Andrew G. Norman

National Renewable Energy Laboratory

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Mowafak Al‐Jassim

National Renewable Energy Laboratory

John F. Geisz

National Renewable Energy Laboratory

A. Mascarenhas

National Renewable Energy Laboratory

William E. McMahon

National Renewable Energy Laboratory

Andriy Zakutayev

National Renewable Energy Laboratory

D. M. Follstaedt

Sandia National Laboratories California

Adele C. Tamboli

National Renewable Energy Laboratory

Helio Moutinho

National Renewable Energy Laboratory

G. R. Booker

University of Oxford

Chun‐Sheng Jiang

National Renewable Energy Laboratory

Cooperative Institutions

National Renewable Energy Laboratory

291

European Organization for Nuclear Research

154

Centre National de la Recherche Scientifique

125

Iowa State University

109

Colorado School of Mines

107

University of Colorado Boulder

University of Oxford

Imperial College London

Karlsruhe Institute of Technology

A. Alikhanyan National Laboratory

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Intense Lateral Composition Modulation in InAs/AlAs Superlattices

APS (1999)

D. M. Follstaedt John Reno Stephen Lee Eric D. Jones Andrew G. Norman

Modulation (music)

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Single-crystalline aluminum grown on MgAl2O4 spinel using molecular-beam epitaxy

Journal of Vacuum Science & Technology B Nanotechnology and Microelectronics Materials Processing Measurement and Phenomena (2011)

Yu-Chieh Lin Andrew G. Norman William E. McMahon Helio Moutinho Chun‐Sheng Jiang

Al thin films were grown on MgAl2O4 spinel substrates using solid-source molecular-beam epitaxy. The structural properties of Al layers were systematically investigated as a function of substrate orientation and growth temperature. Scanning electron microscopy and atomic force microscopy show that low growth temperatures lead to smoother and more coalesced Al films. X-ray diffraction and electron backscatter diffraction (EBSD) measurements demonstrate that Al layers are single crystalline and coherently grown on both (100)- and (111)-oriented spinel substrates. EBSD data also clearly reveal a high density of twin domain structures in Al films grown on (111) spinel substrates, and all twin boundaries were determined to be Σ3 boundaries. High-resolution transmission electron microscopy was used to confirm the presence of twin structures. Al grown on (001) spinel roughens more easily than Al grown on (111) spinel at higher growth temperatures. It is suggested that Al surface energy and thermal expansion mismatch play a critical role in the evolution of surface morphology of Al thin films grown on MgAl2O4 spinel.

10.1116/1.3570869

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Citations (3)

Oxidation and characterization of AlInP under light-soaked, damp heat conditions

Ryan M. France Myles A. Steiner Todd G. Deutsch E.A. Brucker Chun Jiang

AlInP commonly serves as the window layer in high bandgap III-V solar cells where it is responsible for reducing surface recombination by reflecting minority carriers. It must be optically transparent and conductive to majority carriers, and so is typically thin, 25 nm, and doped. It is the semiconductor layer most exposed to the environment during operation, which consists of high temperature and concentrated light in a terrestrial concentrating system. In this paper, the oxidation of AlInP was studied as it relates to III-V terrestrial solar cells. The effects of heat, humidity, and light were investigated. Undoped AlInP samples in a light-soaked, damp heat condition grew more than 20 nm of oxide in 2400 hours, as compared to 3 nm of oxide when in the same damp heat condition without light. Under the light-soaked, damp heat condition, n-type material oxidized faster than p-type material. These effects are indicative of a photoelectrochemical oxidation reaction between the semiconductor and an electrolyte, which is provided by the humidity in this case. The removal of UV light by the use of UV absorbing glass reduced much of this additional oxidation. The removal of humidity and UV limited oxide growth to 1.2 nm after 700 hours exposure. Although direct exposure of AlInP caused oxidation, GaInP solar cells utilizing n-AlInP windows were directly exposed to light and damp heat for over 2800 hours and found stable, an effect attributed to differences between n-AlInP window layers and n-AlInP epilayers.

Damp

Sunlight

10.1109/pvsc.2010.5616977

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Photo- and electro-luminescence studies of uncooled arsenic-rich In(As,Sb) strained layer superlattice light-emitting diodes for the 4-12-μm band

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1995)

P. J. P. Tang M. J. Pullin Sunjae Chung Christopher Phillips R. A. Stradling

4-12 micrometers Photoluminescence (PL) and electroluminescence (EL) at room temperature are observed from In(As,Sb) undoped strained layer superlattices (SLS's) and SLS diodes. The SLS's are grown by molecular beam epitaxy on GaAs substrates and are composed of arsenic rich alloys clad between InAs layers. The long wavelength emission is accounted for by an extreme type II valence band offset equals 830x meV (where x in the Sb composition). Internal PL efficiencies greater than 10% for light emission up to 9 micrometers are observed at 12 K in spite of presumed large dislocation densities due to the epilayer/substrate mismatch (approximately 7%). This is consistent with the thesis that defects in As rich alloys are, as in InAs, resonant with the conduction band instead of forming non-radiative recombination centers in the band gap. The high radiative efficiencies even at room temperature are attributed to the suppression of Auger recombination in the type II superlattice. We report the first Electroluminescence spectra covering the 4 - 12 micrometers wavelength range from a series of uncooled SLS LED's. Clear atmospheric absorption features in the EL spectra demonstrate their usefulness for gas sensing applications. The growth of these devices on GaAs substrates offers the possibility of easy integration with existing III-V fabrication technologies.

Auger effect

10.1117/12.206930

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Citations (2)

Electrodeposited Biaxially Textured Buffer Layers for YBCO Superconductors

IEEE Transactions on Applied Superconductivity (2009)

R. N. Bhattacharya Sovannary Phok Wenjun Zhao Andrew G. Norman

Non-vacuum electrodeposition (ED) was used to prepare simplified Gd ₂ O ₃ /Gd ₂ Zr ₂ O ₇ and CeO ₂ /Gd ₂ Zr ₂ O ₇ buffer layers on a Ni-W substrate. Post-annealing conditions of electrodeposited precursor films were optimized to obtain high-quality biaxially textured buffer layers. The buffer layers were characterized by X-ray diffraction, optical profiling, and transmission electron microscopy (TEM). The effect of the cap layer thickness on the surface morphology and texture of the buffers was also studied. The microstructure of CeO ₂ /Gd ₂ Zr ₂ O ₇ was analysed and compared to Gd ₂ O ₃ /Gd ₂ Zr ₂ O ₇ . The high-resolution TEM shows biaxially textured crystalline elctrodeposited Gd ₂ O ₃ and CeO ₂ cap layers on the electrodeposited Gd ₂ Zr ₂ O ₇ layers without any defects. YBa ₂ Cu ₃ O _7-delta (YBCO) superconductor was deposited by pulsed laser deposition (PLD) on the simplified ED-Gd ₂ O ₃ /Gd ₂ Zr ₂ O ₇ and ED-CeO ₂ /Gd ₂ Zr ₂ O ₇ buffers. Transport current density of 3.3 MA/cm ² at 77 K was obtained for PLD YBCO deposited on ED-Gd ₂ O ₃ /Gd ₂ Zr ₂ O ₇ buffer layers.

10.1109/tasc.2009.2019603

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Citations (13)

Quantum dot materials for solar cell applications: effects of strain-reducing and strain-compensated barriers on dot structural and optical properties

A. Pancholi Y. C. Zhang J. Boyle V. G. Stoleru M. C. Hanna

We present structural and optical analysis of (In,Ga)As quantum dot structures with strain- compensated and strain-reduced barriers for intermediate band solar cell applications. © 2008 Optical Society of America OCIS Codes : (250.5230) Photoluminescence; (040.5350) Photovoltaic

Strain (injury)

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Modulated Contrast and Associated Diffracted Intensity of GaPySb1-y Layers Grown Using Organometallic Vapor Phase Epitaxy

Journal of the Korean Physical Society (2008)

Tae-Yeon Seong G. R. Booker Andrew G. Norman Frank Glas G. B. Stringfellow

Vapor phase

Intensity

10.3938/jkps.52.471

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Citations (2)

Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (2016)

Andrew G. Norman

Buffer (optical fiber)

Lattice (music)

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Ordering-enhanced dislocation glide in III-V alloys

Journal of Applied Physics (2013)

William E. McMahon Joongoo Kang Ryan M. France Andrew G. Norman Daniel J. Friedman

Ordering-induced effects on dislocations in metallic alloys have been extensively studied due to their importance in technology applications. We demonstrate that dislocation behavior in ordered III-V semiconductor alloys can be drastically different. This is because ordering in bulk metallic alloys is generally stable, whereas the surface-stabilized group-III sublattice ordering of a III-V alloy is only metastable in the bulk. Here, we show that dislocation glide can release some of the energy stored by ordering of III-V alloys, enhancing the glide of any dislocation which cuts through the ordered layers to create an antiphase boundary in the ordering pattern. This leads to an experimentally observed glide-plane switch which is unique to ordered III-V alloys. Implications for other unique strain-relaxation processes in III-V ordered alloys are also discussed.

Glide plane

Metastability

10.1063/1.4833244

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Citations (23)

Doping dependence and anisotropy of minority electron mobility in molecular beam epitaxy-grown p type GaInP

Applied Physics Letters (2014)

N. M. Haegel Theresa Christian Clyde L. Scandrett Andrew G. Norman A. Mascarenhas

Direct imaging of minority electron transport via the spatially resolved recombination luminescence signature has been used to determine carrier diffusion lengths in GaInP as a function of doping. Minority electron mobility values are determined by performing time resolved photoluminescence measurements of carrier lifetime on the same samples. Values at 300 K vary from ∼2000 to 400 cm2/V s and decrease with increasing doping. Anisotropic diffusion lengths and strongly polarized photoluminescence are observed, resulting from lateral composition modulation along the [110] direction. We report anisotropic mobility values associated with carrier transport parallel and perpendicular to the modulation direction.

Electron Mobility

Carrier lifetime

10.1063/1.4902316

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Citations (16)