Category:Savannah, GA | Open Energy Information  

Open Energy Info (EERE)

Savannah, GA Savannah, GA Jump to: navigation, search Go Back to PV Economics By Location Media in category "Savannah, GA" The following 16 files are in this category, out of 16 total. SVFullServiceRestaurant Savannah GA Georgia Power Co.png SVFullServiceRestauran... 80 KB SVHospital Savannah GA Georgia Power Co.png SVHospital Savannah GA... 80 KB SVLargeHotel Savannah GA Georgia Power Co.png SVLargeHotel Savannah ... 75 KB SVLargeOffice Savannah GA Georgia Power Co.png SVLargeOffice Savannah... 82 KB SVMediumOffice Savannah GA Georgia Power Co.png SVMediumOffice Savanna... 85 KB SVMidriseApartment Savannah GA Georgia Power Co.png SVMidriseApartment Sav... 80 KB SVOutPatient Savannah GA Georgia Power Co.png SVOutPatient Savannah ... 84 KB SVPrimarySchool Savannah GA Georgia Power Co.png

33

Category:Atlanta, GA | Open Energy Information  

Open Energy Info (EERE)

GA GA Jump to: navigation, search Go Back to PV Economics By Location Media in category "Atlanta, GA" The following 16 files are in this category, out of 16 total. SVFullServiceRestaurant Atlanta GA Georgia Power Co.png SVFullServiceRestauran... 81 KB SVHospital Atlanta GA Georgia Power Co.png SVHospital Atlanta GA ... 81 KB SVLargeHotel Atlanta GA Georgia Power Co.png SVLargeHotel Atlanta G... 74 KB SVLargeOffice Atlanta GA Georgia Power Co.png SVLargeOffice Atlanta ... 82 KB SVMediumOffice Atlanta GA Georgia Power Co.png SVMediumOffice Atlanta... 84 KB SVMidriseApartment Atlanta GA Georgia Power Co.png SVMidriseApartment Atl... 82 KB SVOutPatient Atlanta GA Georgia Power Co.png SVOutPatient Atlanta G... 83 KB SVPrimarySchool Atlanta GA Georgia Power Co.png SVPrimarySchool Atlant...

34

GA SNC Solar | Open Energy Information  

Open Energy Info (EERE)

GA SNC Solar Jump to: navigation, search Name: GA-SNC Solar Place: Nevada Sector: Solar Product: Nevada-based PV project developer and joint venture of GA-Solar North America and...

35

Beta decay of Ga-62  

E-Print Network [OSTI]

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

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

2003-01-01T23:59:59.000Z

36

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

SciTech Connect (OSTI)

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}.

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

2010-10-14T23:59:59.000Z

37

RECIPIENT:Gwinnett Co, GA  

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

Gwinnett Co, GA Gwinnett Co, GA u.s DEPARUIENT OFENllRGY EERE PROJECT MANAGEMENT CENTER NllPA DETERl\JINATION PROJECr TITLE: Gwinnett Co, GA EEC8G Page I or2 STATE: GA Funding Opportunity Announcement Number Procu~ment Instrument Number N[PA Control Number CID Number DE-EEOOOOS05.005 0 Based on my review ortbe information concerning tbe proposed action, as NEPA Compliance Officer (authorized under DOE Order 4SI.IA), I bave made the following determination: ex, EA, EIS APPENDIX AND NUMBER: Description: 8 5.1 Actions to conserve energy, demonstrate potential energy conservation, and promote energy-efficiency that do not increase the indoor concentrations of potentially harmful substances. These actions may involve financial and technical assistance to individuals (such as builders, owners, consultants, designers), organizations (such as utilities), and state

38

Novel GaAs Devices  

Science Journals Connector (OSTI)

As the dimensions of GaAs devices shrink, the effective electron velocity should increase, leading to a shorter transit time and to a ballistic or near-ballistic mode of operation (see Chapter 2). At the same ...

Michael Shur

1987-01-01T23:59:59.000Z

39

Characterisation of Ga-coated and Ga-brazed aluminium  

SciTech Connect (OSTI)

This work is devoted to the brazing of aluminium using liquid gallium. Gallium was deposited on aluminium samples at {approx} 50 Degree-Sign C using a liquid gallium 'polishing' technique. Brazing was undertaken for 30 min at 500 Degree-Sign C in air. EDS (Energy Dispersive X-ray Spectroscopy) and AES (Auger Electron Spectroscopy) characterisation of Ga-coated samples has shown that the Ga surface layer thickness is of ten (or a few tens of) nanometres. Furthermore, aluminium oxide layer (Al{sub 2}O{sub 3}) was shown to be 'descaled' during Ga deposition, which ensures good conditions for further brazing. Cross-section examination of Ga-coated samples shows that liquid gallium penetrates into the aluminium grain boundaries during deposition. The thickness of the grain boundary gallium film was measured using an original EDS technique and is found to be of a few tens of nanometres. The depth of gallium grain boundary penetration is about 300 {mu}m at the deposition temperature. The fracture stress of the brazed joints was measured from tensile tests and was determined to be 33 MPa. Cross-section examination of brazed joints shows that gallium has fully dissolved into the bulk and that the joint is really autogenous. - Highlights: Black-Right-Pointing-Pointer Aluminium can be brazed using liquid gallium deposited by a 'polishing' technique. Black-Right-Pointing-Pointer The aluminium oxide layer is 'descaled' during liquid Ga 'polishing' deposition. Black-Right-Pointing-Pointer EDS can be used for determination of surface and grain boundary Ga film thickness. Black-Right-Pointing-Pointer The surface and grain boundary Ga film thickness is of a few tens of nm. Black-Right-Pointing-Pointer Surface and grain boundary gallium dissolves in the bulk during brazing.

Ferchaud, E. [Universite de Nantes, Polytech'Nantes, Laboratoire Genie des Materiaux et Procedes Associes, Rue Christian Pauc, 44306 Nantes Cedex 3 (France); Christien, F., E-mail: frederic.christien@univ-nantes.fr [Universite de Nantes, Polytech'Nantes, Laboratoire Genie des Materiaux et Procedes Associes, Rue Christian Pauc, 44306 Nantes Cedex 3 (France); Barnier, V. [Ecole Nationale Superieure des Mines, MPI, CNRS UMR5146, Centre SMS, 158 Cours Fauriel, 42023 Saint Etienne (France); Paillard, P. [Universite de Nantes, Polytech'Nantes, Laboratoire Genie des Materiaux et Procedes Associes, Rue Christian Pauc, 44306 Nantes Cedex 3 (France)

2012-05-15T23:59:59.000Z

40

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

SciTech Connect (OSTI)

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.

Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel [National Institute of Physics, University of the Philippines Diliman, Quezon City 1101 (Philippines); Que, Christopher T. [Physics Department, De La Salle University, 2401 Taft Avenue, Manila 1004 (Philippines); Yamamoto, Kohji; Tani, Masahiko [Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507 (Japan)

2012-12-15T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

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

SciTech Connect (OSTI)

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.

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

2005-11-01T23:59:59.000Z

42

High Efficiency Large Area AlGaAs/GaAs Concentrator Solar Cells  

Science Journals Connector (OSTI)

A 1-kWp ( peak at 100 mw/cm2 incident power dencity ) concentrating photovoltaic array with 180 square Presnel plastic lenses and AlGaAs/GaAs concentrator solar cells has been constructed. The AlGaAs/GaAs concetr...

S. Yoshida; K. Mitsui; T. Oda; Y. Yukimoto

1981-01-01T23:59:59.000Z

43

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

E-Print Network [OSTI]

GaSb/GaAs type II quantum dot solar cells for enhanced infrared spectral response R. B Technology Materials, University of New Mexico, 1313 Goddard SE, Albuquerque, New Mexico 87106 Received 27 infrared spectral response of GaAs-based solar cells that incorporate type II GaSb quantum dots QDs formed

Jalali. Bahram

44

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

E-Print Network [OSTI]

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

Saadat, Omair I

2010-01-01T23:59:59.000Z

45

Plasmonic nanoparticle enhanced photocurrent in GaN/InGaN/GaN quantum well solar cells  

E-Print Network [OSTI]

Plasmonic nanoparticle enhanced photocurrent in GaN/InGaN/GaN quantum well solar cells Imogen M of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA 2 Semiconductor Nanoscience Institute, California Institute of Technology, Pasadena, California 91125, USA Received 26

Atwater, Harry

46

GaAsbased quantum cascade lasers  

Science Journals Connector (OSTI)

...N. Murdin GaAs-based quantum cascade lasers Sirtori H. Page C. Becker...state-of-the-art of GaAs-based quantum cascade lasers. These new light sources...2000.0739 GaAs-based quantum cascade lasers By C. Sirtori, H. Page...

2001-01-01T23:59:59.000Z

47

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

SciTech Connect (OSTI)

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

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

2012-01-01T23:59:59.000Z

48

Coulomb excitation of 73Ga  

E-Print Network [OSTI]

The B(E2; Ii -> If) values for transitions in 71Ga and 73Ga were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of 71,73Ga at the REX-ISOLDE on-line isotope mass separator facility. The emitted gamma rays were detected by the MINIBALL-detector array and B(E2; Ii->If) values were obtained from the yields normalized to the known strength of the 2+ -> 0+ transition in the 120Sn target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity towards lower excitation energy when adding neutrons beyond N = 40. This supports conclusions from previous studies of the gallium isotopes which indicated a structural change in this isotopical chain between N = 40 and N = 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2- spin and parity for the ground state, the extracted results revealed evidence for a 1/2-; 3/2- doublet near the ground state in 73 31Ga42 differing by at most 0.8 keV in energy.

J. Diriken; I. Stefanescu; D. Balabanski; N. Blasi; A. Blazhev; N. Bree; J. Cederkll; T. E. Cocolios; T. Davinson; J. Eberth; A. Ekstrm; D. V. Fedorov; V. N. Fedosseev; L. M. Fraile; S. Franchoo; G. Georgiev; K. Gladnishki; M. Huyse; O. V. Ivanov; V. S. Ivanov; J. Iwanicki; J. Jolie; T. Konstantinopoulos; Th. Krll; R. Krcken; U. Kster; A. Lagoyannis; G. Lo Bianco; P. Maierbeck; B. A. Marsh; P. Napiorkowski; N. Patronis; D. Pauwels; P. Reiter; M. Seliverstov; G. Sletten; J. Van de Walle; P. Van Duppen; D. Voulot; W. B. Walters; N. Warr; F. Wenander; K. Wrzosek

2010-10-13T23:59:59.000Z

49

Charakterisierung und Prparation von GaN und Herstellung von In-Plane-Gate Transistoren in AlxGa1-xN/GaN Heterostrukturen.  

E-Print Network [OSTI]

??Gegenstand der Arbeit sind GaN-Volumenmaterial und AlxGa1-xN/GaN HEMTs (high electron mobility transistor), welche ein zweidimensionales Elektronengas (2DEG) besitzen. Die Materialien wurden durch elektrische Messungen, insbesondere (more)

Ebbers, Andr

2003-01-01T23:59:59.000Z

50

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

SciTech Connect (OSTI)

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.

Duong Anh Tuan; Shin, Yooleemi; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Dang Duc Dung [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Department of General Physics, School of Engineering Physics, Ha Noi University of Science and Technology, 1 Dai Co Viet road, Ha Noi (Viet Nam); Vo Thanh Son [Centers for Nanobioenineering and Spintronics, Chungnam National University, Daejon 350-746 (Korea, Republic of)

2012-04-01T23:59:59.000Z

51

Composition dependence of interband transition intensities in GaPN, GaAsN, and GaPAs alloys  

Science Journals Connector (OSTI)

Using large (512-atom) pseudopotential supercell calculations, we have investigated the composition dependence of the momentum matrix element Mv,c for transitions between the valence-band maximum and the conduction-band minimum of three semiconductor alloys:?GaP1-xNx and GaAs1-xNx, exhibiting large chemical and size differences between their alloyed elements, and GaP1-xAsx, which is a weakly perturbed alloy. In the composition ranges where these alloys have a direct band gap, we find that (i) in GaP1-xAsx, Mv,c is large (like the virtual-crystal value) and nearly composition independent; (ii) in GaAs1-xNx, Mv,c is strongly composition dependent: large for small x and small for large x; and (iii) in GaP1-xNx, Mv,c is only slightly composition dependent and is significantly reduced relative to the virtual-crystal value. The different behavior of GaP1-xAsx, GaP1-xNx, and GaAs1-xNx is traced to the existence/absence of impurity levels at the dilute alloy limits: (a) there are no gap-level impurity states at the x?1 or x?0 limits of GaP1-xAsx, (b) an isolated As impurity in GaN (GaN?:As) has a deep band gap impurity level but no deep impurity state is found for N in GaAs, and (c) GaN?:P exhibits a P-localized deep band-gap impurity state and GaP?:N has an N-localized resonant state. The existence of deep levels leads to wave-function localization in real space, thus to a spectral spread in momentum space and to a reduction of Mv,c. These impurity levels are facilitated by atomic relaxations, as evident by the fact that unrelaxed GaN?:As and GaN?:P, show no deep levels, have extended wave functions, and have large interband transition elements.

L. Bellaiche; Su-Huai Wei; Alex Zunger

1997-10-15T23:59:59.000Z

52

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

SciTech Connect (OSTI)

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

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

2007-02-01T23:59:59.000Z

53

Princeton Plasma Physics Lab - General Atomics (GA)  

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

general-atomics-ga General general-atomics-ga General Atomics en The Scorpion's Strategy: "Catch and Subdue" http://www.pppl.gov/node/1132

American Fusion News Category: 
ga">General Atomics (GA)
54

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

SciTech Connect (OSTI)

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%.

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

2005-08-01T23:59:59.000Z

55

Structural and optical properties of InGaNGaN nanowire heterostructures grown by molecular beam epitaxy  

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

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.

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

2011-01-07T23:59:59.000Z

56

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

E-Print Network [OSTI]

focused on the demonstration of ultraviolet UV optoelectronic devices. Such devices hold promise, material related problems complicate the growth of such optoelectronic devices oper- ating at short wavelengths. With the use of InGaN/GaN quantum structures, optoelectronic devices operating in vis- ible

Demir, Hilmi Volkan

57

US SoAtl GA Site Consumption  

Gasoline and Diesel Fuel Update (EIA)

GA GA Site Consumption million Btu $0 $500 $1,000 $1,500 $2,000 $2,500 US SoAtl GA Expenditures dollars ALL ENERGY average per household (excl. transportation) 0 4,000 8,000 12,000 16,000 US SoAtl GA Site Consumption kilowatthours $0 $300 $600 $900 $1,200 $1,500 $1,800 US SoAtl GA Expenditures dollars ELECTRICITY ONLY average per household * Site energy consumption (89.5 million Btu) and energy expenditures per household ($2,067) in Georgia are similar to the U.S. household averages. * Per household electricity consumption in Georgia is among the highest in the country, but similar to other states in the South. * Forty-five percent of homes in Georgia were built since 1990, a characteristic typically associated with lower per household consumption. Georgia homes,

58

US SoAtl GA Site Consumption  

U.S. Energy Information Administration (EIA) Indexed Site

GA GA Site Consumption million Btu $0 $500 $1,000 $1,500 $2,000 $2,500 US SoAtl GA Expenditures dollars ALL ENERGY average per household (excl. transportation) 0 4,000 8,000 12,000 16,000 US SoAtl GA Site Consumption kilowatthours $0 $300 $600 $900 $1,200 $1,500 $1,800 US SoAtl GA Expenditures dollars ELECTRICITY ONLY average per household * Site energy consumption (89.5 million Btu) and energy expenditures per household ($2,067) in Georgia are similar to the U.S. household averages. * Per household electricity consumption in Georgia is among the highest in the country, but similar to other states in the South. * Forty-five percent of homes in Georgia were built since 1990, a characteristic typically associated with lower per household consumption. Georgia homes,

59

Electron Transport in a Two-Dimensional Electron Gas at GaAs/AlGaAs Heterointerface  

E-Print Network [OSTI]

in condensed matters. Two-dimensional electron gas (2DEG) at the GaAs/AlGaAs hetero-interface o ersThesis Electron Transport in a Two-Dimensional Electron Gas at GaAs/AlGaAs Heterointerface under of the art samples, the mean free path of electrons exceeds 10;4 m at low temperature. The achievement

Katsumoto, Shingo

60

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

SciTech Connect (OSTI)

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

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

2014-04-24T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

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

SciTech Connect (OSTI)

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

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

2014-04-28T23:59:59.000Z

62

Ohmic contacts to n-GaSb  

E-Print Network [OSTI]

in the semiconductor is measured during the deposition of the metal contact. In using method 1, the I-V characteristics is plotted. The thermionic emission theory predicts the current-voltage characteristics of Schottky diodes as [13]: J(rhcrmionic) = A" T' exp... of different work functions. This situation is also true for metal contacts to n-GaSb. Polyakov et al. [14] examined the Schottky diodes of Al, Au, In, Pd, Ga, and Sb on Te doped n-GaSb. They used the C-V measurements methods. They reported that barrier...

Yang, Zhengchong

2012-06-07T23:59:59.000Z

63

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

SciTech Connect (OSTI)

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

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

2014-04-24T23:59:59.000Z

64

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

SciTech Connect (OSTI)

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.

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

2013-03-04T23:59:59.000Z

65

Petersburg, Michigan: Energy Resources | Open Energy Information  

Open Energy Info (EERE)

011578°, -83.7149383° 011578°, -83.7149383° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":41.9011578,"lon":-83.7149383,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

66

St. PetersburgStockholm BALTIC MARVELS  

E-Print Network [OSTI]

$11,098 A3 $5,049 $11,198 A2 $5,099 $11,498 A1 $5,249 PENTHOUSE SUITE $13,598 PH3 $6,299 $13,998 PH2 $6,499 $14,598 PH1 $6,799 Obstructed view Porthole #12;PORTS OF CALL HELSINKI, FINLAND Like its Linden, the city's famed tree-lined boulevard that paves the way to the historical heart of Berlin

67

GA Solar | Open Energy Information  

Open Energy Info (EERE)

Solar Solar Jump to: navigation, search Name GA-Solar Place Madrid, Spain Zip 28045 Sector Solar Product Madrid based solar project developer, owned by Spanish industrial group Corporacion Gestamp. Coordinates 40.4203°, -3.705774° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":40.4203,"lon":-3.705774,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

68

Characterization of GaSb/GaAs interfacial misfit arrays using x-ray diffraction  

Science Journals Connector (OSTI)

We report a nondestructive large-area method to characterize dislocation formation at a highly lattice-mismatched interface. The analysis is based on x-ray diffraction and reciprocal space mapping using a standard lab-based diffractometer. We use this technique to identify and analyze a two-dimensional array of 90 misfit dislocations at a GaSb/GaAs interface. The full width at half maximum of the GaSb 004 reciprocal lattice point is shown to decrease with increasing GaSb epilayer thickness as expected from theoretical models. Based on these measurements the variation in the spatial dislocation frequency is calculated to be 1%.

Charles J. Reyner; Jin Wang; Kalyan Nunna; Andrew Lin; Baolai Liang; Mark S. Goorsky; D. L. Huffaker

2011-01-01T23:59:59.000Z

69

GaNInGaN LED efficiency reduction from parasitic electron currents in p-GaN  

Science Journals Connector (OSTI)

Abstract This paper presents observations of a previously unidentified source of performance limitation for GaNInGaN LED devices. While most studies focus on output saturation known as current droop from InGaN layer effects, we show an alike influence from p-type GaNs inherent background electron concentration. p-GaN material was investigated to confirm that, even though the material had an excess of holes, the background electrons were indeed present and were influencing the charge flow across device electrodes. This current does not cross LED heterojunctions but rather drifts toward its proximal device electrode, causing a source of heating while providing no carriers for light emitting recombination. The effects of this current were explored in an LED configuration, whose output showed weak efficiency at very low biases in addition to that from current droop. While the shortcoming under small currents has previously been attributed to electron tunneling across the junction, we propose that the background electrons inside p-GaN could be another explanation.

G. Togtema; V. Georgiev; D. Georgieva; R. Gergova; K.S.A. Butcher; D. Alexandrov

2015-01-01T23:59:59.000Z

70

GaTe semiconductor for radiation detection  

DOE Patents [OSTI]

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.

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

2009-06-23T23:59:59.000Z

71

Direct-bonded GaAs/InGaAs tandem solar cell Katsuaki Tanabe,a  

E-Print Network [OSTI]

Direct-bonded GaAs/InGaAs tandem solar cell Katsuaki Tanabe,a Anna Fontcuberta i Morral,b and Harry, Pasadena, California 91125 Daniel J. Aiken Emcore Photovoltaics, Albuquerque, New Mexico 87123 Mark W. Wanlass National Renewable Energy Laboratory, Golden, Colorado 80401 Received 19 March 2006; accepted 26

Atwater, Harry

72

Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices  

SciTech Connect (OSTI)

The materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for lattice-matched thermophotovoltaic (TPV) devices is reported. Epilayers with cutoff wavelength 2--2.4 {micro}m at room temperature and lattice-matched to GaSb substrates were grown by both low-pressure organometallic vapor phase epitaxy and molecular beam epitaxy. These layers exhibit high optical and structural quality. For demonstrating lattice-matched thermophotovoltaic devices, p- and n-type doping studies were performed. Several TPV device structures were investigated, with variations in the base/emitter thicknesses and the incorporation of a high bandgap GaSb or AlGaAsSb window layer. Significant improvement in the external quantum efficiency is observed for devices with an AlGaAsSb window layer compared to those without one.

Wang, C.A.; Choi, H.K.; Turner, G.W.; Spears, D.L.; Manfra, M.J. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1997-05-01T23:59:59.000Z

73

Study and development of tunable, single mode AlGaAs/GaAs lasers  

SciTech Connect (OSTI)

Liquid phase epitaxy has been employed in this study to fabricate two-section wavelength tunable lasers. GaAs/AlGaAs and In GaAsP/InP material system have been used for fabricating the lasers. Both direct (butt) coupling and evanescent coupling approaches have been studied. The complications associated with the regrowth process have been responsible for poor laser performance. Some DBR gratings for three-section lasers have been made using the electron beam lithography at UCSD. A simple set up has been tested to measure the wavelength shift of GaAs/AlGaAs lasers. Also, a simple structure which avoids the regrowth process has been proposed for the two-section laser. 9 refs., 14 figs.

Yu, P.K.L.; Liu, J.C. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Electrical and Computer Engineering)

1990-09-01T23:59:59.000Z

74

Defect studies in low-temperature-grown GaAs  

SciTech Connect (OSTI)

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.

Bliss, D.E.

1992-11-01T23:59:59.000Z

75

Defect studies in low-temperature-grown GaAs  

SciTech Connect (OSTI)

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.

Bliss, D.E.

1992-11-01T23:59:59.000Z

76

Energy absorption in Ni-Mn-Ga/ polymer composites  

E-Print Network [OSTI]

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 ...

Feuchtwanger, Jorge

2006-01-01T23:59:59.000Z

77

Carrier capture dynamics of single InGaAs/GaAs quantum-dot layers  

SciTech Connect (OSTI)

Using 800 nm, 25-fs pulses from a mode locked Ti:Al{sub 2}O{sub 3} laser, we have measured the ultrafast optical reflectivity of MBE-grown, single-layer In{sub 0.4}Ga{sub 0.6}As/GaAs quantum-dot (QD) samples. The QDs are formed via two-stage Stranski-Krastanov growth: following initial InGaAs deposition at a relatively low temperature, self assembly of the QDs occurs during a subsequent higher temperature anneal. The capture times for free carriers excited in the surrounding GaAs (barrier layer) are as short as 140 fs, indicating capture efficiencies for the InGaAs quantum layer approaching 1. The capture rates are positively correlated with initial InGaAs thickness and annealing temperature. With increasing excited carrier density, the capture rate decreases; this slowing of the dynamics is attributed to Pauli state blocking within the InGaAs quantum layer.

Chauhan, K. N.; Riffe, D. M.; Everett, E. A.; Kim, D. J.; Yang, H. [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States)] [Physics Department, Utah State University, Logan, Utah 84322-4415 (United States); Shen, F. K. [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)] [Center for Surface Analysis and Applications, Utah State University, Logan, Utah 84322-4415 (United States)

2013-05-28T23:59:59.000Z

78

GA-AL-SC | Department of Energy  

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

GA-AL-SC GA-AL-SC GA-AL-SC October 1, 2012 ALA-1-N Wholesale Power Rate Schedule Area: PowerSouth Energy Cooperative System: Georgia-Alabama-South Carolina October 1, 2012 Duke-1-E Wholesale Power Rate Schedule Area: Duke On-System System: Georgia-Alabama-South Carolina October 1, 2012 Duke-2-E Wholesale Power Rate Schedule Area: Central System: Georgia-Alabama-South Carolina October 1, 2012 Duke-3-E Wholesale Power Rate Schedule Area: None System: Georgia-Alabama-South Carolina October 1, 2012 Duke-4-E Wholesale Power Rate Schedule Area: Duke Self-Schedulers System: Georgia-Alabama-South Carolina October 1, 2012 MISS-1-N Wholesale Power Rate Schedule Area: South Mississippi Electric Power Association System: Georgia-Alabama-South Carolina October 1, 2012 Pump-1-A Wholesale Power Rate Schedule

79

Low Efficiency Droop Green Nano-Pyramid {10 -11} InGaN/GaN Multiple Quantum Well LED  

Science Journals Connector (OSTI)

We report a low efficiency droop 520 nm green nano-pyramid InGaN/GaN multiple quantum well (MQW) LED. MQWs were grown on the semipolar {10 1} nano-pyramid facets. The device physics...

Cheng, Yuh-Jen; Chang, Shih-Pang; Lin, Da-Wei; Kuo, Hao-chung; Xiong, Kang-lin

80

InGaN working electrodes with assisted bias generated from GaAs solar cells for efficient water splitting  

Science Journals Connector (OSTI)

Hydrogen generation through water splitting by n-InGaN working electrodes with bias generated from GaAs solar cell was studied. Instead of using an external bias provided by power...

Liu, Shu-Yen; Sheu, J K; Lin, Yu-Chuan; Chen, Yu-Tong; Tu, S J; Lee, M L; Lai, W C

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Reaktive Molekularstrahlepitaxie und Charakterisierung von GaN/(Al,Ga)N-Heterostrukturen auf SiC(0001).  

E-Print Network [OSTI]

??Thema dieser Arbeit ist die Synthese von hexagonalen GaN/(Al,Ga)N-Heterostrukturen mittels reaktiver Molekularstrahlepitaxie (MBE) auf SiC(0001)-Substraten. Der Einflu der Wachstumsbedingungen auf die strukturellen, morphologischen, optischen und (more)

Thamm, Andreas

2001-01-01T23:59:59.000Z

82

Nucleation and Growth of GaN on GaAs (001) Substrates  

SciTech Connect (OSTI)

The nucleation of GaN thin films on GaAs is investigated for growth at 620 "C. An rf plasma cell is used to generate chemically active nitrogen from N2. An arsenic flux is used in the first eight monolayer of nitride growth to enhance nucleation of the cubic phase. Subsequent growth does not require an As flux to preserve the cubic phase. The nucleation of smooth interfaces and GaN films with low stacking fault densities is dependent upon relative concentrations of active nitrogen species in the plasma and on the nitrogen to gallium flux ratio.

Drummond, Timothy J.; Hafich, Michael J.; Heller, Edwin J.; Lee, Stephen R.; Liliental-Weber, Zuzanna; Ruvimov, Sergei; Sullivan, John P.

1999-05-03T23:59:59.000Z

83

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

SciTech Connect (OSTI)

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.

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

2006-01-01T23:59:59.000Z

84

Growth and characterization of M-plane GaN and (In,Ga)N/GaN multiple quantum wells.  

E-Print Network [OSTI]

??Thema dieser Arbeit ist die Synthese von Wurtzit M-plane (In,Ga)N(1-100)-Heterostrukturen auf g-LiAlO2(100) mittels plasmauntersttzter Molekularstrahlepitaxie (MBE). Der Einflu der Wachstumsbedingungen auf die strukturellen, morphologischen, und (more)

Sun, Yue-Jun

2004-01-01T23:59:59.000Z

85

Development of Polarized Electron Source of GaAs-AlGaAs Superlattice and Strained GaAs  

Science Journals Connector (OSTI)

At Nagoya University, we have continued the development of GaAs polarized electron source (PES) for several years. Our test ... a gun producing (15) KeV polarized electrons and a standard 100 KeV Mott polarimete...

T. Nakanishi; S. Nakamura

1991-01-01T23:59:59.000Z

86

Auger recombination suppression and band alignment in GaAsBi/GaAs heterostructures  

SciTech Connect (OSTI)

Using a combination of experimental and theoretical techniques we present the dependence of the bandgap E{sub g} and the spin orbit splitting energy ?{sub so}, with Bi concentration in GaAsBi/GaAs samples. We find that the concentration at which ?{sub so},> E{sub g} occurs at 9%. Both spectroscopic as well as first device results indicate a type I alignment.

Hild, K.; Batool, Z.; Jin, S. R.; Hossain, N.; Marko, I. P.; Sweeney, S. J. [Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom); Hosea, T. JC. [1 Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, GU2 7XH, UK and also, Ibnu Sina Institute, Universiti Teknologi Malaysia, Johor Bahru, 81310 (Malaysia); Lu, X. [Department of Electrical and Computer Engineering, University of Victoria, Victoria BC, V8W 3P6, Canada and now VarianSemiconductor Equipment Associates, Gloucester, MA 01930 (United States); Tiedje, T. [Department of Electrical and Computer Engineering, University of Victoria, Victoria BC, V8W 3P6 (Canada)

2013-12-04T23:59:59.000Z

87

Recent progress in InGaAsSb/GaSb TPV devices  

SciTech Connect (OSTI)

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

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

1996-05-01T23:59:59.000Z

88

Radio-frequency reflectometry on an undoped AlGaAs/GaAs single electron transistor  

SciTech Connect (OSTI)

Radio frequency reflectometry is demonstrated in a sub-micron undoped AlGaAs/GaAs device. Undoped single electron transistors (SETs) are attractive candidates to study single electron phenomena, due to their charge stability and robust electronic properties after thermal cycling. However, these devices require a large top-gate, which is unsuitable for the fast and sensitive radio frequency reflectometry technique. Here, we demonstrate that rf reflectometry is possible in an undoped SET.

MacLeod, S. J.; See, A. M.; Keane, Z. K.; Scriven, P.; Micolich, A. P.; Hamilton, A. R., E-mail: Alex.Hamilton@unsw.edu.au [School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Aagesen, M.; Lindelof, P. E. [Nanoscience Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark)] [Nanoscience Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark)

2014-01-06T23:59:59.000Z

89

Multiband GaNAsP Quaternary Alloys  

SciTech Connect (OSTI)

We have synthesized GaN{sub x}As{sub 1-y}P{sub y} alloys (x {approx} 0.3-1% and y = 0-0.4) using nitrogen N ion implantation into GaAsP epilayers followed by pulsed laser melting and rapid thermal annealing techniques. As predicted by the band anticrossing model, the incorporation of N splits the conduction band (E{sub M}) of the GaAs{sub 1-y}P{sub y} substrate, and strong optical transitions from the valence band to the lower (E{sub -}) and upper (E{sub +}) conduction subbands are observed. The relative strengths of the E{sub -} and E{sub +} transition change as the localized N level E{sub N} emerges from the conduction band forming narrow intermediate band for y > 0.3. The results show that GaN{sub x}As{sub 1-x-y}P{sub y} alloys with y > 0.3 is a three band semiconductor alloy with potential applications for high-efficiency intermediate band solar cells.

Yu, K.M.; Walukiewicz, W.; Ager III, J.W.; Bour, D.; Farshchi,R.; Dubon, O.D.; Li, S.X.; Sharp, I.D.; Haller, E.E.

2005-12-08T23:59:59.000Z

90

Implantation of carbon in GaAs  

SciTech Connect (OSTI)

Carbon implanted into GaAs and thermally annealed typically exhibits very low (<3%) electrical activity. It has been demonstrated that the electrical activity of C can be significantly enhanced by co-implantation with Ga. Improved activation may result from either additional damage of the crystal lattice or from stoichiometric changes, forcing the C atoms onto As sites. To determine the relative importance of each of these effects, I have undertaken a systematic study of carbon activation in GaAs. A range of co-implants have been used: group III (B, Ga), group V (N, P, As) and noble gases (Ar, Kr). The damage introduced to the substrate will depend on the mass of the ion implanted. The group III and group V co-implants will affect the crystal stoichiometry. The results indicate that both lattice damage and crystal stoichiometry are important for high electrical activity of C. Increasing the damage will increase the activation due to the increased number of As vacancies but maximum activation can be obtained only by a co-implant which not only damages the lattice but also forces the C to occupy an As site.

Moll, A.J.

1992-03-01T23:59:59.000Z

91

O?[]O? nuclear ?-decay of ?Ga  

E-Print Network [OSTI]

The branching ratio for the ?-Decay of ?Ga to the first excited O? state in ?Zn has been measured. It is possible to use this branching ratio to test the theoretical method of calculating the [] component of the charge correction term [], which...

Hyman, Bruce Carl

2012-06-07T23:59:59.000Z

92

Nano-scale characterization of GaAsP/GaAs strained superlattice structure by nano-beam electron diffraction  

SciTech Connect (OSTI)

Distribution of lattice strain in a GaAsP/GaAs superlattice with a periodicity of 10?nm thickness, deposited on a 100?nm GaAs basal layer has been measured by nano-beam electron diffraction. The superlattice on the (001) plane of the basal GaAs layer shows a constant lattice strain from the bottom to the top layers, whereas the superlattice on the basal GaAs surface sloped by 16 from the (001) plane shows a variation of the lattice strain and crystal orientation. The difference of the strain distributions was discussed from the viewpoint of average strain. This tilt was explained by an atomistic model.

Jin, Xiuguang [Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Nakahara, Hirotaka [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Saitoh, Koh; Tanaka, Nobuo [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Takeda, Yoshikazu [Nagoya Industrial Science Research Institute, Nagoya 464-0819 (Japan); Aichi Synchrotron Radiation Center, Aichi Science and Technology Foundation, Seto 489-0965 (Japan)

2014-03-17T23:59:59.000Z

93

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

SciTech Connect (OSTI)

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.

Paquette, B.; DeVita, M.; Turala, A.; Kolhatkar, G.; Boucherif, A.; Jaouad, A.; Aimez, V.; Ars, R. [Institut Interdisciplinaire d'Innovation Technologique (3IT), Universit de Sherbrooke, Sherbrooke, Qubec (Canada)] [Institut Interdisciplinaire d'Innovation Technologique (3IT), Universit de Sherbrooke, Sherbrooke, Qubec (Canada); Wilkins, M.; Wheeldon, J. F.; Walker, A. W.; Hinzer, K. [Centre for Research in Photonics, University of Ottawa, Ottawa, ON (Canada)] [Centre for Research in Photonics, University of Ottawa, Ottawa, ON (Canada); Fafard, S. [Cyrium Technologies Inc., Ottawa, ON (Canada)] [Cyrium Technologies Inc., Ottawa, ON (Canada)

2013-09-27T23:59:59.000Z

94

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

SciTech Connect (OSTI)

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.

Yang, Jie, E-mail: jie.yang@yale.edu; Cui, Sharon; Ma, T. P. [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States)] [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520 (United States); Hung, Ting-Hsiang; Nath, Digbijoy; Krishnamoorthy, Sriram; Rajan, Siddharth [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)] [Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

2013-11-25T23:59:59.000Z

95

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

E-Print Network [OSTI]

GaP single QW surrounded by AlGaInP waveguide WG and cladding layers, whereas the NIR laser incorporates a GaInfrared emission from the substrate of GaAs-based semiconductor lasers Mathias Ziegler,1,a Robert in GaAs-based broad-area laser diodes. Spectrally and spatially resolved scanning optical microscopy

Peinke, Joachim

96

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

SciTech Connect (OSTI)

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.

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

2006-01-01T23:59:59.000Z

97

Direct observation of Ga-rich microdomains in crack-free AlGaN grown on patterned GaNsapphire substrates  

E-Print Network [OSTI]

.e., a homogeneous aluminum content, is found near the sample surface. However, the strong rise of quantum efficiency for AlGaN because the Al alloys also nucleate on the mask materials. Recently, growth on patterned structured into a periodic grid of trenches and terraces along 1100 . Prior to the final AlGaN ( Al 0

Nabben, Reinhard

98

Monolithic integration of GaAs and h~~~~Ga~.~Aslasers by molecular epitaxy on GaAs  

E-Print Network [OSTI]

where the thick cladding layer below the active laser region acts as a buffer layer to-yield comparable epitaxial regrowth of Ino.aGaesAs lasers through dielectric masks between GaAs laser stripes on a GaAs substrate has been used for the -first time- to monolithically integrate these two lasers emitting near 1

99

Kohlenstoffhaltige ternre Verbindungen (V-Ge-C, Nb-Ga-C, Ta-Ga-C, Ta-Ge-C, Cr-Ga-C und Cr-Ge-C)  

Science Journals Connector (OSTI)

Die ternren Phasen V2GeC, Cr2GaC und Cr2GeC werden aus den Komponenten hergestellt und als H-Phasen identifiziert. Ferner drften auch die H-Phasen Ti2GaC, und Ti2GeC existieren. In gleicher Weise hergestellte L...

W. Jeitschko; H. Nowotny; F. Benesovsky

1963-01-01T23:59:59.000Z

100

Effect of AlGaN/GaN strained layer superlattice period on InGaN MQW laser diodes[Multiple Quantum Wells  

SciTech Connect (OSTI)

AlGaN/GaN strained layer superlattices have been employed in the cladding layers of InGaN multi-quantum well laser diodes grown by metalorganic chemical vapor deposition (MOCVD). Superlattices have been investigated for strain relief of the cladding layer, as well as an enhanced hole concentration, which is more than ten times the value obtained for bulk AlGaN films. Laser diodes with strained layer superlattices as cladding layers were shown to have superior structural and electrical properties compared to laser diodes with bulk AlGaN cladding layers. As the period of the strained layer superlattices is decreased, the threshold voltage, as well as the threshold current density, is decreased. The resistance to vertical conduction through p-type superlattices with increasing superlattice period is not offset by the increase in hole concentration for increasing superlattice spacing, resulting in higher voltages.

Hansen, M.; Abare, A.C.; Kozodoy, P.; Katona, T.M.; Craven, M.D.; Speck, J.S.; Mishra, U.K.; Coldren, L.A.; DenBaars, S.P.

2000-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Radiation Hard AlGaN Detectors and Imager  

SciTech Connect (OSTI)

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

None

2012-05-01T23:59:59.000Z

102

Optimisation of doping cladding layers in AlGaInP/GaInP laser heterostructures  

SciTech Connect (OSTI)

The influence of cladding doping level on the characteristics of laser diodes, which are based on an AlGaInP/GaInP/GaAs system and emit at wavelengths of 670-680 nm, is studied. It is shown experimentally that, as the ratio of the cladding doping levels P/N increases, the inversion current density J{sub 0} and the differential gain {beta} also increase. A monotonic increase in the characteristic temperature T{sub 0} accompanies this process. The internal quantum yield {eta}{sub 0} of stimulated recombination has a maximum at P/N=2.1. Laser diodes with a mesastripe width of 100 {mu}m are manufactured. The cw radiation power emitted by them is as high as 1000 mW at an efficiency of 1.55 W A{sup -1}. (active media. lasers)

Chel'nyi, A A; Aluev, A V; Maslov, S V [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation)

2004-01-31T23:59:59.000Z

103

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

SciTech Connect (OSTI)

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

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

2014-05-26T23:59:59.000Z

104

Efficiency enhancement of InGaN/GaN solar cells with nanostructures  

SciTech Connect (OSTI)

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%.

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

2014-02-03T23:59:59.000Z

105

Optoelectrical characteristics of green light-emitting diodes containing thick InGaN wells with digitally grown InN/GaN  

Science Journals Connector (OSTI)

Compared with conventionally grown thin InGaN wells, thick InGaN wells with digitally grown InN/GaN exhibit superior optical properties. The activation energy (48 meV) of thick InGaN...

Yu, Chun-Ta; Lai, Wei-Chih; Yen, Cheng-Hsiung; Hsu, Hsu-Cheng; Chang, Shoou-Jinn

2014-01-01T23:59:59.000Z

106

In: Proceedings of the 1995 International environmental conference; 1995 May 7-10; Atlanta, GA. Atlanta, GA: TAPPI PRESS: 445-448; 1995.  

E-Print Network [OSTI]

. Atlanta, GA: TAPPI PRESS: 445-448; 1995. ENVIRONMENTALLY SOUND ALTERNATIVES FOR UPGRADING MIXED OFFICE

Abubakr, Said

107

Surface Science Analysis of GaAs Photocathodes Following Sustained...  

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

Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, strained super-lattice GaAs photocathode samples, removed from the CEBAF...

108

P-type doping of GaN  

SciTech Connect (OSTI)

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

Wong, R.K.

2000-04-10T23:59:59.000Z

109

Electronic properties of the AlGaN/GaN heterostructure and two-dimensional electron gas observed by electroreflectance  

Science Journals Connector (OSTI)

A contacted electroreflectance technique was used to investigate AlGaN/GaN heterostructures and their intrinsic electric field-induced properties. By studying variations in the electroreflectance with applied field spectral features associated with the AlGaN barrier the two-dimensional electron gas at the interface and bulk GaN were identified. Barrier-layer composition and electric field were determined from the AlGaN FranzKeldysh oscillations. For a high mobilityheterostructure grown on SiC measured AlGaN polarizationelectric field and two-dimensional electron gas density approached values predicted by a standard bandstructure model. The two-dimensional electron gas produced a broad field-tunable first derivative electroreflectance feature. With a dielectric function calculation we describe the line shape and relative amplitude of the two-dimensional electron gas electroreflectance feature for a wide range of electron density and applied field values.

S. R. Kurtz; A. A. Allerman; D. D. Koleske; A. G. Baca; R. D. Briggs

2004-01-01T23:59:59.000Z

110

Spectral-kinetic properties of heterostructures with GaAsSb/InGaAs/GaAs-based quantum wells emitting in the range of 1.0-1.2 {mu}m  

SciTech Connect (OSTI)

The spectral-kinetic properties of heterostructures with GaAs/GaAsSb-based and GaAsSb/InGaAs/GaAs-based quantum wells, emitting in the range of 1.0-1.2 {mu}m are studied with picosecond and nanosecond temporal resolution. Intense photoluminescence in the GaAsSb/InGaAs/GaAs structure, as well as an increase in the photoluminescence wavelength by a factor of 2.5 and a shift of the location of the maximum of the peak ({approx}100 meV) to the longer-wavelength region were observed up to room temperature. It is established that as the molar fraction of Sb and the thickness of the InGaAs layer increase, the energy of the fundamental transition decreases by a factor of 140 meV compared with the GaAsSb/InGaAs/GaAs structure with a lower Sb content and a smaller thickness of the InGaAs layer. At 300 K, the emission wavelength of such a structure was 1.18 {mu}m. In addition, an increase in the thickness of the InGaAs layer led to an increase in the room-temperature photoluminescence intensity by a factor of 60, which is associated with a decrease in the energy of the fundamental state for electrons in the InGaAs layer and, consequently, to larger electron localization and smaller temperature quenching of photoluminescence.

Morozov, S. V., E-mail: more@ipm.sci.-nnov.ru; Kryzhkov, D. I.; Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)] [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Zvonkov, B. N.; Vikhrova, O. I. [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)] [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)

2013-11-15T23:59:59.000Z

111

Vacancy-Induced 22 Reconstruction of the Ga(111) Surface of GaAs  

Science Journals Connector (OSTI)

Vacancy formation on the GaAs(111) surface is calculated to be strongly exothermic in character. The creation of one vacancy in each 22 cell allows the remaining Ga surface atoms to have a large inward relaxation, resulting in a 2.3-eV reduction in energy. It also transforms the polar (111) surface into a nonpolar (110)-like surface. The calculations provide strong support for the vacancy model of Tong et al., which is determined from analysis of low-energy-electron-diffraction data.

D. J. Chadi

1984-05-21T23:59:59.000Z

112

GaAs single quantum dot embedded into AlGaAs nanowire  

SciTech Connect (OSTI)

We report on a study of the photoluminescence spectra taken from quasi one-dimensional and quasi zero-dimensional semiconductor heterostructures. The structures were grown by molecular-beam epitaxy in (111) direction and were cylindrical nanowires based on AlGaAs, of 20 - 50 nm in diameter and 0.5 - 1 ?m in length. Inside the nanowires contain one or two GaAs quantum dots, of 2 nm thick and 15 - 45 nm in diameter. We studied a single nanowire. The photoluminescence and photoluminescence excitation spectra were registered as a function of the intensity of optical excitation.

Kochereshko, V. P.; Kats, V. N. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg, Russia and Spin Optics Laboratory, Saint Petersburg State University, Ul'yanovskaya 1, Petrodvorets, St. Petersburg, 198904 (Russian Federation); Platonov, A. V. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg (Russian Federation); Cirlin, G. E.; Bouravleuv, A. D.; Samsonenko, Yu. B. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg, Russia and St. Petersburg Academic University of the RAS Khlopina 8/3, 195220, St. Petersburg (Russian Federation); Besombes, L.; Mariette, H. [CEA-CNRS group Nanophysique et Semiconducteurs, CEA, INAC, SP2M, and Institut Nel, 17 rue des Martyrs, F-38054 Grenoble (France)

2013-12-04T23:59:59.000Z

113

Observation of photo darkening in self assembled InGaAs/GaAs quantum dots  

SciTech Connect (OSTI)

Photo darkening was observed in epitaxial InGaAs/GaAs quantum dots (QDs). The photoluminescence (PL) intensity of the QDs showed a non-reversible decrease under continuous laser irradiation. The time constants varied from tens of minutes to several hours, depending on the applied laser power. Based on the spectral evolution, it was concluded that the observed phenomenon should originate from laser induced structural damage and a sustained increase of non-radiative recombination rate in the wetting layer. Additionally, according to the PL decay dynamics at different laser powers, it is argued that there should exist other processes that hinder PL degradation at a high laser power.

Zhang Hongyi; Chen Yonghai; Zhou Xiaolong; Jia Yanan; Ye Xiaoling; Xu Bo; Wang Zhanguo [Key Laboratory of Semiconductor Materials Science and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

2013-05-07T23:59:59.000Z

114

Nitrogen-concentration control in GaNAs/AlGaAs quantum wells using nitrogen ?-doping technique  

SciTech Connect (OSTI)

GaNAs/Al{sub 0.35}Ga{sub 0.65}As multiple quantum wells (MQWs) with nitrogen ?-doping were fabricated on GaAs (100) substrates by plasma-assisted molecular beam epitaxy. High controllability of nitrogen-concentrations in the MQWs was achieved by tuning nitrogen ?-doping time. The maximum nitrogen concentration in the MQWs was 2.8%. The MQWs exhibit intense, narrow photoluminescence emission.

Mano, Takaaki; Jo, Masafumi; Kuroda, Takashi; Noda, Takeshi; Sugimoto, Yoshimasa; Sakuma, Yoshiki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Elborg, Martin; Sakoda, Kazuaki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan and Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

2014-05-15T23:59:59.000Z

115

Theoretical studies of optical gain tuning by hydrostatic pressure in GaInNAs/GaAs quantum wells  

SciTech Connect (OSTI)

In order to describe theoretically the tuning of the optical gain by hydrostatic pressure in GaInNAs/GaAs quantum wells (QWs), the optical gain calculations within kp approach were developed and applied for N-containing and N-free QWs. The electronic band structure and the optical gain for GaInNAs/GaAs QW were calculated within the 10-band kp model which takes into account the interaction of electron levels in the QW with the nitrogen resonant level in GaInNAs. It has been shown that this interaction increases with the hydrostatic pressure and as a result the optical gain for GaInNAs/GaAs QW decreases by about 40% and 80% for transverse electric and transverse magnetic modes, respectively, for the hydrostatic pressure change from 0 to 40 kilobars. Such an effect is not observed for N-free QWs where the dispersion of electron and hole energies remains unchanged with the hydrostatic pressure. This is due to the fact that the conduction and valence band potentials in GaInAs/GaAs QW scale linearly with the hydrostatic pressure.

Gladysiewicz, M.; Wartak, M. S. [Institute of Physics, Wroclaw University of Technology, 50-370 Wroclaw, Wybrzeze Wyspianskiego 27 (Poland); Department of Physics and Computer Science, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5 (Canada); Kudrawiec, R. [Institute of Physics, Wroclaw University of Technology, 50-370 Wroclaw, Wybrzeze Wyspianskiego 27 (Poland)

2014-01-21T23:59:59.000Z

116

Partially filled intermediate band of Cr-doped GaN films  

SciTech Connect (OSTI)

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

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

2012-05-14T23:59:59.000Z

117

Localized corrosion of GaAs surfaces and formation of porous GaAs  

SciTech Connect (OSTI)

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.

Schmuki, P.; Vitus, C.M.; Isaacs, H.S. [Brookhaven National Lab., Upton, NY (United States); Fraser, J.; Graham, M.J. [National Research Council of Canada, Ottawa, ON (Canada). Inst. for Microstructural Sciences

1995-12-01T23:59:59.000Z

118

GaAs/AlGaAs nanostructured composites for free-space and integrated optical devices  

E-Print Network [OSTI]

after development with MIBK:IPA=1:2 for 2min. Different fillon GaAs developed with MIBK:IPA=1:2 for (a) 1 min; (b) 2d) shows a nonoptimized developer, MIBK:IPA=2:1, used for 3

Tsai, Chia-Ho

2006-01-01T23:59:59.000Z

119

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

SciTech Connect (OSTI)

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.

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.; zgr, .; Morko, H. [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Electrical and Computer Engineering Department, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Chabak, K. D.; Crespo, A.; Gillespie, J. K.; Fitch, R.; Kossler, M.; Walker, D. E.; Trejo, M.; Via, G. D.; Blevins, J. D. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)] [Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States)

2013-11-04T23:59:59.000Z

120

The development of integrated chemical microsensors in GaAs  

SciTech Connect (OSTI)

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

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

1999-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

CoNiGa High Temperature Shape Memory Alloys  

E-Print Network [OSTI]

commercially successful SMAs such as NiTi and Cu-based alloys. In recent years, the CoNiGa system has emerged as a new ferromagnetic shape memory alloy with some compositions exhibiting high martensitic transformation temperatures which makes CoNiGa a potential...

Dogan, Ebubekir

2011-10-21T23:59:59.000Z

122

The Essentials for GA Water Planning The Relationship  

E-Print Network [OSTI]

Water Plan and the Alabama-Florida-Georgia Water Sharing Dispute (The failure to agree on the two Management F. Conservation & Reuse a. Programs for Water Use Efficiency b. Consumptive Use & Return Flows GThe Essentials for GA Water Planning The Relationship Between the Proposed GA State Comprehensive

Rosemond, Amy Daum

123

Structure of a Si(100)22-Ga surface  

Science Journals Connector (OSTI)

The 22 structure formed on a Ga-adsorbed Si(100) surface is determined using tensor low-energy electron diffraction. I-V curves of the parallel dimer model are in excellent agreement with those of the experiment, indicating that the actual surface has parallel dimer structure. Specific displacements of the topmost two surface layers (the protrusion of the Ga dimer toward the vacuum, the increase of the bond length of the Ga dimer, the stretching of the Si dimer, and the movement of the Si dimer toward the Ga dimer) with the elongation of the Si dimer back bond are observed in the optimized geometry. The Ga-Si bond angle measured from the Si(100) surface plane is recovered with these displacements from that of the ideal geometry where each bond length is assumed to be the sum of Pauling covalent radii. Subsurface layers are also deformed to keep the bond lengths near their bulk values.

H. Sakama; K. Murakami; K. Nishikata; A. Kawazu

1994-11-15T23:59:59.000Z

124

Electronic structure of metallic antiperovskite compound GaCMn3  

Science Journals Connector (OSTI)

We have investigated the electronic structures of antiperovskite GaCMn3 and related Mn compounds SnCMn3, ZnCMn3, and ZnNMn3. In the paramagnetic state of GaCMn3, the Fermi surface nesting feature along the ?R direction is observed, which induces the antiferromagnetic (AFM) spin ordering with the nesting vector Q??R. Calculated susceptibilities confirm the nesting scenario for GaCMn3, and also explain various magnetic structures of other antiperovskite compounds. Through the band folding effect, the AFM phase of GaCMn3 is stabilized. Nearly equal densities of states at the Fermi level in the ferromagnetic and AFM phases of GaCMn3 indicate that two phases are competing in the ground state.

J. H. Shim; S. K. Kwon; B. I. Min

2002-07-10T23:59:59.000Z

125

Improved photovoltaic performance of InGaN/GaN solar cells with optimized transparent current spreading layers  

Science Journals Connector (OSTI)

In0.135Ga0.865N/GaN pin solar cells are fabricated and investigated with three types of transparent current spreading layers (TCSLs): Ni/Au layer type (Ni/Au-L), Ni/Au grid type (Ni/Au-G), and ITO layer type (I...

X. M. Cai; Y. Wang; Z. D. Li; X. Q. Lv; J. Y. Zhang; L. Y. Ying

2013-05-01T23:59:59.000Z

126

Analysis of the reduced thermal conductivity in InGaAs/GaAs quantum dot lasers from chirp characteristics  

E-Print Network [OSTI]

injection which we term "thermal impact" , the ther- mal conductivity of the active region is estimatedAnalysis of the reduced thermal conductivity in InGaAs/GaAs quantum dot lasers from chirp; published online 21 September 2006 The thermal conductivity of self-organized quantum dot QD active regions

Klotzkin, David

127

Surface roughening during depth profiling by Secondary Ion Mass Spectrometry (SIMS) in GaAlAs and GaAs  

Science Journals Connector (OSTI)

During bombardment of Ga1?xAlxAs and GaAs with oxygen we found an abrupt transition to higher sputter rates, change of the useful yield and significant increase of surface roughness at a well defined depth, which...

M. Gericke; T. Lill; M. Trapp; C. -E. Richter

128

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

E-Print Network [OSTI]

radiation hardness than Si, GaAs, CdS and GaN, therefore it should be suitable for space applications. Last novel optoelectronic devices circumventing the problem of p-type doping of ZnO. In such Al devices become reality: the problem of p-type doping of ZnO. So far, there is no way to reliably produce

Wetzel, Christian M.

129

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

E-Print Network [OSTI]

AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors using barium strontium-effect transistors have been formed by incorporating barium strontium titanate (BST) deposited by rf magnetron in increased leakage. Due to its large dielectric constant, barium strontium ti- tanate [Ba1-xSrxTiO3, (BST

York, Robert A.

130

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

E-Print Network [OSTI]

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

Johnson, Derek Wade

2014-07-31T23:59:59.000Z

131

High-Performance Integrated Dual-Gate AlGaN/GaN Enhancement-Mode Transistor  

E-Print Network [OSTI]

In this letter, we present a new AlGaN/GaN enhancement-mode (E-mode) transistor based on a dual-gate structure. The dual gate allows the transistor to combine an E-mode behavior with low on-resistance and very high breakdown ...

Lu, Bin

132

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

E-Print Network [OSTI]

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

Lu, Bin

133

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

E-Print Network [OSTI]

Highly Ordered Ga Nanodroplets on a GaAs Surface Formed by a Focused Ion Beam Qiangmin Wei,1 Jie Lian,2,3 Wei Lu,4 and Lumin Wang1,5,* 1 Department of Materials Science and Engineering, University Arbor, Michigan 48109, USA 3 Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer

Lu, Wei

134

An AlGaAsGaAs quantum cascade laser operating with a thermoelectric cooler for spectroscopy of NH3  

E-Print Network [OSTI]

out using a compact thermo-electrically cooled laser package. The QCL described here is designedAn AlGaAs­GaAs quantum cascade laser operating with a thermoelectric cooler for spectroscopy of NH3. Langford b a Department of Electronics and Electrical Engineering, Rankine Building, University of Glasgow

135

Inductively Coupled Plasma Reactive Ion Etching of AlGaAsSb and InGaAsSb for Quaternary Antimonide MIM Thermophotovoltaics  

SciTech Connect (OSTI)

In this letter we report on the inductively coupled plasma reactive ion etching (ICP-RIE) of InGaAsSb and AlGaAsSb for the fabrication of quaternary monolithic interconnected module (MIM) thermophotovoltaic (TPV) devices. A rapid dry etch process is described that produces smooth surfaces using BCl[sub]3 for AlGaAsSb and InGaAsSb capped with GaSb. Uncapped InGaAsSb was etched by adding an H[sub]2 plasma preclean to reduce surface oxides. InGaAsSb etch rate was studied as a function of accelerating voltage, RF power, temperature and pressure. The etch conditions found for InGaAsSb were used for AlGaAsSb etching to determine the effectiveness for isolation of the MIM cells.

Palmisiano, M. N.; Peake, G. M.; Shul, R. J.; Ashby, C. I.; Cederberg, J. G.; Hafich, M. J.; Biefeld, R. M.

2002-10-01T23:59:59.000Z

136

GaAs/AlGaAs quantum wells with indirect-gap AlGaAs barriers for solar cell applications  

SciTech Connect (OSTI)

We have fabricated GaAs/AlGaAs quantum well (QW) solar cells in which 3?nm-thick QWs and indirect-gap Al{sub 0.78}Ga{sub 0.22}As barriers are embedded, and we studied extraction processes of photogenerated carriers in this QW system. The photocurrent under 700?nm light illumination at voltages close to the open-circuit voltage shows only a small reduction, indicating that the carrier recombination inside QWs is largely suppressed. We attribute this result to an efficient extraction of electrons from the QWs through the X-valley of AlGaAs. The insertion of QWs is shown to be effective in extending the absorption wavelengths and in enhancing the photocurrent. The use of indirect-gap materials as barriers is found to enhance carrier extraction processes, and result in an improved performance of QW solar cells.

Noda, T., E-mail: NODA.Takeshi@nims.go.jp; Otto, L. M.; Elborg, M.; Jo, M.; Mano, T.; Kawazu, T.; Han, L. [National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Sakaki, H. [National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Toyota Technological Institute, Nagoya 468-8511 (Japan)

2014-03-24T23:59:59.000Z

137

Magnetic-field effects on quasi-two-dimensional excitons in coupled GaAs?(Ga,Al)As quantum wells  

Science Journals Connector (OSTI)

We have used the variational procedure in the effective-mass and nondegenerate parabolic band approximations in order to investigate the effects of a magnetic field on the exciton effective mass and dispersion in semiconductor heterostructures. Calculations are performed for bulk GaAs, and two-dimensional and quasi-two-dimensional excitons in coupled GaAs?(Ga,Al)As quantum wells for applied magnetic fields perpendicular to the layers. A simple hydrogenlike envelope wave function provides the expected behavior for the exciton dispersion in a wide range of the center-of-mass momenta, and an analytical expression for the exciton effective mass is obtained. Present results lead to a magnetic-field dependent exciton effective mass and dispersion in quite good agreement with available experimental measurements in coupled GaAs?(Ga,Al)As quantum wells.

E. Reyes-Gmez, L. E. Oliveira, and M. de Dios-Leyva

2005-01-14T23:59:59.000Z

138

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

SciTech Connect (OSTI)

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

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

2013-11-14T23:59:59.000Z

139

Large linear magnetoresistance in a GaAs/AlGaAs heterostructure  

SciTech Connect (OSTI)

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.

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

2013-12-04T23:59:59.000Z

140

Enhanced optical property in quaternary GaInAsSb/AlGaAsSb quantum wells  

SciTech Connect (OSTI)

High quality GaInAsSb/AlGaAsSb quantum wells (QWs) have been grown by molecular beam epitaxy using proper interface treatments. By controlling the group-V elements at interfaces, we obtained excellent optical quality QWs, which were free from undesired localized trap states, which may otherwise severely affect the exciton recombination. Strong and highly efficient exciton emissions up to room temperature with a wavelength of 2.2 ?m were observed. A comprehensive investigation on the QW quality was carried out using temperature dependent and power dependent photoluminescence (PL) measurements. The PL emission intensity remains nearly constant at low temperatures and is free from the PL quenching from the defect induced localized states. The temperature dependent emission energy had a bulk-like behavior, indicating high quality well/barrier interfaces. Because of the uniformity of the QWs and smooth interfaces, the low temperature limit of inhomogeneous line width broadening is as small as 5?meV.

Lin, Chien-Hung, E-mail: chlin.ee97g@g2.nctu.edu.tw; Lee, Chien-Ping [Department of Electronics Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan (China)

2014-10-21T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Exciton recombination dynamics in InxGa1-xAs/GaAs quantum wells  

Science Journals Connector (OSTI)

Low-temperature decay times ?PL are reported for a series of InxGa1-xAs/GaAs quantum wells. These show a nearly linear increase with increasing thickness (4?Lz?10 nm, x=0.15) but recombination in the widest well (12 nm) is dominated by nonradiative effects. The decay time increases almost linearly with temperature up to 50 K, as expected for free excitons. An increase in ?PL with increasing In composition (0.05?x?0.25, Lz=8 nm) is also observed. Wells with different In compositions exhibit a similar temperature behavior and there is a weak influence of strain on the decay time. Additional peaks in the photoluminescence spectra occur to the low-energy side of the free-exciton peaks. These features, which exhibit longer decay times, are attributed to excitons localized in In-rich islands arising from indium segregation.

Haiping Yu; Christine Roberts; Ray Murray

1995-07-15T23:59:59.000Z

142

Sidewall passivation for InGaN/GaN nanopillar light emitting diodes  

SciTech Connect (OSTI)

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.

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

2014-07-07T23:59:59.000Z

143

Photovoltaic properties of GaAs:Be nanowire arrays  

SciTech Connect (OSTI)

Arrays of GaAs:Be nanowires are synthesized by molecular beam epitaxy on GaAs(111)B substrates. Prototypes of photovoltaic converters in which the grown nanowire arrays are used as active layers are produced by means of successive photolithography, etching, and metallization processes. Studying the photovoltaic properties of the fabricated structures using a solar radiation simulator demonstrates that the solarenergy conversion efficiency is about 0.1%. The value of the efficiency recalculated with the area occupied by the p-type nanowires on the surface of the n-type GaAs substrate taken into account amounts to 1.1%.

Bouravleuv, A. D.; Beznasyuk, D. V.; Gilstein, E. P. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Tchernycheva, M.; Luna Bugallo, A. De; Rigutti, L. [University Paris Sud 11, Institut d'Electronique Fondamentale UMR CNRS 8622 (France); Yu, L. [CNRS, Laboratoire de Physique des Interfaces et des Couches Minces (LPICM), Ecole Polytechnique (France); Proskuryakov, Yu. [University of Liverpool, Stephenson Institute for Renewable Energy (United Kingdom); Shtrom, I. V.; Timofeeva, M. A. [Russian Academy of Sciences, St. Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation); Samsonenko, Yu. B.; Khrebtov, A. I.; Cirlin, G. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-06-15T23:59:59.000Z

144

Photocurrent Spectroscopy of Single Wurtzite GaAs Nanowires  

SciTech Connect (OSTI)

Photocurrent of single wurtzite GaAs nanowires grown by Au-assisted molecular beam epitaxy is measured at room and low temperature (10 K). At room temperature a high photo-response with more than two orders of magnitude increase of current is observed. The wavelength dependence of the photocurrent shows a sharp change near the zinc blende GaAs band gap. The absence of the free exciton peak in the low temperature photocurrent spectrum, and problems related to determining the exact position of the energy bandgap of wurtzite GaAs from the observed data are discussed.

Kim, D. C.; Ahtapodov, L.; Boe, A. B.; Moses, A. F.; Dheeraj, D. L.; Fimland, B. O.; Weman, H. [Department of Electronics and Telecommunications, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); Choi, J. W.; Ji, H.; Kim, G. T. [School of Electrical Engineering, Korea University, Seoul 136-701 (Korea, Republic of)

2011-12-23T23:59:59.000Z

145

Effects of Ga ion-beam irradiation on monolayer graphene  

SciTech Connect (OSTI)

The effects of Ga ion on the single layer graphene (SLG) have been studied by Raman spectroscopy (RS), SEM, and field-effect characterization. Under vacuum conditions, Ga ion-irradiation can induce disorders and cause red shift of 2D band of RS, rather than lattice damage in high quality SLG. The compressive strain induced by Ga ion decreases the crystalline size in SLG, which is responsible for the variation of Raman scattering and electrical properties. Nonlinear out-put characteristic and resistance increased are also found in the I-V measurement. The results have important implications during CVD graphene characterization and related device fabrication.

Wang, Quan; Mao, Wei; Zhang, Yanmin; Shao, Ying; Ren, Naifei [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China)] [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Ge, Daohan [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China) [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

2013-08-12T23:59:59.000Z

146

Electroreflectance study of effects of indium segregation in molecular-beam-epitaxy-grown InGaAs/GaAs  

Science Journals Connector (OSTI)

Electrolyte electroreflectance (EER) experiments were performed on In 0.22 Ga 0.78 As/GaAs single quantum wells grown by the conventional molecular-beam-epitaxy (MBE) shutter operation and also by modified MBE shutter operation intended to form more compositionally abrupt normal and inverted interfaces. The latter included controlled thermal desorption of the surface segregated In at the InGaAs layer surface (flash off) and the deposition of In at the InGaAs/GaAs interface to eliminate compositional broadening (predeposition). The fundamental energy gap and subband transitions were determined experimentally and compared with an accurate calculation of the potential well problem including strain. These results confirmed the segregation of In atoms near the interface. The segregation was maximum in the conventional (normal) MBE sample and least with the modified growth incorporating predeposition and flash off as expected. The segregated atoms are observed to act as dopants and form junctions near the InGaAs/GaAs interface. This study shows that EER can be used as an effective tool for studying the segregation process in MBE growth.

K. Chattopadhyay; J. Aubel; S. Sundaram; J. E. Ehret; R. Kaspi; Keith R. Evans

1997-01-01T23:59:59.000Z

147

The effect of CdS QDs structure on the InGaP/GaAs/Ge triple junction solar cell efficiency  

Science Journals Connector (OSTI)

This work describes optical and electrical characteristics of InGaP/GaAs/Ge triple-junction (T-J) solar cells with CdS quantum dots (QDs) ... quantum dot effectively enhance the overall power conversion efficiency

Chen-Chen Chung; Binh Tinh Tran; Hau-Vei Han; Yen-Teng Ho

2014-03-01T23:59:59.000Z

148

Improvement of orange ii photobleaching by moderate Ga3+ doping of titania and detrimental effect of structural disorder on Ga overloading  

Science Journals Connector (OSTI)

Highly photoactive Ga3+-doped anatase modification of titania was prepared by homogeneous hydrolysis of aqueous solutions mixture of titanium oxo-sulphate TiOSO4 and gallium(III) nitrate with urea. Incorporation of Ga3+ ...

Vclav tengl, Jil Henych, Michaela Slun, Tom Matys Grygar, Jana Velick, Martin Kormunda

2014-01-01T23:59:59.000Z

149

Kinetics of indirect photoluminescence in GaAs/AlxGa1?x As double quantum wells in a random potential with a large amplitude  

Science Journals Connector (OSTI)

The kinetics of indirect photoluminescence of GaAs/AlxGa1?x As double quantum wells, characterized by a random potential with a large amplitude (the linewidth of the indirect photoluminescence is ...

L. V. Butov; A. V. Mintsev; A. I. Filin

1999-05-01T23:59:59.000Z

150

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

SciTech Connect (OSTI)

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

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

2014-02-21T23:59:59.000Z

151

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

SciTech Connect (OSTI)

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.

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

2013-05-15T23:59:59.000Z

152

Time-resolved photoluminescence, positron annihilation, and Al0.23Ga0.77N/GaN heterostructure growth studies on low defect density polar and nonpolar freestanding GaN substrates grown by hydride vapor phase epitaxy  

Science Journals Connector (OSTI)

Time-resolved photoluminescence(TRPL) and positron annihilation measurements as well as Al0.23Ga0.77N/GaN heterostructuregrowth by metalorganic vapor phase epitaxy were carried out on very low defect density polar c-plane and nonpolar m-plane freestanding GaN (FS-GaN) substrates grown by hydride vapor phase epitaxy. Room-temperature photoluminescence(PL) lifetime for the near-band-edge (NBE) excitonic emission of the FS-GaN substrates increases with increasing positron diffusion length (L +); i.e. decreasing gross concentration of charged and neutral point defects and complexes. The best undoped c-plane FS-GaN exhibits record-long L + being 116?nm. The fast component of the PL lifetime for its NBE emission increases with temperature rise up to 100?K and levels off at approximately 1.1?ns. The result implies a saturation in thermal activation of nonradiative recombination centers. The surface and interface roughnesses for a Si-doped Al0.23Ga0.77N/GaN/Al0.18Ga0.82N/GaN heterostructure are improved by the use of FS-GaN substrates in comparison with the structure fabricated on a standard GaN template. The emission signals related to the recombination of a two-dimensional electron gas and excited holes are recognized for an Al0.23Ga0.77N/GaN single heterostructuregrown on the c-plane FS-GaN substrate.

S. F. Chichibu; K. Hazu; Y. Ishikawa; M. Tashiro; H. Namita; S. Nagao; K. Fujito; A. Uedono

2012-01-01T23:59:59.000Z

153

Polarization charges and polarization-induced barriers in AlxGa1xNGaN and InyGa1yNGaN heterostructures  

E-Print Network [OSTI]

N?GaN heterostructures L. Jia,a) E. T. Yu, D. Keogh, and P. M. Asbeck Department of Electrical and Computer EngineeringGa1 yN surrounded by n-GaN, capacitance­ voltage profiling studies combined with elementary will most likely require further improvements in p-type GaN conduc- tivity and fabrication of low-resistance

Yu, Edward T.

154

FUPWG Meeting Agenda - Atlanta, GA | Department of Energy  

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

Atlanta, GA Atlanta, GA FUPWG Meeting Agenda - Atlanta, GA October 7, 2013 - 3:16pm Addthis Energy on My Mind / FUPWG / Atlanta, GA / May 3-4, 2006 Hosted by: AGL Resources Logo May 3-4, 2006 Hosted by AGL Resources Atlanta, Georgia Tuesday, May 2, 2006 5:00 - 6:30 Steering Committee meeting in the Danube Tigris Room 6:30 until... Networking dinner at the Marriott Wednesday, May 3, 2006 7:45 am Registration/Continental Breakfast 8:30 - 8:45 Welcome from Suzanne Sitherwood, SVP, Southern Operations, President, Atlanta Gas Light, Chattanooga Gas & Florida City Gas 8:45 - 9:00 FEMP Southeast Regional Office Welcome Traci Leath, FEMP 9:00 - 9:45 Washington Update David McAndrew, FEMP 9:45 - 10:15 Break - Networking 10:15 - 11:20 Navy Technical Program Update Paul Kistler, U.S. Navy

155

Elba Island, GA Natural Gas Liquefied Natural Gas Imports from...  

U.S. Energy Information Administration (EIA) Indexed Site

Egypt (Million Cubic Feet) Elba Island, GA Natural Gas Liquefied Natural Gas Imports from Egypt (Million Cubic Feet) Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2011 5,780...

156

Lattice vibrations of pure and doped GaSe  

SciTech Connect (OSTI)

The Bridgman method is used to grow especially undoped and doped single crystals of GaSe. Composition and impurity content of the grown crystals were determined using X-ray fluorescence (XRF) method. X-ray diffraction, Raman scattering, photoluminescence (PL), and IR transmission measurements were performed at room temperature. The long wavelength lattice vibrations of four modifications of GaSe were described in the framework of modified one-layer linear-chain model which also takes into consideration the interaction of the selenium (Se) atom with the second nearest neighbor gallium (Ga) atom in the same layer. The existence of an eight-layer modification of GaSe is suggested and the vibrational frequencies of this modification are explained in the framework of a lattice dynamical model considered in the present work. Frequencies and the type of vibrations (gap, local, or resonance) for the impurity atoms were calculated and compared with the experimental results.

Allakhverdiev, K. [Materials Institute, Marmara Research Center, TUBITAK, Gebze/Kocaeli 41470 (Turkey) and Institute of Physics, Azerbaijan National Academy of Sciences, Baku AZ1143 (Azerbaijan)]. E-mail: kerim.allahverdi@mam.gov.tr; Baykara, T. [Materials Institute, Marmara Research Center, TUBITAK, Gebze/Kocaeli 41470 (Turkey); Ellialtioglu, S. [Department of Physics, Middle East Technical University, Ankara 06531 (Turkey); Hashimzade, F. [Institute of Physics, Azerbaijan National Academy of Sciences, Baku AZ1143 (Azerbaijan); Huseinova, D. [Institute of Physics, Azerbaijan National Academy of Sciences, Baku AZ1143 (Azerbaijan); Kawamura, K. [Institute of Materials Science, University of Tsukuba 305-8573 (Japan); Kaya, A.A. [Materials Institute, Marmara Research Center, TUBITAK, Gebze/Kocaeli 41470 (Turkey); Kulibekov, A.M. [Department of Physics, Mugla University, Mugla 48000 (Turkey); Onari, S. [Institute of Materials Science, University of Tsukuba 305-8573 (Japan)

2006-04-13T23:59:59.000Z

157

GaAs solar cells close to the thermodynamic limit  

Science Journals Connector (OSTI)

The efficiency of GaAs solar cells can be increased by applying angularly selective filters. It is shown in terms of detailed balance model, why this happens and the concept is proven...

Hoehn, Oliver; Kraus, Tobias; Bauhuis, Gerard; Schwarz, Ulrich T; Blsi, Benedikt

158

Transverse acoustic actuation of Ni-Mn-Ga single crystals  

E-Print Network [OSTI]

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

Simon, Jesse Matthew

2007-01-01T23:59:59.000Z

159

Modeling of InGaN/Si tandem solar cells  

Science Journals Connector (OSTI)

We investigate theoretically the characteristics of monolithic InGaN/Si two-junction series-connected solar cells using the air mass 1.5 global irradiance spectrum. The addition of an InGaN junction is found to produce significant increases in the energy conversion efficiency of the solar cell over that of one-junction Si cells. Even when Si is not of high quality such two-junction cells could achieve efficiencies high enough to be practically feasible. We also show that further though smaller improvements of the efficiency can be achieved by adding another junction to form an InGaN/InGaN/Si three-junction cell.

L. Hsu; W. Walukiewicz

2008-01-01T23:59:59.000Z

160

Exciton front propagation in photoexcited GaAs quantum wells  

E-Print Network [OSTI]

We report on the study of spatiotemporal self-organization of carriers in photoexcited GaAs quantum wells. Propagating interfaces between electron-rich and hole-rich regions are seen as expanding and collapsing exciton ...

Yang, Sen

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Evaporation-based Ge/.sup.68 Ga Separation  

DOE Patents [OSTI]

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.

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

1981-01-01T23:59:59.000Z

162

Homogeneous AlGaN/GaN superlattices grown on free-standing (1100) GaN substrates by plasma-assisted molecular beam epitaxy  

SciTech Connect (OSTI)

Two-dimensional and homogeneous growth of m-plane AlGaN by plasma-assisted molecular beam epitaxy has been realized on free-standing (1100) GaN substrates by implementing high metal-to-nitrogen (III/N) flux ratio. AlN island nucleation, often reported for m-plane AlGaN under nitrogen-rich growth conditions, is suppressed at high III/N flux ratio, highlighting the important role of growth kinetics for adatom incorporation. The homogeneity and microstructure of m-plane AlGaN/GaN superlattices are assessed via a combination of scanning transmission electron microscopy and high resolution transmission electron microscopy (TEM). The predominant defects identified in dark field TEM characterization are short basal plane stacking faults (SFs) bounded by either Frank-Shockley or Frank partial dislocations. In particular, the linear density of SFs is approximately 5 10{sup ?5} cm{sup ?1}, and the length of SFs is less than 15 nm.

Shao, Jiayi; Malis, Oana [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States) [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States); Zakharov, Dmitri N. [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Edmunds, Colin [Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States)] [Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States); Manfra, Michael J. [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States) [Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Physics Department, Purdue University, West Lafayette, Indiana 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, Indiana 49707 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 49707 (United States)

2013-12-02T23:59:59.000Z

163

High-efficiency GaAs and GaInP solar cells grown by all solid-state molecular-beam-epitaxy  

Science Journals Connector (OSTI)

We report the initial results of GaAs and GaInP solar cells grown by all solid-state molecular- ... (MBE) technique. For GaAs single-junction solar cell, with the application of AlInP as ... back surface field la...

Shulong Lu; Lian Ji; Wei He; Pan Dai; Hui Yang

2011-10-01T23:59:59.000Z

164

Organometallic Vapor Phase Epitaxy of n-GaSb and n-GaInAsSb for Low Resistance Ohmic Contacts  

SciTech Connect (OSTI)

A comparison of n-GaSb and n-GaInAsSb epilayers for ohmic contacts in GaSb-based devices is studied. The epilayers were grown by organometallic vapor phase epitaxy and doped with Te. At similar electron concentrations, the atomic Te concentration, as determined by secondary ion mass spectroscopy, is more than 2 times higher in n-GaSb compared to n-GaInAsSb. In addition, the electron mobility is lower in n-GaSb than n-GaInAsSb at similar electron concentrations. The electron concentration saturates at about 1.3 x 10{sup 18} cm{sup -3} for n-GaSb, but linearly increases for n-GaInAsSb. Pd/Ge/Au/Pt/Au metallization was studied for ohmic contacts. A specific contact resistivity of 1 x 10{sup -5}{Omega}-cm{sup 2} for n-GaSb was measured. The specific contact resistivity can be greatly improved by contacting n-GaInAsSb, and a significantly lower specific contact resistivity of 2 x 10{sup -6} {Omega}-cm{sup 2} for n-GaInAsSb was measured.

C.A. Wang; D.A. Shiau; R.K. Huang; C.T. Harris; M.K. Connors

2003-07-10T23:59:59.000Z

165

60 GHz Harmonic Optoelectronic Up-Conversion Using an InAlAs/InGaAs Metamorphic High-Electron-Mobility Transistor on a GaAs Substrate  

E-Print Network [OSTI]

60 GHz Harmonic Optoelectronic Up-Conversion Using an InAlAs/InGaAs Metamorphic High optoelectronic up-conversion using an InAlAs/InGaAs metamorphic high-electron-mobility transistor (HEMT) on a Ga 1 GHz signals into a 60 GHz band. After investigating the dependences of optoelectronic mixing

Choi, Woo-Young

166

The crucial role of doping for high repetition rate monolithic mode locking of multiple quantum well GaAs/AlGaAs lasers  

E-Print Network [OSTI]

have been operated in GaAs/AlGaAs and InP/InGaAsP mul- tiple quantum well MQW materials showed no evidence of mode-locked operation. Band-edge absorption spectra are also presented which

167

Electronic properties of the Ga vacancy in GaP(110) surfaces determined by scanning tunneling microscopy  

Science Journals Connector (OSTI)

The electronic properties of uncharged Ga monovacancies in GaP(110) surfaces are determined from voltage-dependent scanning tunneling microscopy images. The signatures of localized defect states in the band gap are analyzed and their spatial location is determined. Empty and occupied defect states exist. Depressed dangling bonds in the occupied-state images indicate an inward relaxation of the neighboring P atoms. The results agree with recent theoretical work.

Ph. Ebert and K. Urban

1998-07-15T23:59:59.000Z

168

Microscopic identification of the compensation mechanisms in Si-doped GaAs  

Science Journals Connector (OSTI)

The compensation mechanisms of SiGa donors in GaAs are determined by scanning tunneling microscopy. With increasing Si concentration the SiGa donors are consecutively electrically deactivated by SiAs acceptors, Si clusters, and SiGa-Ga-vacancy complexes. A microscopic model based on the screened Coulomb interaction between charged dopants, the amphoteric nature of Si, and the Fermi-level effect is proposed. It explains the observed defects, the critical Si concentrations of each identified mechanism, and predicts the solubility limit of Si in GaAs. 1996 The American Physical Society.

C. Domke, Ph. Ebert, M. Heinrich, and K. Urban

1996-10-15T23:59:59.000Z

169

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

E-Print Network [OSTI]

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

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

2009-01-15T23:59:59.000Z

170

Persistent photoconductivity in AlGaN/GaN heterojunction channels caused by the ionization of deep levels in the AlGaN barrier layer  

SciTech Connect (OSTI)

Time-dependent responses of drain current (I{sub d}) in an AlGaN/GaN HEMT under UV (3.3 eV) and red (2.0 eV) light illumination have been studied at 300 K and 250 K. UV illumination enhances I{sub d} by about 10 %, indicating that the density of two-dimensional electrons is raised by about 10{sup 12} cm{sup ?2}. When UV light is turned off at 300 K, a part of increased I{sub d} decays quickly but the other part of increment is persistent, showing a slow decay. At 250 K, the majority of increment remains persistent. It is found that such a persistent increase of I{sub d} at 250 K can be partially erased by the illumination of red light. These photo-responses are explained by a simple band-bending model in which deep levels in the AlGaN barrier get positively charged by the UV light, resulting in a parabolic band bending in the AlGaN layer, while some potion of those deep levels are neutralized by the red light.

Murayama, H.; Akiyama, Y.; Niwa, R.; Sakashita, H.; Sakaki, H. [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan); Kachi, T. [Toyota Central R and D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Sugimoto, M. [Toyota Motor Corporation, 543 Kirigahora, Nishihirose-cho, Toyota, Aichi 470-0309 (Japan)

2013-12-04T23:59:59.000Z

171

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

E-Print Network [OSTI]

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

Jalali. Bahram

172

Growth of Core?Shell Ga?GaN Nanostructures via a Conventional Reflux Method and the Formation of Hollow GaN Spheres  

Science Journals Connector (OSTI)

Gallium nitride (GaN) is an important III?V semiconductor with a wide direct band gap of ?3.4 eV. ... LiHMDS exhibits good solubility in TOA. ... The products were collected by centrifugation twice at 7000 rpm for 2 min in hexane, isopropanol, ethanol, and then deionized water. ...

Tz-Jun Kuo; Chi-Liang Kuo; Chun-Hong Kuo; Michael H. Huang

2009-02-05T23:59:59.000Z

173

Maskless lateral epitaxial overgrowth of GaN on sapphire  

SciTech Connect (OSTI)

The authors demonstrate a technique of lateral epitaxial overgrowth (LEO) of GaN, termed maskless LEO, in which no mask is deposited prior to LEO regrowth. Instead, a bulk (> 2 {micro}m) GaN layer on sapphire is selectively dry etched, leaving {approximately} 5 {micro}m-wide stripe mesas oriented in the <10{bar 1}0>{sub GaN} direction, with a 20 {micro}m period. These stripes serve as seeds for LEO GaN growth, which proceeds from the tops of the stripes and expands laterally, resulting in a T, or overhang, morphology. As for LEO over an SiO{sub 2} mask, significant defect reduction (from {approximately} 10{sup 9} cm{sup {minus}2} to {approximately} 10{sup 6} cm{sup {minus}2}) is observed in cross-sectional transmission electron microscopy (TEM). Atomic force microscopy of the top surface of the LEO GaN reveals that no threading dislocations with screw component terminate at the surfaces of laterally overgrown regions. X-ray diffraction measurements reveal that the wings exhibit a crystallographic tilt away from the seed regions in an azimuth perpendicular to the stripe direction; the tilt angle ({approximately} 0.4--0.5{degree}) is relatively independent of growth temperature and wing aspect ratio.

Fini, P.; Marchand, H.; Ibbetson, J.P.; Moran, B.; Zhao, L.; Denbaars, S.P.; Speck, J.S.; Mishra, U.K.

1999-07-01T23:59:59.000Z

174

Metal contacts on ZnSe and GaN  

SciTech Connect (OSTI)

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.

Duxstad, K.J. [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering; [Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.

1997-05-01T23:59:59.000Z

175

Corrosion-induced degradation of GaAs PHEMTs under operation in high humidity conditions  

E-Print Network [OSTI]

We have comprehensively investigated the degradation mechanism of AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors (PHEMTs) under operation in high humidity conditions. PHEMTs degradation under high humidity ...

Hisaka, Takayuki

176

Site-controlled fabrication of Ga nanodroplets by focused ion beam  

SciTech Connect (OSTI)

Ga droplets are created by focused ion beam irradiation of GaAs surface. We report that ordered Ga droplets can be formed on the GaAs surface without any implantation damage. The droplets are characterized with bigger sizes than those droplets formed on damaged area. These aligned Ga droplets are formed via the migration of Ga atoms from ion irradiation area to the edge of undamaged GaAs surface and further nucleation into droplets. The morphological evolution and size distribution of these nanodroplets are investigated systematically with different beam irradiation time and incident angles. Based on this method, well positioned Ga nanodroplets, such as chains, are achieved by using focus ion beam patterning. The controllable assembly of droplets on undamaged semiconductor surface can be used to fabricate templates, to fabricate quantum structures and quantum devices by droplet epitaxy technique.

Xu, Xingliang; Wang, Zhiming M., E-mail: zhmwang@gmail.com [State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China); Wu, Jiang; Li, Handong; Zhou, Zhihua [State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Wang, Xiaodong [Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China)

2014-03-31T23:59:59.000Z

177

Nonlinear optical waveguides based on near-infrared intersubband transitions in GaN/AlN  

E-Print Network [OSTI]

. Hasama, "Subpicosecond saturation of intersubband absorption in (CdS/ZnSe)/BeTe quantum well waveguides. Cho, "Intersubband absorption at ~ 1.55 m in well- and modulation-doped GaN/AlGaN multiple quantum

178

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

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

Melting Behavior of GaN Nanotubes. Atomic-Level Study of Melting Behavior of GaN Nanotubes. Abstract: Molecular dynamics simulations with a Stillinger-Weber potential have been...

179

Electric field engineering in GaN high electron mobility transistors  

E-Print Network [OSTI]

In the last few years, AlGaN/GaN high electron mobility transistors (HEMTs) have become the top choice for power amplification at frequencies up to 20 GHz. Great interest currently exists in industry and academia to increase ...

Zhao, Xu, S.M. Massachusetts Institute of Technology

2008-01-01T23:59:59.000Z

180

Device-level thermal analysis of GaN-based electronics  

E-Print Network [OSTI]

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 ...

Bagnall, Kevin Robert

2013-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Structural ordering and interface morphology in symmetrically strained(GaIn)As/Ga(PAs) superlattices grown on off-oriented GaAs(100)  

Science Journals Connector (OSTI)

In this work we investigate the structural properties of symmetrically strained (GaIn)As/GaAs/Ga(PAs)/GaAs superlattices by means of x-ray diffraction, reciprocal-space mapping, and x-ray reflectivity. The multilayers were grown by metalorganic vapor-phase epitaxy on (001) GaAs substrates intentionally off-oriented towards one of the nearest ?110? directions. High-resolution triple-crystal reciprocal-space maps recorded for different azimuth angles in the vicinity of the (004) Bragg diffraction clearly show a double periodicity of the x-ray peak intensity that can be ascribed to a lateral and a vertical periodicity occurring parallel and perpendicular to the growth surface. Moreover, from the intensity modulation of the satellite peaks, a lateral-strain gradient within the epilayer unit cell is found, varying from a tensile to a compressive strain. Thus, the substrate off-orientation promotes a lateral modulation of the layer thickness (ordered interface roughness) and of the lattice strain, giving rise to laterally ordered macrosteps. In this respect, contour maps of the specular reflected beam in the vicinity of the (000) reciprocal lattice point were recorded in order to inspect the vertical and lateral interface roughness correlation. A semiquantitative analysis of our results shows that the interface morphology and roughness is greatly influenced by the off-orientation angle and the lateral strain distribution. Two mean spatial wavelengths can be determined, one corresponding exactly to the macrostep periodicity and the other indicating a further interface waviness along the macrosteps. The same spatial periodicities were found on the surface by atomic-force-microscopy images confirming the x-ray results and revealing a strong vertical correlation of the interfaces up to the outer surface.

C. Giannini; L. Tapfer; Y. Zhuang; L. De Caro; T. Marschner; W. Stolz

1997-02-15T23:59:59.000Z

182

THERMAL STUDY OF A GaN-BASED HEMT A Dissertation  

E-Print Network [OSTI]

of gallium-nitride (GaN) high-electron-mobility transistors (HEMTs) under bias conditions. An experimental

Sen, Mihir

183

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

SciTech Connect (OSTI)

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

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

2007-08-15T23:59:59.000Z

184

Doping and isolation of GaN, InGaN and InAlN using ion implantation  

SciTech Connect (OSTI)

Both n- and p-type doping have been achieved in GaN using Si{sup +} or Mg{sup +}/P{sup +} implantation, respectively, followed annealing at {ge} 1050{degrees}C. Using proximity rapid thermal annealing (10sec) the GaN surface retains both smooth morphology and its original stoichiometry. Variable temperature Hall measurements reveal approximate energy levels of 62meV for the implanted Si and 171meV for the Mg, which are similar to their values in epitaxially grown GaN. Implant isolation of both n- and p-type GaN, and n-type In{sub 0.75}Al{sub 0.25}N with multiple energy inert species (e.g. N{sup +} or F{sup +}) produces high resistivity ({ge}10{sup 8}{omega}/{open_square}) after subsequent annealing in the range 600-700{degrees}C. Smaller increases in sheet resistance are observed for In{sub x}Ga{sup 1-x}N (x=0.33-0.75) under the same conditions due to the smaller energy bandgaps and the shallower energy levels of the damage-related states controlling the resistivity.

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

1995-08-01T23:59:59.000Z

185

Simulation of Npn and Pnp AlGaN/GaN heterojunction bipolar transistors performances: Limiting factors and optimum design  

SciTech Connect (OSTI)

The performance capabilities of Npn and Pnp AlGaN/GaN heterojunction bipolar transistors have been investigated by using a drift-diffusion transport model. Numerical results have been employed to study the effect of the p-type Mg doping and its incomplete ionization on device performance. The high base resistance induced by the deep acceptor level is found to be the cause of limited current gain values for Npn devices. Several computation approaches have been considered to improve their performance. Reasonable improvement of the DC current gain {beta} is observed by realistically reducing the base thickness in accordance with processing limitations. Base transport enhancement is also predicted by the introduction of a quasi-electric field in the base. The impact of the base resistivity on high-frequency characteristics is investigated for Npn AlGaN/GaN devices. Optimized predictions with maximum oscillation frequency value as high as f{sub MAX} = 20 GHz and a unilateral power gain--U = 25 dB make this bipolar GaN-based technology compatible with communication applications. Simulation results reveal that the restricted amount of free carriers from the p-doped emitter limits Pnp's DC performances operating in common emitter configuration. A preliminary analysis of r.f. characteristics for the Pnp counterpart indicates limited performance mainly caused by the degraded hole mobility.

MONIER,C.; REN,F.; HAN,JUNG; CHANG,PING-CHIH; SHUL,RANDY J.; LEE,K.P.; ZHANG,A.P.; BACA,ALBERT G.; PEARTON,S.J.

2000-04-25T23:59:59.000Z

186

Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer  

SciTech Connect (OSTI)

We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

Liang, S. H.; Tao, L. L.; Liu, D. P., E-mail: dpliu@iphy.ac.cn; Han, X. F., E-mail: xfhan@iphy.ac.cn [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Lu, Y. [Institut Jean Lamour, UMR 7198, CNRS-Nancy Universit, BP 239, 54506 Vandoeuvre (France)

2014-04-07T23:59:59.000Z

187

Novel photoaffinity ligands for the GA-receptor  

SciTech Connect (OSTI)

Previous studies from this laboratory have shown that certain N-substituted phthalimides (NSPs) exhibit GA-like activity in a range of specific bioassays and that bioactive NSPs compete with ({sup 3}H)-GA{sub 4} for soluble binding sites in cucumber homogenates. As such, these compounds may prove useful in the purification and characterization of GA receptor proteins. To this end, five azido-NSPs have been synthesized and are currently being screened for biological activity and photochemical stability. Three azido-NSPs elicit {alpha}-amylase production in barley half-seeds and stimulate tissue elongation in d{sub 5} maize, lettuce, sunflower, and soybean. Further evaluations are in progress and these data as well as the utility of these compounds as photo-affinity ligands will be discussed.

Suttle, J.C.; Hultstrand, J.F.; Tanaka, F.S. (USDA/ARS Biosciences Research Laboratory, Fargo, ND (USA))

1990-05-01T23:59:59.000Z

188

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

SciTech Connect (OSTI)

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.

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.)

2012-03-01T23:59:59.000Z

189

Invited Paper GaAs/A1O photonic bandgap material fabrication and characterization  

E-Print Network [OSTI]

semiconductor crystals, photonic crystals do not occur naturally. There are, therefore, several seemingly direct bandgap semiconductors, such as GaAs, A1GaAs, InP, InGaAsP, etc., in which the radiative-dimensional photonic bandgaps for microwave and millimeter-wave radiation, and for shorter optical wavelengths in one

Zhou, Weidong

190

Drift dominated InP/GaP photodiodes Yanning Sun a,*, Aristo Yulius a  

E-Print Network [OSTI]

Drift dominated InP/GaP photodiodes Yanning Sun a,*, Aristo Yulius a , Guohua Li b , Jerry MP photodiodes fabricated on GaP substrate with unique drift dominated design, which can build an electric field throughout the active region by varying the doping concentration. The InP/GaP photodiodes have been grown

Woodall, Jerry M.

191

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

E-Print Network [OSTI]

DISSERTATION DEVICE PHYSICS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS Submitted by Markus Gloeckler PHYSICS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS BE ACCEPTED AS FULFILLING IN PART REQUIREMENTS OF Cu(In,Ga)Se2 THIN-FILM SOLAR CELLS Thin-film solar cells have the potential to be an important

Sites, James R.

192

Free carrier induced spectral shift for GaAs filled metallic hole arrays  

E-Print Network [OSTI]

. Soref, and J. A. D. Alamo, "Carrier-induced change in refractive index of InP, GaAs, and InGaAsP," IEEE-photon absorption (3PA) assisted by strongly enhanced local fields, reduce the refractive index of GaAs in ~200-nm thick active area through band filling and free carrier absorption. Therefore, the surface plasma wave

New Mexico, University of

193

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

E-Print Network [OSTI]

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

Myers, Tom

194

Visit Russia A trip to St. Petersburg will be arranged  

E-Print Network [OSTI]

to contact staff at LUT Summer School. Visit us Lappeenranta University of Technology International Services Skinnarilankatu 34 FI- 53850 LAPPEENRANTA FINLAND LUT Summer School 2012 Harbour of Lappeenranta 25 June ­ 8 July 2012, Lappeenranta, Finland Unique cultural experience Lappeenranta's safe and green environment

Hellebrand, Sybille

195

GA Hot Cell D&D Closeout Report  

Office of Legacy Management (LM)

GENERAL ATOMICS GENERAL ATOMICS HOT CELL FACILITY DECONTAMINATION & DECOMMISSIONING PROJECT FINAL PROJECT CLOSEOUT REPORT prepared for GA HOT CELL D&D PROJECT CONTRACT NUMBERS DE-AC03-84SF11962 and DE-AC03-95SF20798 PBS VL-GA-0012 Approvals Prepared by: James Davis, III Date Project Manager, Oakland Environmental Programs Office Reviewed by: John Lee Date Deputy, Oakland Environmental Programs Office Approved by: Laurence McEwen Date Acting Director, Oakland Environmental Programs Office General Atomics Hot Cell Facility D&D Project Closeout Report Contents Page i CONTENTS CONTENTS.....................................................................................................................................

196

Simple intrinsic defects in GaAs : numerical supplement.  

SciTech Connect (OSTI)

This Report presents numerical tables summarizing properties of intrinsic defects in gallium arsenide, GaAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz and O.A. von Lilienfeld, 'Simple intrinsic defects in GaAs', Modelling Simul. Mater. Sci Eng., Vol. 17, 084007 (2009), and intended for use as reference tables for a defect physics package in device models. The numerical results for density functional theory calculations of properties of simple intrinsic defects in gallium arsenide are presented.

Schultz, Peter Andrew

2012-04-01T23:59:59.000Z

197

Surface morphology and magnetic anisotropy in (Ga,Mn)As  

E-Print Network [OSTI]

Atomic Force Microscopy and Grazing incidence X-ray diffraction measurements have revealed the presence of ripples aligned along the $[1\\bar{1}0]$ direction on the surface of (Ga,Mn)As layers grown on GaAs(001) substrates and buffer layers, with periodicity of about 50 nm in all samples that have been studied. These samples show the strong symmetry breaking uniaxial magnetic anisotropy normally observed in such materials. We observe a clear correlation between the amplitude of the surface ripples and the strength of the uniaxial magnetic anisotropy component suggesting that these ripples might be the source of such anisotropy.

S. Piano; X. Marti; A. W. Rushforth; K. W. Edmonds; R. P. Campion; O. Caha; T. U. Schulli; V. Holy; B. L. Gallagher

2010-10-01T23:59:59.000Z

198

Operating experience with a GaAs photoemission electron source  

SciTech Connect (OSTI)

We report on the development of several operating procedures that promise to make GaAs photoemission electron sources easier to construct, more reliable to operate, and more amenable to use in dynamic vacuum systems. We describe in particular a method for ''ohmically'' heating a <100> crystal of GaAs under vacuum to approximately 600 /sup 0/C. We also discuss our observations of the role of oxygen in the activation of the crystal surface, the use of continuous cesiation, and of the performance of the crystal under varying vacuum conditions.

Tang, F.C.; Lubell, M.S.; Rubin, K.; Vasilakis, A.; Eminyan, M.; Slevin, J.

1986-12-01T23:59:59.000Z

199

An investigation on reliable passivation of GaP  

E-Print Network [OSTI]

reports the results of a study of sputtered Silicon Nitride 3N4) and Anodic Oxide as passivating techniques for Gallium Phosphide. Anodic Oxide was grown on GaP by anodizing the semiconductor in 30% hydrogen peroxide. The resulting oxide had an index... reports the results of a study of sputtered Silicon Nitride 3N4) and Anodic Oxide as passivating techniques for Gallium Phosphide. Anodic Oxide was grown on GaP by anodizing the semiconductor in 30% hydrogen peroxide. The resulting oxide had an index...

Greaves King, Carlos A.

2012-06-07T23:59:59.000Z

200

Interband transitions in molecular?beam?epitaxial Al x Ga1?x As/GaAs  

Science Journals Connector (OSTI)

Interband transition energies for Al x Ga1?x As layers grown by molecular?beam epitaxy(MBE) techniques have been determined using the electrolyte electroreflectance (EER) technique. The observed data fit quadratic relations for E 0 E 0+?0 E 1 and E 1+?1 to describe variations of energy with composition. Although the x values were not accurately known the internal consistency of the data is excellent. Given a single bowing parameter we show that accurate values of x can be determined. The EER technique can provide x values with an accuracy better than 0.02 and information on changes in x as small as 0.002. It is thus ideally suited for studying MBE materials.

J. L. Aubel; U. K. Reddy; S. Sundaram; W. T. Beard; James Comas

1985-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Ultralow damage depth by electron cyclotron resonance plasma etching of GaAs/InGaAs quantum wells  

Science Journals Connector (OSTI)

Dry etch induced damage of GaAs/InGaAs/GaAs heterostructures in an electron cyclotron resonance (ECR) argon discharge has been investigated as a function of additional radio frequency self?biasing of the sample and process pressure in argon ECR discharges. We used depth resolved photoluminescence measurements to determine the influence of the etch process on the samples. We observe a decreasing damage depth for smaller bias voltages reaching its lowest value of 1.7 nm at 20 V bias and a pressure of 0.15 Pa. For lower pressures we observe a strong increase of the damage which is attributed predominantly to high energetic vacuum ultraviolet radiation from the ECR region.

T. Bickl; B. Jacobs; J. Straka; A. Forchel

1993-01-01T23:59:59.000Z

202

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

SciTech Connect (OSTI)

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.

Young, N. G., E-mail: ngyoung@engineering.ucsb.edu; Farrell, R. M.; Iza, M.; Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Perl, E. E.; Keller, S. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States); Bowers, J. E.; Nakamura, S.; DenBaars, S. P. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106 (United States)

2014-04-21T23:59:59.000Z

203

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

SciTech Connect (OSTI)

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.

Estacio, Elmer; Pham, Minh Hong; Takatori, Satoru; Cadatal-Raduban, Marilou; Nakazato, Tomoharu; Shimizu, Toshihiko; Sarukura, Nobuhiko [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Somintac, Armando; Defensor, Michael; Awitan, Fritz Christian B.; Jaculbia, Rafael B.; Salvador, Arnel [National Institute of Physics, University of the Philippines, Diliman, Quezon City 1101 (Philippines); Garcia, Alipio [Department of Physical Sciences, University of the Philippines, Baguio City 2600 (Philippines)

2009-06-08T23:59:59.000Z

204

Ga-assisted catalyst-free growth mechanism of GaAs nanowires by molecular beam epitaxy  

Science Journals Connector (OSTI)

The mechanisms of Ga-assisted GaAs nanowires grown by molecular beam epitaxy are addressed. The axial and radial growth rates as a function of the Ga rate and As pressure indicate that on the opposite of what is observed in thin film epitaxy, the growth rate of the nanowires is arsenic limited. As a consequence, the axial growth rate of the wires can be controlled by the As4 pressure. Additionally, due to the small As4 pressure leading to nanowire growth, the deposition on the facets is very slow, leading to a much lower radial growth rate. Finally, we present a model that is able to accurately describe the presented observations and predicts a maximum length of nontapered nanowires of 40?m.

C. Colombo; D. Spirkoska; M. Frimmer; G. Abstreiter; A. Fontcuberta i Morral

2008-04-28T23:59:59.000Z

205

Carrier effective masses in symmetrically strained (GaIn)As/Ga(PAs) multiple-quantum-well structures  

Science Journals Connector (OSTI)

The carrier effective masses in symmetrically strained (GaIn)As/Ga(PAs) multiple-quantum-well heterostructures have been determined as a function of the incorporated compressive strain in the (GaIn)As quantum-well layer by applying magneto-optical studies. The precise structural parameters, i.e., individual layer thicknesses, strain values, and crystalline perfection, have been determined independently by high-resolution x-ray diffraction and transmission electron microscopy. By analyzing both the allowed and forbidden optical transitions as a function of the magnetic field, detected by polarization-dependent magnetophotoluminescence excitation spectroscopy, the exciton binding energy as well as the effective in-plane electron and heavy-hole masses have been determined quantitatively as a function of strain. The theoretically predicted significant decrease of the in-plane heavy-hole mass with increasing strain has been observed. The obtained results are discussed and compared with the contradictory results reported in the literature.

M. Volk; S. Lutgen; T. Marschner; W. Stolz; E. O. Gbel; P. C. M. Christianen; J. C. Maan

1995-10-15T23:59:59.000Z

206

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

SciTech Connect (OSTI)

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

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

2014-03-15T23:59:59.000Z

207

InGaAs heterostructure formation in catalyst-free GaAs nanopillars by selective-area metal-organic vapor phase epitaxy  

SciTech Connect (OSTI)

We investigate axial GaAs/InGaAs/GaAs heterostructures embedded in GaAs nanopillars via catalyst-free selective-area metal-organic chemical vapor deposition. Structural characterization by transmission electron microscopy with energy dispersive x-ray spectroscopy (EDS) indicates formation of axial In{sub x}Ga{sub 1-x}As (x{approx}0.20) inserts with thicknesses from 36 to 220 nm with {+-}10% variation and graded Ga:In transitions controlled by In segregation. Using the heterointerfaces as markers, the vertical growth rate is determined to increase linearly during growth. Photoluminescence from 77 to 290 K and EDS suggest the presence of strain in the shortest inserts. This capability to control the formation of axial nanopillar heterostructures is crucial for optimized device integration.

Shapiro, J. N.; Lin, A.; Wong, P. S.; Scofield, A. C.; Tu, C.; Senanayake, P. N.; Mariani, G.; Liang, B. L.; Huffaker, D. L. [Department of Electrical Engineering and California Nano-Systems Institute, University of California at Los Angeles, Los Angeles, California 90095 (United States)

2010-12-13T23:59:59.000Z

208

Tunneling and nonlinear transport in a vertically coupled GaAs/AlGaAs double quantum wire system.  

SciTech Connect (OSTI)

We report low-dimensional tunneling in an independently contacted vertically coupled quantum wire system. This nanostructure is fabricated in a high quality GaAs/AlGaAs parallel double quantum well heterostructure. Using a unique flip chip technique to align top and bottom split gates to form low-dimensional constrictions in each of the independently contacted quantum wells we explicitly control the subband occupation of the individual wires. In addition to the expected two-dimensional (2D)-2D tunneling results, we have found additional tunneling features that are related to the one-dimensional quantum wires.

Seamons, John Andrew; Lilly, Michael Patrick; Reno, John Louis; Bielejec, Edward Salvador

2004-11-01T23:59:59.000Z

209

Structure of negatively charged muonium in n-type GaAs  

Science Journals Connector (OSTI)

Muon level-crossing resonance and muon-spin-rotation measurements on heavily doped n-type GaAs:Si and GaAs:Te show that the majority of positive muons implanted at room temperature form an isolated diamagnetic muonium center located at a high-symmetry site with Ga neighbors along the ?111? direction(s). These experiments, together with theoretical considerations, imply that negatively charged muonium is at or near the tetrahedral interstitial site with four Ga nearest-neighbor atoms. Except for zero-point energy differences, these results should model negatively charged isolated hydrogen in GaAs.

K.H. Chow; R.F. Kiefl; W.A. MacFarlane; J.W. Schneider; D.W. Cooke; M. Leon; M. Paciotti; T.L. Estle; B. Hitti; R.L. Lichti; S.F.J. Cox; C. Schwab; E.A. Davis; A. Morrobel-Sosa; L. Zavieh

1995-05-15T23:59:59.000Z

210

Metal-insulator-semiconductor structures on p-type GaAs with low interface state density  

E-Print Network [OSTI]

Metal-insulator-semiconductor structures on p-type GaAs with low interface state density Zhi Chen properties of in situ deposited Si3N4 /Si/p-GaAs metal-insulator-semiconductor structures have been offered by a low gate leakage technology in GaAs, such as metal insulator structures, func- tional Ga

Chen, Zhi

211

INCREASED CELL EFFICIENCY IN InGaAs THIN FILM SOLAR CELLS WITH DIELECTRIC AND METAL BACK REFLECTORS  

E-Print Network [OSTI]

INCREASED CELL EFFICIENCY IN InGaAs THIN FILM SOLAR CELLS WITH DIELECTRIC AND METAL BACK REFLECTORS solar cells using back reflectors. We studied absorption enhancement in InGaAs and InGaAsP thin film and metal, on InGaAs thin film solar cell performance by device modeling and nu- merical simulations. DEVICE

Atwater, Harry

212

Optical phonon modes in InGaN/GaN dot-in-a-wire heterostructures grown by molecular beam epitaxy  

SciTech Connect (OSTI)

We report on the studies of optical phonon modes in nearly defect-free GaN nanowires embedded with intrinsic InGaN quantum dots by using oblique angle transmission infrared spectroscopy. These phonon modes are dependent on the nanowire fill-factor, doping densities of the nanowires, and the presence of InGaN dots. These factors can be applied for potential phonon based photodetectors whose spectral responses can be tailored by varying a combination of these three parameters. The optical anisotropy along the growth (c-) axis of the GaN nanowire contributes to the polarization agility of such potential photodetectors.

Titus, J.; Perera, A. G. U. [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States)] [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Nguyen, H. P. T.; Mi, Z. [Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)] [Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec H3A 2A7 (Canada)

2013-03-25T23:59:59.000Z

213

GA103 a microprogrammable processor for online filtering  

E-Print Network [OSTI]

GA103 is a 16 bit microprogrammable processor, which emulates the PDP 11 instruction set. It is based on the Am2900 slices. It allows user- implemented microinstructions and addition of hardwired processors. It will perform online filtering tasks in the NA14 experiment at CERN, based on the reconstruction of transverse momentum of photons detected in a lead glass calorimeter. (3 refs).

Calzas, A; Danon, G

1981-01-01T23:59:59.000Z

214

1ACM SIGCSE'14, Atlanta, GA Using Gamification in Technical  

E-Print Network [OSTI]

1ACM SIGCSE'14, Atlanta, GA Using Gamification in Technical Higher Education: An XP Report. Epema, An Experience Report on Using Gamification in Technical Higher Education, ACM SIGCSE'14. http's not you, it's me · New ambition of GamificationU (Top-20 Eng/Tech*) ·

Iosup, Alexandru

215

Response of GaAs to fast intense laser pulses  

E-Print Network [OSTI]

Motivated by recent experiments, we have performed simulations which show in detail how the electrons and ions in GaAs respond to fast intense laser pulses (with durations of order 100 fs and intensities of order 1-10 TW/cm(2)). The method of tight...

Graves, JS; Allen, Roland E.

1998-01-01T23:59:59.000Z

216

Recombination in Low-Bandgap InGaAs  

SciTech Connect (OSTI)

We review our investigation of recombination in In{sub x}Ga{sub 1-x}As with indium concentrations ranging between x=0.53 (i.e., lattice-matched to InP) and x=0.78. External radiative efficiency measurements were used to study how defect-related and Auger mechanisms compete with radiative recombination. The results indicated that deep mid-gap levels facilitate defect-related recombination in lattice-matched InGaAs while shallower levels play a more important role in the indium-rich alloys. Subsequent sub-bandgap photoluminescence measurements confirmed the presence of deep levels in the lattice-matched InGaAs. The superlinear excitation dependence of the sub-gap emission led to a defect-related deep-donor/shallow-acceptor pair model. Recent cathodoluminescence measurements of the subgap transitions show no spatial contrast, supporting the assignment of this mechanism to evenly distributed point defects. We hypothesize that the deep states observed in lattice-matched InGaAs are related to imperfections in the incorporation of indium or gallium, which become less likely as the indium concentration is increased.

Gfroerer, T. H.; Wanlass, M. W.

2006-01-01T23:59:59.000Z

217

High-quality InP on GaAs  

E-Print Network [OSTI]

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, ...

Quitoriano, Nathaniel Joseph

2006-01-01T23:59:59.000Z

218

MOCVD Growth of AlGaInN for UV Emitters  

SciTech Connect (OSTI)

Issues related to the growth of nitride-based UV emitters are investigated in this work. More than 100 times of improved in the optical efficiency of the GaN active region can be attained with a combination of raising the growth pressure and introducing a small amount of indium. The unique issue in the UV emitter concerning the use of AlGaN for confinement and the associated tensile cracking is also investigated. They showed that the quaternary AlGaInN is potentially capable of providing confinement to GaN and GaN:In active regions while maintaining lattice matching to GaN, unlike the AlGaN ternary system.

Crawford, Mary; Han, Jung

1999-07-07T23:59:59.000Z

219

Projected Performance of Three- and Four-Junction Devices Using GaAs and GaInP  

E-Print Network [OSTI]

This paper explores the efficiencies expected for three- and four-junction devices for both space and terrestrial applications. For space applications, the effects of temperature and low concentration are investigated. For terrestrial applications, a concentration of 500 suns is assumed and the theoretical efficiencies are calculated as a function of spectral variations including the effects of air mass, turbidity, and water-vapor content. INTRODUCTION Ga 0.5 In 0.5 P/GaAs two-terminal, two-junction solar cells, invented and developed at the National Renewable Energy Laboratory, are in production at both TECSTAR and Spectrolab. The immediate market for these devices is in space; a future (potentially larger) market is terrestrial concentrator systems. The next-generation cells will add additional junction(s) in order to increase the efficiency. Work on a three-junction cell using an active Ge junction under the Ga 0.5 In 0.5 P/GaAs dual-junction cell has already been reported [1]. Ho...

Gainp; S. R. Kurtz; Sarah R. Kurtz; D. Myers; D. Myers; J.M. Olson; J. M. Olson

1997-01-01T23:59:59.000Z

220

Cross-plane lattice and electronic thermal conductivities of ErAs:InGaAs/InGaAlAs superlattices  

E-Print Network [OSTI]

of thermoelectric energy conversion devices depends on the thermoelectric figure of merit ZT of a material, which- troduced charge carriers in the ErAs:InGaAs regions of 0, 2 1018 , 4 1018 , and 8 1018 cm-3 , respectively. There- fore, the effective carrier concentrations in the four samples were 2 1018 , 4 1018 , 6 1018

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Dependence on proton energy of degradation of AlGaN/GaN high electron mobility transistors  

SciTech Connect (OSTI)

The effects of proton irradiation energy on dc, small signal, and large signal rf characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. AlGaN/GaN HEMTs were irradiated with protons at fixed fluence of 51015/cm2 and energies of 5, 10, and 15 MeV. Both dc and rf characteristics revealed more degradation at lower irradiation energy, with reductions of maximum transconductance of 11%, 22%, and 38%, and decreases in drain saturation current of 10%, 24%, and 46% for HEMTs exposed to 15, 10, and 5MeV protons, respectively. The increase in device degradation with decreasing proton energy is due to the increase in linear energy transfer and corresponding increase in nonionizing energy loss with decreasing proton energy in the active region of the HEMTs. After irradiation, both subthreshold drain leakage current and reverse gate current decreased more than 1 order of magnitude for all samples. The carrier removal rate was in the range 121 336 cm1 over the range of proton energies employed in this study

Liu, L. [University of Florida, Gainesville; Xi, Y. Y. [University of Florida, Gainesville; Wang, Y.l. [University of Florida; Ren, F. [University of Florida; Pearton, S. J. [University of Florida; Kim, H.-Y. [Korea University; Kim, J. [Korea University; Fitch, Robert C [Air Force Research Laboratory, Wright-Patterson AFB, OH; Walker, Dennis E [Air Force Research Laboratory, Wright-Patterson AFB, OH; Chabak, Kelson D [Air Force Research Laboratory, Wright-Patterson AFB, OH; Gillespie, James k [Air Force Research Laboratory, Wright-Patterson AFB, OH; Tetlak, Stephen E [Air Force Research Laboratory, Wright-Patterson AFB, OH; Via, Glen D [Air Force Research Laboratory, Wright-Patterson AFB, OH; Crespo, Antonio [Air Force Research Laboratory, Wright-Patterson AFB, OH; Kravchenko, Ivan I [ORNL

2013-01-01T23:59:59.000Z

222

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

E-Print Network [OSTI]

GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates Melissa J. Archer,1,a Daniel C Richard R. King,2 and Harry A. Atwater1 1 California Institute of Technology, Pasadena, California 91125, USA 2 Spectrolab, Inc., Sylmar, California 91342, USA 3 Aonex Technologies, Pasadena, California 91106

Atwater, Harry

223

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

E-Print Network [OSTI]

FIRST DEMONSTRATION OF MONOLITHIC InP-BASED InAlAs/InGaAsP/InGaAs TRIPLE JUNCTION SOLAR CELLS Robyn C. Law 1 1 Spectrolab, Inc., A Boeing Company, Sylmar, California 91342, USA 2 California Institute of Technology, Pasadena, California 91125, USA ABSTRACT Spectrolab has demonstrated the first lattice matched In

Atwater, Harry

224

The evolution of Ga and As core levels in the formation of Fe/GaAs (001):A high resolution soft x-ray photoelectron spectroscopic study  

SciTech Connect (OSTI)

A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness. This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer--a quantitative analysis of the acquired spectra indicates significantly differing behavior of Ga and As during Fe growth, and our observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence on the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 Angstrom results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two additional As environments of metallic character: one bound to the interfacial region and another which, as confirmed by in situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three additional environments--also metallic in nature. Two of the three are interface resident whereas the third undergoes outdiffusion at low Fe coverages. Based on the variations of the integrated intensities of each component, we present a schematic of the proposed chemical makeup of the Fe/GaAs (001) system.

Thompson, Jamie; Neal, James; Shen, Tiehan; Morton, Simon; Tobin, James; Waddill, George Dan; Matthew, Jim; Greig, Denis; Hopkinson, Mark

2008-07-14T23:59:59.000Z

225

Band-filling effect on the light emission spectra of InGaN/GaN quantum wells with highly doped barriers  

Science Journals Connector (OSTI)

We investigate spectra of InGaN/GaN quantum well (QW) light-emitting diode (LED) structures with heavily doped barriers at different excitation levels. We model the spectral shape and energy position in frames of dominating mechanism of free electron ... Keywords: Band filling, Doped barriers, Emission spectra, Quantum well

B. Arnaudov; D. S. Domanevskii; S. Evtimova; Ch. Ivanov; R. Kakanakov

2009-02-01T23:59:59.000Z

226

Effects of internal fields on deep-level emission in InGaN/GaN quantum-well light-emitting diodes  

Science Journals Connector (OSTI)

We report on the important role played by internal quantum well (QW) fields in the anomalous inversion of capacitance transients in InGaN/GaN multi-QW light-emitting diodes (LEDs). This effect was observed by deep-level transient spectroscopy (DLTS) ... Keywords: Deep level, III-Nitride, Internal fields, Quantum well

L. Rigutti; A. Castaldini; A. Cavallini

2009-02-01T23:59:59.000Z

227

Light output enhancement of InGaN/GaN light-emitting diodes with contrasting indium tin-oxide nanopatterned structures  

Science Journals Connector (OSTI)

Various nanopatterns on the transparent conducting indium tin oxide (ITO) layer are investigated to enhance the light extraction efficiency of the InGaN/GaN light-emitting diodes (LEDs). Triangular, square, and circular nanohole patterns with the square ...

Sang Hyun Jung; Keun Man Song; Young Su Choi; Hyeong-Ho Park; Hyun-Beom Shin; Ho Kwan Kang; Jaejin Lee

2013-01-01T23:59:59.000Z

228

Direct and indirect exciton states in GaAs-(Ga, Al)As double quantum wells under crossed electric and magnetic fields  

Science Journals Connector (OSTI)

A theoretical study of the direct and indirect exciton states in GaAs/Ga1-xAlxAs coupled double quantum wells under crossed electric and magnetic fields is presented. The setup of the system under consideration consists of an ... Keywords: 71.55.Eq, 73.20.Mf, 73.21.Fg, Diamagnetic shifts, Double quantum-wells, Magnetoexcitons

L. E. Oliveira; M. de Dios-Leyva; C. A. Duque

2008-03-01T23:59:59.000Z

229

Exciton diamagnetic shift in GaAs/Ga1-xAlxAs quantum wells under in-plane magnetic fields  

Science Journals Connector (OSTI)

Using a variational procedure in the effective-mass and parabolic-band approximations we investigate the effects of in-plane magnetic fields on the exciton states in single GaAs/Ga1-xAlxAs quantum wells. Exciton properties ... Keywords: 71.55.Eq, 73.20.Mf, 73.21.Fg, Diamagnetic shifts, Magnetoexcitons, Quantum wells

C. A. Duque; M. de Dios-Leyva; L. E. Oliveira

2008-03-01T23:59:59.000Z

230

Determination of70Ge(n,p)70Ga and74Ge(n,p)74Ga reaction cross sections for a fission neutron spectrum  

Science Journals Connector (OSTI)

The fission neutron spectrum averaged cross-sections for the reactions70Ge(n,p)70Ga and74Ge(n,p)74Ga have been determined. The averages of four determinations are, respectively, (3.100.30) mb and (0.009380.0005...

I. M. Cohen; A. J. Kestelman; J. C. Furnari

1996-03-14T23:59:59.000Z

231

Polarity driven simultaneous growth of free-standing and lateral GaAsP epitaxial nanowires on GaAs (001) substrate  

SciTech Connect (OSTI)

Simultaneous growth of ?111?{sub B} free-standing and [110] lateral GaAsP epitaxial nanowires on GaAs (001) substrates were observed and investigated by electron microscopy and crystallographic analysis. It was found that the growth of both free-standing and lateral ternary nanowires via Au catalysts was driven by the fact that Au catalysts prefer to maintain low-energy (111){sub B} interfaces with surrounding GaAs(P) materials: in the case of free-standing nanowires, Au catalysts maintain (111){sub B} interfaces with their underlying GaAsP nanowires; while in the case of lateral nanowires, each Au catalyst remain their side (111){sub B} interfaces with the surrounding GaAs(P) material during the lateral nanowire growth.

Sun, Wen; Xu, Hongyi [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia)] [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia); Guo, Yanan [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia) [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia); Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Gao, Qiang; Hoe Tan, Hark; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia)] [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Zou, Jin, E-mail: j.zou@uq.edu.au [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia) [Materials Engineering, The University of Queensland, St Lucia QLD 40732 (Australia); Centre for Microscopy and Microanalysis, The University of Queensland, St Lucia QLD 4072 (Australia)

2013-11-25T23:59:59.000Z

232

Dynamic Model of Hydrogen in GaN  

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

Dynamic Model of Hydrogen in GaN by S. M. Myers and A. F. Wright Motivation-Hydrogen is incorporated into p-type GaN during MOCVD growth, producing highly stable passivation of the Mg acceptors. Complete acceptor activation by thermal H release requires temperatures that threaten material integrity, prompting compromises in device processing. At lower temperatures, forward bias of p-n junctions or electron-beam irradiation produces a metastable, reversible activation without H release. To understand and control such effects, we are developing a mathematical model of H behavior wherein state energies from density-functional theory are employed in diffusion-reaction equations. Previously, we used the greatly simplifying assumptions of local equilibrium among states

233

GaNAsP: An intermediate band semiconductor grown by gas-source molecular beam epitaxy  

SciTech Connect (OSTI)

Dilute nitride GaNAsP thin films were grown via a GaAsP metamorphic buffer on GaP(100) substrate with gas-source molecular beam epitaxy. The compositions of this III-V-V-V compound were determined by channeling Rutherford backscattering spectroscopy and nuclear reaction analysis. Photoreflectance shows two distinctive transitions from the valence band to the split conduction bands due to N incorporation. Photoluminescence and optical absorption show the fundamental bandgap of Ga(N)AsP is largely tailored by the small amount of N. The observed multiband characteristics and the bandgap tunability of GaNAsP are two merits that fit into the intermediate-band solar cell roadmap, and GaNAsP of high crystal quality provides a strong candidate for intermediate band solar cell materials.

Kuang, Y. J. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States)] [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Yu, K. M.; Walukiewicz, W. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kudrawiec, R. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States) [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Institute of Physics, Wroclaw University of Technology, Wybrzeze, Wyspianskiego 27, 50-370 Wroclaw (Poland); Luce, A. V. [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States) [Electronic Materials Program, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Ting, M. [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)] [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States); Tu, C. W. [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)] [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

2013-03-18T23:59:59.000Z

234

Ga configurations in hydrogenated amorphous silicon as studied by x-ray photoemission spectroscopy  

Science Journals Connector (OSTI)

Samples of crystalline silicon and glow-discharge-deposited hydrogenated amorphous silicon were doped with gallium by low-energy (4-keV) ion implantation. X-ray photoemission spectroscopy was used to study the chemical-bonding states of the Ga. From Ga 3d core-level studies, we found that elementary interstitial, threefold-coordinated, and fourfold-coordinated Ga coexist in the ion-implanted and annealed amorphous silicon network. The percentage of activated threefold- and fourfold-coordinated Ga atoms is found to increase with increasing annealing temperature, prior to crystallization. The energy released by the amorphous silicon lattice upon annealing contributes to the activation of the gallium from the elementary state to the threefold- or fourfold-coordinated state. No evidence of Ga-H bond formation is found. The percentage of fourfold-coordinated Ga, which we call the doping efficiency, ranges from 5% to 10%, depending upon the thermal treatment.

Z. H. Lu; S. Poulin-Dandurand; E. Sacher; A. Yelon

1990-09-15T23:59:59.000Z

235

Accurate characterization and improvement of GaAs microstrip attenuation  

E-Print Network [OSTI]

Mason Carroll, B. S. , Rose-Hulman Institute of Technology Chair of Advisory Committee: Dr. Kai Chang Microstrip transmission lines are widely used in microv, ave circuits. The high frequencies cause the microstrip characteristics, especially... OF CONTENTS . . LIST OF FIGURES LIST OF TABLES. . CHAPTER I INTRODUCTION . . I. A Introduction. I. B Thesis Research Il GaAs MICROSTRlp ATTENUATION . II. A Characterization ol'Transmission Line Attenuation. . . . II. A. I Introduction. II. A. 2...

Carroll, James Mason

2012-06-07T23:59:59.000Z

236

InGaAsSb thermophotovoltaic diode physics evaluation  

SciTech Connect (OSTI)

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.

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

1998-06-01T23:59:59.000Z

237

(22) reconstructions of the {111} polar surfaces of GaAs  

Science Journals Connector (OSTI)

Ab initio total-energy calculations were used to examine (22) reconstruction models for the (111) and (111) surfaces of GaAs. For the (111) surface the lowest-energy Ga-vacancy geometry is determined; several mechanisms for Ga-vacancy formation are examined and other reconstructions are discussed. For the (111) surface it is shown that the As-vacancy model is unlikely and other geometries are considered.

E. Kaxiras; Y. Bar-Yam; J. D. Joannopoulos; K. C. Pandey

1986-03-15T23:59:59.000Z

238

Synthesis and Structure of Sr3GaN3 and Sr6GaN5:? Strontium Gallium Nitrides with Isolated Planar [GaN3]6- Anions  

Science Journals Connector (OSTI)

Synthesis and Structure of Sr3GaN3 and Sr6GaN5:? Strontium Gallium Nitrides with Isolated Planar [GaN3]6- Anions ... 9-19 In most cases, an alkaline earth metal is introduced into a Na melt to enhance the solubility of nitrogen, and is incorporated in the nitride product. ... The container was sealed by welding its open end in an argon atmosphere with active water-cooling so that NaN3 did not decompose due to heating during the welding. ...

Dong Gon Park; Zoltn A. Gl; Francis J. DiSalvo

2003-02-13T23:59:59.000Z

239

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

SciTech Connect (OSTI)

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

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

1993-05-01T23:59:59.000Z

240

Carrier-induced change in refractive index of InP, GaAs, and InGaAsP  

SciTech Connect (OSTI)

The authors have theoretically estimated the change in refractive index {Delta}{ital n} produced by injection of free carriers in InP, GaAs, and InGaAsP. Bandfilling (Burstein-Moss effect), band-gap shrinkage, and free-carrier absorption (plasma effect) were included. Carrier concentrations of 10{sup 16}/cm{sup 3} to 10{sup 19}/cm{sup 3} and photon energies of 0.8 to 2.0 eV were considered. Predictions of {Delta}{ital n} are in reasonably good agreement with the limited experimental data available. Refractive index changes as large as 10{sup {minus} 2} are predicted for carrier concentrations of 10{sup 18}/cm{sup 3}, suggesting that low-loss optical phase modulators and switches using carrier injection are feasible in these materials.

Bennett, B.R. (Dept. of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA (US)); Soref, R.A. (Solid State Sciences Directorate, Rome Air Development Center, Hanscom Air Force Base, Bedford, MA (US)); Del Alamo, J.A. (Dept. of Electrical Engineering and Computer Science, Massachussets Institute of Technology, Cambridge, MA (US))

1990-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Photoluminescence kinetics of indirect excitons in GaAs/AlxGa1-xAs coupled quantum wells  

Science Journals Connector (OSTI)

Photoluminescence (PL) kinetics of long-lifetime indirect excitons in a GaAs/AlxGa1-xAs coupled quantum well characterized by a small in-plane random potential was studied at temperatures 1.5<~T<~15 K for a wide range of exciton densities. Strong deviations of the indirect exciton PL kinetics from monoexponential PL rise/decay were observed at low temperatures and high exciton densities. In particular, right after the excitation is switched off, the spectrally integrated indirect exciton PL intensity increased sharply. Simultaneously, the indirect exciton energy distribution was observed to narrow significantly. The observed increase in intensity is attributed to the sharp increase of occupation of the optically active exciton states. The energy distribution narrowing is explained in terms of the phonon mediated exciton energy relaxation in momentum space and in the in-plane random potential.

L. V. Butov, A. Imamoglu, A. V. Mintsev, K. L. Campman, and A. C. Gossard

1999-01-15T23:59:59.000Z

242

Sensitivity of absorption spectra to surface segregation in InGaN/GaN quantum well structures  

SciTech Connect (OSTI)

We investigate the influence of the indium surface segregation on absorption spectra in InGaN/GaN quantum well structures having different indium amount. Results of the mathematical modeling show that such influence is more pronounced in quantum well structures with high indium amounts. The origin of this effect is related to the interplay between the indium surface segregation and internal electrostatic fields. Our theoretical analysis is performed using semiconductor Bloch equations within the Hartree-Fock approximation including into consideration excitonic effects. Results of the global sensitivity analysis evidence that the influence of the indium surface segregation is less than one order of magnitude in comparison with the impact of the quantum-well width and indium molar fraction. Also, the influence of the indium surface segregation is not the same for each interface of the quantum well.

Klymenko, M. V.; Shulika, O. V. [Lab. Photonics, Kharkov National University of Radio Electronics, Kharkov, 61166 (Ukraine); Sukhoivanov, I. A. [Department of Electronics, Engineering Division, University of Guanajuato, Salamanca, Guanajuato, 36885 (Mexico)

2014-05-15T23:59:59.000Z

243

Band offsets from two special GaAs-AlxGa1-xAs quantum-well structures  

Science Journals Connector (OSTI)

Half-parabolic quantum wells and two-stepped quantum wells have been grown by molecular-beam epitaxy with the GaAs-AlxGa1-xAs system and investigated by photoluminescence techniques to determine the band offsets at the heterointerfaces. Both structures provide interband transitions that are sensitive to the partitioning of the energy-gap discontinuity ?Eg=?Ec+?Ev between the conduction and valence bands. It is concluded that the data require valence-band offsets ?Ev equal to 38% and 41% of ?Eg for the half-parabolic wells and the two-stepped wells, respectively. These band offsets are therefore in agreement with the trend of other recent determinations.

R. C. Miller; A. C. Gossard; D. A. Kleinman

1985-10-15T23:59:59.000Z

244

ArF laser-based quantum well intermixing in InGaAs/InGaAsP heterostructures  

SciTech Connect (OSTI)

Radiation from a 193 nm ArF laser was investigated to modify surface properties of InGaAs/InGaAsP quantum well (QW) heterostructures and introduce defects required to enhance intermixing during the annealing process. A top 200 nm thick sacrificial layer of InP served as a reservoir for laser generated defects. The irradiation with up to 90 pulses at 65-150 mJ/cm{sup 2} allowed to generate an array of 1.2x1 mm{sup 2} sites of QW intermixed material, with bandgap energy blueshifted up to 107 nm. We discuss the mechanism and advantages of this approach for postgrowth wafer level fabrication of multibandgap QW material.

Genest, Jonathan; Beal, Romain; Aimez, Vincent; Dubowski, Jan J. [Department of Electrical and Computer Engineering, Center of Excellence for Information Engineering, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1 (Canada)

2008-08-18T23:59:59.000Z

245

E-Print Network 3.0 - algorithm ga technique Sample Search Results  

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

for: algorithm ga technique Page: << < 1 2 3 4 5 > >> 1 GAMMA: Global Arrays Meets MATLAB Rajkiran Panuganti Summary: is a straightforward implementa- tion of a standard...

246

Band-structure analysis from photoreflectance spectroscopy in (Ga,Mn)As  

SciTech Connect (OSTI)

Modulation photoreflectance spectroscopy has been applied to study the band-structure evolution in (Ga,Mn)As epitaxial layers with increasing Mn content. Structural and magnetic properties of the layers were characterized with high-resolution X-ray diffractometry and SQUID magnetometery, respectively. The revealed results of decrease in the band-gap-transition energy in the (Ga,Mn)As layers with increasing Mn content are interpreted in terms of a disordered valence band, extended within the band gap, formed, in highly Mn-doped (Ga,Mn)As, as a result of merging the Mn-related impurity band with the host GaAs valence band.

Yastrubchak, Oksana; Gluba, Lukasz; Zuk, Jerzy [Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin (Poland); Wosinski, Tadeusz; Andrearczyk, Tomasz; Domagala, Jaroslaw Z. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Sadowski, Janusz [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland and MAX-Lab, Lund University, 22100 Lund (Sweden)

2013-12-04T23:59:59.000Z

247

Assessment of the Passivation Capabilities of Two Different Covalent Chemical Modifications on GaP(100)  

Science Journals Connector (OSTI)

With respect to toxicity, the UDA-functionalized GaP provided better passivation which was confirmed by less gallium leaching into water and saline solutions. ... Due to its promising characteristics for device fabrication, gallium arsenide (GaAs) has been extensively studied and the formation of self-assembled monolayers has been of interest. ... A general increase in the Ga/P ratio can be seen in the surfaces exposed to solutions compared to the clean surface which is attributed to the greater solubility of the phosphorus oxide (P2O5) compared to the gallium oxide (Ga2O3). ...

David Richards; Dmitry Zemlyanov; Albena Ivanisevic

2010-02-03T23:59:59.000Z

248

Interface Reactions and Electrical Characteristics of Au/GaSb Contacts  

SciTech Connect (OSTI)

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.

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

2000-07-07T23:59:59.000Z

249

Si in GaN -- On the nature of the background donor  

SciTech Connect (OSTI)

A characterization of the Si impurity in GaN is performed by Raman spectroscopy. Applying hydrostatic pressure up to 25 GPa the authors study the behavior of the LO phonon-plasmon mode in a series of high mobility Si doped GaN films. In contrast to earlier results on unintentionally doped bulk GaN crystals no freeze out of the free carriers could be observed in Si doped samples. The authors find that Si is a shallow hydrogenic donor throughout the pressure range studied. This result positively excludes Si incorporation as a dominant source of free electrons in previously studied bulk GaN samples.

Wetzel, C.; Chen, A.L.; Suski, T.; Ager, J.W. III; Walukiewicz, W. [Lawrence Berkeley National Lab., CA (United States). Materials Science Div.

1996-08-01T23:59:59.000Z

250

Structural defects in GaN revealed by Transmission Electron Microscopy  

SciTech Connect (OSTI)

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.

Liliental-Weber, Zuzanna

2014-04-18T23:59:59.000Z

251

Performance analysis of AlGaAs/GaAs tunnel junctions for ultra-high concentration photovoltaics  

Science Journals Connector (OSTI)

An n++-GaAs/p++-AlGaAs tunnel junction with a peak current density of 10?100Acm?2 is developed. This device is a tunnel junction for multijunction solar cells, grown lattice-matched on standard GaAs or Ge substrates, with the highest peak current density ever reported. The voltage drop for a current density equivalent to the operation of the multijunction solar cell up to 10?000suns is below 5mV. Trap-assisted tunnelling is proposed to be behind this performance, which cannot be justified by simple band-to-band tunnelling. The metal-organic vapour-phase epitaxy growth conditions, which are in the limits of the transport-limited regime, and the heavy tellurium doping levels are the proposed origins of the defects enabling trap-assisted tunnelling. The hypothesis of trap-assisted tunnelling is supported by the observed annealing behaviour of the tunnel junctions, which cannot be explained in terms of dopant diffusion or passivation. For the integration of these tunnel junctions into a triple-junction solar cell, AlGaAs barrier layers are introduced to suppress the formation of parasitic junctions, but this is found to significantly degrade the performance of the tunnel junctions. However, the annealed tunnel junctions with barrier layers still exhibit a peak current density higher than 2500Acm?2 and a voltage drop at 10?000suns of around 20mV, which are excellent properties for tunnel junctions and mean they can serve as low-loss interconnections in multijunction solar cells working at ultra-high concentrations.

I Garca; I Rey-Stolle; C Algora

2012-01-01T23:59:59.000Z

252

Growth of 5 mm GaN Single Crystals at 750 C from an Na?Ga Melt  

Science Journals Connector (OSTI)

Laser diodes using GaN-based III?V nitrides have been developed, and nitride semiconductor devices are now of considerable interest. ... When the inclusions were exposed to air, they reacted with water vapor in air and produced sodium hydroxide and small gallium metal droplets at the fracture surface of the crystal. ... The solubility of nitrogen in liquid sodium is extremely low (7.1 10-9 mol % N at 600 C). ...

Masato Aoki; Hisanori Yamane; Masahiko Shimada; Seiji Sarayama; Francis J. DiSalvo

2001-02-03T23:59:59.000Z

253

Effect of Mg ionization efficiency on performance of Npn AlGaN/GaN heterojunction bipolar transistors  

SciTech Connect (OSTI)

A drift-diffusion transport model has been used to examine the performance capabilities of AlGaN/GaN Npn heterojunction bipolar transistors (HBTs). The Gummel plot from the first GaN-based HBT structure recently demonstrated is adjusted with simulation by using experimental mobility and lifetime reported in the literature. Numerical results have been explored to study the effect of the p-type Mg doping and its incomplete ionization in the base. The high base resistance induced by the deep acceptor level is found to be the cause of limiting current gain values. Increasing the operating temperature of the device activates more carriers in the base. An improvement of the simulated current gain by a factor of 2 to 4 between 25 and 300 C agrees well with the reported experimental results. A preliminary analysis of high frequency characteristics indicates substantial progress of predicted rf performances by operating the device at higher temperature due to a reduced extrinsic base resistivity.

MONIER,C.; PEARTON,S.J.; CHANG,PING-CHIH; BACA,ALBERT G.

2000-03-10T23:59:59.000Z

254

Local indium segregation and band structure in high efficiencygreen light emitting InGaN/GaN diodes  

SciTech Connect (OSTI)

GaN/InGaN light emitting diodes (LEDs) are commercialized for lighting applications because of the cost efficient way that they produce light of high brightness. Nevertheless, there is significant room for improving their external emission efficiency from typical values below 10 percent to more than 50 percent, which are obtainable by use of other materials systems that, however, do not cover the visible spectrum. In particular, green-light emitting diodes fall short in this respect, which is troublesome since the human eye is most sensitive in this spectral range. In this letter advanced electron microscopy is used to characterize indium segregation in InGaN quantum wells of high-brightness, green LEDs (with external quantum efficiency as high as 15 percent at 75 A/cm2). Our investigations reveal the presence of 1-3 nm wide indium rich clusters in these devices with indium concentrations as large as 0.30-0.40 that narrow the band gap locally to energies as small as 2.65 eV.

Jinschek, Joerg R.; Erni, Rolf; Gardner, Nathan F.; Kim, AndrewY.; Kisielowski, Christian

2004-11-23T23:59:59.000Z

255

Deep Levels in p-Type InGaAsN Lattice Matched to GaAs  

SciTech Connect (OSTI)

Deep level transient spectroscopy (DLTS) measurements were utilized to investigate deep level defects in metal-organic chemical deposition (MOCVD)-grown unintentionally doped p-type InGaAsN films lattice matched to GaAs. The as-grown material displayed a high concentration of deep levels distributed within the bandgap, with a dominant hole trap at E{sub v} + 0.10 eV. Post-growth annealing simplified the deep level spectra, enabling the identification of three distinct hole traps at 0.10 eV, 0.23 eV, and 0.48 eV above the valence band edge, with concentrations of 3.5 x 10{sup 14} cm{sup {minus}3}, 3.8 x 10{sup 14} cm{sup {minus}3}, and 8.2 x 10{sup 14} cm{sup {minus}3}, respectively. A direct comparison between the as-grown and annealed spectra revealed the presence of an additional midgap hole trap, with a concentration of 4 x 10{sup 14} cm{sup {minus}3} in the as-grown material. The concentration of this trap is sharply reduced by annealing, which correlates with improved material quality and minority carrier properties after annealing. Of the four hole traps detected, only the 0.48 eV level is not influenced by annealing, suggesting this level may be important for processed InGaAsN devices in the future.

Allerman, A.A.; Jones, E.D.; Kaplar, R.J.; Kurtz, S.R.; Kwon, D.; Ringel, S.A.

1999-03-02T23:59:59.000Z

256

Avalanche buildup time of an InP/InGaAsP/InGaAs APD at high gain  

SciTech Connect (OSTI)

Under a high-gain operating condition, the presence of a multiplication process in the InGaAs(P) regions of an InP/InGaAsP/InGaAs avalanche photodiode having a structure of separated absorption and multiplication regions (SAM-APD) could lead to significant enhancement of the avalanche buildup time. As a result, the bandwidth of the device could be reduced considerably. The dependence of the avalanche multiplication factor and the intrinsic response time on the reverse bias voltage, the heterointerface field, the doping concentrations, and the width of the InP layer are examined in detail for the case in which hole injection is assumed. It is shown, for example, that for a fixed value of doping concentrations, the reduction of the excess noise factor and the enhancement of the gain-bandwidth product of the device can be made at the same time by a proper increase of the width of the InP layer.

Hsieh, H.C.; Sargeant, W. (Iowa State Univ. of Science and Technology, Ames, IA (USA). Dept. of Electrical Engineering)

1989-09-01T23:59:59.000Z

257

Wafer Bonding and Epitaxial Transfer of GaSb-based Epitaxy to GaAs for Monolithic Interconnection of Thermophotovoltaic Devices  

SciTech Connect (OSTI)

GaInAsSb/AlGaAsSb/InAsSb/GaSb epitaxial layers were bonded to semi-insulating GaAs handle wafers with SiO{sub x}/Ti/Au as the adhesion layer for monolithic interconnection of thermophotovoltaic (TPV) devices. Epitaxial transfer was completed by removal of the GaSb substrate, GaSb buffer, and InAsSb etch-stop layer by selective chemical etching. The SiO{sub x}/TiAu provides not only electrical isolation, but also high reflectivity and is used as an internal back-surface reflector. Characterization of wafer-bonded epitaxy by high-resolution x-ray diffraction and time-decay photoluminescence indicates minimal residual stress and enhancement in optical quality. 0.54-eV GaInAsSb cells were fabricated and monolithically interconnected in series. A 10-junction device exhibited linear voltage building with an open-circuit voltage of 1.8 V.

C.A. Wang; D.A. Shiau; P.G. Murphy; P.W. O'brien; R.K. Huang; M.K. Connors; A.C. Anderson; D. Donetsky; S. Anikeev; G. Belenky; D.M. Depoy; G. Nichols

2003-06-16T23:59:59.000Z

258

Critical size for the generation of misfit dislocations and their effects on electronic properties in GaAs nanosheets on Si substrate  

E-Print Network [OSTI]

-Queisser limit6 for the solar-cell efficiency. Recently, NWs of various semi- conductors such as GaAs/AlGaAs,7

Southern California, University of

259

IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 42, NO. 4, APRIL 2006 397 Design and Performance of an InGaAsInP  

E-Print Network [OSTI]

, focusing on the effect of the critical InGaAsP grading layer between the narrow-gap InGaAs absorption layer

Buller, Gerald S.

260

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

SciTech Connect (OSTI)

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.

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

2014-02-03T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Enhancing the Light Extraction of InGaN Light-Emitting Diodes by Patterning the Dicing Streets  

Science Journals Connector (OSTI)

Patterning the dicing streets technology was used to define the high extraction efficiency region of InGaN-GaN multiple-quantum-well light-emitting diodes (LEDs). The external quantum...

Lin, Hung Cheng; Tseng, Yen Chun; Chyi, Jen Inn; Lee, Chia Ming

262

Photodiode characteristics and band alignment parameters of epitaxial Al0.5Ga0.5P  

E-Print Network [OSTI]

Photodiode characteristics and band alignment parameters of epitaxial Al0.5Ga0.5P An Chen1,a-bandgap semiconductor AlxGa1-xP is a promising material candidate for low-noise photodiodes in blue/UV spectrum. Photodiodes were fabricated on Al0.5Ga0.5P epitaxial layer grown lattice matched on GaP substrate by molecular

Woodall, Jerry M.

263

IEEE PHOTONICS TECHNOLOGY LETTERS 1 High-Power 2.3-m GaSb-Based Linear Laser Array  

E-Print Network [OSTI]

2.3-m laser. Al Ga As Sb cladding layers. Details of the lasers' heterostructure design can be foundIEEE PHOTONICS TECHNOLOGY LETTERS 1 High-Power 2.3-m GaSb-Based Linear Laser Array L. Shterengas, G--High-power 2.3- m In(Al)GaAsSb­GaSb type-I double quantum-well diode laser arrays were fabricated

264

Analyzing the Performance of a Multiobjective GA-P Algorithm for Learning Fuzzy Queries in  

E-Print Network [OSTI]

Analyzing the Performance of a Multiobjective GA-P Algorithm for Learning Fuzzy Queries in a Machine Learning Environment Oscar Cord´on1 , Enrique Herrera-Viedma1 , Mar´ia Luque1 , F´elix de Moya2- tionary algorithms (EAs) [1], such as genetic algorithm-programming (GA-P) [11] or simulated annealing

Fernandez, Thomas

265

Modeling of InAs/GaAs Quantum Dot Solar Cells  

Science Journals Connector (OSTI)

This paper reports electrical characteristics of an intermediate band p-i-n GaAs solar cell with InAs quantum dots embedded in the intrinsic region using Synopsis TCAD simulation tools. Up to five layers of quantum dots have been taken into consideration ... Keywords: Quantum dots, Intermediate band, InAs, GaAs, Solar Cells, TCAD

Ayman Rizk; Kazi Islam; Ammar Nayfeh

2013-11-01T23:59:59.000Z

266

2=picosecond, GaAs photodiode optoelectronic circuit for optical correlation applications  

E-Print Network [OSTI]

2=picosecond, GaAs photodiode optoelectronic circuit for optical correlation applications K. D. Li GaAs Schottky photodiode is monolithically integrated with a microwave detector. By using this new optoelectronic circuit.in place of a nonlinear crystal in an optical correlation setup, the high-speed photodiode

Ozbay, Ekmel

267

Ultralow noise midwave infrared InAsGaSb strain layer superlattice avalanche photodiode  

E-Print Network [OSTI]

Ultralow noise midwave infrared InAs­GaSb strain layer superlattice avalanche photodiode InAs­GaSb strain layer superlattice p+ -n- -n homojunction avalanche photodiodes APDs grown by solid characteristics. © 2007 American Institute of Physics. DOI: 10.1063/1.2817608 Photodiodes operating in the eye

Krishna, Sanjay

268

14 MHz rate photon counting with room temperature InGaAs/InP avalanche photodiodes  

E-Print Network [OSTI]

14 MHz rate photon counting with room temperature InGaAs/InP avalanche photodiodes PAUL L. VOSS based on InGaAs/InP avalanche photodiodes for use at 1.55 mm wavelength. Operation at room temperature at the above wavelengths for conventional high light-level measurements with PIN or ava- lanche photodiodes

Köprülü, Kahraman Güçlü

269

Diffusion of indium and gallium in Cu(In,Ga)Se2 thin film solar cells  

E-Print Network [OSTI]

Diffusion of indium and gallium in Cu(In,Ga)Se2 thin film solar cells O. Lundberga,*, J. Lua , A. Rockettb , M. Edoffa , L. Stolta a A°ngstro¨m Solar Center, Uppsala University, P.O. Box 534, SE-751 21 Abstract The diffusion of indium and gallium in polycrystalline thin film Cu(In,Ga)Se2 layers has been

Rockett, Angus

270

Resonant Raman scattering in an InAs/GaAs monolayer structure  

E-Print Network [OSTI]

), embedded in bulklike GaAs with two Al- GaAs cladding layers forming a waveguide. The InAs- mono- layer system used. Raman spectra were excited with a Ti-Sapphire laser, tuned from 1.41 eV to 1.435 e

Nabben, Reinhard

271

Electro-optic imagery of high-voltage GaAs photoconductive switches  

SciTech Connect (OSTI)

The authors present electro-optic images of GaAs high-voltage photoconductive switches utilizing the electro-optic effect of the semi-insulating GaAs substrate. Experimental methodology for obtaining the images is described along with a self-calibrating data reduction algorithm. Use of the technique for observing fabrication defects is shown.

Falk, R.A.; Adams, J.C.; Capps, C.D.; Ferrier, S.G.; Krinsky, J.A. (Boeing Defense and Space Group, Seattle, WA (United States))

1995-01-01T23:59:59.000Z

272

Variation of lattice constant and cluster formation in GaAsBi  

SciTech Connect (OSTI)

We investigate the structural properties of GaAsBi layers grown by molecular beam epitaxy on GaAs at substrate temperatures between 220315 C. Irrespective of the growth temperature, the structures exhibited similar Bi compositions, and good overall crystal quality as deduced from X-Ray diffraction measurements. After thermal annealing at temperatures as low as 500 C, the GaAsBi layers grown at the lowest temperatures exhibited a significant reduction of the lattice constant. The lattice variation was significantly larger for Bi-containing samples than for Bi-free low-temperature GaAs samples grown as a reference. Rutherford backscattering spectrometry gave no evidence of Bi diffusing out of the layer during annealing. However, dark-field and Z-contrast transmission electron microscopy analyses revealed the formation of GaAsBi clusters with a Bi content higher than in the surrounding matrix, as well as the presence of metallic As clusters. The apparent reduction of the lattice constant can be explained by a two-fold process: the diffusion of the excess As incorporated within As{sub Ga} antisites to As clusters, and the reduction of the Bi content in the GaAs matrix due to diffusion of Bi to GaAsBi clusters. Diffusion of both As and Bi are believed to be assisted by the native point defects, which are present in the low-temperature as-grown material.

Puustinen, J.; Schramm, A.; Guina, M. [Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland)] [Optoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland); Wu, M.; Luna, E. [Paul-Drude Institut fr Festkrperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)] [Paul-Drude Institut fr Festkrperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Laukkanen, P. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)] [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Laitinen, M.; Sajavaara, T. [Department of Physics, University of Jyvskyl, P.O. Box 35, FI-40014 Jyvskyl (Finland)] [Department of Physics, University of Jyvskyl, P.O. Box 35, FI-40014 Jyvskyl (Finland)

2013-12-28T23:59:59.000Z

273

ORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission  

E-Print Network [OSTI]

ORIGINAL ARTICLE Highly efficient GaAs solar cells by limiting light emission angle Emily D Kosten1 solar cell under direct sunlight, light is received from the solar disk, but is re-emitted isotropically.1038/lsa.2013.1; published online 4 January 2013 Keywords: detailed balance; GaAs solar cell; light

Atwater, Harry

274

Plasmonic nanoparticle enhanced light absorption in GaAs solar cells Keisuke Nakayama,a  

E-Print Network [OSTI]

Plasmonic nanoparticle enhanced light absorption in GaAs solar cells Keisuke Nakayama,a Katsuaki 22 September 2008 We demonstrate an improvement in efficiency of optically thin GaAs solar cells-ratio nanoparticles effectively increases the optical path of the incident light in the absorber layers resulting

Atwater, Harry

275

Calculated spin polarization of field-assisted GaAs electron source  

Science Journals Connector (OSTI)

Calculations are reported showing that for the field-assisted GaAs NEA photocathode, the spin polarization of emitted electrons can be 3.6 times higher than for non-field GaAs sources. The reason for this is that...

B. Yang; V. Guidi; L. Tecchio

1993-02-01T23:59:59.000Z

276

Coupling of nitrogen-vacancy centers in diamond to a GaP waveguide  

E-Print Network [OSTI]

The optical coupling of guided modes in a GaP waveguide to nitrogen-vacancy (NV) centers in diamond is demonstrated. The electric field penetration into diamond and the loss of the guided mode are measured. The results indicate that the GaP-diamond system could be useful for realizing coupled microcavity-NV devices for quantum information processing in diamond.

K. -M. C. Fu; C. Santori; P. E. Barclay; I. Aharonovich; S. Prawer; N. Meyer; A. M. Holm; R. G. Beausoleil

2008-11-03T23:59:59.000Z

277

Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part II. InP, InSb, InGaP and InGaAs  

SciTech Connect (OSTI)

A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than IC1/Ar, but the etched surface mophologies were fairly poor for both chemistries.

Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B.; Lambers, E.S.; Pearton, S.J.; Shul, R.J.

1998-11-23T23:59:59.000Z

278

Strain modified/enhanced ferromagnetism in Mn{sub 3}Ge{sub 2} thin films on GaAs(001) and GaSb(001)  

SciTech Connect (OSTI)

Ferromagnetic Mn{sub 3}Ge{sub 2} thin films were successfully grown on GaAs(001) and GaSb(001) substrates using molecular beam epitaxy. The results of our work revealed that the substrate facilitates to modify magnetic and electrical properties of Mn{sub 3}Ge{sub 2} films due to tensile/compressive strain effect between films and substrates. The characteristic spin-flopping transition at around 150 K for the bulk Mn{sub 3}Ge{sub 2} disappeared completely for both samples. The antiferromagnetism below 150 K changed to ferromagnetism and retained above room temperature. The saturation magnetization was found to be 0.23 and 1.32 {mu}{sub B}/Mn atom at 10 K for the samples grown on GaSb(001) and GaAs(001), respectively.

Dang Duc Dung; Duong Van Thiet [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Department of General Physics, School of Engineering Physics, Ha Noi University of Science and Technology, 1 Dai Co Viet Road, Ha Noi (Viet Nam); Feng Wuwei; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Park, In-Sung [Department of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Bo Lee, Sung [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

2013-04-21T23:59:59.000Z

279

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

E-Print Network [OSTI]

der Laan,8 C. T. Foxon,2 and B. L. Gallagher2 1Institute of Physics ASCR, Cukrovarnick? 10, 162 53 Praha 6, Czech Republic 2School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom 3Institute of Physics ASCR, Na... is organized as follows. In Sec. II we identify the key physical considerations related to ground-state mag- netization of #1;Ga,Mn#2;As ferromagnets by focusing first on a single Mn#1;d5+hole#2; complex and approximating the total magnetization...

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.

2006-01-01T23:59:59.000Z

280

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

E-Print Network [OSTI]

&M University, College Station, Texas 77843-4242, USA 3Institute of Physics, ASCR, v.v.i., Cukrovarnicka 10, 162 53 Praha 6, Czech Republic 4School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom #1;Received 27 November.... Unlike earlier theoretical work15,16 which ad- dressed quantum interference in ferromagnets, we focus our study on a four-band model which is directly relevant to the valence bands of #1;Ga,Mn#2;As. We demonstrate that the quan- tum interference...

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

2009-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Magnetization relaxation in (Ga,Mn)As ferromagnetic semiconductors  

E-Print Network [OSTI]

- Magnetization relaxation in ?Ga,M Jairo Sinova,1 T. Jungwirth,2,3 X. Liu,4 Y. Sasaki,4 J. K 1Department of Physics, Texas A&M Universit 2Institute of Physics ASCR, Cukrovarnick 3Department of Physics, University of Texa 4Department of Physics, University... is currently the focus of a considerable experimental16 and theoretical17 research. Spin-transfer switching has not yet been demonstrated in all-semiconductor systems, but the effect promises to have a richer phenomenology in this case because...

Sinova, Jairo; Jungwirth, T.; Liu, X.; Sasaki, Y.; Furdyna, JK; Atkinson, WA; MacDonald, AH.

2004-01-01T23:59:59.000Z

282

Quantum effects in electron beam pumped GaAs  

SciTech Connect (OSTI)

Propagation of waves in nano-sized GaAs semiconductor induced by electron beam are investigated. A dispersion relation is derived by using quantum hydrodynamics equations including the electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures. It is found that the propagating modes are instable and strongly depend on the electron beam parameters, as well as the quantum recoil effects and degenerate pressures. The instability region shrinks with the increase of the semiconductor number density. The instability arises because of the energetic electron beam produces electron-hole pairs, which do not keep in phase with the electrostatic potential arising from the pair plasma.

Yahia, M. E. [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt) [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt); National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Azzouz, I. M. [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt)] [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Moslem, W. M. [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)] [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)

2013-08-19T23:59:59.000Z

283

Exciton front propagation in photoexcited GaAs quantum wells  

Science Journals Connector (OSTI)

We report on the study of spatiotemporal self-organization of carriers in photoexcited GaAs quantum wells. Propagating interfaces between electron-rich and hole-rich regions are seen as expanding and collapsing exciton rings in exciton emission patterns. The interfaces preserve their integrity during expansion, remaining as sharp as in the steady state, which indicates that the dynamics is controlled by carrier transport. The front propagation velocity is measured and compared to theoretical model. The measurements of expanding and collapsing exciton rings afford a contactless method for probing the electron and hole transport.

Sen Yang, L. V. Butov, L. S. Levitov, B. D. Simons, and A. C. Gossard

2010-03-16T23:59:59.000Z

284

IEEE ELECTRON DEVICE LETTERS, VOL. 30, NO. 6, JUNE 2009 593 GaAs MESFET With a High-Mobility  

E-Print Network [OSTI]

systems, including InGaAs [4], CdS [5], ZnO [6], and GaN [7]. To the best of our knowledge FET (MESFET) fabricated with an intentionally doped n-type planar GaAs NW channel grown on a semi

Li, Xiuling

285

Determination of piezoelectric fields in strained GaInN quantum wells using the quantum-confined Stark effect  

E-Print Network [OSTI]

fields on optical prop- erties in the cases of GaInAs/GaAs QWs2 and CdS/CdSe superlattices4 on GaAs 111 MOVPE . The total un- doped region sandwiched by n and p layers is 51 nm. The carrier concentrations

Wetzel, Christian M.

286

Enhanced Performance of Small GaAs Solar Cells via Edge and Surface Passivation with Trioctylphosphine Sulfide  

E-Print Network [OSTI]

Enhanced Performance of Small GaAs Solar Cells via Edge and Surface PassivationAs solar cells. Photoluminescence (PL) measurements indicate monolayers of TOP:S on GaAs significantly" GaAs solar cell (0.31 mm2 ) to test its ability to passivate devices with the relevant dimensions

Atwater, Harry

287

Intrinsic vacancy induced nanoscale wire structure in heteroepitaxial Ga2Se3/Si(001) Taisuke Ohta,1,  

E-Print Network [OSTI]

Intrinsic vacancy induced nanoscale wire structure in heteroepitaxial Ga2Se3/Si(001) Taisuke Ohta,1-blende structure of -Ga2Se3, which contains ordered 110 arrays of Ga vacancies. These ordered vacancy lines structural vacancies of semiconducting chalcogenides lead to numerous interesting structural, electronic

Olmstead, Marjorie

288

Identification of the Parasitic Chemical Reactions during AlGaN OMVPE  

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

Identification of the Parasitic Chemical Reactions during AlGaN OMVPE Identification of the Parasitic Chemical Reactions during AlGaN OMVPE by J. R. Creighton, M. E. Coltrin, and W. G. Breiland Motivation-GaN and AlGaN alloys are ex- tremely important materials with widespread applications for optoelectronics (e.g. solid state lighting) and high power electronics. Or- ganometallic vapor phase epitaxy (OMVPE) is the primary deposition methodology, but it suf- fers from several growth chemistry anomalies. Growth rate and alloy composition are often a sensitive function of temperature and other reac- tor variables. These factors make the AlGaN OMVPE process difficult to control and in- crease the cost of the material. Conventional wisdom has been that the non-ideal OMVPE behavior is due to parasitic "pre-reactions" be-

289

Enhanced photoelectrochemical responses of ZnO films through Ga and N codoping  

SciTech Connect (OSTI)

We report on the crystallinity and photoelectrochemical (PEC) response of ZnO thin films codoped by Ga and N. The ZnO:(Ga,N) thin films were deposited by cosputtering at room temperature and followed by postannealing at 500 deg. C in air for 2 h. We found that ZnO:(Ga,N) thin films exhibited significantly enhanced crystallinity compared to ZnO doped solely with N at the same growth conditions. Furthermore, ZnO:(Ga,N) thin films exhibited enhanced N incorporation over ZnO doped solely with N at high temperatures. As a result, ZnO:(Ga,N) thin films achieved dramatically improved PEC response, compared to ZnO thin films doped solely with N at any conditions. Our results suggest a general way to improve PEC response for wide-band-gap oxides.

Ahn, Kwang-Soon; Yan, Yanfa; Shet, Sudhakar; Deutsch, Todd; Turner, John; Al-Jassim, Mowafak [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

2007-12-03T23:59:59.000Z

290

Infrared spectroscopy of amorphous hydrogenated GaAs: Evidence for H bridges  

Science Journals Connector (OSTI)

The infrared absorption spectra of hydrogenated amorphous GaAs show two prominent hydrogen-related bands at 530 and 1460 cm-1. These bands are very broad and they amount to most of the hydrogen-induced infrared absorption. The remaining structures are a number of comparatively sharp lines which we interpret as Ga-H and As-H modes in partial agreement with earlier investigations. We argue that the broad bands arise from near-stretching (1460 cm-1) and from wagging (530 cm-1) vibrations of H atoms situated in bridging positions between two Ga atoms. This assignment is supported by similar bands in Al-H polymers, a-GaP: H, and a-GaSb: H. A model calculation of the mode frequencies is also presented.

Z. P. Wang; L. Ley; M. Cardona

1982-09-15T23:59:59.000Z

291

In situ chemical sensing in AlGaN/GaN high electron mobility transistor metalorganic chemical vapor deposition process for real-time  

E-Print Network [OSTI]

; accepted 14 June 2005; published 18 July 2005 Gallium nitride and its alloys promise to be key materials.1116/1.1993616 I. INTRODUCTION In recent years, gallium-nitride GaN - and aluminum- gallium-nitride AlGaN -based are grown at high temperatures e.g., up to 1100 °C using large concentrations of H2 carrier and NH3 N source

Rubloff, Gary W.

292

Dynamic nuclear polarization and Hanle effect in (In,Ga)As/GaAs quantum dots. Role of nuclear spin fluctuations  

SciTech Connect (OSTI)

The degree of circular polarization of photoluminescence of (In,Ga)As quantum dots as a function of magnetic field applied perpendicular to the optical axis (Hanle effect) is experimentally studied. The measurements have been performed at various regimes of the optical excitation modulation. The analysis of experimental data has been performed in the framework of a vector model of regular nuclear spin polarization and its fluctuations. The analysis allowed us to evaluate the magnitude of nuclear polarization and its dynamics at the experimental conditions used.

Gerlovin, I. Ya. [Spin Optics Laboratory, Saint Petersburg State University, Petrodvorets, 198504 St. Petersburg (Russian Federation); Cherbunin, R. V.; Ignatiev, I. V.; Kuznetsova, M. S.; Verbin, S. Yu. [Spin Optics Laboratory, Saint Petersburg State University, Petrodvorets, 198504 St. Petersburg, Russia and Experimentelle Physik 2, Technische Universitt Dortmund, D-44221 Dortmund (Germany); Flisinski, K.; Bayer, M. [Experimentelle Physik 2, Technische Universitt Dortmund, D-44221 Dortmund (Germany); Reuter, D.; Wieck, A. D. [Angewandte Festkrperphysik, Ruhr-Universitt Bochum, D-44780 Bochum (Germany); Yakovlev, D. R. [Experimentelle Physik 2, Technische Universitt Dortmund, D-44221 Dortmund, Germany and A. F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation)

2013-12-04T23:59:59.000Z

293

Optical resonance modes in GaN pyramid microcavities  

SciTech Connect (OSTI)

An array of GaN hexagonal pyramids with a side length of 8.0 {mu}m was fabricated by selective epitaxial overgrowth. These microsized pyramids are highly efficient microcavities. Three types of optical resonance modes with mode spacings of 10, 5.0, and 6.0 {Angstrom} were observed when a single pyramid was pumped optically by an intense ultraviolet laser beam. An optical ray tracing method has been developed for calculating the optical resonance modes inside the pyramid microcavities. It was shown that a single pyramidal cavity can support several different types of optical resonance modes. The calculated mode spacing agrees very well with the observations. The uniqueness and advantages of this class of hexagonal pyramidal microcavities over the other microcavities are discussed. The implications of our finding on the future GaN microcavity light emitters including micro-light-emitting diodes, microcavity lasers, and vertical-cavity-surface emitting lasers are also discussed. {copyright} {ital 1999 American Institute of Physics.}

Jiang, H.X.; Lin, J.Y.; Zeng, K.C. [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States)] [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States); Yang, W. [Honeywell Technology Center, Plymouth, Minnesota 55441 (United States)] [Honeywell Technology Center, Plymouth, Minnesota 55441 (United States)

1999-08-01T23:59:59.000Z

294

Journal of Crystal Growth 293 (2006) 273277 A study of semi-insulating GaN grown on AlN buffer/sapphire  

E-Print Network [OSTI]

-temperature GaN interlayer. In comparison with the normal GaN grown on sapphire, the crystal quality measurement results of GaN grown directly on an AlN buffer indicated that the as-grown-undoped Ga, or high density of edge-type dislocations [6­10]. However, Fe and other heavy metals tend to have reactor

Ozbay, Ekmel

295

Effects of crossed electric and magnetic fields on the electronic and excitonic states in bulk GaAs and GaAs?Ga1?xAlxAs quantum wells  

Science Journals Connector (OSTI)

The variational procedure in the effective-mass and parabolic-band approximations is used in order to investigate the effects of crossed electric and in-plane magnetic fields on the electronic and exciton properties in semiconductor heterostructures. Calculations are performed for bulk GaAs and GaAs?Ga1?xAlxAs quantum wells, for applied magnetic fields parallel to the layers and electric fields in the growth direction, and it is shown that the combined effects on the heterostructure properties of the applied crossed electric and magnetic fields and the direct coupling between the center-of-mass and internal exciton motions may be dealt with via a simple parameter representing the spatial distance between the centers of the electron and hole magnetic parabolas. Exciton properties are analyzed by using a simple hydrogenlike envelope excitonic wave function and present theoretical results are found in fair agreement with available experimental measurements on the diamagnetic shift of the photoluminescence peak position of GaAs?Ga1?xAlxAs quantum wells under in-plane magnetic fields.

M. de Dios-Leyva, C. A. Duque, and L. E. Oliveira

2007-01-02T23:59:59.000Z

296

Enhanced quality thin film Cu(In,Ga)Se.sub.2 for semiconductor device applications by vapor-phase recrystallization  

DOE Patents [OSTI]

Enhanced quality thin films of Cu.sub.w (In,Ga.sub.y)Se.sub.z for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu.sub.x Se on a substrate to form a large-grain precursor and then converting the excess Cu.sub.x Se to Cu(In,Ga)Se.sub.2 by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga).sub.y Se.sub.z. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300.degree.-600.degree. C., where the Cu(In,Ga)Se.sub.2 remains solid, while the excess Cu.sub.x Se is in a liquid flux. The characteristic of the resulting Cu.sub.w (In,Ga).sub.y Se.sub.z can be controlled by the temperature. Higher temperatures, such as 500.degree.-600.degree. C., result in a nearly stoichiometric Cu(In,Ga)Se.sub.2, whereas lower temperatures, such as 300.degree.-400.degree. C., result in a more Cu-poor compound, such as the Cu.sub.z (In,Ga).sub.4 Se.sub.7 phase.

Tuttle, John R. (Denver, CO); Contreras, Miguel A. (Golden, CO); Noufi, Rommel (Golden, CO); Albin, David S. (Denver, CO)

1994-01-01T23:59:59.000Z

297

Enhanced quality thin film Cu(In,Ga)Se[sub 2] for semiconductor device applications by vapor-phase recrystallization  

DOE Patents [OSTI]

Enhanced quality thin films of Cu[sub w](In,Ga[sub y])Se[sub z] for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu[sub x]Se on a substrate to form a large-grain precursor and then converting the excess Cu[sub x]Se to Cu(In,Ga)Se[sub 2] by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga)[sub y]Se[sub z]. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300--600 C, where the Cu(In,Ga)Se[sub 2] remains solid, while the excess Cu[sub x]Se is in a liquid flux. The characteristic of the resulting Cu[sub w](In,Ga)[sub y]Se[sub z] can be controlled by the temperature. Higher temperatures, such as 500--600 C, result in a nearly stoichiometric Cu(In,Ga)Se[sub 2], whereas lower temperatures, such as 300--400 C, result in a more Cu-poor compound, such as the Cu[sub z](In,Ga)[sub 4]Se[sub 7] phase. 7 figs.

Tuttle, J.R.; Contreras, M.A.; Noufi, R.; Albin, D.S.

1994-10-18T23:59:59.000Z

298

Many-body effects on optical gain in GaAsPN/GaPN quantum well lasers for silicon integration  

SciTech Connect (OSTI)

Many-body effects on the optical gain in GaAsPN/GaP QW structures were investigated by using the multiband effective-mass theory and the non-Markovian gain model with many-body effects. The free-carrier model shows that the optical gain peak slightly increases with increasing N composition. In addition, the QW structure with a larger As composition shows a larger optical gain than that with a smaller As composition. On the other hand, in the case of the many-body model, the optical gain peak decreases with increasing N composition. Also, the QW structure with a smaller As composition is observed to have a larger optical gain than that with a larger As composition. This can be explained by the fact that the QW structure with a smaller As or N composition shows a larger Coulomb enhancement effect than that with a larger As or N composition. This means that it is important to consider the many-body effect in obtaining guidelines for device design issues.

Park, Seoung-Hwan, E-mail: shpark@cu.ac.kr [Department of Electronics Engineering, Catholic University of Daegu, Hayang, Kyeongbuk 712-702 (Korea, Republic of)

2014-02-14T23:59:59.000Z

299

26. 1% solar cell efficiency for Ge mechanically stacked under GaAs  

SciTech Connect (OSTI)

We have processed a diffused Ge wafer into a Ge concentrator solar cell and mechanically stacked it under a GaAs cell fabricated by Varian. We measured this stack's efficiency to be 26.1% for terrestrial air mass 1.5 direct (AM1.5D) conditions at a 285 x concentration ratio. We showed that this efficiency is limited by optical absorption in the Varian GaAs cell caused by high 2--4 (10/sup 18/) cm/sup -3/ substrate doping. We used a 2 x 10/sup 17/ cm/sup -3/ doped GaAs filter to estimate the stack efficiency as 27.4%, which would be achieved with the same Varian GaAs cell formed on a lower doped substrate. We project efficiencies assuming the best properties reported for a GaAs device. This gives a 29.6% efficiency for an improved, planar Ge cell and 31.6% efficiency for a proposed point contact geometry for the Ge cell. The corresponding space (AM0) efficiencies at a 159 x concentration ratio range from the 23.4% value we measured on the stack up to 28.4% projected for the point contact Ge place under the best GaAs cell. We showed that Ge cells give higher efficiencies than Si when stacked under GaAs.

Partain, L.D.; Kuryla, M.S.; Weiss, R.E.; Ransom, R.A.; McLeod, P.S.; Fraas, L.M.; Cape, J.A.

1987-10-01T23:59:59.000Z

300

Lattice dynamics of GaN: Effects of 3d electrons  

Science Journals Connector (OSTI)

We perform first-principles calculations of structural, dielectric, and lattice-dynamical properties of cubic GaN. The equilibrium structure is obtained using the plane-wave pseudopotential approach within the density-functional theory and local-density approximation. The dielectric and vibrational properties are computed within the density-functional perturbation theory. The effect of the Ga 3d electrons is treated by taking into account the nonlinear core corrections for the exchange and correlation energy. The importance of 3d electrons for the bonding strength is determined, and their influence on the dielectric and dynamical properties of GaN is analyzed and discussed.

K. Karch; F. Bechstedt; T. Pletl

1997-08-15T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Atomic geometry of the 22 GaP(111) surface  

Science Journals Connector (OSTI)

Integral and fractional order beam low-energy electron-diffraction intensity-voltage (I-V) data have been taken on a bombardment-annealed GaP(111)-(22) surface. We have compared these data with calculated I-V curves using a dynamical multiple scattering theory and found very good agreement for the following model: One out of every four Ga surface atoms is missing and the surface Ga-P bilayer is almost coplanar. Surface and deeper layer atoms undergo vertical and lateral displacements from bulk positions. Similar results in other systems suggest that the vacancy model applies on the (111) face of many compound semiconductors.

G. Xu; W. Y. Hu; M. W. Puga; S. Y. Tong; J. L. Yeh; S. R. Wang; B. W. Lee

1985-12-15T23:59:59.000Z

302

Integration of inverted InGaAs MSM array on Si substrate through low temperature  

E-Print Network [OSTI]

to reduce thermal stress at the interface. Huang et al. [2] presented a thin-film InGaAs MSM PD bonded to Si layers including those on InGaAs MSMs and Si/SiO2 is 860 nm. eching window InP epi-layer SiO2 Si Ti Au Au HCl:H3PO4 (1:1) to open a photodetection window. Citric acid was used to remove the InGaAs etching

Huang, Zhaoran "Rena"

303

Growth and optical characterization of multilayers of InGaN quantum dots  

E-Print Network [OSTI]

GaN quantum dots Article Type: Research Paper Section/Category: General subjects Keywords: B2. InGaN quantum dots; A1. Photoluminescence; B1. Nitrides; A3. Metal-organic vapour phase epitaxy Corresponding Author: Dr Tongtong Zhu, Ph... , Cambridge, CB2 3QZ, UK Dr Tongtong Zhu Tel: +44 1223 334368 Fax: +44 1223 334437 E-mail: tz234@cam.ac.uk 9 Sep 2011 Dear Editor, Title: Growth and optical characterization of multilayers of InGaN quantum dots Authors: Tongtong Zhu, Haitham A...

Zhu, Tontong; El-Ella, Haitham; Reid, Benjamin; Holmes, Mark; Taylor, Robert; Kappers, Menno; Oliver, Rachel

2012-01-01T23:59:59.000Z

304

Low threshold for optical damage in AlGaN epilayers and heterostructures  

SciTech Connect (OSTI)

Laser pulses with duration much shorter than the effective carrier lifetime cause permanent photoluminescence (PL) quenching and enhancement of PL decay rate in bare-faceted and capped AlGaN epilayers and multiple quantum wells at pulse energies about an order of magnitude lower than those causing the surface to melt and degrade. In contrast, GaN epilayers exhibit no photomodification in the same excitation intensity range. PL spectra and decay kinetics show that lattice heating is not responsible for the observed changes in AlGaN, which result from the formation of nonradiative recombination centers via recombination-enhanced defect reactions occurring at high nonequilibrium carrier densities.

Saxena, Tanuj [Department of ECSE, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Tamulaitis, Gintautas [Institute of Applied Research and Semiconductor Physics Department, Vilnius University, Sauletekio al. 9-III, Vilnius, LT-10222 (Lithuania); Shatalov, Max; Yang, Jinwei; Gaska, Remis [Sensor Electronic Technology, Inc., 1195 Atlas Road, Columbia, South Carolina 29209 (United States); Shur, Michael S. [Department of ECSE, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Department of PAPA, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2013-11-28T23:59:59.000Z

305

Ferromagnetism of GaMnAs studied by polarized neutron reflectometry  

Science Journals Connector (OSTI)

Polarized neutron reflectometry has been used to investigate details of spin ordering in ferromagnetic (FM) GaMnAs/GaAs superlattices. The reflectivity spectra measured below the Curie temperature reveal additional magnetic contributions to the structural superlattice Bragg peaks, clearly indicating the existence of FM interlayer correlations. Closer investigation of the magnetic reflectivity maxima using a full polarization analysis provides direct evidence that the FM order in the GaMnAs layers is truly long range. Moreover, as shown by the data, the system exhibits a strong tendency of forming a single-domain FM arrangement, even when cooled through TC in zero external field.

H. K?pa; J. Kutner-Pielaszek; A. Twardowski; C. F. Majkrzak; J. Sadowski; T. Story; T. M. Giebultowicz

2001-09-05T23:59:59.000Z

306

Suppression of bulk conductivity in InAs/GaSb broken gap composite quantum wells  

SciTech Connect (OSTI)

The two-dimensional topological insulator state in InAs/GaSb quantum wells manifests itself by topologically protected helical edge channel transport relying on an insulating bulk. This work investigates a way of suppressing bulk conductivity by using gallium source materials of different degrees of impurity concentrations. While highest-purity gallium is accompanied by clear conduction through the sample bulk, intentional impurity incorporation leads to a bulk resistance over 1 M?, independent of applied magnetic fields. In addition, ultra high electron mobilities for GaAs/AlGaAs structures fabricated in a molecular beam epitaxy system used for the growth of Sb-based samples are reported.

Charpentier, Christophe; Flt, Stefan; Reichl, Christian; Nichele, Fabrizio; Nath Pal, Atindra; Pietsch, Patrick; Ihn, Thomas; Ensslin, Klaus; Wegscheider, Werner [Laboratory for Solid State Physics, ETH Zrich, 8093 Zrich (Switzerland)] [Laboratory for Solid State Physics, ETH Zrich, 8093 Zrich (Switzerland)

2013-09-09T23:59:59.000Z

307

Formation energy of excess arsenic atoms in n-type GaAs  

Science Journals Connector (OSTI)

We report the first determination of the formation energy of excess-As-atomrelated defects in Te-doped GaAs. The photocapacitance method in the constant-capacitance condition is applied to GaAs:Te prepared by 67-h annealing at 8501100 C under various As vapor pressures followed by rapid cooling. From an Arrhenius plot of the saturating deep-level density at quasi thermal equilibrium under high As vapor pressure, the formation energy of the defect is determined to be 1.16 eV in Te-doped horizontal-Bridgeman-grown GaAs crystals.

Jun-ichi Nishizawa; Yutaka Oyama; Kazushi Dezaki

1990-11-12T23:59:59.000Z

308

Development of a Multifilament PIT V3Ga Conductor for Fusion Applications  

SciTech Connect (OSTI)

Previous studies on V{sub 3}Ga assert its suitability for use in proposed fusion reactors. V{sub 3}Ga may outperform Nb{sub 3}Sn in a fusion reactor environment based on its relatively flat critical-current profile in the 15 T-20 T range, resilience to applied strain, and reduced risk of induced radioactivity. A multifilament powder-in-tube V{sub 3}Ga conductor was designed, fabricated and tested with a focus on evaluating critical current versus applied field and applied strain performance, wire drawing difficulties, heat-treatment optimization, and overall feasibility of the concept.

Distin, J.S.; Ghosh, A.; Motowidlo, L.R.; Lee, P.J.; Larbalestier, D.C.; Lu, X.F.; Cheggour, N.; Stauffer, T.C.; Goodrich, L.F.

2011-08-03T23:59:59.000Z

309

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)

Intersubband transition energies and absorption lineshape in staggered InGaN/GaN quantum wells surrounded by GaN barriers are computed as functions of structural parameters such as well width, In concentrations, and the doping level in the well. Schrdinger and Poisson equations are solved self-consistently by taking the free and bound surface charge concentrations into account. Many-body effects, namely, depolarization and excitonic shifts are also included in the calculations. Results for transition energies, oscillator strength, and the absorption lineshape up to nonlinear regime are represented as functions of the parameters mentioned. The well width (total and constituent layers separately) and In concentration dependence of the built-in electric field are exploited to tune the intersubband transition energies.

Y?ld?r?m, Hasan, E-mail: hasanyildirim@karabuk.edu.tr [Department of Occupational Health and Safety, School of Health, Karabuk University, Karabuk 78050 (Turkey); Aslan, Bulent, E-mail: bulentaslan@anadolu.edu.tr [Department of Physics, Faculty of Science, Anadolu University Yunus Emre Campus, Eskisehir 26470 (Turkey)

2014-04-28T23:59:59.000Z

310

Electronic parameters and interfacial properties of GaAs/AlxGa1-xAs multiquantum wells grown on (111)A GaAs by metalorganic vapor phase epitaxy  

Science Journals Connector (OSTI)

We report a comprehensive study of the optical and interfacial properties of GaAs/AlxGa1-xAs multiquantum wells grown on (111)A GaAs substrates by metalorganic vapor phase epitaxy which allowed the determination of the electronic parameters appropriate for such quantum wells. High-resolution x-ray diffractometry studies indicate an excellent crystal quality and good periodicity for the multiquantum wells and provided their structural parameters accurately. The photoreflectance spectra exhibit all the allowed and almost all the weakly allowed optical transitions between the confined hole and electron states. From an analysis of the photoreflectance spectra it is shown that the quantum well interfaces have an abruptness better than 1 ML. Photoluminescence spectroscopy was also performed to evaluate independently the roughness of the interfaces and multiquantum well period reproducibility. For a 25-period multiquantum well structure with a well width of 55 , a photoluminescence linewidth of 12.5 meV, which corresponds to a combined well-width fluctuation and interface roughness of less than 1 monolayer over the 25 periods, proves the achievement of heterointerfaces with excellent interfacial quality. From a detailed analysis of the high-order transitions observed in the photoreflectance spectra we determined key quantum well electronic parameters, such as, the heavy-hole valence-band offset Qv=0.330.02, the transverse GaAs heavy-hole effective mass mhh=(0.950.02)m0, and the light-hole effective mass mlh=0.08m0 in ?111? directions, for ?111?-oriented GaAs/AlxGa1-xAs quantum well structures.

Soohaeng Cho; A. Sanz-Hervs; A. Majerfeld; B. W. Kim

2003-07-10T23:59:59.000Z

311

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

SciTech Connect (OSTI)

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.

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

2006-05-01T23:59:59.000Z

312

Carrier cooling and exciton formation in GaSe  

Science Journals Connector (OSTI)

The initial cooling of hot carriers and the subsequent exciton formation in GaSe are studied by time-resolved photoluminescence (PL) using femtosecond up-conversion techniques. From the time-resolved PL spectra of this layered III-VI semiconductor two different energy relaxation channels are derived. After an initial subpicosecond cooling due to Frhlich-type interaction of carriers with longitudinal optical E?(22) phonons a slower regime follows, which is dominated by deformation potential interaction with the nonpolar optical A1?(12) phonons. The coupling constant for nonpolar optical phonon scattering is derived. The subsequent formation of excitons is studied at different carrier densities and detection energies. A cross section for the free-exciton formation is determined based on a rate equation model.

S. Nsse; P. Haring Bolivar; H. Kurz; V. Klimov; F. Levy

1997-08-15T23:59:59.000Z

313

Dimensionality of InGaAs nonlinear optical response  

SciTech Connect (OSTI)

In this thesis the ultrafast optical properties of a series of InGaAs samples ranging from the two to the three dimensional limit are discussed. An optical system producing 150 fs continuum centered at 1.5 microns was built. Using this system, ultrafast pump-probe and four wave mixing experiments were performed. Carrier thermalization measurements reveal that screening of the Coulomb interaction is relatively unaffected by confinement, while Pauli blocking nonlinearities at the band edge are approximately twice as strong in two dimensions as in three. Carrier cooling via phonon emission is influenced by confinement due both to the change in electron distribution function and the reduction in electron phonon coupling. Purely coherent band edge effects, as measured by the AC Stark effect and four wave mixing, are found to be dominated by the changes in excitonic structure which take place with confinement.

Bolton, S.R. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.

1995-07-01T23:59:59.000Z

314

Temperature dependence of optical transitions in AlGaAs  

Science Journals Connector (OSTI)

AlGaAs structures with different aluminum concentration (x=0.0 0.17 0.30 and 0.40) were characterized by photoluminescence and photoreflectance techniques. The temperature dependence of optical transitions in the temperature ranging from 2 to 300 K were investigated. Y. P. Varshni [Physica (Utrecht) 34 194 (1967)] L. Via et al. [Phys. Rev. B 30 1979 (1984)] and R. Pssler [Phys. Status Solidi B 200 155 (1997)] models were used to fit the experimental points. The Pssler model gave the best adjustment to the experimental points. The tree models showed that the empirical parameters obtained through the adjustment of the experimental data in the three different models are aluminum composition dependent in the ternary alloy.

S. A. Loureno; I. F. L. Dias; J. L. Duarte; E. Laureto; E. A. Meneses; J. R. Leite; I. Mazzaro

2001-01-01T23:59:59.000Z

315

Strain-driven transition from stepped interfaces to regularly spaced macrosteps in (GaIn)As/Ga(PAs) symmetrically strained superlattices  

Science Journals Connector (OSTI)

We investigate the morphological transition from a steplike interface modulation to a highly periodic lateral thickness modulation that occurs on symmetrically strained (GaIn)As/GaAs/Ga(PAs)/GaAs superlattices grown by metal-organic vapor phase epitaxy on miscut (001)GaAs substrate. The combination of x-ray reciprocal-space mapping, around the (004) as well as the (200) and (020) reciprocal-lattice points, and transmission electron microscopy allowed us to monitor and analyze accurately the structural periodicities and ordering of heterointerfaces and to relate them to the elastic strain field. The laterally ordered macrosteps on the growth surface are investigated and discussed as a function of the strain misfit between epitaxial layer and substrate. Within this purpose, the complementary information obtained by grazing-incidence x-ray diffraction, by looking at different reciprocal-lattice points, is discussed in relationship to the effects of strain and morphological modulation of the interfaces in the process of macrostep formation.

C. Giannini; T. Baumbach; D. Lbbert; R. Felici; L. Tapfer; T. Marschner; W. Stolz; N. Y. Jin-Phillipp; F. Phillipp

2000-01-15T23:59:59.000Z

316

Development of 1.25 eV InGaAsN for triple junction solar cells  

SciTech Connect (OSTI)

Development of next generation high efficiency space monolithic multifunction solar cells will involve the development of new materials lattice matched to GaAs. One promising material is 1.05 eV InGaAsN, to be used in a four junction GaInP{sub 2}/GaAs/InGaAsN/Ge device. The AMO theoretical efficiency of such a device is 38--42%. Development of the 1.05 eV InGaAsN material for photovoltaic applications, however, has been difficult. Low electron mobilities and short minority carrier lifetimes have resulted in short minority carrier diffusion lengths. Increasing the nitrogen incorporation decreases the minority carrier lifetime. The authors are looking at a more modest proposal, developing 1.25 eV InGaAsN for a triple junction GaInP{sub 2}/InGaAsN/Ge device. The AMO theoretical efficiency of this device is 30--34%. Less nitrogen and indium are required to lower the bandgap to 1.25 eV and maintain the lattice matching to GaAs. Hence, development and optimization of the 1.25 eV material for photovoltaic devices should be easier than that for the 1.05 eV material.

LI,N.Y.; SHARPS,P.R.; HILLS,J.S.; HOU,H.; CHANG,PING-CHIH; BACA,ALBERT G.

2000-05-16T23:59:59.000Z

317

Dry patterning of InGaN and InAlN  

Science Journals Connector (OSTI)

Dry etch rates of In x Ga1?x N and In x Al1?x N alloys are found to increase with In mole fraction in CH4/H2microwave (2.45 GHz) discharges and to decrease under the same conditions in Cl2/H2 mixtures. Both plasma chemistries produce smooth anisotropicetching across the entire composition range from InN to either GaN or AlN. Addition of SF6 rather than H2 to a Cl2discharge produces faster etch rates and retains smooth morphologies. This suggests that either atomic hydrogen or fluorine is capable of effective removal of N from the III?V nitride materials. Ar+ ion milling rates for InGaAlN alloys are found to be approximately a factor of 2 lower than for more conventional III?V semiconductors like GaAs.

S. J. Pearton; C. R. Abernathy; F. Ren

1994-01-01T23:59:59.000Z

318

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

E-Print Network [OSTI]

Vision, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and Department of Chemistry, Uni and experimentally demonstrated that congruent sublimation of GaN is possible, which yields diatomic or polymeric

Yang, Peidong

319

Efficiency enhancement in GaAs solar cells using self-assembled microspheres  

Science Journals Connector (OSTI)

In this study we develop an efficient light harvesting scheme that can enhance the efficiency of GaAs solar cells using self-assembled microspheres. Based on the scattering of the...

Chang, Te-Hung; Wu, Pei-Hsuan; Chen, Sheng-Hui; Chan, Chia-Hua; Lee, Cheng-Chung; Chen, Chii -Chang; Su, Yan-Kuin

2009-01-01T23:59:59.000Z

320

In situ studies of the effect of silicon on GaN growth modes.  

SciTech Connect (OSTI)

We present real-time X-ray scattering studies of the influence of silicon on the homoepitaxial growth mode of GaN grown by metal-organic vapor-phase epitaxy. Both annealing of Si-doped GaN and surface dosing of GaN with disilane are shown to change the mode of subsequent growth from step-flow to layer-by-layer. By comparing the growth behavior induced by doped layers which have been annealed to that induced by surface dosing, we extract an approximate diffusion coefficient for Si in GaN of 3.5 x 10{sup -18} cm{sup 2}/s at 810{sup o}C.

Munkholm, A.; Stephenson, G. B.; Eastman, J. A.; Auciello, O.; Murty, M. V. R.; Thompson, C.; Fini, P.; Speck, J. S.; DenBaars, S. P.; Northern Illinois Univ.; Univ. of California at Santa Barbara

2000-12-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

Price of Elba Island, GA Natural Gas LNG Imports from Equatorial...  

Annual Energy Outlook 2013 [U.S. Energy Information Administration (EIA)]

Equatorial Guinea (Dollars per Thousand Cubic Feet) Price of Elba Island, GA Natural Gas LNG Imports from Equatorial Guinea (Dollars per Thousand Cubic Feet) Decade Year-0 Year-1...

322

Price of Elba Island, GA Natural Gas LNG Imports from Nigeria...  

Annual Energy Outlook 2013 [U.S. Energy Information Administration (EIA)]

Nigeria (Nominal Dollars per Thousand Cubic Feet) Price of Elba Island, GA Natural Gas LNG Imports from Nigeria (Nominal Dollars per Thousand Cubic Feet) Decade Year-0 Year-1...

323

Nanoscale Materials for Thin Film Cu(In,Ga)Se2 Solar Cells  

Science Journals Connector (OSTI)

Cu(In,Ga)Se2 solar cells show the highest efficiencies of all thin film technologies. Nano-particulate precursor materials could have the potential to lead this technology to...

Ahlswede, Erik

324

Deeply-scaled GaN high electron mobility transistors for RF applications  

E-Print Network [OSTI]

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 ...

Lee, Dong Seup

2014-01-01T23:59:59.000Z

325

A Constraint Handling Strategy for Bit-Array Representation GA in Structural Topology Optimization  

E-Print Network [OSTI]

In this study, an improved bit-array representation method for structural topology optimization using the Genetic Algorithm (GA) is proposed. The issue of representation degeneracy is fully addressed and the importance of ...

Wang, Shengyin

326

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

E-Print Network [OSTI]

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. ...

Chung, Jinwook W. (Jinwook Will)

2011-01-01T23:59:59.000Z

327

Computational Thermodynamics of CoNiGa High Temperature Shape Memory Alloys  

E-Print Network [OSTI]

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 Temperature Shape Memory...

Chari, Arpita

2012-10-19T23:59:59.000Z

328

Large area, low capacitance, GaAs nanowire photodetector with a transparent Schottky collecting junction  

SciTech Connect (OSTI)

We present experimental results on a GaAs/Indium-Tin-Oxide Schottky-like heterojunction photodetector based on a nanowire device geometry. By distributing the active detecting area over an array of nanowires, it is possible to achieve large area detection with low capacitance. Devices with bare GaAs and passivated AlGaAs/GaAs nanowires are fabricated to compare the responsivity with and without surface passivation. We are able to achieve responsivity of >0.5A/W and Signal-Noise-Ratio in excess of 7?dB for 2?V applied reverse bias with passivated nanowire devices. Capacitance-voltage measurement yields <5?nF/cm{sup 2}, which shows a strong possibility for high-speed applications with a broad area device.

Seyedi, M. A., E-mail: seyedi@usc.edu; Yao, M.; O'Brien, J.; Dapkus, P. D. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States)] [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States); Wang, S. Y. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States) [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States); Nanostructured Energy Conversion Technology and Research (NECTAR), Advanced Studies Laboratories, University of California, Santa Cruz, California 95064, USA and NASA Ames Research Center, Moffett Field, California 94035 (United States)

2013-12-16T23:59:59.000Z

329

GA CLASSROOM ASSIGNMENT PROCEDURES POST-PUBLICATION REASONS YOU MAY WANT TO CHANGE A CLASSROOM ASSIGNMENT  

E-Print Network [OSTI]

GA CLASSROOM ASSIGNMENT PROCEDURES POST-PUBLICATION REASONS YOU MAY WANT TO CHANGE A CLASSROOM for disabled instructor and/or students PROCEDURES FOR GENERAL ASSIGNMENT CLASSROOM ASSIGNMENTS Requests

Wisconsin at Madison, University of

330

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

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

and small crystalline zones that are randomly oriented. Citation: Jiang W, WJ Weber, LM Wang, and K Sun.2004."Amorphization Processes in Au Ion Irradiated GaN at 150 - 300...

331

Lattice-Mismatched GaInP LED Devices and Methods of Fabricating...  

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

Stories News Events Find More Like This Return to Search Lattice-Mismatched GaInP LED Devices and Methods of Fabricating Same United States Patent Application Publication...

332

Fabrication and Electronic Investigation of GaAs nanowire/Graphene Hybrid Devices.  

E-Print Network [OSTI]

?? In the present study, a process for fabricating GaAs nanowire/graphene hybrid devices using electron beam lithography processing techniques is presented and demonstrated. Fabricated devices (more)

Bang, Ambjrn Dahle

2014-01-01T23:59:59.000Z

333

Identification of the gallium vacancy-oxygen pair defect in GaN  

SciTech Connect (OSTI)

Cation vacancies like V{sub Ga}, V{sub Al} and their complexes with oxygen are predicted to be abundant in III-nitrides and to play an important role in nonradiative recombination. Appearing in triple or double negatively charged states, they are not paramagnetic and have not so far been detected by magnetic resonance even under illumination. In this Brief Report, we demonstrate an efficient way to make cation vacancy defects in GaN detectable by electron paramagnetic resonance and present our identification of the V{sub Ga}O{sub N} pair in GaN which is the model material for the III-nitrides and their alloys.

Son, N. T.; Hemmingsson, C. G.; Janzen, E. [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Paskova, T.; Evans, K. R. [Kyma Technologies Inc., 8829 Midway West Road, Raleigh, North Carolina 27617 (United States); Usui, A. [R and D Division, Furukawa Co., Ltd., Tsukuba, Ibaraki 305-0856 (Japan); Morishita, N.; Ohshima, T. [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Isoya, J. [Graduate School of Library, Information and Media Studies, University of Tsukuba, Tsukuba, Ibaraki 305-8550 (Japan); Monemar, B. [Department of Physics, Chemistry and Biology, Linkoeping University, SE-581 83 Linkoeping (Sweden); Nanometer Structure Consortium, Lund University, P.O. Box 118, S-221 00 Lund (Sweden)

2009-10-15T23:59:59.000Z

334

Thermal annealing characteristics of Si and Mg-implanted GaN thin films  

SciTech Connect (OSTI)

In this letter, we report the results of ion implantation of GaN using {sup 28}Si and {sup 24}Mg species. Structural and electrical characterizations of the GaN thin films after thermal annealing show that native defects in the GaN films dominate over implant doping effects. The formation energies of the annealing induced defects are estimated to range from 1.4 to 3.6 eV. A 40 keV 10{sup 14} cm{sup {minus}2} Mg implant results in the decrease of the free-carrier concentration by three orders of magnitude compared to unimplanted GaN up to an annealing temperature of 690{degree}C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties. {copyright} {ital 1996 American Institute of Physics.}

Chan, J.S.; Cheung, N.W. [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States)] [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States); Schloss, L.; Jones, E.; Wong, W.S.; Newman, N.; Liu, X.; Weber, E.R. [Department of Material Science and Mineral Engineering, University of California, Berkeley, California 64720 (United States)] [Department of Material Science and Mineral Engineering, University of California, Berkeley, California 64720 (United States); Gassman, A.; Rubin, M.D. [Lawrence Berkeley Laboratory, 1 Cyclotron Road, University of California, Berkeley, California 64720 (United States)] [Lawrence Berkeley Laboratory, 1 Cyclotron Road, University of California, Berkeley, California 64720 (United States)

1996-05-01T23:59:59.000Z

335

In-situ ellipsometry: Identification of surface terminations during GaN growth , T. Schmidtling1  

E-Print Network [OSTI]

1 In-situ ellipsometry: Identification of surface terminations during GaN growth C. Cobet1 , T SE, one is not limited to any special bulk or surface symmetry for optical characterisation. In PAMBE

Feenstra, Randall

336

Unambiguous determination of carrier concentration and mobility for InAs/GaSb superlattice photodiode optimization  

SciTech Connect (OSTI)

In this communication we report on electrical properties of nonintentionally doped (nid) type II InAs/GaSb superlattice grown by molecular beam epitaxy. We present a simple technological process which, thanks to the suppression of substrate, allows direct Hall measurement on superlattice structures grown on conductive GaSb substrate. Two samples were used to characterize the transport: one grown on a semi-insulating GaAs substrate and another grown on n-GaSb substrate where a etch stop layer was inserted to remove the conductive substrate. Mobilities and carrier concentrations have been measured as a function of temperature (77-300 K), and compared with capacitance-voltage characteristic at 80 K of a photodiode comprising a similar nid superlattice.

Cervera, C.; Rodriguez, J. B.; Perez, J. P.; Aiet-Kaci, H.; Chaghi, R.; Christol, P. [Institut d'Electronique du Sud (IES), UMR CNRS 5214, Case 067, Universite Montpellier 2, 34095 Montpellier Cedex 05 (France); Konczewicz, L.; Contreras, S. [Groupe d'Etude des Semiconducteurs (GES), UMR CNRS 5650, Case 074, Universite Montpellier 2, 34095 Montpellier Cedex 5 (France)

2009-08-01T23:59:59.000Z

337

Ambipolar spin diffusion and D'yakonov-Perel' spin relaxation in GaAs quantum wells  

E-Print Network [OSTI]

We report theoretical and experimental studies of ambipolar spin diffusion in a semiconductor. A circularly polarized laser pulse is used to excite spin-polarized carriers in a GaAs multiple quantum-well sample at 80 K. ...

Zhao, Hui; Mower, Matt; Vignale, G.

2009-03-01T23:59:59.000Z

338

GaN quantum dot superlattices grown by molecular beam epitaxy at high temperature  

E-Print Network [OSTI]

P-based optoelectronic devices with Si microelectronic devices. This method uses a Au-Ge eutectic alloy as the bonding. The realization of integrafion of GaAs- and InP-based optoelectronic devices with Si microelectronic components

339

Terahertz absorption in AlGaAs films and detection using heterojunctions  

E-Print Network [OSTI]

a Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA b NDP Optronics, LLC-mail address: uperera@gsu.edu (A.G.U. Perera). 1 Also at NDP Optronics LLC. Infrared Physics & Technology 47

Perera, A. G. Unil

340

Recombination Lifetime of InxGa1-xAs Alloys Used in Thermophotovoltaic Converters  

SciTech Connect (OSTI)

The family of ternary compounds of composition InxGa1-xAs are of considerable interest for thermophotovoltaic energy converters. The recombination lifetimes of the various compositions are critical to the successful application of these materials as efficient converters. Here we will describe experimental results on the composition. In0.53Ga0.47 that is lattice-matched to InP. We will also describe lifetime results on the compositions In0.68Ga0.32As, with bandgap of 0.60 eV to compositions In0.78Ga0.22As with a bandgap of 0.50 eV. Double heterostructure confinement devices have been made over a range of both n- and p-type doping. These results are preliminary, but the goal is to obtain the radiative and Auger recombination coefficients for the alloys in this composition range.

Ahrenkiel, R. K.; Ellingson, R.; Johnston, S.; Webb, J.; Carapella, J.; Wanlass, M.

1999-02-16T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Understanding and development of combined acoustic and magnetic actuation of Ni?MnGa single crystals  

E-Print Network [OSTI]

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 ...

Techapiesancharoenkij, Ratchatee, 1979-

2007-01-01T23:59:59.000Z

342

Frequency Response of Acoustic-Assisted NiMnGa Ferromagnetic- Shape-Memory-Alloy Actuator  

E-Print Network [OSTI]

A prototype of NiMnGa based ferromagnetic-shape-memory-alloy (FSMA) actuator was designed and built; an acoustic-assist technique was applied to the actuator to enhance its performance. A piezoelectric stack actuator was ...

Techapiesancharoenkij, Ratchatee

343

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

SciTech Connect (OSTI)

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

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

2012-06-05T23:59:59.000Z

344

Electronic structure of the Ge/RbF/GaAs(100) heterostructure: LCAO calculations  

Science Journals Connector (OSTI)

The electronic structure of Ge/RbF/GaAs(100) system ... known however about their reactivity. In these calculations the reactive contacts were postulated and modelled. ... obtained results, compared with those of...

Barbara Stankiewicz

345

Transmission electron microscopy studies of GaN/gamma-LiAlO 2 heterostructures.  

E-Print Network [OSTI]

??Die vorliegende Arbeit beschaeftigt sich mit dem strukturellen Aufbau von (1-100) M-plane GaN, das mit plasmaunterstuetzter Molekularstrahlepitaxie auf gamma-LiAlO2(100) Substraten gewachsen wurde. Die heteroepitaktische Ausrichtung (more)

Liu, Tian-Yu

2005-01-01T23:59:59.000Z

346

Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials  

SciTech Connect (OSTI)

Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system have been explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering (LSMS) method to explore the magnetic states responsible for the magnet-caloric effect in this material. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy were investigated using differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). Neutron scattering experiments were performed to observe the structural and magnetic phase transformations at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Ni-Mn-Ga-Cu-Fe. Data from the observations are discussed in comparison with the computational studies.

Nicholson, Don M [ORNL; Odbadrakh, Khorgolkhuu [ORNL; Rios, Orlando [ORNL; Hodges, Jason P [ORNL; Ludtka, Gerard Michael [ORNL; Porter, Wallace D [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Rusanu, Aurelian [ORNL; Evans III, Boyd Mccutchen [ORNL

2012-01-01T23:59:59.000Z

347

GaInAsSb/A1GaAsSb/Sb Thermophotovoltaic Devices With an Internal Back-Surface Reflector Formed by Wafer Bonding  

SciTech Connect (OSTI)

A novel implementation for GAInAsSb/AlGaAsSb/GaSb TPV cells with an internal back-surface reflector (BSR) formed by wafer bonding to GaAs is demonstrated. The SiO{sub x}/Ti/Au internal BSR enhances optical absorption within the device, while the dielectric layer provides electrical isolation. This configuration has the potential to improve TPV device performance; is compatible with monolithic series-interconnection of TPV cells for building voltage; and can mitigate the requirements of filters used for front-surface spectral control. At a short-circuit density of 0.4 A/cm{sup 2}, the open-circuit voltage of a single TPV cell is 0.2 V, compared to 0.37 and 1.8 V for 2- and 10-junction series-interconnected TPV cells, respectively.

C.A. Wang; R.K. Huang; D.A. Shiau; M.K. Connors; P.G. Murphy; P.W. O'brien; A.C. Anderson; D.M. DePoy; G. Nichols; M.N. Palmasiano

2002-12-18T23:59:59.000Z

348

Vacancy-Buckling Model for the (22) GaAs(111) Surface  

Science Journals Connector (OSTI)

A vacancy-buckling model is proposed for the (22) structure of the GaAs(111) surface. The model is confirmed by analysis of low-energy electron diffraction spectra. A reconstruction mechanism, basic to III-V compound surfaces, is proposed which favors equal numbers of dangling bonds on the nearest Ga and As neighbors. This model explains the (22) and (11) periodicities observed on (111) and (110) surfaces, respectively.

S. Y. Tong; G. Xu; W. N. Mei

1984-05-07T23:59:59.000Z

349

Electron transfer and capture dynamics in ZnSe quantum wells grown on GaAs  

SciTech Connect (OSTI)

We investigate the transfer and capture dynamics of electrons in phase coherent photorefractive ZnSe quantum wells grown on GaAs using degenerate three-beam four-wave-mixing. The measurements reveal electron capture times by the quantum well in the order of several tens of picoseconds and a transit time of approximately 5 picoseconds from the GaAs substrate through the ZnMgSe barrier.

Dongol, A.; Wagner, H. P. [Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221 (United States)

2013-12-04T23:59:59.000Z

350

Growth and characterization of liquid phase epitaxial GaP layers  

E-Print Network [OSTI]

Inside a High-vacuum Chamber . . . . . . . . . . . . . . . . . . . . . . . 3 3. Cross Section of Multi-well Sliding Graphite Boat. Solubility Curve of P in Ga Melt 5. Apparatus of LPE Growth by Tipping Method. 10 Dipping System Schematic for LPE... Growth. 10 7. Sliding Boat System Block Diagram for LPE Growth 12 Temperature Profile Along the Graphite Boat. 13 9. Disassembled Graphite Boat for Multi-layer LPE Growth. . . 14 10. Ga-P Phase Diagram 17 Solution Cooling Procedure for Three...

Kao, Yung-Chung

2012-06-07T23:59:59.000Z

351

Further observations on the operation of a GaAs polarized electron source  

SciTech Connect (OSTI)

We report on several important features of GaAs polarized electron source operation. Specifically we point out the beneficial effect on crystal lifetime produced by the constant low-level application of cesium from a dispenser embedded in an extraction anode. Using our experience in low-energy polarized electron-atom scattering as a reference, we also discuss the importance of frequent energy calibrations of GaAs electron beams for high-resolution investigations.

Guo, X.Q.; Crowe, D.M.; Lubell, M.S.; Tang, F.C.; Vasilakis, A. (Department of Physics, The City College of CUNY, New York, New York 10031 (USA)); Eminyan, M. (Laboratoire de Physique Atomique, Tour 24, Universite Paris VII, F-75251 Paris (France)); Slevin, J. (Department of Experimental Physics, St. Patrick's College, Maynooth, County Kildare (Ireland))

1990-07-01T23:59:59.000Z

352

Combustion of Nano-Aluminum and Liquid Water G.A. Risha, S.F. Son  

E-Print Network [OSTI]

1 Combustion of Nano-Aluminum and Liquid Water G.A. Risha, S.F. Son , R.A. Yetter, V. Yang, and B: Supplemental materials submitted #12;2 Combustion of Nano-Aluminum and Liquid Water G.A. Risha, S.F. Son, R of nano-aluminum (nAl) and liquid water has been conducted. In particular, linear and mass-burning rates

Yang, Vigor

353

Tunnel optical radiation in In{sub x}Ga{sub 1?x}N  

SciTech Connect (OSTI)

An investigation of tunnel optical radiation in epitaxial layers of n-type In{sub x}Ga{sub 1?x}N grown on p-type GaN by novel plasma based migration enhanced epitaxy is presented. Experimental results of electro-luminescence spectra for In{sub x}Ga{sub 1?x}N/p?GaN hetero-junctions were obtained and they show two well expressed optical bands - one in range 500-540 nm and other in range 550-610 nm. An interesting detail is that each band begins and ends by sharp drops of the radiation, which nearly approach zero. A theoretical investigation of the unusual behavior of these spectra was done using LCAO electron band structure calculations. The optical ranges of these bands show that the radiation occurs in the In{sub x}Ga{sub 1?x}N region. In fact, substitutions of In atoms in Ga sites creates defects in the structure of In{sub x}Ga{sub 1?x}N and the corresponding LCAO matrix elements are found on this basis. The LCAO electron band structures are calculated considering the interactions between nearest-neighbor orbitals. Electron energy pockets are found in both the conduction and the valence bands at the ? point of the electron band structures. Also it is found that these pockets are separated by distances, for which there is overlapping between the electron wave functions describing localized states belonging to the pockets, and as a result tunnel optical radiation can take place. This type of electron transition - between such a pocket in the conduction band and a pocket in the valence band - occurs in In{sub x}Ga{sub 1?x}N, causing the above described optical bands. This conclusion concurs with the fact that the shapes of these bands change with change of the applied voltage.

Alexandrov, Dimiter; Skerget, Shawn [Semiconductor Research Laboratory, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B5E1 (Canada)

2014-02-21T23:59:59.000Z

354

Theoretical investigation of spin-filtering in CrAs/GaAs heterostructures  

SciTech Connect (OSTI)

The electronic structure of bulk zinc-blende GaAs, zinc-blende and tetragonal CrAs, and CrAs/GaAs supercells, computed within linear muffin-tin orbital (LMTO) local spin-density functional theory, is used to extract the band alignment for the [1,0,0] GaAs/CrAs interface in dependence of the spin orientation. With the lateral lattice constant fixed to the experimental bulk GaAs value, a local energy minimum is found for a tetragonal CrAs unit cell with a longitudinal ([1,0,0]) lattice constant reduced by ?2%. Due to the identified spin-dependent band alignment, half-metallicity of CrAs no longer is a key requirement for spin-filtering. Based on these findings, we study the spin-dependent tunneling current in [1,0,0] GaAs/CrAs/GaAs heterostructures within the non-equilibrium Green's function approach for an effective tight-binding Hamiltonian derived from the LMTO electronic structure. Results indicate that these heterostructures are promising candidates for efficient room-temperature all-semiconductor spin-filtering devices.

Stickler, B. A.; Ertler, C.; Ptz, W., E-mail: walter.poetz@uni-graz.at [Institute of Physics, Karl-Franzens Universitt Graz, Graz (Austria); Chioncel, L. [Institute of Physics, Theoretical Physics III, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86135 Augsburg (Germany)

2013-12-14T23:59:59.000Z

355

Realizing InGaN monolithic solar-photoelectrochemical cells for artificial photosynthesis  

SciTech Connect (OSTI)

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.

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)

2014-04-07T23:59:59.000Z

356

Heteroepitaxial growth and surface structure of L1{sub 0}-MnGa(111) ultra-thin films on GaN(0001)  

SciTech Connect (OSTI)

L1{sub 0}-structured MnGa(111) ultra-thin films were heteroepitaxially grown on GaN(0001) under lightly Mn-rich conditions using molecular beam epitaxy. Room-temperature scanning tunneling microscopy (STM) investigations reveal smooth terraces and angular step edges, with the surface structure consisting primarily of a 2 2 reconstruction along with small patches of 1 2. Theoretical calculations were carried out using density functional theory, and the simulated STM images were calculated using the Tersoff-Hamman approximation, revealing that a stoichiometric 1 2 and a Mn-rich 2 2 surface structure give the best agreement with the observed experimental images.

Mandru, Andrada-Oana; Wang, Kangkang; Cooper, Kevin; Ingram, David C.; Smith, Arthur R. [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States)] [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Garcia Diaz, Reyes; Takeuchi, Noboru [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States) [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Centro de Nanociencias y Nanotecnologia, Universidad Nacional Autnoma de Mxico, Apartado Postal 14, Ensenada Baja California, Codigo Postal 22800 (Mexico); Haider, Muhammad [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States) [Department of Physics and Astronomy, Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701 (United States); Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran, 31261 (Saudi Arabia)

2013-10-14T23:59:59.000Z

357

Gain uniformity of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions  

SciTech Connect (OSTI)

We report on the spatial uniformity of the gain M of InP/ InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions (SAGM-APD's). Typically, these APD's exhibit less than 10 percent variation in the gain (for M less than or equal to 10) over the entire photosensitive area. The small nonuniformity which is observed shows a one-to-one correspondence with inhomogeneities in the epitaxial layers of the SAGM-APD structure. We also observe a reduction in the effective photosensitive diameter with increasing bias voltage.

Holden, W.S.; Campbell, J.C.; Dental, A.G.

1985-09-01T23:59:59.000Z

358

Frequency response of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption ''grading'' and multiplication regions  

SciTech Connect (OSTI)

We have measured the frequency response of InP/ InGaAsP/InGaAs photodiodes with separate absorption, ''grading,'' and multiplication regions (SAGM-APD's) for a wide range (2 less than or equal to M/sub 0/ less than or equal to 35) of dc gains. The results are explained in terms of a theoretical model which incorporates the transit time of carriers through the depletion region, the RC time constant, the accumulation of holes at the valence band discontinuity of the heterojunction interfaces, and the gainbandwidth limit.

Campbell, J.C.; Dentai, A.G.; Holden, W.S.; Qua, G.J.

1985-11-01T23:59:59.000Z

359

Repulsive interaction in the macroscopically ordered exciton state in GaAs?AlxGa1?xAs coupled quantum well structures  

Science Journals Connector (OSTI)

The macroscopically ordered exciton state (MOES)a periodic array of beads with spatial order on a macroscopic lengthappears in the external exciton rings in coupled GaAs?(Al,Ga)As quantum wells at low temperatures below a few Kelvin. Here, we report on the experimental study of the interaction in the MOES. The exciton photoluminescence energy varies in concert with the intensity along the circumference of the ring, with the largest energy found in the brightest regions. This shows that the MOES is characterized by the repulsive interaction and is not driven by the attractive interaction.

Sen Yang, A. V. Mintsev, A. T. Hammack, L. V. Butov, and A. C. Gossard

2007-01-17T23:59:59.000Z

360

How much better are InGaN/GaN nanodisks than quantum wellsOscillator strength enhancement and changes in optical properties  

SciTech Connect (OSTI)

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.

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

2014-02-03T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Impact of stress relaxation in GaAsSb cladding layers on quantum dot creation in InAs/GaAsSb structures grown on GaAs (001)  

SciTech Connect (OSTI)

We describe InAs quantum dot creation in InAs/GaAsSb barrier structures grown on GaAs (001) wafers by molecular beam epitaxy. The structures consist of 20-nm-thick GaAsSb barrier layers with Sb content of 8%, 13%, 15%, 16%, and 37% enclosing 2 monolayers of self-assembled InAs quantum dots. Transmission electron microscopy and X-ray diffraction results indicate the onset of relaxation of the GaAsSb layers at around 15% Sb content with intersected 60 dislocation semi-loops, and edge segments created within the volume of the epitaxial structures. 38% relaxation of initial elastic stress is seen for 37% Sb content, accompanied by the creation of a dense net of dislocations. The degradation of In surface migration by these dislocation trenches is so severe that quantum dot formation is completely suppressed. The results highlight the importance of understanding defect formation during stress relaxation for quantum dot structures particularly those with larger numbers of InAs quantum-dot layers, such as those proposed for realizing an intermediate band material.

Bremner, S. P. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia)] [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney 2052 (Australia); Ban, K.-Y.; Faleev, N. N.; Honsberg, C. B. [School of Electrical, Computer and Energy Engineering, Ira A. Fulton Schools of Engineering, Solar Power Lab, Arizona State University, Tempe, Arizona 85287 (United States)] [School of Electrical, Computer and Energy Engineering, Ira A. Fulton Schools of Engineering, Solar Power Lab, Arizona State University, Tempe, Arizona 85287 (United States); Smith, D. J. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)] [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

2013-09-14T23:59:59.000Z

362

Direct measurements of large near-band edge nonlinear index change from 1.48 to 1.55 m in InGaAsInAlGaAs multiquantum wells  

E-Print Network [OSTI]

used to measure di- rectly the nonlinear index change in bulk InGaAsP.10 Com- parison of DFWM results measurements of nonlinear refractive index change and nonlinear absorption in In0.530Al0.141Ga0.329As/In0.530Ga . The index-change-over-absorption figure of merit, F, is greater than unity over much of the spectrum

363

Performance improvement of Ge-Sb-Te material by GaSb doping for phase change memory  

SciTech Connect (OSTI)

Effects of GaSb doping on phase change characteristics of Ge-Sb-Te material are investigated by in situ resistance and x-ray diffraction measurement, optical spectroscopy, and x-ray photoelectron spectroscopy. The crystallization temperature and data retention of Ge-Sb-Te material increase significantly by the addition of GaSb, which results from the high thermal stability of amorphous GaSb. In addition, GaSb-doped Ge-Sb-Te material exhibits faster crystallization speed due to the change in electronic states as a result of the formation of chemical bonds with Ga element. Incorporation of GaSb is highly effective way to enhance the comprehensive performance of Ge-Sb-Te material for phase change memory.

Lu, Yegang [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China) [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Zhonghua; Song, Sannian; Cheng, Limin; Song, Zhitang [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)] [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shen, Xiang; Wang, Guoxiang; Dai, Shixun [Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211 (China)] [Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211 (China)

2013-06-17T23:59:59.000Z

364

Recreation of Brnsted acid sites in phosphorus-modified HZSM-5(Ga) by modification with various metal cations  

Science Journals Connector (OSTI)

Abstract To investigate the recreation of Brnsted acid sites in phosphorus-modified HZSM-5(Ga) zeolites by modification with various metal cations, we prepared several HZSM-5(Ga) zeolites co-modified with Mg, Ca, La or Zr and P (M/P/HZSM-5(Ga)). From FT-IR, 31P MAS NMR, and NH3-TPD measurements, it was found that the introduced metal cations (M) of Mg, Ca, La, and Zr react with the pre-introduced phosphorus to generate phosphorus species such as Mx(PO4)y, resulting in the recreation of some native Brnsted acid sites (Si(OH)Ga). The degree of recreation of the Brnsted acid sites was strongly dependent on the M/Ga ratio and doped metal valence. Modification with La and Zr that have higher valences more effectively recreated the Brnsted acid sites compared to Mg and Ca, which have di-valence. The conversion of ethanol to propylene was carried out over the M/P/HZSM-5(Ga). The propylene yield increased with increasing M/Ga ratio and reached maximum values of ca. 26C-% for Zr/P/HZSM-5(Ga) with a Zr/Ga ratio of 0.25 and ca. 29C-% for La/P/HZSM-5(Ga) with a La/Ga ratio of 0.4. The propylene yield hardly changed for the co-modified HZSM-5(Ga) zeolites during the 24h of reaction time, indicating the suppression of both carbonaceous deposition and the release of gallium from the zeolite framework.

Nao Tsunoji; Takushi Sonoda; Yoshiyasu Furumoto; Masahiro Sadakane; Tsuneji Sano

2014-01-01T23:59:59.000Z

365

Trends in semiconductor laser design: Balance between leakage, gain and loss in InGaAsP/InP  

E-Print Network [OSTI]

GaAsP MQW high power lasers with broadened waveguide and doped p-cladding/SCH interface. Introduction In1 Trends in semiconductor laser design: Balance between leakage, gain and loss in InGaAsP/InP MQW due to placement of the p-doping in 1.3-1.55µm InGaAsP MQW edge- emitting lasers is detailed

366

Nonlinear absorption edge properties of 1.3-m GaInNAs saturable R. Grange,a  

E-Print Network [OSTI]

-starting and stable operation of the laser at tens of GHz repetition rates.4 So far, InGaAsP,5 InGaAs,6,7 and AlNonlinear absorption edge properties of 1.3- m GaInNAs saturable absorbers R. Grange,a A. Rutz, V above the PL peak and R scales with the linear absorption even in the bandtail. The product R

Keller, Ursula

367

Novel InGaAsN pn Junction for High-Efficiency Multiple-Junction Solar Cells  

SciTech Connect (OSTI)

We report the application of a novel material, InGaAsN, with bandgap energy of 1.05 eV as a junction in an InGaP/GaAs/InGaAsN/Ge 4-junction design. Results of the growth and structural, optical, and electrical properties were demonstrated, showing the promising perspective of this material for ultra high efficiency solar cells. Photovoltaic properties of an as-grown pn diode structure and improvement through post growth annealing were also discussed.

Allerman, A.A.; Chang, P.C.; Gee, J.M.; Hammons, B.E.; Hou, H.Q.; Jones, E.D.; Kurtz, S.R.; Reinhardt, K.C.

1999-03-26T23:59:59.000Z

368

Fabrication of ?-Ga2O3 thin films and solar-blind photodetectors by laser MBE technology  

Science Journals Connector (OSTI)

Laser molecular beam epitaxy technology has been employed to deposit ?-gallium oxide (?-Ga2O3) on (0001) sapphire substrates. After optimizing the...

Guo, Daoyou; Wu, Zhenping; Li, Peigang; An, Yuehua; Liu, Han; Guo, Xuncai; Yan, Hui; Wang, Guofeng; Sun, Changlong; Li, Linghong; Tang, Weihua

2014-01-01T23:59:59.000Z

369

Roughening surface morphology on free-standing GaN membrane with laser lift-off technique  

Science Journals Connector (OSTI)

An ultraviolet (UV) laser lift-off (LLO) technique was presented to form a roughened surface morphology on GaN membrane grown by...

Ting Wang; Xia Guo; Yuan Fang; GuangDi Shen

2007-04-01T23:59:59.000Z

370

Physics based analytical modelling of Gallium Nitride(GaN) MESFET considering different ion implantation energy with high temperature annealing.  

E-Print Network [OSTI]

??A physics based analytical model of ion implanted GaN MESFET has been presented considering high temperature annealing effects. Choosing appropriate activation energy of impurity atoms, (more)

Raghavan, Vinay

2015-01-01T23:59:59.000Z

371

Structure and strain-relaxation effects of defects in InxGa1-xN epilayers  

E-Print Network [OSTI]

The direct band gap of InxGa1-xN can be engineered to emit light over the entire visible spectrum depending on the In content (x) of the film. InGaN-based alloys are thereby used to fabricate light-emitting diodes (LEDs), laser diodes (LDs) [1] [2... ] and solar cells [3] [4]. InGaN alloys are excellent candidates for the light-absorption layers in solar cell applications because of their high-energy radiation resistance [3] and because InGaN alloys across the 2 range of In compositions absorb light...

Rhode, S. L.; Fu, W. Y.; Moram, M. A.; Massabuau, F. C.-P.; Kappers, M. J.; McAleese, C.; Oehler, F.; Humphreys, C. J.; Dusane, R. O.; Sahonta, S.-L.

2014-09-10T23:59:59.000Z

372

ELSEWER Journal of Magnetism and Magnetic Materials 169 (1997) 261-270 Superparamagnetic behavior of Fe,GaAs precipitates in GaAs  

E-Print Network [OSTI]

ELSEWER Journal of Magnetism and Magnetic Materials 169 (1997) 261-270 Superparamagnetic behavior; revised 6 December 1996 Abstract We present magnetization measurements on Fe3GaAs clusters distributed-dependent magnetization well above the blocking temperature indicate a particle size distribution in agreement

Woodall, Jerry M.

373

Effects of growth-direction electric and magnetic fields on excitons in GaAs-Ga1?xAlxAs coupled double quantum wells  

Science Journals Connector (OSTI)

Direct and indirect excitons in GaAs-Ga1?xAlxAs coupled double quantum wells, under growth-direction applied electric and magnetic fields, have been theoretically investigated within a variational procedure in the effective-mass and parabolic-band approximations. The exciton hydrogenic 1s-like envelope wave function is obtained through a variational procedure and an appropriate expansion in trigonometric functions of the electron and hole wave functions. The applied electric field produces a polarization of the exciton by pushing the electron and hole away from each other, whereas the magnetic field contracts the exciton by pushing the electron and hole closer to each other. Intersubband mixing produced by the Coulomb interaction of electron-hole pairs is taken into account and a detailed analysis of the properties of direct- and indirect-exciton states in GaAs-Ga1?xAlxAs coupled double quantum wells is presented, with theoretical results in good agreement with available experimental measurements.

A. L. Morales, N. Raigoza, C. A. Duque, and L. E. Oliveira

2008-03-17T23:59:59.000Z

374

Pulsed Laser Deposition of Photoresponsive Two-Dimensional GaSe Nanosheet Networks  

SciTech Connect (OSTI)

Here we explore pulsed laser deposition (PLD), a well known and versatile synthesis method principally used for epitaxial oxide thin film growth, for the synthesis of functional metal chalcogenide (GaSe) nanosheet networks by stoichiometric transfer of laser vaporized material from bulk GaSe targets in Ar background gas. Uniform coverage of interconnected, crystalline, few-layer, photoresponsive GaSe nanosheets in both in-plane and out-of-plane orientations were achieved under different ablation plume conditions over ~1.5 cm2 areas. Plume propagation was characterized by in situ ICCD-imaging. High (1 Torr) Ar background gas pressures were found to be crucial for the stoichiometric growth of GaSe nanosheet networks. Individual 1-3 layer GaSe triangular nanosheets of ~ 200 nm domain size were formed within 30 laser pulses, coalescing to form nanosheet networks in as few as 100 laser pulses. The thickness of the deposited networks increased linearly with pulse number, adding layers in a two-dimensional (2D) growth mode while maintaining a surface roughness of 2 GaSe layers for increasing overall thickness. Field effect transistors using these interconnected crystalline GaSe networks showed p-type semiconducting characteristics with mobilities reaching as high as 0.1 cm2V-1s-1. Spectrally-resolved photoresponsivities and external quantum efficiencies ranged from 0.4 AW-1 and 100% at 700 nm, to 1.4 AW-1 and 600 % at 240 nm, respectively. Pulsed laser deposition under these conditions appears to provide a versatile and rapid approach to stoichiometrically transfer and deposit photoresponsive networks of 2D nanosheets with digital thickness control and substrate-scale uniformity for a variety of applications.

Mahjouri-Samani, Masoud [ORNL; Gresback, Ryan G [ORNL; Tian, Mengkun [ORNL; Puretzky, Alexander A [ORNL; Rouleau, Christopher M [ORNL; Eres, Gyula [ORNL; Ivanov, Ilia N [ORNL; Xiao, Kai [ORNL; McGuire, Michael A [ORNL; Duscher, Gerd [University of Tennessee, Knoxville (UTK); Geohegan, David B [ORNL

2014-01-01T23:59:59.000Z

375

Recent progress in GaInAsSb thermophotovoltaics grown by organometallic vapor phase epitaxy  

SciTech Connect (OSTI)

Studies on the materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for thermophotovoltaic (TPV) devices are reviewed. Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, respectively. The overall material quality of these alloys depends on growth temperature, In content, V/III ratio, substrate misorientation, and to a lesser extent, growth rate. A mirror-like surface morphology and room temperature photoluminescence (PL) are obtained for GaInAsSb layers with peak emission in the wavelength range between 2 and 2.5 {micro}m. The crystal quality improves for growth temperature decreasing from 575 to 525 C, and with decreasing In content, as based on epilayer surface morphology and low temperature PL spectra. A trend of smaller full width at half-maximum for low temperature PL spectra is observed as the growth rate is increased from 1.5 to 2.5 and 5 {micro}m/h. In general, GaInAsSb layers grown on (100) GaSb substrates with a 6{degree} toward (111)B misorientation exhibited overall better material quality than layers grown on the more standard substrate (100)2{degree} toward (110). Consistent growth of high performance lattice-matched GaInAsSb TPV devices is also demonstrated.

Wang, C.A.; Choi, H.K.; Oakley, D.C. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-06-01T23:59:59.000Z

376

OMVPE growth and characterization of GaInAsSb for thermophotovoltaics  

SciTech Connect (OSTI)

Studies on the materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for thermophotovoltaic (TPV) devices are reviewed. Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, respectively. The overall material quality of these alloys depends on growth temperature, In content, V/III ratio, substrate misorientation, and to a lesser extent, growth rate. A mirror-like surface morphology and room temperature photoluminescence (PL) are obtained for GaInAsSb layers with peak emission in the wavelength range between 2 and 2.5 {micro}m. The crystal quality improves for growth temperature decreasing from 575 to 525 C, and with decreasing In content, as based on epilayer surface morphology and low temperature PL spectra. A trend of smaller full width at half-maximum for low temperature PL spectra is observed as the growth rate is increased from 1.5 to 2.5 and 5 {micro}m/h. In general, GaInAsSb layers grown on (100) GaSb substrates with a 6{degree} toward (111)B misorientation exhibited overall better material quality than layers grown on the more standard substrate (100) 2{degree} toward (110). Consistent growth of high performance lattice-matched GaInAsSb TPV devices is also demonstrated.

Wang, C.A.; Charache, G.W.

1998-06-01T23:59:59.000Z

377

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

SciTech Connect (OSTI)

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

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

2014-05-28T23:59:59.000Z

378

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

SciTech Connect (OSTI)

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.

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

2009-07-01T23:59:59.000Z

379

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

SciTech Connect (OSTI)

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

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

2013-12-02T23:59:59.000Z

380

Photovoltaic properties of GaAsP coreshell nanowires on Si(001) substrate  

Science Journals Connector (OSTI)

We report on the growth and electro-optical studies of photovoltaic properties of GaAsP nanowires. Low density GaAsP nanowires were grown by Auassisted MOVPE on Si(001) substrates using a two step procedure to form a radial pn junction. The STEM analyses show that the nanowires have cubic structure with the alloy composition GaAs0.88P0.12 in the nanowire core and GaAs0.76P0.24 in the shell. The nanowire ensembles were processed in the form of sub-millimeter size mesas. The photovoltaic properties were characterized by optical beam induced current (OBIC) and electronic beam induced current (EBIC) maps. Both OBIC and EBIC maps show that the photovoltage is generated by the nanowires; however, a strong signal variation from wire to wire is observed. Only one out of six connected nanowires produce a measurable signal. These strong fluctuations can be tentatively explained by the variation of the resistance of the nanowire-to-substrate connection, which is highly sensitive to the quality of the SiGaAsP interface. This study demonstrates the importance of the spatially resolved charge collection microscopy techniques for the diagnosis of failures in nanowire photovoltaic devices.

M Tchernycheva; L Rigutti; G Jacopin; A de Luna Bugallo; P Lavenus; F H Julien; M Timofeeva; A D Bouravleuv; G E Cirlin; V Dhaka; H Lipsanen; L Largeau

2012-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
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381

HfO{sub x}N{sub y} gate dielectric on p-GaAs  

SciTech Connect (OSTI)

Plasma nitridation method is used for nitrogen incorporation in HfO{sub 2} based gate dielectrics for future GaAs-based devices. The nitrided HfO{sub 2} (HfO{sub x}N{sub y}) films on p-GaAs improve metal-oxide-semiconductor device characteristics such as interface state density, accumulation capacitance, hysteresis, and leakage current. An equivalent oxide thickness of 3.6 nm and a leakage current density of 10{sup -6} A cm{sup -2} have been achieved at V{sub FB}-1 V for nitrided HfO{sub 2} films. A nitride interfacial layer (GaAsO:N) was observed at HfO{sub 2}-GaAs interface, which can reduce the outdiffusion of elemental Ga and As during post-thermal annealing process. Such suppression of outdiffusion led to a substantial enhancement in the overall dielectric properties of the HfO{sub 2} film.

Dalapati, G. K.; Sridhara, A.; Wong, A. S. W.; Chia, C. K.; Chi, D. Z. [Institute of Materials Research and Engineering, A-STAR - Agency for Science, Technology and Research, 3 Research Link, Singapore 117602 (Singapore)

2009-02-16T23:59:59.000Z

382

Lattice-registered growth of GaSb on Si (211) with molecular beam epitaxy  

SciTech Connect (OSTI)

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.

Hosseini Vajargah, S.; Botton, G. A. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Ghanad-Tavakoli, S. [Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Preston, J. S.; Kleiman, R. N. [Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

2012-11-01T23:59:59.000Z

383

Structural properties of Bi-terminated GaAs(001) surface  

Science Journals Connector (OSTI)

Electronic and structural properties of Bi-terminated reconstructions on GaAs(001) surface have been studied by scanning tunneling microscopy (STM) and synchrotron radiation core-level spectroscopy. A 23 monolayer thick Bi-layer was evaporated on a Ga-terminated GaAs(001) surface. By heating the surface, the reconstruction changed from (2נ1) to (2נ4). The ?2 phase with one top Bi dimer and one As or Bi dimer in the third atomic layer per surface unit cell is proposed to explain the STM images of the Bi/GaAs(001)(2נ4) surface heated at 400C. Bi 5d photoemission from the Bi/GaAs(2נ4) consisted of two components suggesting two different bonding sites for Bi atoms on the (2נ4) surface. The variation of the surface sensitivity of the photoemission induced no changes in the intensities of the components indicating that the origins of both components lie in the first surface layer.

M. Ahola-Tuomi; P. Laukkanen; R.E. Perl; M. Kuzmin; J. Pakarinen; I.J. Vyrynen; M. Adell

2006-01-01T23:59:59.000Z

384

Electronic- and band-structure evolution in low-doped (Ga,Mn)As  

SciTech Connect (OSTI)

Modulation photoreflectance spectroscopy and Raman spectroscopy have been applied to study the electronic- and band-structure evolution in (Ga,Mn)As epitaxial layers with increasing Mn doping in the range of low Mn content, up to 1.2%. Structural and magnetic properties of the layers were characterized with high-resolution X-ray diffractometry and SQUID magnetometery, respectively. The revealed results of decrease in the band-gap-transition energy with increasing Mn content in very low-doped (Ga,Mn)As layers with n-type conductivity are interpreted as a result of merging the Mn-related impurity band with the host GaAs valence band. On the other hand, an increase in the band-gap-transition energy with increasing Mn content in (Ga,Mn)As layers with higher Mn content and p-type conductivity indicates the Moss-Burstein shift of the absorption edge due to the Fermi level location within the valence band, determined by the free-hole concentration. The experimental results are consistent with the valence-band origin of mobile holes mediating ferromagnetic ordering in the (Ga,Mn)As diluted ferromagnetic semiconductor.

Yastrubchak, O.; Gluba, L.; ?uk, J. [Institute of Physics, UMCS, Pl. Marii Curie-Sk?odowskiej 1, 20-031 Lublin (Poland)] [Institute of Physics, UMCS, Pl. Marii Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Sadowski, J. [Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa (Poland) [Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa (Poland); MAX-Lab, Lund University, 22100 Lund (Sweden); Krzy?anowska, H. [Institute of Physics, UMCS, Pl. Marii Curie-Sk?odowskiej 1, 20-031 Lublin (Poland) [Institute of Physics, UMCS, Pl. Marii Curie-Sk?odowskiej 1, 20-031 Lublin (Poland); Department of Physics and Astronomy, Vanderbilt University, 6506 Stevenson Center, Nashville, Tennessee 37325 (United States); Domagala, J. Z.; Andrearczyk, T.; Wosinski, T. [Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa (Poland)] [Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa (Poland)

2013-08-07T23:59:59.000Z

385

GaAs Blocked-Impurity-Band Detectors for Far-Infrared Astronomy  

SciTech Connect (OSTI)

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.

Cardozo, Benjamin Lewin

2004-12-21T23:59:59.000Z

386

Transport properties, specific heat and thermal conductivity of GaN nanocrystalline ceramic  

SciTech Connect (OSTI)

The structural and transport properties (resistivity, thermopower and Hall effect), specific heat and thermal conductivity have been measured for GaN nanocrystalline ceramic prepared by hot pressing. It was found that the temperature dependence of resistivity in temperature range 10-300 K shows the very low activation energy, which is ascribed to the shallow donor doping originating in amorphous phase of sample. The major charge carriers are electrons, what is indicated by negative sign of Hall constant and Seebeck coefficient. The thermopower attains large values (-58 {mu}V/K at 300 K) and was characterized by linear temperature dependence which suggests the diffusion as a major contribution to Seebeck effect. The high electron concentration of 1.3x10{sup 19} cm{sup -3} and high electronic specific heat coefficient determined to be 2.4 mJ/molK{sup 2} allow to conclude that GaN ceramic demonstrates the semimetallic-like behavior accompanied by very small mobility of electrons ({approx}0.1 cm{sup 2}/V s) which is responsible for its high resistivity. A low heat conductivity of GaN ceramics is associated with partial amorphous phase of GaN grains due to high pressure sintering. - Graphical Abstract: Thermal resistivity and thermopower measurements indicates the high phonon scattering and lack of phonon-drag contribution to thermopower in GaN nanoceramics pressed under 4 GPa at 800 {sup o}C.

Sulkowski, Czeslaw [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); ChuchmaLa, Andrzej, E-mail: andrzej.chuchmala@pwr.wroc.p [Wroclaw University of Technology, Institute of Electrical Engineering Fundamentals (I7), Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Zaleski, Andrzej J.; Matusiak, Marcin; Mucha, Jan; GLuchowski, PaweL; Strek, WiesLaw [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland)

2010-10-15T23:59:59.000Z

387

Self-cleaning and surface recovery with arsine pretreatment in ex situ atomic-layer-deposition of Al2O3 on GaAs  

E-Print Network [OSTI]

. heavily doped GaAs 001 substrates at 650 °C with TMG Ga CH3 3 and arsine AsH3 V/III=23 with disilane Si2H6

388

White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum wells to colloidal CdSe/ZnS core/shell quantum dots  

E-Print Network [OSTI]

White light generation by resonant nonradiative energy transfer from epitaxial InGaN/GaN quantum n a l f o r p h y s i c s New Journal of Physics White light generation by resonant nonradiative white-light-generating nonradiative energy transfer (ET) from epitaxial quantum wells (QWs) to colloidal

Demir, Hilmi Volkan

389

314 IEEE MICROWAVE AND GUIDED WAVE LETTERS, VOL. 9, NO. 8, AUGUST 1999 39-GHz GaN-Based Microwave Power  

E-Print Network [OSTI]

As-based counterparts of the same sizes. Index Terms--Amplifier, field-effect transistors, gallium-nitride (Ga

York, Robert A.

390

Suppression of thermal conductivity in InxGa12xN alloys by nanometer-scale disorder  

E-Print Network [OSTI]

power requires low lattice thermal conductivity while maintaining high mobility of the charge carriers. The binary InN and GaN materials have high ther- mal conductivity materials9­14 (the room-temperature thermalSuppression of thermal conductivity in InxGa12xN alloys by nanometer-scale disorder T. Tong,1,a) D

Wu, Junqiao

391

Anomalous nonlinear photoresponse in a InGaNGaN heterostructure J. Zeller,* W. Rudolph, and M. Sheik-Bahae  

E-Print Network [OSTI]

and nonlinear carrier transport phenomena. The same model also explains the observed subpicosecond. Design guidelines for GaN-based nonlinear photodetectors used in autocorrelation measurements ) and 5.5 m silicon doped n-GaN (nSi 1017 cm 3 ). This structure was grown by metal-organic chemical vapor

Sheik-Bahae, Mansoor

392

Resonant Raman scattering on free and bound excitons in GaN A. Kaschner,* A. Hoffmann, and C. Thomsen  

E-Print Network [OSTI]

scattering RRS has been studied for a variety of semiconductor materials, such as CdS,1 GaP,2 and GaAs,3 since the late 1960. In particular, effects of RRS on free and bound excitons in CdS were extensively investigated4­6 because crystals of high structural quality were synthesized and intentionally doped

Nabben, Reinhard

393

Molecular Beam Epitaxy on Gas Cluster Ion Beam Prepared GaSb Substrates: Towards Improved Surfaces and Interfaces  

SciTech Connect (OSTI)

A key problem in producing mid-infrared optoelectronic and low-power electronic devices in the GaSb material system is the lack of substrates with appropriate surfaces for epitaxial growth. Chemical mechanical polishing (CMP) of GaSb results in surface damage accompanied by tenacious oxides that do not easily desorb. To overcome this, we have developed a process using gas cluster ion beams (GCIB) to remove surface damage and produce engineered surface oxides. In this paper, we present surface modification results on GaSb substrates using O2-, CF4/O2-, and HBr-GCIB processes. X-ray photoelectron spectroscopy of GCIB produced surface layers showed the presence of mixed Ga- and Sb-oxides, with mostly Ga-oxides at the interface, desorbing at temperatures ranging 530C to 560C. Cross-sectional transmission electron microscopy of molecular beam epitaxy grown GaSb/AlGaSb layers showed that GCIB surfaces yielded smooth defect free substrate to epi transitions as compared to CMP surfaces. Furthermore, HBr-GCIB surfaces exhibited neither dislocation layers nor discernable interfaces, indicating complete oxide desorbtion prior to epigrowth on a clean single crystal template. Atomic force microscopy of GCIB epilayers exhibited smooth surfaces with characteristic step-terrace formations comprising monatomic steps and wide terraces. The HBr-GCIB process can be easily adapted to a large scale manufacturing process for epi-ready GaSb.

Krishnaswami, Kannan; Shivashankar, Vangala; Dauplaise, Helen; Allen, Lisa; Dallas, Gordon; Bakken, Daniel; Bliss, David; Goodhue, William

2008-04-01T23:59:59.000Z

394

2174 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 44, NO. 12, DECEMBER 1997 In Ga As MSM Photodiodes with  

E-Print Network [OSTI]

2174 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 44, NO. 12, DECEMBER 1997 In Ga As MSM Photodiodes, IEEE Abstract-- Metal-semiconductor-metal (MSM) photodiodes with an In0:53Ga0:47As active region were the low responsivity of conventional MSM photodiodes with opaque electrodes. CTO is suitable as a Schottky

395

2.9 to 1.9 Ga paleoalterations ofArchean granitic basement of the Franceville basin (Gabon).  

E-Print Network [OSTI]

1 2.9 to 1.9 Ga paleoalterations ofArchean granitic basement of the Franceville basin (Gabon: Paleocirculation and Diagenesis in Archean basement, Franceville basin, Gabon3 4 Abstract The Archean granitoids in the Ki�n� area, Gabon, are overlained by the Paleoproterozoic sediments of the Franceville basin (2.1 Ga

Paris-Sud XI, Université de

396

Growth mechanisms of GaSb heteroepitaxial films on Si with an AlSb buffer layer  

SciTech Connect (OSTI)

The initial growth stages of GaSb epilayers on Si substrates and the role of the AlSb buffer layer were studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Heteroepitaxy of GaSb and AlSb on Si both occur by Volmer-Weber (i.e., island mode) growth. However, the AlSb and GaSb islands have distinctly different characteristics as revealed through an atomic-resolution structural study using Z-contrast of HAADF-STEM imaging. While GaSb islands are sparse and three dimensional, AlSb islands are numerous and flattened. The introduction of 3D island-forming AlSb buffer layer facilitates the nucleation of GaSb islands. The AlSb islands-assisted nucleation of GaSb islands results in the formation of drastically higher quality planar film at a significantly smaller thickness of films. The interface of the AlSb and GaSb epilayers with the Si substrate was further investigated with energy dispersive X-ray spectrometry to elucidate the key role of the AlSb buffer layer in the growth of GaSb epilayers on Si substrates.

Vajargah, S. Hosseini; Botton, G. A. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada) [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Ghanad-Tavakoli, S. [Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)] [Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Preston, J. S.; Kleiman, R. N. [Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada) [Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada); Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

2013-09-21T23:59:59.000Z

397

A InP Lattice-Matched Ga0.47.In0.53As Cell for Multispectral Photovoltaics  

Science Journals Connector (OSTI)

GaInAs (0.75 eV) photovoltaic cells with a GaInAsP (0.94 eV) window layer are lattice-matched grown by LPE on InP substrates. These cells are devised for the conversion of the solar energy spectrum with a cut-...

B. Beaumont; P. Garabedian; J. C. Guillaume

1987-01-01T23:59:59.000Z

398

Direct measurement of curvature dependent ion etching of GaN Bentao Cui and P.I. Cohen  

E-Print Network [OSTI]

Direct measurement of curvature dependent ion etching of GaN Bentao Cui and P.I. Cohen Department of Electrical and Computer Engineering and Department of Chemical Engineering and Materials Science, University of nanoscale pores or dimples during ion etching of GaN was used to measure the magnitude of the curvature

Cohen, Philip I.

399

Theoretical study of defect formation during the initial stages of native-oxide growth on GaSb (001)  

SciTech Connect (OSTI)

The formation of defects during the initial stages of native-oxide growth on the GaSb (001)-?(4??3) surface has been studied computationally using spin-unrestricted density functional theory. It is found that insertion into a Ga-Sb adatom dimer to form a peroxo Ga-O-O-Sb bridge is the most energetically favorable process with insertion into Ga-Sb back-bonds being somewhat less so. A Ga-O-O-Ga bridge between dimers is also favorable, but Sb-O-O-Sb bridges show little if any stability. In the course of analyzing molecular adsorption, a particularly reactive site has been identified that leads to O{sub 2} dissociation with little or no barrier. This process is initiated in the vicinity of an Sb-Sb dimer in the terminating layer and leads to sub-surface Ga and Sb defect sites (i.e., coordinatively unsaturated atoms) and to strained Ga-Sb bonds that may be susceptible to further O{sub 2} attack. However, the defects formed in these reactions do not produce states in the gap.

Bermudez, V. M., E-mail: victor.bermudez@nrl.navy.mil [Electronics Science and Technology Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States)

2014-04-07T23:59:59.000Z

400

Doubly resonant second harmonic generation of 2.0 pm light in coupled InGaAs/AIAs quantum wells  

E-Print Network [OSTI]

energiesin n-type QWs to reach the technologically important 2 pm wavelength,6,7 where compact InGaAsP and Ga. The absorption spectrum of the sample is shown in Fig. 2. Absorption peaks at Et,=300 meV (4.1

Fejer, Martin M.

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Improved electrical properties of wafer-bonded p-GaAs/n-InP interfaces with sulfide passivation  

E-Print Network [OSTI]

subcells InGaAsP, InGaAs via direct wafer bonding.8 In order to monolithically interconnect between the top materials, enable increased conversion efficiency due to the higher absorption efficiency obtained from. The additional layer reduces the incident light inten- sity because of the free carrier absorption. A wafer

Atwater, Harry

402

Femtosecond gain and index dynamics in an InAs/InGaAsP quantum dot amplifier  

E-Print Network [OSTI]

Femtosecond gain and index dynamics in an InAs/InGaAsP quantum dot amplifier operating at 1.55 µm and refractive index dynamics of an InAs/InGaAsP self-assembled quantum dot semiconductor optical amplifier (SOA-carrier absorption and stimulated transition processes. ©2006 Optical Society of America OCIS codes: (320

Mojahedi, Mohammad

403

Room Temperature, Intrinsic Vacancy Mediated Ferromagnetism in Cr:Ga2Se3/Si E. N. Yitamben,1,  

E-Print Network [OSTI]

Room Temperature, Intrinsic Vacancy Mediated Ferromagnetism in Cr:Ga2Se3/Si E. N. Yitamben,1, T. C of 4 µB/Cr. The intrinsic- vacancy structure of defected-zinc-blende -Ga2Se3 enables Cr incorporation, as well as strong overlap between Cr 3d states and the Se 4p states lining the intrinsic vacancy rows, ob

Olmstead, Marjorie

404

Optically-pumped UV Lasing from a GaN-based VCSEL  

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

Optically-pumped UV Lasing from a GaN-based VCSEL Optically-pumped UV Lasing from a GaN-based VCSEL by J. Han, K. E. Waldrip, J. J. Figiel, S. R. Lee, and A. J. Fischer* Motivation-Compact ultraviolet sources are required for advanced chemical and biological sensors, high density optical storage, and as pump sources for phosphors used in solid-state white lighting. Although GaN-based edge- emitting lasers operating near 400 nm are available commercially, shorter wavelengths as well as other lasing geometries have remained a challenge. In particular, electrically-injected vertical-cavity surface-emitting lasers (VCSELs) have not been demonstrated in the III-Nitrides. VCSELs have unique advantages due to their low cost, compact size, and well- defined circular output beam. Optoelectronic sources based on UV VCSELS will be the

405

Growth and properties of crystalline barium oxide on the GaAs(100) substrate  

SciTech Connect (OSTI)

Growing a crystalline oxide film on III-V semiconductor renders possible approaches to improve operation of electronics and optoelectronics heterostructures such as oxide/semiconductor junctions for transistors and window layers for solar cells. We demonstrate the growth of crystalline barium oxide (BaO) on GaAs(100) at low temperatures, even down to room temperature. Photoluminescence (PL) measurements reveal that the amount of interface defects is reduced for BaO/GaAs, compared to Al{sub 2}O{sub 3}/GaAs, suggesting that BaO is a useful buffer layer to passivate the surface of the III-V device material. PL and photoemission data show that the produced junction tolerates the post heating around 600?C.

Yasir, M.; Dahl, J.; Lng, J.; Tuominen, M.; Punkkinen, M. P. J.; Laukkanen, P., E-mail: pekka.laukkanen@utu.fi; Kokko, K. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)] [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Kuzmin, M. [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland) [Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Korpijrvi, V.-M.; Polojrvi, V.; Guina, M. [Optoelectronics Research Centre, Tampere University of Technology, FI-33101 Tampere (Finland)] [Optoelectronics Research Centre, Tampere University of Technology, FI-33101 Tampere (Finland)

2013-11-04T23:59:59.000Z

406

Disilane: A new silicon doping source in metalorganic chemical vapor deposition of GaAs  

Science Journals Connector (OSTI)

Disilane (Si2H6) is presented as a new silicon doping source in the metalorganic chemical vapor deposition of GaAs together with comparison results obtained using the conventional silane (SiH4) doping source. The dopingcharacteristics of disilane were studied over a wide range of growth conditions: temperature gas phase stoichiometry and disilane concentration in the growth ambient. Silicon incorporation by means of disilane pyrolysis showed no temperature dependence in sharp contrast to the strong temperature activated dependence found when employing silane. The decomposition reaction of disilane proved to be very efficient reducing the amount of dopant gas required by about two orders of magnitude at the lower growth temperatures. Electrical measurements on disilane?doped GaAs yield the same high mobilities as obtained in silane?doped GaAs films indicative of low compensation.

T. F. Kuech; B. S. Meyerson; E. Veuhoff

1984-01-01T23:59:59.000Z

407

Epitaxial growth and ferrimagnetic properties of Mn film on GaSb(100)  

SciTech Connect (OSTI)

We report on the epitaxial stabilization and magnetic properties of Mn films on GaSb(100) using molecular beam epitaxy, a follow-up to our previous work on the growth of Mn films on GaAs(100) [Phys. Rev. B 79, 045309 (2009)]. A strong ferrimagnetic ordering was observed which was attributed to the largely expanded lattice parameter resulting from the lattice mismatch with substrate and the enhanced thermal energy with increasing growth temperature. The observed magnetic moment of 1.16{mu}{sub B}/Mn atom was several times larger than that observed in the Mn/GaAs(100) films due to the lattice constant difference of substrates. The in-plane magnetoresistance behavior demonstrated the magnetic anisotropy that might result from the slightly distorted cubic structure of {alpha}-Mn phase under low-dimensional growth.

Feng Wuwei; Dung, Dang Duc; Shin, Yooleemi; Cho, Sunglae [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Choi, Jeongyong [IT Convergence Technology Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-700 (Korea, Republic of)

2010-05-15T23:59:59.000Z

408

Comparison of the (22) reconstructions of GaAs{111} surfaces  

Science Journals Connector (OSTI)

The {111} surfaces of GaAs have been examined using scanning tunneling microscopy and soft x-ray photoelectron spectroscopy and a comparison has been made between the three different (22) reconstructions observed. We find that both the (111)A and (111)B surfaces initially exhibit (22) ordered adstructures following the thermal desorption of an As cap, though spectroscopy shows them to be chemically inequivalent. With increasing temperature, the (111)A surface is found to develop into a Ga-vacancy (22) structure, in many ways similar to a (110) surface. The GaAs(111)B surface, however, loses its (22) periodicity with increasing annealing temperature, following a sequence of less As-rich structures.

J. M. C. Thornton; P. Weightman; D. A. Woolf; C. J. Dunscombe

1995-05-15T23:59:59.000Z

409

Band offsets in HfO{sub 2}/InGaZnO{sub 4} heterojunctions  

SciTech Connect (OSTI)

The valence band discontinuity ({Delta}E{sub V}) of sputter deposited HfO{sub 2}/InZnGaO{sub 4} (IGZO) heterostructures was obtained from x-ray photoelectron spectroscopy measurements. The HfO{sub 2} exhibited a bandgap of 6.07 eV from absorption measurements. A value of {Delta}E{sub V} = 0.48 {+-} 0.025 eV was obtained by using the Ga 2p{sub 3/2}, Zn 2p{sub 3/2}, and In 3d{sub 5/2} energy levels as references. This implies a conduction band offset {Delta}E{sub C} of 2.39 eV in HfO{sub 2}/InGaZnO{sub 4} heterostructures and a nested interface band alignment.

Cho, Hyun [Department of Nanomechatronics Engineering, Pusan National University, Gyeongnam 627-706 (Korea, Republic of); Douglas, E. A.; Gila, B. P.; Craciun, V.; Lambers, E. S.; Pearton, S. J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States); Ren Fan [Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2012-01-02T23:59:59.000Z

410

Green light emitting diode grown on thick strain-reduced GaN template  

Science Journals Connector (OSTI)

Abstract We report a green light-emitting diode (LED) grown on thick strain-reduced GaN template. As the injection current changes from 20mA to 120mA, blue-shift of EL peak wavelength reduces from 9.3nm for the LED on sapphire substrate to 6.8nm for the LED grown on thick strain-reduced GaN template. Furthermore, the light output power and external quantum efficiency of the LED on thick strain-reduced GaN template are respectively 1.48mW and 2.5% at the forward current of 20mA, which is twice as much as the LED on sapphire substrate. In contrast, the reverse current is 2?A lower than that of the LED on the sapphire at ?8V.

Jiankun Yang; Tongbo Wei; Qiang Hu; Ziqiang Huo; Baojuan Sun; Ruifei Duan; Junxi Wang

2015-01-01T23:59:59.000Z

411

Spin injection and filtering in halfmetal/semiconductor (CrAs/GaAs) heterostructures  

SciTech Connect (OSTI)

Theoretical investigations of spin-dependent transport in GaAS/CrAs/GaAs halfmetal-semiconductor heterostructures indicate that this system is a candidate for an efficient room temperature spin injector and filter. The spin dependent electronic structure of zincblende CrAs and the band offset between GaAs and CrAs are determined by ab-initio calculations within the method of linear muffin tin orbitals (LMTO). This band structure is mapped onto an effective sp{sup 3}d{sup 5}s* nearest neighbor tight-binding (TB) Hamiltonian and the steady-state transport characteristic is calculated within a non-equilibrium Greens function approach. Even at room temperature we find current spin polarizations up to 97%.

Stickler, B. A.; Ertler, C.; Ptz, W. [Institute of Physics, Karl-Franzens Universitt Graz (Austria); Chioncel, L. [Institute of Physics, Universitt Augsburg (Germany); Arrigoni, E. [Institute of Theoretical and Computational Physics, TU Graz (Austria)

2013-12-04T23:59:59.000Z

412

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

SciTech Connect (OSTI)

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

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

2014-02-21T23:59:59.000Z

413

Temperature behavior of optical absorption in InGaAsP lasers  

SciTech Connect (OSTI)

The temperature dependence of the optical absorption in InGaAsP laser emitting at 1.3 ..mu..m is studied by measuring the relaxation frequency as a function of output power at various temperatures. Our results show that the optical absorption does not vary significantly with increasing temperature. This suggests that the threshold carrier density in InGaAsP lasers is weakly temperature dependent compared to the threshold current density. Thus, the strong temperature dependence of threshold current in 1.3-..mu..m InGaAsP lasers is primarily due to the temperature dependence of the carrier lifetime at threshold. The shorter carrier lifetime (i.e., increased carrier loss) at high temperature can be due to Auger recombination.

Shen, T.M.; Dutta, N.K.

1984-12-15T23:59:59.000Z

414

Photoresponse of the FR3 electron-spin-resonance signal in GaAs  

Science Journals Connector (OSTI)

The photoresponse of the FR3 electron-spin-resonance (ESR) signal in GaAs has been studied. Excitation and quenching of the FR3 ESR is shown to result from the optically induced charge exchange between the FR3 center and the AsGa antisite. The FR3 ESR can be persistently excited with photons in the range 1.0eVGa antisite. Conclusive evidence for the acceptor nature of the FR3 center is presented, the corresponding level lying between Ev+0.03 eV and Ev+0.52 eV.

U. Kaufmann; W. Wilkening; M. Baeumler

1987-11-15T23:59:59.000Z

415

Physical Properties of GaN Nanotubes as Revealed by Computer Simulation  

SciTech Connect (OSTI)

Single-crystalline wurtzite GaN nanotubes have been synthesized recently with proposed applications in nanoscale electronics, optoelectronics and the biochemical-sensing field. Molecular dynamics methods with a Stillinger-Weber potential are used to investigate the melting behavior, thermal conductivity and mechanical properties of these wurtzite-type single crystalline GaN nanotubes. Four major topical areas are summarized in this chapter. (1) The melting temperature of the GaN nanotubes increases with the thickness of the nanotubes to a saturation value, which is close to the melting temperature of bulk GaN. The simulations result reveal that the nanotubes begin to melt at the surface, and then the melting rapidly extends to the interior of the nanotubes as the temperature increases. (2) The thermal conductivity of nanotubes is smaller than that of the bulk GaN single crystal. The thermal conductivity is also found to decrease with temperature and increase with increasing wall thickness of the nanotubes. The change of phonon spectrum and surface inelastic scattering may account for the reduction of thermal conductivity in the nanotubes, while thermal softening and high frequency phonon interactions at high temperatures may provide an explanation for its decrease with increasing temperature. (3) At low temperatures, the simulation results show that the nanotubes exhibit brittle properties; whereas at high temperatures, they behave as ductile materials. The brittle to ductile transition temperature generally increases with increasing wall thickness of the nanotubes and increasing strain rate. (4) The simulation temperature, tube length and strain rate affect the buckling behavior of GaN nanotubes. The critical stress decreases with the increase of simulation temperature and tube length. The dependence of buckling on tube length is consistent with the analysis of equivalent continuum structures using Euler buckling theory.

Wang, Zhiguo; Gao, Fei; Zu, Xiaotao; Weber, William J.

2008-07-25T23:59:59.000Z

416

Near-infrared InN quantum dots on high-In composition InGaN  

SciTech Connect (OSTI)

We report the growth of InN quantum dots (QDs) on thick InGaN layers with high In composition (>50%) by molecular beam epitaxy. Optimized growth conditions are identified for the InGaN layers at reduced growth temperature and increased active N flux resulting in minimized phase separation and defect generation. The InN QDs grown on top of the optimized InGaN layer exhibit small size, high density, and photoluminescence up to room temperature. The InN/InGaN QDs reveal excellent potential for intermediate band solar cells with the InGaN and InN QD bandgap energies tuned to the best match of absorption to the solar spectrum.

Soto Rodriguez, Paul E. D.; Gomez, Victor J.; Kumar, Praveen; Calleja, Enrique; Noetzel, Richard [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)] [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

2013-04-01T23:59:59.000Z

417

Ionic conductivity and dielectric relaxation in {gamma}-irradiated TlGaTe{sub 2} crystals  

SciTech Connect (OSTI)

The switching effect, field and temperature dependences of the permittivity and conductivity of TlGaTe{sub 2} crystals subjected to various {gamma}-irradiation doses are studied. Under rather low electric fields, the phenomenon of threshold switching with an S-shaped current-voltage characteristic containing a portion with negative differential resistance is observed in the crystals. In the region of critical voltages, current and voltage oscillations and imposed modulation are observed. Possible mechanisms of switching, ionic conductivity, disorder, and electrical instability in TlGaTe{sub 2} crystals are discussed.

Sardarli, R. M., E-mail: sardarli@yahoo.com; Samedov, O. A.; Abdullayev, A. P. [National Academy of Sciences of Azerbaijan, Institute of Radiation Problems (Azerbaijan); Huseynov, E. K. [National Academy of Sciences of Azerbaijan, Institute of Physics (Azerbaijan); Salmanov, F. T.; Alieva, N. A.; Agaeva, R. Sh. [National Academy of Sciences of Azerbaijan, Institute of Radiation Problems (Azerbaijan)

2013-05-15T23:59:59.000Z

418

Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors  

E-Print Network [OSTI]

by the energy cost of flipping one MnGa moment, which can be calculated for a given chemical composition.50 This effec- tive field Hef f corresponds to HMF in the semi- phenomenological kinetic-exchange model used in the previ- ous section, i.e., k... by the energy cost of flipping one MnGa moment, which can be calculated for a given chemical composition.50 This effec- tive field Hef f corresponds to HMF in the semi- phenomenological kinetic-exchange model used in the previ- ous section, i.e., k...

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.

2005-01-01T23:59:59.000Z

419

Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs  

SciTech Connect (OSTI)

We demonstrate second harmonic generation at telecommunications wavelengths in photonic crystal cavities in (111)-oriented GaAs. We fabricate 30 photonic crystal structures in both (111)- and (100)-oriented GaAs and observe an increase in generated second harmonic power in the (111) orientation, with the mean power increased by a factor of 3, although there is a large scatter in the measured values. We discuss possible reasons for this increase, in particular, the reduced two photon absorption for transverse electric modes in (111) orientation, as well as a potential increase due to improved mode overlap.

Buckley, Sonia, E-mail: bucklesm@stanford.edu; Radulaski, Marina; Vu?kovi?, Jelena [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States)] [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States); Biermann, Klaus [Paul-Drude-Institut fr Festkrperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)] [Paul-Drude-Institut fr Festkrperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

2013-11-18T23:59:59.000Z

420

Ferromagnetic transition temperature enhancement in (Ga,Mn)As semiconductors by carbon codoping  

E-Print Network [OSTI]

by a recent experimental observation of a marked enhancement of the Curie temperature in Mn-implanted GaAs:C samples compared to the Mn-implanted undoped GaAs layers.11 We focus on two key issues related to high-density carbon dop- ing. ~i.... Jungwirth,1,2 J. Mas?ek,3 Jairo 1Institute of Physics ASCR, Cukrovarnick 2University of Texas at Austin, Physics Department, 1 U 3Institute of Physics ASCR, Na Slovanc 4Department of Physics, Texas A&M Universit ~Received 23 June 2003; revised...

Jungwirth, T.; Masek, J.; Sinova, Jairo; MacDonald, AH.

2003-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Density-functional electronic structure of PuCoGa5  

Science Journals Connector (OSTI)

Density-functional electronic-structure calculations for PuCoGa5 are performed to address the possibility of magnetic interactions in this high-temperature superconductor. Within an itinerant 5f-electron picture, cohesion and crystallographic parameters compares favorably with experiment, whereas only when spin and orbital interactions are accounted for the calculated electronic density of states agrees with photoemission spectra. This fact suggests that spin and orbital correlations are important for a correct description of the PuCoGa5 electronic structure and may play a role in an unconventional mechanism for superconductivity.

P. Sderlind

2004-09-24T23:59:59.000Z

422

Wafer-fused p-i-n InGaAs/Si photodiode with photogain  

SciTech Connect (OSTI)

Using high temperature fusion of InGaAs/InP on Si, we demonstrated an InGaAs/Si p-i-n photodiode with a photomultiplication gain of 11 at relatively low bias of -15 V. The photodiode exhibited a dark current of 30 nA at -5 V, and a responsivity of 0.3 A/W at 1.32 {mu}m wavelength without antireflection coating. The measured device behavior were consistent with that predicted by a model of charged interface states resulting from the fusion. {copyright} 2001 American Institute of Physics.

Kang, Y.; Mages, P.; Clawson, A. R.; Lau, S. S.; Lo, Y. H.; Yu, P. K. L.; Pauchard, A.; Zhu, Z.; Zhou, Y.

2001-08-13T23:59:59.000Z

423

THz laser based on quasi-periodic AlGaAs superlattices  

SciTech Connect (OSTI)

The use of quasi-periodic AlGaAs superlattices as an active element of a quantum cascade laser of terahertz range is proposed and theoretically investigated. A multi-colour emission, having from three to six peaks of optical gain, is found in Fibonacci, Thue-Morse, and figurate superlattices in electric fields of intensity F = 11 - 13 kV cm{sup -1} in the frequency range f = 2 - 4 THz. The peaks depend linearly on the electric field, retain the height of 20 cm{sup -1}, and strongly depend on the thickness of the AlGaAs-layers. (lasers)

Malyshev, K V [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

2013-06-30T23:59:59.000Z

424

Efficient vertical coupling of photodiodes to InGaAsP rib waveguides  

SciTech Connect (OSTI)

We demonstrate vertical integration of InGaAs mesa photodiodes with InGaAsP rib waveguides employing an intermediate optical impedance matching layer. The diode length necessary for 90% light absorption at 1.52 {mu}m wavelength was 42 {mu}m, a threefold reduction in diode length with respect to previous work employing similar waveguides without a matching layer. The quantum efficiency was observed to be almost independent of the optical wavelength and polarization. The influence of spatial transient intensity redistribution effects on these devices is investigated in detail.

Deri, R.J.; Doldissen, W.; Hawkins, R.J.; Bhat, R.; Soole, J.B.D.; Schiavone, L.M.; Seto, M.; Andreadakis, N.; Silberberg, Y.; Koza, M.A. (Bellcore, 331 Newman Springs Road, Red Bank, New Jersey 07701-7040 (USA))

1991-06-17T23:59:59.000Z

425

Localization of degradation in InP/InGaAsP mushroom stripe lasers  

SciTech Connect (OSTI)

The rapid degradation observed in InP/InGaAsP mushroom stripe lasers covered with phosphosilicate glass (PSG) was investigated by comparing the light-current characteristics as a function of the preparation technique. We were able to show that the PSG-covering layer is not the reason for the rapid degradation. By inspecting the light-current characteristics before and after degradation and by additional underetching the laser structure after degradation we were able to localize the degraded regions on the open side walls of the InGaAsP active layer.

Jung, H.; Marschall, P.

1987-07-13T23:59:59.000Z

426

High excitation power photoluminescence studies of ultra-low density GaAs quantum dots  

SciTech Connect (OSTI)

We fabricate GaAs epitaxial quantum dots (QDs) by filling of self-organized nanoholes in AlGaAs. The QDs are fabricated under optimized process conditions and have ultra-low density in the 10{sup 6} cm{sup ?2} regime. At low excitation power the optical emission of single QDs exhibit sharp excitonic lines, which are attributed to the recombination of excitonic and biexcitonic states. High excitation power measurements reveal surprisingly broad emission lines from at least six QD shell states.

Sonnenberg, D.; Graf, A.; Paulava, V.; Heyn, Ch.; Hansen, W. [Institut fr Angewandte Physik und Zentrum fr Mikrostrukturforschung, Universitt Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany)

2013-12-04T23:59:59.000Z

427

Biexciton emission from single isoelectronic traps formed by nitrogen-nitrogen pairs in GaAs  

SciTech Connect (OSTI)

We have studied photoluminescence (PL) from individual isoelectronic traps formed by nitrogen-nitrogen (NN) pairs in GaAs. Sharp emission lines due to exciton and biexciton were observed from individual isoelectronic traps in nitrogen atomic-layer doped (ALD) GaAs. The binding energy of biexciton bound to individual isoelectronic traps was approximately 8 meV. Both the exciton and biexciton luminescence lines show completely random polarization and no fine-structure splitting. These results are desirable to the application to the quantum cryptography used in the field of quantum information technology.

Takamiya, Kengo; Fukushima, Toshiyuki; Yagi, Shuhei; Hijikata, Yasuto; Yaguchi, Hiroyuki [Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku , Saitama 338-8570 (Japan); Mochizuki, Toshimitsu; Yoshita, Masahiro; Akiyama, Hidefumi [Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Kuboya, Shigeyuki; Onabe, Kentaro [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Katayama, Ryuji [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

2013-12-04T23:59:59.000Z

428

Selective etching of dislocations in GaN grown by low-pressure solution growth  

Science Journals Connector (OSTI)

This work presents an experimental study on the identification and quantification of different types of dislocations in GaN grown by low-pressure solution growth. A reliable defect selective etching procedure in a NaOH-KOH melt is developed and validated using transmission electron microscopy that permits to define groups of etch pits that belong each to dislocations with a specific Burgers vector. This way a comparably fast method is provided for determining the total, the specific dislocation densities and the type of dislocation in a statistically representative way. The results for the solution grown samples are compared to those obtained for MOCVD GaN.

I.Y. Knoke; P. Berwian; E. Meissner; J. Friedrich; H.P. Strunk; G. Mller

2010-01-01T23:59:59.000Z

429

Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials  

SciTech Connect (OSTI)

Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

Nicholson, Don M [ORNL; Odbadrakh, Khorgolkhuu [ORNL; Shassere, Benjamin [ORNL; Rios, Orlando [ORNL; Hodges, Jason P [ORNL; Ludtka, Gerard Michael [ORNL; Porter, Wallace D [ORNL; Safa-Sefat, Athena [ORNL; Rusanu, Aurelian [ORNL; Brown, Greg [ORNL; Evans III, Boyd Mccutchen [ORNL

2014-01-01T23:59:59.000Z

430

Ge doped GaN with controllable high carrier concentration for plasmonic applications  

SciTech Connect (OSTI)

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

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

2013-12-09T23:59:59.000Z

431

Shot noise at the quantum point contact in InGaAs heterostructure  

SciTech Connect (OSTI)

We study the shot noise at a quantum point contact (QPC) fabricated in an InGaAs/InGaAsP heterostructure, whose conductance can be electrically tuned by the gate voltages. Shot noise suppression is observed at the conductance plateau of N(2e{sup 2}/h) (N = 4,5,and 6), which indicates the coherent quantized channel formation in the QPC. The electron heating effect generated at the QPC explains the deviation of the observed Fano factor from the theory.

Nishihara, Yoshitaka; Nakamura, Shuji; Ono, Teruo [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Kobayashi, Kensuke [Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Kohda, Makoto [Department of Materials Science, Tohoku University, 6-6-02 Aramaki-aza Aoba, Aoba-ku, Sendai 980-8579, Japan and PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Nitta, Junsaku [Department of Materials Science, Tohoku University, 6-6-02 Aramaki-aza Aoba, Aoba-ku, Sendai 980-8579 (Japan)

2013-12-04T23:59:59.000Z

432

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

SciTech Connect (OSTI)

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

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

2014-09-01T23:59:59.000Z

433

Magnetic and electronic properties of the ferromagnetic Kondo-lattice system Np2PdGa3  

Science Journals Connector (OSTI)

Intermetallic compounds Lu2PdGa3 and Np2PdGa3 have been found to crystallize in an orthorhombic CeCu2-type structure with the Imma space group. The lattice parameters at room temperature are: a=0.4382(2), b=0.6870(3), and c=0.7593(3)?nm for Lu2PdGa3 and a=0.4445(2), b=0.7089(3), and c=0.7691(3)?nm for Np2PdGa3. The electronic ground-state properties of these compounds were established by magnetic, calorimetric, electrical resistivity, magnetoresistance, and Hall coefficient measurements. The experimental data reveal a metallic behavior for Pauli paramagnetic Lu2PdGa3, characterized by Sommerfeld ratio ?=2.5?mJ/K2?mol?Lu and temperature-independent susceptibility ?0?110?4?emu/mol. In contrast to the nonmagnetic Lu2PdGa3 reference, Np2PdGa3 behaves as a local-moment ferromagnet with the Curie temperature TC=62.5(2)?K. Low-temperature properties of Np2PdGa3 are characterized by a large Sommerfeld ratio ?=120(2)?mJ/K2?mol?Np and a small Fermi momentum kF=0.44??1. The observed features in Np2PdGa3 are well interpreted by assuming competition of three different interactions: Rudermann-Kittel-Kasuya-Yosida (RKKY), crystal electric field (CEF) and Kondo effect, which are represented by respective energies kBTRKKY, ?CEF, and kBTK. We argue that Np2PdGa3 is the Np-based ferromagnetic Kondo-lattice system with TK

V. H. Tran; J.-C. Griveau; R. Eloirdi; W. Miiller; E. Colineau

2010-09-03T23:59:59.000Z

434

Exciton relaxation and coupling dynamics in a GaAs/AlxGa1-xAs quantum well and quantum dot ensemble  

Science Journals Connector (OSTI)

Exciton inter- and intra-actions in a GaAs/AlGaAs quantum well (QW) and quantum dot (QD) ensemble are studied using optical two-dimensional Fourier transform spectroscopy. We measure population dynamics for times up to 300 ps and temperatures up to 50 K and observe biexponential decay for both QW and QD excitons, strong QW ? QD relaxation, and weak QD ? QW activation. The population dynamics are modeled using a system of rate equations that incorporate radiative and nonradiative decay, coupling between bright and dark exciton states, and QW ? QD coupling. The fast decay rates are attributed to exciton-bound hole spin flips between optically active and inactive states and are similar for the QW and QDs, indicating excitons are weakly localized in the QDs. The QW ? QD relaxation rate increases with temperature, and QD ? QW excitation is observed at temperatures ?35 K.

G. Moody; M. E. Siemens; A. D. Bristow; X. Dai; A. S. Bracker; D. Gammon; S. T. Cundiff

2011-06-27T23:59:59.000Z

435

Mid-infrared pump-related electric-field domains in GaAs/(Al,Ga)As quantum-cascade structures for terahertz lasing without population inversion  

SciTech Connect (OSTI)

We investigate the effect of mid-infrared (MIR) pumping on the transport properties of GaAs/(Al,Ga)As terahertz (THz) quantum lasers (TQLs), which rely on quantum coherence effects of intersubband transitions. Aiming at THz lasing at elevated temperatures, we extend the concept of THz gain with and without population inversion of a single, MIR-pumped, electrically driven THz stage proposed by Waldmueller et al.[Phys. Rev. Lett. 99, 117401 (2007)] to an entire TQL. However, experiments using a CO{sub 2} as well as a free-electron laser and numerical simulations show that this resonant MIR pumping causes a negative differential conductivity (NDC) in addition to the NDC caused by sequential tunneling. Lasing of these TQLs is prevented by the formation of electric-field domains below the resonance field strength for gain of each single THz stage.

Giehler, M.; Wienold, M.; Schrottke, L.; Hey, R.; Grahn, H. T. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Pavlov, S. G. [Deutsches Zentrum fuer Luft- und Raumfahrt, Rutherfordstr. 2, 12489 Berlin (Germany); Huebers, H.-W. [Deutsches Zentrum fuer Luft- und Raumfahrt, Rutherfordstr. 2, 12489 Berlin (Germany); Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Winnerl, S.; Schneider, H. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden (Germany)

2011-11-15T23:59:59.000Z

436

High Peak-to-Valley Current Ratio GaAs/InGaAs/InAs Double Stepped Quantum Well Resonant Interband Tunneling Diodes at Room Temperature  

Science Journals Connector (OSTI)

A high ratio of the peak current density to the valley current density of current-voltage characteristic is accomplished for the double stepped quantum well resonant interband tunneling diode (DSQW RITD). Results for good quantum confinement effect and long drift layer with deep quantum well GaAs/In0.59Ga0.41As/InAs DSQW RITD that has a lower valley current density of about 0.98 A/cm2 and a higher peak-to-valley current ratio (PVCR) reached 622 at room temperature than conventionally designed double quantum well resonant interband tunneling diodes (DQW RITDs) are presented. This PVCR value is also the highest value than those of the other resonant tunneling diodes.

Chih-Chin Yang; Kuang-Chih Huang; Yan-Kuin Su

1996-01-01T23:59:59.000Z

437

Magneto-optics of the spatially separated electron and hole layers in GaAs/AlxGa1-xAs coupled quantum wells  

Science Journals Connector (OSTI)

We report on the magneto-optical study of the spatially separated electron and hole layers in GaAs/AlxGa1-xAs coupled quantum wells at low temperatures T>~50 mK and high magnetic fields B<~16 T. At high magnetic fields cusps are observed in the energy and intensity of the indirect (interwell) exciton photoluminescence. We tentatively attribute these to the commensurability effects of the magnetoexciton with island structures in the sample. The indirect exciton lifetime is found to increase with magnetic field. The increase is attributed to the reduction of indirect exciton localization area caused by the increase of the magnetoexciton mass. The indirect exciton photoluminescence energy is found to enhance with density, which reflects the net repulsive interaction between indirect excitons.

L. V. Butov, A. A. Shashkin, V. T. Dolgopolov, K. L. Campman, and A. C. Gossard

1999-09-15T23:59:59.000Z

438

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

SciTech Connect (OSTI)

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

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

2014-06-23T23:59:59.000Z

439

Issues associated with the metalorganic chemical vapor deposition of ScGaN and YGaN alloys.  

SciTech Connect (OSTI)

The most energy efficient solid state white light source will likely be a combination of individually efficient red, green, and blue LED. For any multi-color approach to be successful the efficiency of deep green LEDs must be significantly improved. While traditional approaches to improve InGaN materials have yielded incremental success, we proposed a novel approach using group IIIA and IIIB nitride semiconductors to produce efficient green and high wavelength LEDs. To obtain longer wavelength LEDs in the nitrides, we attempted to combine scandium (Sc) and yttrium (Y) with gallium (Ga) to produce ScGaN and YGaN for the quantum well (QW) active regions. Based on linear extrapolation of the proposed bandgaps of ScN (2.15 eV), YN (0.8 eV) and GaN (3.4 eV), we expected that LEDs could be fabricated from the UV (410 nm) to the IR (1600 nm), and therefore cover all visible wavelengths. The growth of these novel alloys potentially provided several advantages over the more traditional InGaN QW regions including: higher growth temperatures more compatible with GaN growth, closer lattice matching to GaN, and reduced phase separation than is commonly observed in InGaN growth. One drawback to using ScGaN and YGaN films as the active regions in LEDs is that little research has been conducted on their growth, specifically, are there metalorganic precursors that are suitable for growth, are the bandgaps direct or indirect, can the materials be grown directly on GaN with a minimal defect formation, as well as other issues related to growth. The major impediment to the growth of ScGaN and YGaN alloys was the low volatility of metalorganic precursors. Despite this impediment some progress was made in incorporation of Sc and Y into GaN which is detailed in this report. Primarily, we were able to incorporate up to 5 x 10{sup 18} cm{sup -3} Y atoms into a GaN film, which are far below the alloy concentrations needed to evaluate the YGaN optical properties. After a no-cost extension was granted on this program, an additional more 'liquid-like' Sc precursor was evaluated and the nitridation of Sc metals on GaN were investigated. Using the Sc precursor, dopant level quantities of Sc were incorporated into GaN, thereby concluding the growth of ScGaN and YGaN films. Our remaining time during the no-cost extension was focused on pulsed laser deposition of Sc metal films on GaN, followed by nitridation in the MOCVD reactor to form ScN. Finally, GaN films were deposited on the ScN thin films in order to study possible GaN dislocation reduction.

Koleske, Daniel David; Knapp, James Arthur; Lee, Stephen Roger; Crawford, Mary Hagerott; Creighton, James Randall; Cross, Karen Charlene; Thaler, Gerald

2009-07-01T23:59:59.000Z

440

Theoretical and Experimental Examination of the Intermediate-Band Concept for Strain-Balanced (In,Ga)As/Ga(As,P) Quantum Dot Solar Cells  

SciTech Connect (OSTI)

The intermediate-band solar cell (IBSC) concept has been recently proposed to enhance the current gain from the solar spectrum while maintaining a large open-circuit voltage. Its main idea is to introduce a partially occupied intermediate band (IB) between the valence band (VB) and conduction band (CB) of the semiconductor absorber, thereby increasing the photocurrent by the additional VB {yields} IB and IB {yields} CB absorptions. The confined electron levels of self-assembled quantum dots (QDs) were proposed as potential candidates for the implementation of such an IB. Here we report experimental and theoretical investigations on In{sub y}Ga{sub 1-y}As dots in a GaAs{sub 1-x}P{sub x} matrix, examining its suitability for acting as IBSCs. The system has the advantage of allowing strain symmetrization within the structure, thus enabling the growth of a large number of defect-free QD layers, despite the significant size mismatch between the dot material and the surrounding matrix. We examine the various conditions related to the optimum functionality of the IBSC, in particular those connected to the optical and electronic properties of the system. We find that the intensity of absorption between QD-confined electron states and host CB is weak because of their localized-to-delocalized character. Regarding the position of the IB within the matrix band gap, we find that, whereas strain symmetrization can indeed permit growth of multiple dot layers, the current repertoire of GaAs{sub 1-x}P{sub x} barrier materials, as well as In{sub y}Ga{sub 1-y} As dot materials, does not satisfy the ideal energetic locations for the IB. We conclude that other QD systems must be considered for QD-IBSC implementations.

Popescu, V.; Bester, G.; Hanna, M. C.; Norman, A. G.; Zunger, A.

2008-11-01T23:59:59.000Z

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441

High?quality focused?ion?beam?made mirrors for InGaP/InGaAlP visible?laser diodes  

Science Journals Connector (OSTI)

We employed a focused ion beam(FIB) to sputter the end mirrors on InGaP/InGaAlP laser diodes. This particular diode operates at a wavelength of about 670 nm. For this wavelength the quality of the sputteredmirrors is far more critical than for longer wavelength devices. The present lasers do in fact show a relatively large increase in their threshold current after FIBmicromachining. In this article we investigate the origins of this increase and how to prevent it. After optimization the lasers with a FIB?made end mirror have a threshold current comparable to that of cleaved?facet devices. We have seen that the polycrystalline structure of the device metallization on top of the laser diode causes roughening of the mirror during sputtering which results in severe scatter losses of the laser light. A method to decrease the surface roughness is given. A further reason for the increase in threshold current is optical absorption at the mirror presumably by a Ga?rich layer. This can be circumvented by chemical etching after FIB treatment to remove the absorbing layer. Finally to demonstrate the quality and the applicability of the FIB?made mirrors the influence of the tilt angle of the end mirror on the threshold current of the laser has been investigated. This dependency can be excellently described by theory.

M. H. F. Overwijk; J. A. de Poorter

1993-01-01T23:59:59.000Z

442

Transport mechanism of ?- and X-band electrons in AlxGa1-xAs/AlAs/GaAs double-barrier quantum-well infrared photodetectors  

Science Journals Connector (OSTI)

The effect of the ?- and X-band electrons in the Al0.25Ga0.75As/AlAs/GaAs double-barrier quantum well (DBQW) is investigated by a microscopic empirical pseudopotential calculation. The DBQW structure used in the calculation is designed as a 35-?m quantum-well infrared photodetector with an associated transition energy of 313 meV. DBQW tunneling transmission via ?- and X-like states as a function of electron energy and applied voltage are described and compared to that in a single-barrier AlAs/GaAs quantum well. The dark current is simulated by the confined ground-state electron tunneling out of the well. We find that, at high-bias voltage, tunneling via X-like states increases the current by a few orders of magnitude. We have also varied the additional barrier thickness and found that for a very thin (<20 ) additional barrier DBQW, the excited-state electrons are not blocked by the ?-band barrier, and may give a high photocurrent without the assistance of the X band, although the dark current also increases. 1996 The American Physical Society.

T. Osotchan; V. W. L. Chin; T. L. Tansley

1996-07-15T23:59:59.000Z

443

Magnetotransport studies of AlGaN/GaN heterostructures with two-dimensional electron gas in parallel with a three-dimensional Al-graded layer: Incorrect hole type determination  

Science Journals Connector (OSTI)

We report magnetotransport measurements performed on AlGaN/GaN devices with different buffer layers. Standard samples with a 1??m thick GaN buffer show a linear Hall resistance and an almost constant magnetoresistance as expected from a single two-dimensional electron gas (2DEG) at the AlGaN/GaN interface. Other samples with an Al x Ga1 x N buffer (x?=?5%) and a buried linear aluminium gradient have an additional three-dimensional electron slab (3DES) close to the GaN substrate. In this case the Hall resistance is strongly non-linear and presents an incorrect hole-type carrier signature evidenced by low field mobility spectrum analysis. This effect is strengthened when the 3D layer parallel to the mesa-etched 2DEG is infinite. We suggest that the misplacement of the electrical contacts in the 3DES i.e. far from the sample edges could explain the wrong carrier type determination.

L. Konczewicz

2013-01-01T23:59:59.000Z

444

Materials for light-induced water splitting: In situ controlled surface preparation of GaPN epilayers grown lattice-matched on Si(100)  

SciTech Connect (OSTI)

Energy storage is a key challenge in solar-driven renewable energy conversion. We promote a photochemical diode based on dilute nitride GaPN grown lattice-matched on Si(100), which could reach both high photovoltaic efficiencies and evolve hydrogen directly without external bias. Homoepitaxial GaP(100) surface preparation was shown to have a significant impact on the semiconductor-water interface formation. Here, we grow a thin, pseudomorphic GaP nucleation buffer on almost single-domain Si(100) prior to GaPN growth and compare the GaP{sub 0.98}N{sub 0.02}/Si(100) surface preparation to established P- and Ga-rich surfaces of GaP/Si(100). We apply reflection anisotropy spectroscopy to study the surface preparation of GaP{sub 0.98}N{sub 0.02} in situ in vapor phase epitaxy ambient and benchmark the signals to low energy electron diffraction, photoelectron spectroscopy, and x-ray diffraction. While the preparation of the Ga-rich surface is hardly influenced by the presence of the nitrogen precursor 1,1-dimethylhydrazine (UDMH), we find that stabilization with UDMH after growth hinders well-defined formation of the V-rich GaP{sub 0.98}N{sub 0.02}/Si(100) surface. Additional features in the reflection anisotropy spectra are suggested to be related to nitrogen incorporation in the GaP bulk.

Supplie, Oliver, E-mail: oliver.supplie@tu-ilmenau.de [Technische Universitt Ilmenau, Institut fr Physik, Gustav-Kirchhoff-Str. 5, 98684 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institute for Solar Fuels, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Humboldt-Universitt zu Berlin, Institut fr Physik, Newtonstr. 15, 12489 Berlin (Germany); May, Matthias M.; Stange, Helena [Helmholtz-Zentrum Berlin, Institute for Solar Fuels, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Humboldt-Universitt zu Berlin, Institut fr Physik, Newtonstr. 15, 12489 Berlin (Germany); Hhn, Christian [Helmholtz-Zentrum Berlin, Institute for Solar Fuels, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Lewerenz, Hans-Joachim [Helmholtz-Zentrum Berlin, Institute for Solar Fuels, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); California Institute of Technology, Joint Center for Artificial Photosynthesis, 1200 East California Boulevard, Pasadena, California 91125 (United States); Hannappel, Thomas [Technische Universitt Ilmenau, Institut fr Physik, Gustav-Kirchhoff-Str. 5, 98684 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institute for Solar Fuels, Hahn-Meitner-Platz 1, 14109 Berlin (Germany)

2014-03-21T23:59:59.000Z

445

Dry, laser?assisted rapid HBr etching of GaAs  

Science Journals Connector (OSTI)

Dry rapid etching of GaAs has been accomplished using an excimer laser (ArF 193 nm) with HBr etching gas by photochemical initiation. Spatially uniform etch rates of up to 8 ?m/min have been achieved on large?area masked substrates. Selective crystallographic etching is observed and controlled in the process.

P. D. Brewer; D. McClure; R. M. Osgood Jr.

1985-01-01T23:59:59.000Z

446

Modeling the Last Mile of the Smart Grid G.A. Pagani  

E-Print Network [OSTI]

Modeling the Last Mile of the Smart Grid G.A. Pagani Johann Bernoulli Institute of Mathematics in the grid and allowing for micro-production to be part of the smart grid. Such changes will have a major- archical, unidirectional and capillary, though the new smart grid scenario calls for an infrastructure

Aiello, Marco

447

Photoconductivity and luminescence in GaSe crystals at high levels of optical excitation  

SciTech Connect (OSTI)

The photoconductivity and luminescence of GaSe layered crystals at high levels of optical excitation are studied experimentally. The specific features observed in the photoconductivity and photoluminescence spectra are controlled by the nonlinear optical absorption in the region of excitonic resonance.

Kyazym-zade, A. G.; Salmanov, V. M., E-mail: vagif_salmanov@yahoo.com; Salmanova, A. A. [Baku State University (Azerbaijan); Alieva, A. M.; Ibaeva, R. Z. [National Academy of Sciences, Institute of Physics (Azerbaijan)

2010-03-15T23:59:59.000Z

448

Siting and sizing of distributed generation units using GA and OPF  

Science Journals Connector (OSTI)

This paper deals with the important task of finding the optimal siting and sizing of Distributed Generation (DG) units for a given distribution network so that the cost of active and reactive power generation can be minimized. The optimization technique ... Keywords: distributed generation, genetic alghorithm(GA), optimal power flow(OPF)

M. Hosseini Aliabadi; M. Mardaneh; B. Behbahan

2008-01-01T23:59:59.000Z

449

Nonstoichiometry and chemical purity effects in thermoelectric Ba 8 Ga 16 Ge 30 clathrate  

Science Journals Connector (OSTI)

Zone melting purification experiments have been carried out on the clathrate Ba 8 Ga 16 Ge 30 . The impurities present have been identified and their approximate concentrations measured. Trace impurities were determined to be approximately 240 parts per million (ppm) in the most impure sample to 17 ppm in the most pure sample. The temperature-dependent Seebeck coefficient thermal conductivity and electrical conductivity are reported as a function of sample purity as well as the room-temperature Hall coefficient. Microprobe analysis suggests that the samples are nonstoichiometric with excess Ge relative to Ga and there are indications of the presence of defects. Single-crystal x-ray investigations as well as synchrotron powderdiffraction measurements support the presence of defects but the x-ray data cannot accurately determine the relative amounts of Ga and Ge. Band-structure calculations in the generalized gradient approximation show that the measured Hall and Seebeck coefficients are consistent with a defect lattice of approximate stoichiometry Ba 8 Ga 14 Ge 31 . Although the figure of merit (ZT) is found to be the highest for the purest sample the dominant contribution to transport is conjectured to arise from deviations from the ideal stoichiometry and not impurities.

J. Daniel Bryan; Nick P. Blake; Horia Metiu; Galen D. Stucky; Bo B. Iversen; Rasmus D. Poulsen; Anders Bentien

2002-01-01T23:59:59.000Z

450

GaInAsP Microdisk Injection Laser with Benzocyclobutene Polymer Cladding and Its Athermal Effect  

E-Print Network [OSTI]

GaInAsP Microdisk Injection Laser with Benzocyclobutene Polymer Cladding and Its Athermal Effect, which decreased the fragility and the thermal resistance of the conventional air cladding device and simplified the current injection using the metal pad electrode. The threshold current for a 7-m

Baba, Toshihiko

451

High Resolution Parameter Space from a Two Level Model on Semi-Insulating GaAs  

E-Print Network [OSTI]

Semi-insulating Gallium Arsenide (SI-GaAs) samples experimentally show, under high electric fields and even at room temperature, negative differential conductivity in N-shaped form (NNDC). Since the most consolidated model for n-GaAs, namely, "the model", proposed by E. Scholl was not capable to generate the NNDC curve for SI-GaAs, in this work we proposed an alternative model. The model proposed, "the two-valley model" is based on the minimal set of generation recombination equations for two valleys inside of the conduction band, and an equation for the drift velocity as a function of the applied electric field, that covers the physical properties of the nonlinear electrical conduction of the SI-GaAs system. The "two valley model" was capable to generate theoretically the NNDC region for the first time, and with that, we were able to build a high resolution parameter-space of the periodicity (PSP) using a Periodicity-Detection (PD) routine. In the parameter space were observed self-organized periodic structu...

da Silva, S L; de Oliveira, A G; Ribeiro, G M; da Silva, R L

2014-01-01T23:59:59.000Z

452

DOE Zero Energy Ready Home Case Study: The Imery Group, Serenbe, GA  

Broader source: Energy.gov [DOE]

Case study of a DOE Zero Energy Ready home in Serenbe, GA, that scored a HERS 40 without PV or HERS -10 with PV. The 2,811-ft2, two-story custom home has 2x6, advanced framed walls filled with R-20...

453

Difference-frequency generation in AlGaAs Bragg reflection waveguides  

E-Print Network [OSTI]

-matching (BPM) [5,6] and quasi-phase-matching [7,8]. Among these, BPM has been shown to be the most efficient with the absorption of GaAs below 870 nm in wavelength, limits the operating window of BPM devices for infrared

454

Thermophotovoltaic furnacegenerator for the home using low bandgap GaSb cells  

Science Journals Connector (OSTI)

It is well known that distributed combined heat and power (CHP) systems for commercial and industrial buildings are economically desirable because they conserve energy. Here, a thermophotovoltaic (TPV) unit is described that brings CHP into the home providing both heat and electric power by replacing the typical home heating furnace with a combined TPV furnacegenerator. First, the design of a 1.5 kWelectric/12.2 kWthermal TPV furnacegenerator is described along with the key components that make it possible. Diffused junction GaSb cells are one of these key components. Secondly, an economic cost target is determined for this system where the cost of the photovoltaic array will be key to the economical implementation of this concept. Finally, it is argued that the GaSb cells and arrays can be manufactured at the required low cost. The cost target can be reached because the GaSb cells in the TPV furnacegenerator can produce an electrical power density of 1 W cm?2 which is 100 times higher than the typical solar cell. The cost target can also be reached because the GaSb cell fabrication process parallels the silicon solar cell process where no toxic gases are used, no wafer polish is required and cast polycrystalline cells can be used.

L M Fraas; J E Avery; H X Huang

2003-01-01T23:59:59.000Z

455

Measuring and mi-ga-ng impact of offshore oil development on  

E-Print Network [OSTI]

Measuring and mi-ga-ng impact of offshore oil development on seabirds and other effects are concentrated in the offshore ­ vicinity of the oil field J. 2001. Seabirds at risk around offshore oil pla=orms in the north

Jones, Ian L.

456

Observation of the potential distribution in GaN-based devices by a scanning electron microscope  

Science Journals Connector (OSTI)

......potential. On the other hand, higher accelerating voltages resulted in blurred images. The second sample was a light emitting diode structure based on AlN where a multiple quantum well (MQW) structure was sandwiched by p- and n-AlGaN materials......

Takahiro Karumi; Shigeyasu Tanaka; Takayoshi Tanji

2014-11-01T23:59:59.000Z

457

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

E-Print Network [OSTI]

Near perfect solar absorption in ultra-thin-film GaAs photonic crystals Sergey Eyderman,*a Alexei Deinegaa and Sajeev Johnab We present designs that enable a significant increase of solar absorption­99.5% solar absorption is demonstrated depending on the photonic crystal architecture used and the nature

John, Sajeev

458

Identification of As-vacancy complexes in Zn-diffused GaAs  

SciTech Connect (OSTI)

We have used positron annihilation spectroscopy to study the introduction of point defects in Zn-diffused semi-insulating GaAs. The diffusion was performed by annealing the samples for 2 h at 950 Degree-Sign C. The samples were etched in steps of 7 {mu}m. Both Doppler broadening using slow positron beam and lifetime spectroscopy studies were performed after each etching step. Both techniques showed the existence of vacancy-type defects in a layer of about 45 {mu}m. Secondary ion mass spectroscopy measurements illustrated the presence of Zn at high level in the sample almost up to the same depth. Vacancy-like defects as well as shallow positron traps were observed by lifetime measurements. We distinguish two kinds of defects: As vacancy belongs to defect complex, bound to most likely one Zn atom incorporated on Ga sublattice, and negative-ion-type positron traps. Zn acceptors explained the observation of shallow traps. The effect of Zn was evidenced by probing GaAs samples annealed under similar conditions but without Zn treatment. A defect-free bulk lifetime value is detected in this sample. Moreover, our positron annihilation spectroscopy measurements demonstrate that Zn diffusion in GaAs system is governed by kick-out mechanism.

Elsayed, M. [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Department of Physics, Faculty of Science, Minia University, 61519 Minia (Egypt); Krause-Rehberg, R. [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Korff, B. [Bremen Center for Computational Materials Science, University Bremen, 28359 Bremen (Germany); Richter, S. [Fraunhofer Center for Silicon Photovoltaics CSP, 06120 Halle (Saale) (Germany); Leipner, H. S. [Center of Materials Science, Martin Luther University Halle, 06099 Halle (Germany)

2013-03-07T23:59:59.000Z

459

Winnowing Wheat from Chaff: The Chunking GA Hal Stringer and Annie S. Wu  

E-Print Network [OSTI]

a farmer who separates wheat from the chaff. We refer to this property as the "winnowing effectWinnowing Wheat from Chaff: The Chunking GA Hal Stringer and Annie S. Wu School of Computer Science are then made available to other individuals in the population for evolving potential future solutions. The Ch

Wu, Annie S.

460

GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies  

E-Print Network [OSTI]

LETTERS GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies-frequency electronics3,4 and most forms of optoelectronics5,6 . However, growing large, high quality wafers implementation. More tractable, yet still difficult, problems appear in advanced electronics and optoelectronics

Rogers, John A.

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Optoelectronic Properties of Self-Assembled InAs/InGaAs Quantum SANJAY KRISHNA  

E-Print Network [OSTI]

CHAPTER 10 Optoelectronic Properties of Self-Assembled InAs/InGaAs Quantum Dots SANJAY KRISHNA that exists in zero-dimensional systems but also for their application in electronic and optoelectronic-speed- and opto-electronics". In particular, with the advent of optical fibers and the ever increasing need

Krishna, Sanjay

462

Piezo-Phototronic Effect on Electroluminescence Properties of p-Type GaN Thin Films  

E-Print Network [OSTI]

significance on the practical applications of GaN in optoelectronic devices under a working environment where,9 Recent studies have shown its applications in improving the performance of optoelectronic devices based result in great influence for this most popular III-V semiconductor used in optoelectronic devices

Wang, Zhong L.

463

0.52eV Quaternary InGaAsSb Thermophotovoltaic Diode Technology  

SciTech Connect (OSTI)

Thermophotovoltaic (TPV) diodes fabricated from 0.52eV lattice-matched InGaAsSb alloys are grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on GaSb substrates. 4cm{sup 2} multi-chip diode modules with front-surface spectral filters were tested in a vacuum cavity and attained measured efficiency and power density of 19% and 0.58 W/cm{sup 2} respectively at operating at temperatures of T{sub radiator} = 950 C and T{sub diode} = 27 C. Device modeling and minority carrier lifetime measurements of double heterostructure lifetime specimens indicate that diode conversion efficiency is limited predominantly by interface recombination and photon energy loss to the GaSb substrate and back ohmic contact. Recent improvements to the diode include lattice-matched p-type AlGaAsSb passivating layers with interface recombination velocities less than 100 cm/s and new processing techniques enabling thinned substrates and back surface reflectors. Modeling predictions of these improvements to the diode architecture indicate that conversion efficiencies from 27-30% and {approx}0.85 W/cm{sup 2} could be attained under the above operating temperatures.

MW Dashiell; JF Beausang; G Nichols; DM Depoy; LR Danielson; H Ehsani; KD Rahner; J Azarkevich; P Talamo; E Brown; S Burger; P Fourspring; W Topper; PF Baldasaro; CA Wang; R Huang; M Connors; G Turner; Z Shellenbarger; G Taylor; Jizhong Li; R Marinelli; D Donetski; S Anikeev; G Belenky; S Luryi; DR Taylor; J Hazel

2004-06-09T23:59:59.000Z

464

Electrical properties of Er-doped In0.53Ga0.47As  

E-Print Network [OSTI]

03C117-3 Burke et al. : Electrical properties of Er-doped InElectrical properties of Er-doped In 0.53 Ga 0.47 As PeterBahk and John E. Bowers Electrical and Computer Engineering

Burke, Peter G.; Lu, Hong; Rudawski, Nicholas G.; Gossard, Arthur G.; Bahk, Je-Hyeong; Bowers, John E.

2011-01-01T23:59:59.000Z

465

Highly Responsive Ultrathin GaS Nanosheet Photodetectors on Rigid and Flexible Substrates  

E-Print Network [OSTI]

, 37831, E-mail: xiaok@ornl.gov 4 Nanosystem Research Institute, National Institute of Advanced Industrial Information The GaS laminar precursor was obtained by the following method: The method uses a two-zone horizontal furnace with a fused silica tube, into which the sulfur powder and gallium were placed in the low

Geohegan, David B.

466

Reverse-bias leakage current reduction in GaN Schottky diodes by electrochemical surface treatment  

E-Print Network [OSTI]

Reverse-bias leakage current reduction in GaN Schottky diodes by electrochemical surface treatment Received 15 July 2002; accepted 27 December 2002 An electrochemical surface treatment has been developed to the large power consumption and noise levels that can be present in circuits that incorporate such devices.1

Yu, Edward T.

467

VISIBLE AND INFRARED RARE-EARTH ACTIVATED ELECTROLUMINESCENCE FROM ERBIUM DOPED GaN  

E-Print Network [OSTI]

. At the same time novel work is being conducted using rare earth elements as sources of light emission. Results. III-V semiconductors doped with rare-earth elements have also been used10VISIBLE AND INFRARED RARE-EARTH ACTIVATED ELECTROLUMINESCENCE FROM ERBIUM DOPED GaN M. Garter*, R

Steckl, Andrew J.

468

Improvement of the quality of graphene-capped InAs/GaAs quantum dots  

SciTech Connect (OSTI)

In this paper, we study the transfer of graphene onto InAs/GaAs quantum dots (QDs). The graphene is first grown on Cu foils by chemical vapor deposition and then polymer Polymethyl Methacrylate (PMMA) is deposited on the top of graphene/Cu. High quality graphene sheet has been obtained by lowering the dissolving rate of PMMA using vapor processing. Uncapped as well as capped graphene InAs/GaAs QDs have been studied using optical microscopy, scanning electron microscopy, and Raman spectroscopy. We gather from this that the average shifts ?? of QDs Raman peaks are reduced compared to those previously observed in graphene and GaAs capped QDs. The encapsulation by graphene makes the indium atomic concentration intact in the QDs by the reduction of the strain effect of graphene on QDs and the migration of In atoms towards the surface. This gives us a new hetero-structure grapheneInAs/GaAs QDs wherein the graphene plays a key role as a cap layer.

Othmen, Riadh, E-mail: othmenriadh@yahoo.fr; Rezgui, Kamel; Ajlani, Hosni; Oueslati, Meherzi [Facult des Sciences de Tunis, Universit de Tunis El Manar, Campus, 2092 El Manar Tunis (Tunisia); Cavanna, Antonella; Madouri, Ali [CNRS/LPN, Route de Nozay, F-91460 Marcoussis (France); Arezki, Hakim; Gunes, Fethullah [Laboratoire de Gnie Electrique de Paris, 11, rue Joliot Curie Plateau de Moulon, 91192 Gif sur Yvette (France)

2014-06-07T23:59:59.000Z

469

Electronic structure of Co-Ni-Ga Heusler alloys studied by resonant photoemission  

SciTech Connect (OSTI)

The electronic structures of Co{sub 2.01}Ni{sub 1.05}Ga{sub 0.94} and Co{sub 1.76}Ni{sub 1.46}Ga{sub 0.78} Heusler alloys have been investigated by resonant photoemission spectroscopy across the 3p-3d transition of Co and Ni. For the Ni excess composition Co{sub 1.76}Ni{sub 1.46}Ga{sub 0.78}, the valence band peak shows a shift of 0.25 eV as compared to the near stoichiometric composition Co{sub 2.01}N1{sub 1.05}Ga{sub 0.94}. Also an enhancement is observed in the Ni related satellite features in the valence band for the Ni excess composition. Due to hybridization of Co and Ni 3d states in these systems, the Co and Ni 3p-3d resonance energies are found to be higher as compared to Co and Ni metals. Theoretical first principle calculation is performed to understand the features in the valence band and the shape of the resonance profile.

Baral, Madhusmita, E-mail: madhusmita@rrcat.gov.in; Banik, Soma, E-mail: madhusmita@rrcat.gov.in; Ganguli, Tapas, E-mail: madhusmita@rrcat.gov.in; Chakrabarti, Aparna, E-mail: madhusmita@rrcat.gov.in; Deb, S. K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Thamizhavel, A. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005 (India); Wadikar, Avinash; Phase, D. M. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore-452017 (India)

2014-04-24T23:59:59.000Z

470

Band gaps in InN/GaN superlattices: Nonpolar and polar growth directions  

SciTech Connect (OSTI)

The electronic structures of nonpolar short-period InN/GaN superlattices (SLs) grown in the wurtzite a- and m-directions have been calculated and compared to previous calculations for polar superlattices (grown in the c-direction). The variation of the band gaps with the composition (m, n) of the mInN/nGaN unit cells of the superlattices was examined. The band structures were obtained by self-consistent calculations based on the local density approximation to the density functional theory using the Linear-Muffin-Tin-Orbital method with a semi-empirical correction for the band gaps. The calculated band gaps and their pressure coefficients for nonpolar superlattices are similar to those calculated for bulk InGaN alloys with an equivalent In/Ga concentration ratio. This is very different from what has been found in polar superlattices where the band gaps are much smaller and vanish when the number m of InN layers in the unit cell exceeds three. A strong internal electric field is responsible for this behavior of polar structures. Experimental photoluminescence data for polar SLs agree very well with gaps calculated for the nonpolar structures. It is suggested that this is caused by screening of the electric field in the polar structures by carriers originating from unintentional defects.

Gorczyca, I., E-mail: iza@unipress.waw.pl; Skrobas, K.; Suski, T. [Institute of High Pressure Physics, UNIPRESS, 01-142 Warsaw (Poland); Christensen, N. E.; Svane, A. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2013-12-14T23:59:59.000Z

471

Electrodeposition of Crystalline GaAs on Liquid Gallium Electrodes in Aqueous Electrolytes  

Science Journals Connector (OSTI)

Crystalline gallium arsenide (c-GaAs) possesses many desirable optoelectronic properties suited for solar energy conversion,(1) light and radiation detection,(2) chemical sensing,(3) lighting,(4) and high speed electronics. ... In contrast to conflicting previous reports on the electrodeposition of GaAs,(17, 18) we posit that c-GaAs(s) can be synthesized predictably through the electrodeposition of As from dissolved As2O3 specifically on a Ga(l) electrode at modest temperatures in water. ... Specifically, for any binary system composed of a solid dissolving into a liquid, the rate of dissolution of the solid into the liquid phase is given by eq 5:(60)(5)where kdiss is the dissolution rate constant, s is the surface area of the solid in contact with the liquid, V is the volume of the liquid, Csat is the solubility of the solid in the liquid, and Cdiss is the concentration of the dissolved solid in the bulk of the liquid phase. ...

Eli Fahrenkrug; Junsi Gu; Stephen Maldonado

2012-12-24T23:59:59.000Z

472

A Fixed Point Analysis of a Gene Pool GA with Mutation Alden H. Wright #  

E-Print Network [OSTI]

A Fixed Point Analysis of a Gene Pool GA with Mutation Alden H. Wright # Computer Science University of Montana USA wright@cs.umt.edu 44 121 414 2793 Jonathan E. Rowe Computer Science University Alden Wright was visiting the School of Computer Science, University of Birmingham, UK, supported

Wright, Alden H.

473

A Fixed Point Analysis of a Gene Pool GA with Mutation Alden H. Wright  

E-Print Network [OSTI]

A Fixed Point Analysis of a Gene Pool GA with Mutation Alden H. Wright Computer Science Department University of Montana, USA wright@cs.umt.edu Jonathan E. Rowe School of Computer Science The University is to move the population closer to This paper was written while Alden Wright was visiting the School

Poli, Riccardo

474

Reconstructing the Shifting Balance Theory in a GA: Taking Sewall Wright Seriously  

E-Print Network [OSTI]

Reconstructing the Shifting Balance Theory in a GA: Taking Sewall Wright Seriously Franz Oppacher@scs.carleton.ca Abstract- We attempt to reconstruct Sewall Wright's Shifting Balance Theory in order to address some the Shifting Balance Genetic Algorithm (SBGA), which is shown to behave as Wright intended. For example

Wineberg, Mark

475

Invited Paper AlGaN-based high-performance metalsemiconductormetal  

E-Print Network [OSTI]

combustion monitor- ing, furnace monitoring and missile warning; secure non-line-of-sight and space photodetector was demonstrated by Khan et al. [11] in 1993. Shortly after, the first AlGaN based solar that they are not responsive to the background radiation from the sun, since the solar radiation within their spectral band (l

Ozbay, Ekmel

476

Metalorganic Chemical Vapor Deposition Route to GaN Nanowires with Triangular  

E-Print Network [OSTI]

Metalorganic Chemical Vapor Deposition Route to GaN Nanowires with Triangular Cross Sections Tevye widths of 15-200 nm. Transmission electron microscopy confirmed that the wires were single as a carrier gas, was percolated through the TMG precursor and coupled with a second nitrogen line to give

Yang, Peidong

477

Cu(In,Ga)Se2based Photovoltaics: Challenges and Opportunities  

E-Print Network [OSTI]

Cu(In,Ga)Se2­based Photovoltaics: Challenges and Opportunities William Shafarman Institute of Energy Conversion University of Delaware #12;Thin Film Photovoltaics Potential for low cost PV using a Thickness K.Kim, et al., IEEE J. Photovoltaics, 3, 446 (2013). 2 µm, 60 min reaction 1 µm, 25 min reaction 0

Firestone, Jeremy

478

A novel approach for the improvement of open circuit voltage and fill factor of InGaAsSb/GaSb thermophotovoltaic cells  

SciTech Connect (OSTI)

Heterojunction n-Al{sub 0.25}Ga{sub 0.75}As{sub 0.02}Sb{sub 098}/p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96} thermophotovoltaic (TPV) cells were grown by molecular-beam epitaxy on n-GaSb-substrates. In the spectral range from 1 {micro}m to 2.1 {micro}m these cells, as well as homojunction n-p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96} cells, have demonstrated internal quantum efficiencies exceeding 80%, despite about a 200 meV barrier in the conduction band at the heterointerface. Estimation shows that the thermal emission of the electrons photogenerated in p-region over this barrier can provide high efficiency for hetero-cells if the electron recombination time in p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96}is longer than 10 ns. Keeping the same internal efficiency as homojunction cells, hetero-cells provide a unique opportunity to decrease the dark forward current and thereby increase open circuit voltage (V{sub {proportional_to}}) and fill factor at a given illumination level. It is shown that the decrease of the forward current in hetero-cells is due to the lower recombination rate in n-type wider-bandgap space-charge region and to the suppression of the hole component of the forward current. The improvement in V{sub {proportional_to}} reaches 100% at illumination level equivalent to 1 mA/cm{sup 2} and it decreases to 5% at the highest illumination levels (2--3 A/cm{sup 2}), where the electron current component dominates in both the homo- and heterojunction cells. Values of V{sub {proportional_to}} as high as 310 meV have been obtained for a hetero-cell at illumination levels of 3 A/cm{sup 2}. Under this condition, the expected fill factor value is about 72% for a hetero-cell with improved series resistance. The heterojunction concept provides excellent prospects for further reduction of the dark forward current in TPV cells.

Garbuzov, D.Z.; Martinelli, R.U.; Khalfin, V.; Lee, H.; Morris, N.A.; Taylor, G.C.; Connolly, J.C. [Sarnoff Corp., Princeton, NJ (United States); Charache, G.W.; DePoy, D.M. [Lockheed-Martin, Inc., Schenectady, NY (United States)

1997-10-01T23:59:59.000Z

479

Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe Crystals with High Photoresponse  

SciTech Connect (OSTI)

Abstract Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 m in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their atomic resolution structure were characterized. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

Li, Xufan [ORNL; Lin, Ming-Wei [ORNL; Zhang, Huidong [University of Tennessee, Knoxville (UTK); Puretzky, Alexander A [ORNL; Idrobo Tapia, Juan C [ORNL; Ma, Cheng [ORNL; Chi, Miaofang [ORNL; Yoon, Mina [ORNL; Rouleau, Christopher M [ORNL; Kravchenko, Ivan I [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL

2014-01-01T23:59:59.000Z

480

Composition pulling effect and strain relief mechanism in AlGaN/AlN distributed Bragg reflectors  

SciTech Connect (OSTI)

We report on the composition pulling effect and strain relief mechanism in AlGaN/AlN distributed Bragg reflectors (DBRs) grown on GaN template/{alpha}-Al{sub 2}O{sub 3}(0001) by metal organic chemical vapor deposition. The reciprocal space mapping contours reveal that these DBRs are coherently grown. Cross-section transmission electron microscopy image of the AlGaN/AlN DBRs and the energy-dispersive x-ray analysis indicate that an AlGaN layer with gradient Al composition is located between the Al{sub 0.4}Ga{sub 0.6}N and AlN layers along the [0001] direction. It is attributed to the fact that Ga atoms in AlGaN are pulled and segregated to the upper layer by the strain. The density of strain energy is estimated to reduce more than one order by forming this quasi-three-sublayer structure comparing to the designed bi-sublayer structure.

Liu, B.; Zhang, R.; Ji, X. L.; Fu, D. Y.; Xie, Z. L.; Chen, D. J.; Chen, P.; Jiang, R. L.; Zheng, Y. D. [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China); Zheng, J. G. [California Institute for Telecommunications and Information Technology, University of California, Irvine, California 92697-2800 (United States)

2011-06-27T23:59:59.000Z

Note: This page contains sample records for the topic "tampa-st petersburg ga" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


481

Method of fabricating high-efficiency Cu(In,Ga)(SeS).sub.2 thin films for solar cells  

DOE Patents [OSTI]

A process for producing a slightly Cu-poor thin film of Cu(In,Ga)(Se,S).sub.2 comprises depositing a first layer of (In,Ga).sub.x (Se,S).sub.y followed by depositing just enough Cu+(Se,S) or Cu.sub.x (Se,S) to produce the desired slightly Cu-poor material. In a variation, most, but not all, (about 90 to 99%) of the (In,Ga).sub.x (Se,S).sub.y is deposited first, followed by deposition of all the Cu+(Se,S) or Cu.sub.x (Se,S) to go near stoichiometric, possibly or even preferably slightly Cu-rich, and then in turn followed by deposition of the remainder (about 1 to 10%) of the (In,Ga).sub.x (Se,S).sub.y to end with a slightly Cu-poor composition. In yet another variation, a small portion (about 1 to 10%) of the (In,Ga).sub.x (Se,S).sub.y is first deposited as a seed layer, followed by deposition of all of the Cu+(Se,S) or Cu.sub.x (Se,S) to make a very Cu-rich mixture, and then followed deposition of the remainder of the (In,Ga).sub.x (Se,S).sub.y to go slightly Cu-poor in the final Cu(In,Ga)(Se,S).sub.2 thin film.

Noufi, Rommel (Golden, CO); Gabor, Andrew M. (Boulder, CO); Tuttle, John R. (Denver, CO); Tennant, Andrew L. (Denver, CO); Contreras, Miguel A. (Golden, CO); Albin, David S. (Denver, CO); Carapella, Jeffrey J. (Evergreen, CO)

1995-01-01T23:59:59.000Z

482

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

SciTech Connect (OSTI)

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