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James S Speck - One of the best experts on this subject based on the ideXlab platform.
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low Threading Dislocation density aluminum nitride on silicon carbide through the use of reduced temperature interlayers
Journal of Crystal Growth, 2018Co-Authors: Humberto M Foronda, Christian J Zollner, Muhammad Esmed Alif, Burhan Saifaddin, Abdullah Almogbel, Michael Iza, Shuji Nakamura, Steven P Denbaars, James S SpeckAbstract:Abstract In this work, reduced Threading Dislocation density AlN on (0 0 0 1) 6H-SiC was realized through the use of reduced temperature AlN interlayers in the metalorganic chemical vapor deposition growth. We explored the dependence of the interlayer growth temperature on the AlN crystal quality, defect density, and surface morphology. The crystal quality was characterized using omega rocking curve scans and the Threading Dislocation density was determined by plan view transmission electron microscopy. The growth resulted in a Threading Dislocation density of 7 × 108 cm−2 indicating a significant reduction in the defect density of AlN in comparison to direct growth of AlN on SiC (∼1010 cm−2). Atomic force microscopy images demonstrated a clear step-terrace morphology that is consistent with step flow growth at high temperature. Reducing the interlayer growth temperature increased the TD inclination and thus enhanced TD-TD interactions. The TDD was decreased via fusion and annihilation reactions.
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correlation between Threading Dislocation density and sheet resistance of algan aln gan heterostructures grown by plasma assisted molecular beam epitaxy
Applied Physics Letters, 2012Co-Authors: Stephen W Kaun, Man Hoi Wong, U K Mishra, James S SpeckAbstract:AlGaN/AlN/GaN heterostructures were grown on 6H-SiC, GaN-on-sapphire, and free-standing GaN, resulting in heterostructures with Threading Dislocation densities of ∼2 × 1010, ∼5 × 108, and ∼5 × 107 cm−2, respectively. Growths were carried out under Ga-rich conditions by plasma-assisted molecular beam epitaxy to determine the influence of Threading Dislocation density on the sheet resistance of AlGaN/AlN/GaN heterostructures. High Threading Dislocation density was observed to significantly degrade Hall mobility. An AlGaN/AlN/GaN heterostructure with a ∼2 nm AlN interlayer and a Threading Dislocation density of ∼5 × 107 cm−2 achieved the very low room temperature sheet resistance of 175 Ω/□.
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influence of Threading Dislocation density on early degradation in algan gan high electron mobility transistors
Applied Physics Letters, 2011Co-Authors: M ťapajna, Stephen W Kaun, Man Hoi Wong, U K Mishra, James S Speck, Feng Gao, Tomas Palacios, Martin KuballAbstract:Early stage degradation of AlGaN/GaN high electron mobility transistors (HEMTs) with different Threading Dislocation densities (TDDs) submitted to off-state voltage bias stress was studied. It was found that, for the stress conditions used, HEMTs with TDD ∼1010 cm−2 show pronounced degradation in terms of maximum drain current, gate-lag, and trap generation measured by drain current trapping characteristics, a slight degradation in gate leakage was observed also for HEMTs with TDD of ∼108 cm−2, and no significant degradation for devices with TDD in the ∼107 cm−2 range. The results illustrate the importance of TDD for degradation and reliability of AlGaN/GaN HEMTs.
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misfit Dislocation formation via pre existing Threading Dislocation glide in 112 2 semipolar heteroepitaxy
Applied Physics Letters, 2011Co-Authors: Po Shan Hsu, Shuji Nakamura, Steven P Denbaars, A. E. Romanov, Erin C Young, Kenji Fujito, James S SpeckAbstract:Cathodoluminescence (CL) was used to study the onset of mechanical stress relaxation in low indium composition semipolar (112¯2) InxGa1−xN lattice-mismatched layers grown on bulk GaN substrates. Monochromatic CL of short interfacial misfit Dislocation (MD) segments showed a single Threading Dislocation (TD) associated with each MD segment—demonstrating that the initial stage of MD formation in semipolar III-nitride heterostructures proceeded by the bending and glide of pre-existing TDs on the (0001) slip plane. The state of coherency as determined by panchromatic CL is also compared to that determined by x-ray diffraction analysis based on crystallographic epilayer tilt and Matthew-Blakeslee’s critical thickness calculations.
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effects of Threading Dislocation density on the gate leakage of algan gan heterostructures for high electron mobility transistors
Applied Physics Express, 2011Co-Authors: Stephen W Kaun, Man Hoi Wong, U K Mishra, Sansaptak Dasgupta, Soojeong Choi, Roy B Chung, James S SpeckAbstract:AlGaN/GaN heterostructures were regrown on three semi-insulating GaN templates with Threading Dislocation densities of ~2×1010, ~5×108, and ~5×107 cm-2. Regrowths were carried out under Ga-rich conditions by plasma-assisted molecular beam epitaxy to determine the effects of Threading Dislocation density on leakage through Schottky contacts on the AlGaN/GaN heterostructures. A similar AlGaN/GaN heterostructure was directly grown on 4H-SiC under Ga-rich conditions for comparison with the regrown heterostructures. High electron mobility transistors were fabricated. Decreasing the Threading Dislocation density from ~2×1010 to ~5×107 cm-2 yielded up to a 45-fold decrease in the average reverse Schottky diode current at -10 V bias.
Eduard Arzt - One of the best experts on this subject based on the ideXlab platform.
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In situ transmission electron microscopy investigation of Threading Dislocation motion in passivated thin aluminum films
Journal of Materials Research, 1999Co-Authors: R.-m. Keller-flaig, Wilfried Sigle, Subra Suresh, Andrew Gouldstone, Marc Legros, Kevin J. Hemker, Eduard ArztAbstract:In situ transmission electron microscopy (TEM) was performed to study Dislocation motion during temperature cycles in aluminum films passivated with a SiO2 layer. The films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between Dislocations and interfaces, the movement of Threading Dislocations within the constrained aluminum film was observed. This observation provides an experimental corroboration of the occurrence of Threading Dislocation motion, which is the basis for rationalizing the high-ield strength of thin films in available models of thin-film plasticity.
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In situ transmission electron microscopy investigation of Threading Dislocation motion in passivated thin aluminum films
Journal of Materials Research, 1999Co-Authors: R.-m. Keller-flaig, Wilfried Sigle, Subra Suresh, Andrew Gouldstone, Marc Legros, Kevin J. Hemker, Eduard ArztAbstract:In situ transmission electron microscopy (TEM) was performed to study Dislocation motion during temperature cycles in aluminum films passivated with a SiO2 layer. The films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between Dislocations and interfaces, the movement of Threading Dislocations within the constrained aluminum film was observed. This observation provides an experimental corroboration of the occurrence of Threading Dislocation motion, which is the basis for rationalizing the high-ield strength of thin films in available models of thin-film plasticity.
Kangsa Pak - One of the best experts on this subject based on the ideXlab platform.
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Suppression of Threading Dislocation generation in GaAs-on-Si with strained short-period superlattices
Journal of Crystal Growth, 1995Co-Authors: Yasufumi Takagi, Hiroo Yonezu, Takahiro Kawai, Keiji Hayashida, K. Samonji, Naoki Ohshima, Kangsa PakAbstract:Abstract We investigated the suppression of Threading Dislocation generation in GaAs-on-Si(100) with strained short-period superlattices by reflection high-energy electron diffraction and transmission electron microscopy. A two-dimensional growth mode was kept during the lattice relaxation process. As a result, the density of Threading Dislocations in the GaAs epilayer was markedly reduced. A lattice mismatch of 4% was accommodated at hetero-interfaces by generating misfit Dislocations in the directions of 〈011〉.
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Suppression of Threading Dislocation generation in highly lattice mismatched heteroepitaxies by strained short-period superlattices
Applied Physics Letters, 1993Co-Authors: Takahiro Kawai, Hiroo Yonezu, Y. Ogasawara, D. Saito, Kangsa PakAbstract:The Threading Dislocation density was remarkably reduced in highly lattice mismatched heteroepitaxies of the In0.5Ga0.5As/GaAs(001) and GaAs/GaP(001) systems. The two‐dimensional growth mode was obtained even after the lattice relaxation by applying the strained short‐period superlattices. The misfit Dislocations aligned along the 〈110〉 direction were mainly generated at heterointerfaces. The misfit strain was relieved by the generation of the misfit Dislocations in the absence of three‐dimensional island growth. It was found that the generation of Threading Dislocations is effectively suppressed by introducing strained short‐period superlattices at the initial growth stage of highly lattice mismatched heteroepitaxies.
R.-m. Keller-flaig - One of the best experts on this subject based on the ideXlab platform.
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In situ transmission electron microscopy investigation of Threading Dislocation motion in passivated thin aluminum films
Journal of Materials Research, 1999Co-Authors: R.-m. Keller-flaig, Wilfried Sigle, Subra Suresh, Andrew Gouldstone, Marc Legros, Kevin J. Hemker, Eduard ArztAbstract:In situ transmission electron microscopy (TEM) was performed to study Dislocation motion during temperature cycles in aluminum films passivated with a SiO2 layer. The films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between Dislocations and interfaces, the movement of Threading Dislocations within the constrained aluminum film was observed. This observation provides an experimental corroboration of the occurrence of Threading Dislocation motion, which is the basis for rationalizing the high-ield strength of thin films in available models of thin-film plasticity.
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In situ transmission electron microscopy investigation of Threading Dislocation motion in passivated thin aluminum films
Journal of Materials Research, 1999Co-Authors: R.-m. Keller-flaig, Wilfried Sigle, Subra Suresh, Andrew Gouldstone, Marc Legros, Kevin J. Hemker, Eduard ArztAbstract:In situ transmission electron microscopy (TEM) was performed to study Dislocation motion during temperature cycles in aluminum films passivated with a SiO2 layer. The films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between Dislocations and interfaces, the movement of Threading Dislocations within the constrained aluminum film was observed. This observation provides an experimental corroboration of the occurrence of Threading Dislocation motion, which is the basis for rationalizing the high-ield strength of thin films in available models of thin-film plasticity.
Eugene A. Fitzgerald - One of the best experts on this subject based on the ideXlab platform.
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reduction of Threading Dislocation density in gan grown on strain relaxed nanoporous gan template
Applied Physics Letters, 2007Co-Authors: H Hartono, C B Soh, S Y Chow, S J Chua, Eugene A. FitzgeraldAbstract:Growth of gallium nitride (GaN) on strain relaxed nanoporous GaN template by metal-organic chemical vapor deposition has produced GaN layer with 60% reduction in Threading Dislocation density (TDD). The porous GaN was annealed at 850°C for 3min in a mixed of nitrogen and ammonia ambient, which annihilated most TDs within the porous region via air-gap formation coupled with surface edge step pinning of Dislocations. Enhancement of optical quality was indicated by doubled Raman intensity of E2 phonon peak of annealed porous as compared to as-fabricated porous GaN. Besides, a redshift of 0.7cm−1 in E2 phonon peak of porous GaN with respect to as-grown GaN corresponds to a relaxation of compressive stress by 0.17±0.05GPa. Further overgrowth of GaN on annealed porous GaN template gives high quality GaN with reduction in TDD.
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Controlling Threading Dislocation densities in Ge on Si using graded SiGe layers and chemical-mechanical polishing
Applied Physics Letters, 1998Co-Authors: M. T. Currie, S. B. Samavedam, Thomas A. Langdo, Christopher W. Leitz, Eugene A. FitzgeraldAbstract:A method of controlling Threading Dislocation densities in Ge on Si involving graded SiGe layers and chemical-mechanical polishing (CMP) is presented. This method has allowed us to grow a relaxed graded buffer to 100% Ge without the increase in Threading Dislocation density normally observed in thick graded structures. This sample has been characterized by transmission electron microscopy, etch-pit density, atomic force microscopy, Nomarski optical microscopy, and triple-axis x-ray diffraction. Compared to other relaxed graded buffers in which CMP was not implemented, this sample exhibits improvements in Threading Dislocation density and surface roughness. We have also made process modifications in order to eliminate particles due to gas-phase nucleation and cracks due to thermal mismatch strain. We have achieved relaxed Ge on Si with a Threading Dislocation density of 2.1×106 cm−2, and we expect that further process refinements will lead to lower Threading Dislocation densities on the order of bulk Ge su...
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totally relaxed gexsi1 x layers with low Threading Dislocation densities grown on si substrates
Applied Physics Letters, 1991Co-Authors: Eugene A. Fitzgerald, Yahong Xie, M L Green, D Brasen, A R Kortan, Jurgen Michel, Y J Mii, B E WeirAbstract:We have grown compositionally graded GexSi1−x layers on Si at 900 °C with both molecular beam epitaxy and rapid thermal chemical vapor deposition techniques. Triple‐crystal x‐ray diffraction reveals that for 0.10
