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Virginia Commonwealth University

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Articles 361 - 364 of 364

Full-Text Articles in Electrical and Computer Engineering

Plasma Heating In Highly Excited Gan/Algan Multiple Quantum Wells, K. C. Zeng, R. Mair, J. Y. Lin, H. X. Jiang, W. W. Chow, A. Botchkarev, Hadis Morkoç Jan 1998

Plasma Heating In Highly Excited Gan/Algan Multiple Quantum Wells, K. C. Zeng, R. Mair, J. Y. Lin, H. X. Jiang, W. W. Chow, A. Botchkarev, Hadis Morkoç

Electrical and Computer Engineering Publications

Time-resolvedphotoluminescence(PL)spectroscopy was used to investigate carrier distributions in a GaN/AlGaN multiple quantum well(MQW) sample under high excitation intensities necessary to achieve lasing threshold. Room temperaturePL spectra showed optical transitions involving both confined and unconfined states in the quantum well structure. Analysis of the experimental results using a microscopic theory, indicates that at high excitation the carrier distributions are characterized by plasma temperatures which are significantly higher than the lattice temperature. The implications of our findings on GaN MQW laser design are also discussed.

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Deep Level Defects In N-Type Gan Grown By Molecular Beam Epitaxy, C. D. Wang, L. S. Yu, S. S. Lau, E. T. Yu, W. Kim, A. E. Botchkarev, Hadis Morkoç Jan 1998

Deep Level Defects In N-Type Gan Grown By Molecular Beam Epitaxy, C. D. Wang, L. S. Yu, S. S. Lau, E. T. Yu, W. Kim, A. E. Botchkarev, Hadis Morkoç

Electrical and Computer Engineering Publications

Deep-level transient spectroscopy has been used to characterize electronic defects in n-type GaN grown by reactive molecular-beam epitaxy. Five deep-level electronic defects were observed, with activation energiesE1=0.234±0.006, E2=0.578±0.006, E3=0.657±0.031, E4=0.961±0.026, and E5=0.240±0.012 eV. Among these, the levels labeled E1, E2, and E3are interpreted as corresponding to deep levels previously reported in n-GaN grown by both hydride vapor-phase epitaxy and metal organic chemical vapor deposition. Levels E4 and E5do not correspond to any previously reported defect levels, and are characterized for the first time in our studies.

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Optical Modes Within Iii-Nitride Multiple Quantum Well Microdisk Cavities, R. A. Mair, K. C. Zeng, J. Y. Lin, H. X. Jiang, B. Zhang, L. Dai, A. Botchkarev, W. Kim, Hadis Morkoç, M. A. Khan Jan 1998

Optical Modes Within Iii-Nitride Multiple Quantum Well Microdisk Cavities, R. A. Mair, K. C. Zeng, J. Y. Lin, H. X. Jiang, B. Zhang, L. Dai, A. Botchkarev, W. Kim, Hadis Morkoç, M. A. Khan

Electrical and Computer Engineering Publications

Optical resonance modes have been observed in optically pumped microdisk cavitiesfabricated from 50 Å/50 Å GaN/AlxGa1−xN(x∼0.07) and 45 Å/45 Å InxGa1−xN/GaN(x∼0.15)multiple quantum well structures. Microdisks, approximately 9 μm in diameter and regularly spaced every 50 μm, were formed by an ion beametch process. Individual disks were pumped at 300 and 10 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical modes corresponding to (i) the radial mode type with a spacing of 49–51 meV (both TE and TM) and (ii) the Whispering Gallery mode with a spacing of 15–16 meV were …

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Effect Of Ammonia Flow Rate On Impurity Incorporation And Material Properties Of Si-Doped Gan Epitaxial Films Grown By Reactive Molecular Beam Epitaxy, Wook Kim, A. E. Botchkarev, H. Morkoç, Z.-Q. Fang, D. C. Look, David J. Smith Jan 1998

Effect Of Ammonia Flow Rate On Impurity Incorporation And Material Properties Of Si-Doped Gan Epitaxial Films Grown By Reactive Molecular Beam Epitaxy, Wook Kim, A. E. Botchkarev, H. Morkoç, Z.-Q. Fang, D. C. Look, David J. Smith

Electrical and Computer Engineering Publications

Effect of ammonia flow rate on the impurity incorporation and material properties of Si-doped GaN films grown by reactive molecular beam epitaxy (RMBE) process is discussed. It appears that the ammonia flow rate has a marginal effect on the incorporation of impurities into the Si-doped GaN films except there was a little decrease in O and Si with increasing ammonia flow rate when the Si concentration in the film is higher than 1018 cm−3. Electron Hall mobility of Si-doped GaN films grown by RMBE varies with ammonia flow rate used during film growth. From deep level transient spectroscopy(DLTS) measurements for …

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