The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Drew Hanser - One of the best experts on this subject based on the ideXlab platform.
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Thermal conductivity, Dislocation Density and GaN device design
Superlattices and Microstructures, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:Abstract The performance of high power transistor devices is intimately connected to the substrate thermal conductivity. In this study, the relationship between thermal conductivity and Dislocation Density is examined using the 3 omega technique and free standing HVPE GaN substrates. Dislocation Density is measured using imaging cathodoluminescence. In a low Dislocation Density regime below 105 cm−2, the thermal conductivity appears to plateau out near 230 W/K m and can be altered by the presence of isotopic defects and point defects. For high Dislocation densities the thermal conductivity is severely degraded due to phonon scattering from Dislocations. These results are applied to the design of homoepitaxially and heteroepitaxially grown HEMT devices and the efficiency of heat extraction and the influence of lateral heat spreading on device performance are compared.
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Accurate dependence of gallium nitride thermal conductivity on Dislocation Density
Applied Physics Letters, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:The authors experimentally find that the thermal conductivity of gallium nitride depends critically on Dislocation Density using the 3-omega technique. For GaN with Dislocation densities lower than 106cm−2, the thermal conductivity is independent with Dislocation Density. The thermal conductivity decreases with a logarithmic dependence for material with Dislocation densities in the range of 107–1010cm−2. These results are in agreement with theoretical predictions. This study indicates that the hydride vapor phase epitaxy method offers an attractive route for the formation of semi-insulating gallium nitride with optimal thermal conductivity values around 230W∕mK and very low Dislocation Density near 5×104cm−2.
C. Mion - One of the best experts on this subject based on the ideXlab platform.
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Thermal conductivity, Dislocation Density and GaN device design
Superlattices and Microstructures, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:Abstract The performance of high power transistor devices is intimately connected to the substrate thermal conductivity. In this study, the relationship between thermal conductivity and Dislocation Density is examined using the 3 omega technique and free standing HVPE GaN substrates. Dislocation Density is measured using imaging cathodoluminescence. In a low Dislocation Density regime below 105 cm−2, the thermal conductivity appears to plateau out near 230 W/K m and can be altered by the presence of isotopic defects and point defects. For high Dislocation densities the thermal conductivity is severely degraded due to phonon scattering from Dislocations. These results are applied to the design of homoepitaxially and heteroepitaxially grown HEMT devices and the efficiency of heat extraction and the influence of lateral heat spreading on device performance are compared.
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Accurate dependence of gallium nitride thermal conductivity on Dislocation Density
Applied Physics Letters, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:The authors experimentally find that the thermal conductivity of gallium nitride depends critically on Dislocation Density using the 3-omega technique. For GaN with Dislocation densities lower than 106cm−2, the thermal conductivity is independent with Dislocation Density. The thermal conductivity decreases with a logarithmic dependence for material with Dislocation densities in the range of 107–1010cm−2. These results are in agreement with theoretical predictions. This study indicates that the hydride vapor phase epitaxy method offers an attractive route for the formation of semi-insulating gallium nitride with optimal thermal conductivity values around 230W∕mK and very low Dislocation Density near 5×104cm−2.
Edward A. Preble - One of the best experts on this subject based on the ideXlab platform.
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Thermal conductivity, Dislocation Density and GaN device design
Superlattices and Microstructures, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:Abstract The performance of high power transistor devices is intimately connected to the substrate thermal conductivity. In this study, the relationship between thermal conductivity and Dislocation Density is examined using the 3 omega technique and free standing HVPE GaN substrates. Dislocation Density is measured using imaging cathodoluminescence. In a low Dislocation Density regime below 105 cm−2, the thermal conductivity appears to plateau out near 230 W/K m and can be altered by the presence of isotopic defects and point defects. For high Dislocation densities the thermal conductivity is severely degraded due to phonon scattering from Dislocations. These results are applied to the design of homoepitaxially and heteroepitaxially grown HEMT devices and the efficiency of heat extraction and the influence of lateral heat spreading on device performance are compared.
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Accurate dependence of gallium nitride thermal conductivity on Dislocation Density
Applied Physics Letters, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:The authors experimentally find that the thermal conductivity of gallium nitride depends critically on Dislocation Density using the 3-omega technique. For GaN with Dislocation densities lower than 106cm−2, the thermal conductivity is independent with Dislocation Density. The thermal conductivity decreases with a logarithmic dependence for material with Dislocation densities in the range of 107–1010cm−2. These results are in agreement with theoretical predictions. This study indicates that the hydride vapor phase epitaxy method offers an attractive route for the formation of semi-insulating gallium nitride with optimal thermal conductivity values around 230W∕mK and very low Dislocation Density near 5×104cm−2.
John F. Muth - One of the best experts on this subject based on the ideXlab platform.
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Thermal conductivity, Dislocation Density and GaN device design
Superlattices and Microstructures, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:Abstract The performance of high power transistor devices is intimately connected to the substrate thermal conductivity. In this study, the relationship between thermal conductivity and Dislocation Density is examined using the 3 omega technique and free standing HVPE GaN substrates. Dislocation Density is measured using imaging cathodoluminescence. In a low Dislocation Density regime below 105 cm−2, the thermal conductivity appears to plateau out near 230 W/K m and can be altered by the presence of isotopic defects and point defects. For high Dislocation densities the thermal conductivity is severely degraded due to phonon scattering from Dislocations. These results are applied to the design of homoepitaxially and heteroepitaxially grown HEMT devices and the efficiency of heat extraction and the influence of lateral heat spreading on device performance are compared.
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Accurate dependence of gallium nitride thermal conductivity on Dislocation Density
Applied Physics Letters, 2006Co-Authors: C. Mion, John F. Muth, Edward A. Preble, Drew HanserAbstract:The authors experimentally find that the thermal conductivity of gallium nitride depends critically on Dislocation Density using the 3-omega technique. For GaN with Dislocation densities lower than 106cm−2, the thermal conductivity is independent with Dislocation Density. The thermal conductivity decreases with a logarithmic dependence for material with Dislocation densities in the range of 107–1010cm−2. These results are in agreement with theoretical predictions. This study indicates that the hydride vapor phase epitaxy method offers an attractive route for the formation of semi-insulating gallium nitride with optimal thermal conductivity values around 230W∕mK and very low Dislocation Density near 5×104cm−2.
T. Buonassisi - One of the best experts on this subject based on the ideXlab platform.
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Dislocation Density Reduction During Impurity Gettering in Multicrystalline Silicon
IEEE Journal of Photovoltaics, 2013Co-Authors: H. J. Choi, M. I. Bertoni, J. Hofstetter, D. P. Fenning, D. M. Powell, S. Castellanos, T. BuonassisiAbstract:Isothermal annealing above 1250 °C has been reported to reduce the Dislocation Density in multicrystalline silicon (mc-Si), presumably by pairwise Dislocation annihilation. However, this high-temperature process may also cause significant impurity contamination, canceling out the positive effect of Dislocation Density reduction on cell performance. Here, efforts are made to annihilate Dislocations in mc-Si in temperatures as low as 820 °C, with the assistance of an additional driving force to stimulate Dislocation motion. A reduction of more than 60% in Dislocation Density is observed for mc-Si containing intermediate concentrations of certain metallic species after P gettering at 820 °C. While the precise mechanism remains in discussion, available evidence suggests that the net unidirectional flux of impurities in the presence of a gettering layer may cause Dislocation motion, leading to Dislocation Density reduction. Analysis of minority carrier lifetime as a function of Dislocation Density suggests that lifetime improvements after P diffusion in these samples can be attributed to the combined effects of Dislocation Density reduction and impurity concentration reduction. These findings suggest there may be mechanisms to reduce Dislocation densities at standard solar cell processing temperatures.
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Stress and temperature coupling effects on Dislocation Density reduction in multicrystalline silicon
2010 35th IEEE Photovoltaic Specialists Conference, 2010Co-Authors: S. Castellanos, M. I. Bertoni, Michelle Vogl, Alexandria Fecych, T. BuonassisiAbstract:In multicrystalline silicon (mc-Si), the presence of Dislocation-rich areas limits solar cell conversion efficiencies [1–2]. Previous studies have demonstrated that Dislocation densities higher than 106 cm−2 can dramatically decrease the minority carrier lifetime [3]. High Dislocation densities, and their decoration with impurities, can limit minority carrier lifetime even after phosphorous diffusion or hydrogen passivation [4–5]. We previously proposed a method to remove Dislocations from mc-Si by high-temperature annealing, demonstrating Dislocation Density reductions of 95% approximately [6]. We demonstrated that the dependence of Dislocation Density reduction on annealing temperature is much more pronounced that the dependence on annealing time [7]. In this contribution, we propose stress as an additional mechanism to enhance Dislocation Density reduction. We discuss the relationship between temperature, stresses and Dislocation Density in string ribbon.