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Full-Text Articles in Physics
Effect Of Multistep Wafer-Annealing On Main Traps In Czochralski-Grown Semi-Insulating Gaas, Z-Q. Fang, David C. Look, H. Yamamoto, H. Shimakura
Effect Of Multistep Wafer-Annealing On Main Traps In Czochralski-Grown Semi-Insulating Gaas, Z-Q. Fang, David C. Look, H. Yamamoto, H. Shimakura
Physics Faculty Publications
Both multistep wafer‐annealed (MWA) and ingot‐annealed semi‐insulating (SI) GaAs wafers, grown by the Czochralski technique, are characterized by using normalized thermally stimulated current (NTSC) spectroscopy. Two main NTSC traps, T3 at 200 K and T5 at 140 K, which are thought to be related to arsenic vacancy defects, are found to be largely suppressed by MWA processes, especially by a new MWA process. Concomitant with a decrease of these traps, a significant increase of the threshold electrical field for both the thermal quenching of T5 and the low‐temperature photocurrent saturation has been observed
Simple Measurement Of 300 K Electron Capture Cross Section For El2 In Gaas, David C. Look, Z-Q. Fang
Simple Measurement Of 300 K Electron Capture Cross Section For El2 In Gaas, David C. Look, Z-Q. Fang
Physics Faculty Publications
A simple experiment involving only the measurement of dark current Idark and 1.1 μm photocurrent IPC in semi‐insulating (SI) GaAs allows an accurate determination of the electron capture cross section σn for the important defect EL2 in GaAs. For 45 SI GaAs samples, from 12 different boules, grown by three different techniques, we find that IPC/Idark=1.96±0.05 at 300 K. This relationship gives σn=1.4±0.4×10−16 cm2, which is compared to previously estimated values.
Deep-Center Hopping Conduction In Gan, David C. Look, D. C. Reynolds, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç
Deep-Center Hopping Conduction In Gan, David C. Look, D. C. Reynolds, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç
Physics Faculty Publications
Molecular‐beam‐epitaxial GaN layers change from strongly conductive (ρ≂10−2 Ω cm at 300 K) to semi‐insulating (ρ≂106 Ω cm) as the N flux is increased. Layers grown at low fluxes show strong n‐type conduction, with transport in the conduction band at high temperatures and in a shallow donor band at low temperatures. For layers grown at high N fluxes, the Hall coefficients become too small to measure, suggesting hopping conduction among deep centers. The temperature‐dependent resistivity data are most consistent with multiphonon, rather than single‐phonon, hopping.
On Hall Scattering Factors For Holes In Gaas, David C. Look, C. E. Stutz, J. R. Sizelove, K. R. Evans
On Hall Scattering Factors For Holes In Gaas, David C. Look, C. E. Stutz, J. R. Sizelove, K. R. Evans
Physics Faculty Publications
Hall scattering factors for electrons and holes in molecular beam epitaxial GaAs layers have been determined by comparing carrier concentrations measured by the Hall effect with those measured by the electrochemical capacitance–voltage technique. The conclusion is that both the electron and hole scattering factors are near unity for n ranging from 2×1016 to 7×1017 cm−3, and p ranging from 5×1016 to 4×1019 cm−3. This conclusion is consistent with the present theory for electrons, but not with that for holes.
Ground And Excited State Exciton Spectra From Gan Grown By Molecular-Beam Epitaxy, D. C. Reynolds, David C. Look, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç, D. N. Talwar
Ground And Excited State Exciton Spectra From Gan Grown By Molecular-Beam Epitaxy, D. C. Reynolds, David C. Look, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç, D. N. Talwar
Physics Faculty Publications
The emission and reflection spectra of GaN have been investigated in the intrinsic region and the data have been interpreted in terms of the wurtzite crystal band structure. Three intrinsic exciton transitions have been observed, one associated with each of the valence bands. Exciton excited states associated with the two top valence bands were also observed. The exciton binding energies, the band-gap energies, and the exciton Bohr radii are all reported along with the dielectric constant and the spin-orbit and crystal-field parameters for GaN.
Thermally Stimulated Current Trap In Gan, David C. Look, Z-Q. Fang, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç
Thermally Stimulated Current Trap In Gan, David C. Look, Z-Q. Fang, W. Kim, Ö. Aktas, A. Botchkarev, A. Salvador, H. Morkoç
Physics Faculty Publications
A thermally stimulated current peak, occurring at 100 K for a heating rate of 0.4 K/s, has been found in semi‐insulating GaN grown by molecular beam epitaxy. This peak has contributions from two traps, with the main trap described by the following parameters: emission thermal activation energy E≂90±2 meV, effective capture cross‐section σ≂3±1×10−22 cm−2, and Nμτ≂3±1 × 1014 cm−1 V −1, where N is the trap concentration, μ the mobility, and τ the free‐carrier lifetime. This trap is much deeper than the typical shallow donors in conducting GaN, but shallower than any …
Stability Analysis Of A Model For The Defect Structure Of Yba2cu3ox, Gregory Kozlowski, Tom Svobodny
Stability Analysis Of A Model For The Defect Structure Of Yba2cu3ox, Gregory Kozlowski, Tom Svobodny
Physics Faculty Publications
Unusual microstructures of YBa2Cu3Ox (123) crystals have been observed. These structures have been shown to pass very high transport currents. A model of the solidification of 123 from a melt with Y2BaCuO5 (211) inclusions indicates that the stability of the 123 interface can depend on the sizes of the 211 inclusions. The observed formations are interpreted in the light of this instability.
Electron Impact Vibrational Excitation Cross Sections Of Sif4, R. Nagpal, A. Garscadden, Jerry D. Clark
Electron Impact Vibrational Excitation Cross Sections Of Sif4, R. Nagpal, A. Garscadden, Jerry D. Clark
Physics Faculty Publications
Electron drift velocities in mixtures of SiF4 and Ar have been measured using a pulsed‐Townsend type drift tube. A set of vibrational excitation cross sections of electron scattering in SiF4 has been subsequently determined by the swarm analyses of measured transport data in highly dilute SiF4−Ar mixtures. The derived cross sections are consistent with the electron transport properties over an order of magnitude in SiF4 concentration in gas mixtures, thus providing evidence that the main features of their near threshold behavior, and of their absolute magnitude have been captured.
Effects Of In Profile On Material And Device Properties Of Algaas/Ingaas/Gaas High Electron Mobility Transistors, David C. Look, B. Jogai, R. Kaspi, J. L. Ebel, K. R. Evans, R. L. Jones, K. Nakano, R. E. Sherriff, C. E. Stutz, G. C. Desalvo, C. Ito
Effects Of In Profile On Material And Device Properties Of Algaas/Ingaas/Gaas High Electron Mobility Transistors, David C. Look, B. Jogai, R. Kaspi, J. L. Ebel, K. R. Evans, R. L. Jones, K. Nakano, R. E. Sherriff, C. E. Stutz, G. C. Desalvo, C. Ito
Physics Faculty Publications
The molecular‐beam‐epitaxial growth of InxGa1−xAs on GaAs or AlyGa1−yAs leads to a variation of In content with depth, due to In segregation. However, by predepositing In at the beginning of InxGa1−xAs growth, and also thermally removing the excess In at the end, we can produce a layer with the ideal ‘‘square’’ In profile. We find that the performance of AlyGa1−yAs/InxGa1−xAs/GaAs high electron mobility transistors is most enhanced by the predeposition step alone.
Wet Chemical Digital Etching Of Gaas At Room Temperature, Gregory C. Desalvo, Christopher A. Bozada, John L. Ebel, David C. Look, John P. Barrette, Charles L. A. Cerny, Ross W. Dettmer, James K. Gillespie, Charles K. Havasy, Thomas J. Jenkins, Kenichi Nakano, Carl I. Pettiford, Tony K. Quach, James S. Sewell, G. David Via
Wet Chemical Digital Etching Of Gaas At Room Temperature, Gregory C. Desalvo, Christopher A. Bozada, John L. Ebel, David C. Look, John P. Barrette, Charles L. A. Cerny, Ross W. Dettmer, James K. Gillespie, Charles K. Havasy, Thomas J. Jenkins, Kenichi Nakano, Carl I. Pettiford, Tony K. Quach, James S. Sewell, G. David Via
Physics Faculty Publications
A new room temperature wet chemical digital etching technique for GaAs is presented which uses hydrogen peroxide and an acid in a two‐step etching process to remove GaAs in approximately 15 Å increments. In the first step, GaAs is oxidized by 30% hydrogen peroxide to form an oxide layer that is diffusion limited to a thickness of 14 to 17 Å for time periods from 15 to 120 s. The second step removes this oxide layer with an acid that does not attack unoxidized GaAs. These steps are repeated in succession until the desired etch depth is obtained. Experimental results …
Magnetophotoluminescence Study Of Excited States Associated With Donor Bound Excitons In High-Purity Gaas, D. C. Reynolds, David C. Look, B. Jogai, G. L. Mccoy, K. K. Bajaj
Magnetophotoluminescence Study Of Excited States Associated With Donor Bound Excitons In High-Purity Gaas, D. C. Reynolds, David C. Look, B. Jogai, G. L. Mccoy, K. K. Bajaj
Physics Faculty Publications
Detailed magnetic-field splitting of the two rotator states designated as (Γ6+Γ8, J=5/2) and (Γ7, J=1/2) associated with donor bound excitons in high-purity epitaxial GaAs is observed in magnetophotoluminescence spectra. These two states are associated with the light-hole mass and are split by the spin-orbit interaction. The ordering in energy of these two states agrees with that predicted by theory. Also observed are the rotator states in which, after the radiative collapse of the exciton, the donor is left in the excited states. A good agreement between the energies of the excited states of the …