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Full-Text Articles in Physics
Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look
Ga-Doped Zno Films Grown On Gan Templates By Plasma-Assisted Molecular-Beam Epitaxy, H. J. Ko, Yanfang Chen, S. K. Hong, H. Wenisch, T. Yao, David C. Look
Physics Faculty Publications
We have investigated the structural and optical properties of Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy. The carrier concentration in Ga-doped ZnO films can be controlled from 1.33×1018/cm3 to 1.13×1020/cm3. Despite high Ga incorporation, the linewidth of (0002) ω-rocking curves of Ga-doped ZnO films still lies in the range from 5 to 15 arc min. Photoluminescence (PL) spectra of Ga-doped ZnO films show dominant near-bandedge emission with negligibly weak deep-level emission, independent of carrier concentration. The PL spectrum exhibits a new emission line at 3.358 eV, which corresponds to …
Combined Effects Of Screening And Band Gap Renormalization On The Energy Of Optical Transitions In Zno And Gan, D. C. Reynolds, David C. Look, B. Jogai
Combined Effects Of Screening And Band Gap Renormalization On The Energy Of Optical Transitions In Zno And Gan, D. C. Reynolds, David C. Look, B. Jogai
Physics Faculty Publications
The energy positions of the optical transitions in both GaN and ZnO were investigated when the samples were excited simultaneously with a HeCd laser and an Ar+ ion laser. The increased number of free electrons excited by the Ar+ ion laser will effectively screen both the free exciton and bound exciton transitions, resulting in a blueshift. The increased number of free electrons also produces many-body effects, which lead to a reduction of the band gap energy and thus a redshift. The resultant of screening and renormalization results in a redshift of the optical transitions in ZnO but a …
Electron Beam And Optical Depth Profiling Of Quasibulk Gan, L. Chernyak, A. Osinsky, G. Nootz, A. Schulte, J. Jasinski, M. Benamara, Z. Liliental-Weber, David C. Look, Richard J. Molnar
Electron Beam And Optical Depth Profiling Of Quasibulk Gan, L. Chernyak, A. Osinsky, G. Nootz, A. Schulte, J. Jasinski, M. Benamara, Z. Liliental-Weber, David C. Look, Richard J. Molnar
Physics Faculty Publications
Electron beam and optical depth profiling of thick (5.5–64 μm) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), and transmission electron microscopy (TEM). The minority carrier diffusion length, L, was found to increase linearly from 0.25 μm, at a distance of about 5 μm from the GaN/sapphire interface, to 0.63 μm at the GaN surface, for a 36-μm-thick sample. The increase in L was accompanied by a corresponding increase in PL band-to-band radiative transition intensity as a function of distance from the GaN/sapphire interface. We attribute …
Identification Of The Gamma(5) And Gamma(6) Free Excitons In Gan, D. C. Reynolds, David C. Look, B. Jogai, A. W. Saxler, Seong-Ju S. Park, J. Y. Hahn
Identification Of The Gamma(5) And Gamma(6) Free Excitons In Gan, D. C. Reynolds, David C. Look, B. Jogai, A. W. Saxler, Seong-Ju S. Park, J. Y. Hahn
Physics Faculty Publications
The Γ5 and Γ6 free excitons have been identified in GaN from emission measurements. Another emission peak is also observed which we believe to be the longitudinal free exciton. These measurements along with electrical measurements, which show the sample to have very high peak mobility, attest to the high quality of the sample.
Photoluminescence Measurements From The Two Polar Faces Of Zno, R. E. Sherriff, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, T. C. Collins, G. Cantwell, W. C. Harsch
Photoluminescence Measurements From The Two Polar Faces Of Zno, R. E. Sherriff, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, T. C. Collins, G. Cantwell, W. C. Harsch
Physics Faculty Publications
The crystal structure of ZnO is wurtzite and the stacking sequence of atomic layers along the “c” axis is not symmetric. As a result, a ZnO crystal surface that is normal to the c axis exposes one of two distinct polar faces, with (0001̄) being considered the O face and (0001) the Zn face. Photoluminescence (PL) measurements on the two faces reveal a striking difference. Two transitions are observed in PL that are dominant from the O face and barely observed in PL from the Zn face. These lines are identified as phonon replicas of a particular D …
Properties Of Semi‐Insulating Gaas:Fe Grown By Hydride Vapor Phase Epitaxy, E. Rodríguez Messmer, D. Söderström, P. Hult, S. Marcinkevicius, S. Lourdudoss, David C. Look
Properties Of Semi‐Insulating Gaas:Fe Grown By Hydride Vapor Phase Epitaxy, E. Rodríguez Messmer, D. Söderström, P. Hult, S. Marcinkevicius, S. Lourdudoss, David C. Look
Physics Faculty Publications
In this paper we analyze GaAs grown by hydride vapor phase epitaxy (HVPE) and doped with four different iron concentrations between and . From temperature dependent current‐voltage measurements we observed the highest resistivity in the lowest doped sample. We also quantified the activation energy. These results together with those of time resolved photoluminescence measurements indicate that in the sample with the lowest Fe concentration, EL2 may be dominant. From the analysis of the time resolved photoluminescence measurements, the intrinsic EL2 concentration and the electron and hole capture cross sections of Fe in GaAs were estimated. © 2000 The Electrochemical Society. …
Strain Variation With Sample Thickness In Gan Grown By Hydride Vapor Phase Epitaxy, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, Richard J. Molnar
Strain Variation With Sample Thickness In Gan Grown By Hydride Vapor Phase Epitaxy, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, Richard J. Molnar
Physics Faculty Publications
High quality GaN crystals can be grown on sapphire by hydride vapor phase epitaxy. The thermal expansion mismatch between sapphire and GaN produces strain in the GaN crystal as it is cooled from the growth temperature to room temperature. The strain is evidenced by shifts in the photoluminescence and reflectance line positions. By analyzing the surface strain as the crystal thickness is increased, the thickness required to obtain zero surface strain can be estimated. This structure might provide a lattice matched and thermally matched substrate for further epitaxial growth of GaN.
Time-Resolved Photoluminescence Lifetime Measurements Of The Gamma(5) And Gamma(6) Free Excitons In Zno, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, M. T. Harris, M. J. Callahan
Time-Resolved Photoluminescence Lifetime Measurements Of The Gamma(5) And Gamma(6) Free Excitons In Zno, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, M. T. Harris, M. J. Callahan
Physics Faculty Publications
Time-resolved photoluminescence spectroscopy at 2 K was used to measure the radiative recombination lifetime of the allowed (Γ5) and forbidden (Γ6) free excitons in ZnO. The measurements were made on a sample containing internal strain, which altered the sample symmetry, and resulted in relaxed selection rules, allowing the Γ6 exciton to be observed. A radiative recombination lifetime of 259 ps was measured for the Γ5 exciton and 245 ps for the Γ6 exciton. The decay of the free excitons was of single-exponential form, and the decay times were obtained using a least-squares fit …
Electrical Properties Of Boron-Doped P-Sigec Grown On N(-)-Si Substrate, M. Ahoujja, Y. K. Yeo, R. L. Hengehold, G. S. Pomrenke, David C. Look, J. Huffman
Electrical Properties Of Boron-Doped P-Sigec Grown On N(-)-Si Substrate, M. Ahoujja, Y. K. Yeo, R. L. Hengehold, G. S. Pomrenke, David C. Look, J. Huffman
Physics Faculty Publications
Electrical properties of fully strained boron-doped Si0.90−yGe0.10Cy/n−–Si grown by low pressure chemical vapor deposition have been investigated as a function of carbon content (0.2%–1.5%), using the variable temperature (25–650 K) Hall-effect technique. The results of Hall-effect measurements show that the Si substrate and the SiGeC/Si interfacial layer affect significantly the electrical properties of the SiGeC epitaxial layer. Thus, a three-layer conducting model has been used to extract the carrier concentration and mobility of the SiGeC layer alone. At room temperature, the hole carrier concentration decreases from 6.8×1017 to 2.4×10 …
Dissociation Of Al2o3(0001) Substrates And The Roles Of Silicon And Oxygen In N-Type Gan Thin Solid Films Grown By Gas-Source Molecular Beam Epitaxy, J. E. Van Nostrand, J. Solomon, A. Saxler, Q. H. Xie, D. C. Reynolds, David C. Look
Dissociation Of Al2o3(0001) Substrates And The Roles Of Silicon And Oxygen In N-Type Gan Thin Solid Films Grown By Gas-Source Molecular Beam Epitaxy, J. E. Van Nostrand, J. Solomon, A. Saxler, Q. H. Xie, D. C. Reynolds, David C. Look
Physics Faculty Publications
Unintentionally doped and silicon doped GaN films prepared by molecular beam epitaxy using ammonia are investigated. Hall, secondary ion mass spectroscopy (SIMS), photoluminescence, and x-ray data are utilized for analysis of sources of autodoping of GaN epitaxial films in an effort to identify whether the n-type background electron concentration is of impurity origin or native defect origin. We identify and quantify an anomalous relationship between the Si doping concentration and free carrier concentration and mobility using temperature dependent Hall measurements on a series of 2.0-μm-thick GaN(0001) films grown on sapphire with various Si doping concentrations. SIMS is used to …
Zno Diode Fabricated By Excimer-Laser Doping, Toru Aoki, Yoshinori Hatanaka, David C. Look
Zno Diode Fabricated By Excimer-Laser Doping, Toru Aoki, Yoshinori Hatanaka, David C. Look
Physics Faculty Publications
A ZnO diode was fabricated by using a laser-doping technique to form a p-type ZnO layer on an n-type ZnO substrate. A zinc-phosphide compound, used as a phosphorous source, was deposited on the ZnO wafer and subjected to excimer-laser pulses. The current–voltage characteristics showed a diode characteristic between the phosphorous-doped p-layer and the n-type substrate. Moreover, light emission, with a band-edge component, was observed by forward current injection at 110 K.
On The Main Irradiation-Induced Defect In Gan, L. Polenta, Z-Q. Fang, David C. Look
On The Main Irradiation-Induced Defect In Gan, L. Polenta, Z-Q. Fang, David C. Look
Physics Faculty Publications
We show that the usual Arrhenius analysis of the main electron-irradiation-induced defect trap in n-type GaN, observed by deep-level transient spectroscopy (DLTS), is not sufficiently accurate. Instead, an exact fitting of the DLTS spectrum for this trap reveals two components, each of which has a thermal energy near 60 meV, not the apparent 140–200 meV, as given in other DLTS studies. This result resolves the discrepancy between Hall-effect and DLTS determinations of the thermal energy of this defect center.