The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Huiyun Liu - One of the best experts on this subject based on the ideXlab platform.
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solid solution strengthening in gasb gaas a mode to reduce the td density through be doping
Applied Physics Letters, 2017Co-Authors: M Gutierrez, D Araujo, Pamela Jurczak, Huiyun LiuAbstract:The need for a Low bandgap semiconductor on a GaAs substrate for thermophotovoltaic applications has motivated research on GaSb alloys, in particular, the control of plastic relaxation of its active layer. Although interfacial misfit arrays offer a possibility of growing strain-free GaSb-based devices on GaAs substrates, a high density of threading dislocations is normally observed. Here, we present the effects of the combined influence of Be dopants and Low Growth Temperature on the threading dislocation density observed by Transmission Electron Microscopy. The Be-related hardening mechanism, occurring at island coalescence, is shown to prevent dislocations to glide and hence reduce the threading dislocation density in these structures. The threading density in the doped GaSb layers reaches the values of seven times less than those observed in undoped samples, which confirms the proposed Be-related hardening mechanism.
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p doped 1 3 μm inas gaas quantum dot laser with a Low threshold current density and high differential efficiency
Applied Physics Letters, 2006Co-Authors: Huiyun Liu, D. J. Mowbray, S L Liew, T J Badcock, M S Skolnick, S K Ray, T L Choi, K M Groom, B J Stevens, F HasbullahAbstract:A modification of the thickness of the Low-Growth-Temperature component of the GaAs spacer layers in multilayer 1.3μm InAs∕GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15to2nm results in a reduced reverse bias leakage current and an increase in the intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room Temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very Low density of dislocated dots and a smaller number of defects in the thinner Low-Growth-Temperature component of the GaAs spacer layer.
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p-doped 1.3 μm InAs/GaAs quantum-dot laser with a Low threshold current density and high differential efficiency
Applied Physics Letters, 2006Co-Authors: Huiyun Liu, D. J. Mowbray, S L Liew, T J Badcock, M S Skolnick, S K Ray, T L Choi, K M Groom, B J Stevens, F HasbullahAbstract:A modification of the thickness of the Low-Growth-Temperature component of the GaAs spacer layers in multilayer 1.3μm InAs∕GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15to2nm results in a reduced reverse bias leakage current and an increase in the intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room Temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very Low density of dislocated dots and a smaller number of defects in the thinner Low-Growth-Temperature component of the GaAs spacer layer.
F Hasbullah - One of the best experts on this subject based on the ideXlab platform.
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p doped 1 3 μm inas gaas quantum dot laser with a Low threshold current density and high differential efficiency
Applied Physics Letters, 2006Co-Authors: Huiyun Liu, D. J. Mowbray, S L Liew, T J Badcock, M S Skolnick, S K Ray, T L Choi, K M Groom, B J Stevens, F HasbullahAbstract:A modification of the thickness of the Low-Growth-Temperature component of the GaAs spacer layers in multilayer 1.3μm InAs∕GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15to2nm results in a reduced reverse bias leakage current and an increase in the intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room Temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very Low density of dislocated dots and a smaller number of defects in the thinner Low-Growth-Temperature component of the GaAs spacer layer.
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p-doped 1.3 μm InAs/GaAs quantum-dot laser with a Low threshold current density and high differential efficiency
Applied Physics Letters, 2006Co-Authors: Huiyun Liu, D. J. Mowbray, S L Liew, T J Badcock, M S Skolnick, S K Ray, T L Choi, K M Groom, B J Stevens, F HasbullahAbstract:A modification of the thickness of the Low-Growth-Temperature component of the GaAs spacer layers in multilayer 1.3μm InAs∕GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15to2nm results in a reduced reverse bias leakage current and an increase in the intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room Temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very Low density of dislocated dots and a smaller number of defects in the thinner Low-Growth-Temperature component of the GaAs spacer layer.
Wolfgang Stolz - One of the best experts on this subject based on the ideXlab platform.
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High-efficiency (AlGa)As/GaAs solar cells grown by MOVPE using TBAs at Low-Temperatures and Low V/III-ratios
Solar Energy Materials and Solar Cells, 2000Co-Authors: Carsten Agert, Frank Dimroth, U. Schubert, Andreas W. Bett, S. Leu, Wolfgang StolzAbstract:Abstract The alternative As-precursor tertiarybutylarsine (TBAs) is used to grow (AlGa)As–GaAs heteroface solar cell structures. In a horizontal reactor (AIX200) a Low Growth Temperature of 625°C and a Low V/III-ratio of 10 was used. Solar cell structures using a arsine (AsH3)-based MOVPE process were grown in a multi-wafer reactor (AIX2600G3) using Growth Temperatures of 700°C and a V/III-ratio of 31. The solar cell efficiencies of both structures are 24.2% (AM 1.5 g). The obtained efficiency values are state of the art and demonstrate that TBAs can be an alternative to the more commonly used arsine with no decrease in the solar cell performance.
B.w. Kim - One of the best experts on this subject based on the ideXlab platform.
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Interfacial properties of (111)A GaAs/AlGaAs multiquantum-well structures grown by metalorganic vapor phase epitaxy
Applied Physics Letters, 2000Co-Authors: A. Sanz-hervás, Soohaeng Cho, A. Majerfeld, B.w. KimAbstract:We present the heterointerfacial properties of GaAs/AlGaAs multiquantum-well structures grown by atmospheric-pressure metalorganic vapor phase epitaxy on (111)A GaAs substrates at a relatively Low Growth Temperature of 600 °C. For a 25-period GaAs/Al0.27Ga0.73As multiquantum-well structure with a well width of 44 A, a photoluminescence linewidth of 10.5 meV was observed, which is smaller than previously reported for a similar GaAs/AlGaAs multiquantum-well structure grown by molecular beam epitaxy on (111)A GaAs. As this linewidth corresponds to a combined well-width fluctuation and interfacial roughness throughout the 25 periods of at most ±1 monolayer, it is concluded that epitaxial Growth on the (111)A surface can result in high-quality heterointerfaces, particularly at Low Growth Temperatures.
Neil R. Baker - One of the best experts on this subject based on the ideXlab platform.
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Factors Associated with Depression of Photosynthetic Quantum Efficiency in Maize at Low Growth Temperature
Plant physiology, 1995Co-Authors: Michael J. Fryer, Kevin Oxborough, Barry A. Martin, Donald R. Ort, Neil R. BakerAbstract:The photosynthetic productivity of maize (Zea mays) in temperate regions is often limited by Low Temperatures. The factors responsible for the sensitivity of photosynthesis in maize to Growth at suboptimal Temperature were investigated by measuring (a) the quantum yields of CO2 fixation and photosystem II (PSII) photochemistry, (b) the pigments of the xanthophyll cycle, (c) the concentrations of active and inactive PSII reaction centers, and (d) the synthesis of core components of PSII reaction centers. Measurements were made on fully expanded leaves grown at 14[deg]C, both before and during the first 48 h after transfer of these plants to 25[deg]C. Our findings indicate that zeaxanthin-related quenching of absorbed excitation energy at PSII is, quantitatively, the most important factor determining the depressed photosynthetic efficiency in 14[deg]C-grown plants. Despite the photoprotection afforded by zeaxanthin-related quenching of absorbed excitation energy, a significant and more persistent depression of photosynthetic efficiency appears to result from Low Temperature-induced inhibition of the rate at which damaged PSII centers can be replaced.
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Chloroplast thylakoid protein changes induced by Low Growth Temperature in maize revealed by immunocytology
Plant Cell and Environment, 1993Co-Authors: E. J. Robertson, Neil R. Baker, Rachel M. LeechAbstract:Tissue-specific effects of Low Growth Temperature on maize chloroplast thylakoid protein accumulation were analysed using immunocytology. Sections of leaves from plants grown at 25 and 14°C were probed with antibodies to specific chloroplast thylakoid proteins from the four major protein multisubunit complexes of the thylakoid membrane folLowed by fluorescein-conjugated goat anti-rabbit antibodies. At a normal Growth Temperature of 25°C, the 32 kDa D1 protein of the photosystem II reaction centre and the 33 kDa protein of the extrinsic oxygen-evolving complex of photosystem II are both accumulated to a greater degree in the mesophyll than in the bundle sheath chloroplasts. In contrast, subunit II of photosystem I, cytochrome f and the α- and β-subunits of ATP synthetase are predominant in the bundle sheath thylakoids at 25°C. A striking difference between the 25°C-grown and the 14°C-grown leaf tissue was the presence in the latter of (20–30%) cells whose chloroplasts apparently completely lack several of the thylakoid proteins. In plants grown at 14°C, the accumulation of the 33 kDa protein of the extrinsic oxygen-evolving complex of photosystem II was apparently unchanged, but other thylakoid proteins showed a significant reduction. The uneven distribution of proteins between the bundle sheath and mesophyll chloroplasts observed at 25°C was also maintained at 14°C. Reduction in the fluorescence at 14°C was manifested either as an overall reduction in the diffuse fluorescence across the chloroplast profiles or less frequently as a reduction to small discrete bodies of intense fluorescence. The significance of these results to Low-Temperature-induced reduction in the photosynthetic productivity of maize is discussed.
