Page 23 of 23:  Prev << 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23    (567 Items)

4.  Electrical Transport Properties of Highly Doped N-type GaN Epilayers
H.J. Lee, M.G. Cheong, E.K. Suh, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 28, 1998 ...[Visit Journal]
Temperature-dependent Hall-effects in MOCVD-grown Si-doped GaN epilayers were measured as a function of temperature in the range 10-800 K. The results were satisfactorily analyzed in terms of a two-band model including the (Gamma) and impurity bands at lower temperatures than room. The (Gamma) band electrons are dominant only high temperatures. The ionized impurity scattering is the most important in the (Gamma) band except at very high temperatures. [reprint (PDF)]
 
4.  Study on the effects of minority carrier leakage in InAsSb/InPAsSb double heterostructure
B. Lane, D. Wu, H.J. Yi, J. Diaz, A. Rybaltowski, S. Kim, M. Erdtmann, H. Jeon and M. Razeghi
Applied Physics Letters 70 (11)-- April 17, 1997 ...[Visit Journal]
InAsxSb1−x/InP1−x−yAsxSby double heterostructures have been grown on InAs substrates by metal-organic chemical vapor deposition. The minority carrier leakage to the cladding layers was studied with photoluminescence measurements on the InAsSb/InPAsSb double heterostructures. A carrier leakage model is used to extract parameters related to the leakage current (diffusion-coefficient and length) from experimental results. Using the obtained parameters, the temperature dependence of the threshold current density of InAsSb/InPAsSb double heterostructure lasers is predicted and compared with experimental results. [reprint (PDF)]
 
4.  Growth of AlxGa1-xN:Ge on sapphire and silicon substrates
X. Zhang, P. Kung, A. Saxler, D. Walker, T.C. Wang, and M. Razeghi
Applied Physics Letters 67 (12)-- September 18, 1995 ...[Visit Journal]
AlxGa1–xN were grown on (00.1) sapphire and (111) silicon substrates in the whole composition range (0 <= x <= 1). The high optical quality of the epilayers was assessed by room-temperature optical absorption and photoluminescence measurements. Layers with higher Al composition are more resistive. Resistive AlxGa1–xN epilayers were successfully doped with Ge and free-electron concentration as high as 3 × 1019 cm–3 was achieved. [reprint (PDF)]
 
4.  High-power InGaAsP/GaAs 0.8 μm laser diodes and peculiarities of operational characteristics
J. Diaz, I. Eliashevich, X. He, H. Yi, L. Wang, E. Kolev, D. Garbuzov, and M. Razeghi
Applied Physics Letters 65 (8)-- August 22, 1994 ...[Visit Journal]
High-power operation of 3 W in pulse mode, 750 mW in quasi-continuous wave and 650 mW in continuous wave per uncoated facet from 100 μm aperture has been demonstrated for 1 mm long cavity InGaAsP/GaAs 808 nm laser diodes prepared by low-pressure metalorganic chemical vapor deposition. Threshold current density of 300 A/cm², differential efficiency of 1.1 W/A, T0=155 °C, transverse beam divergence of 27°, and less than 2 nm linewidth at 808 nm have been measured. No degradation has been observed after 1000 h of operation in a quasi-continuous wave regime. [reprint (PDF)]
 
3.  Efficiency of photoluminescence and excess carrier confinement in InGaAsP/GaAs structures prepared by metal-organic chemical vapor deposition
J. Diaz, H.J. Yi, M. Erdtmann, X. He, E. Kolev, D. Garbuzov, E. Bigan, and M. Razeghi
Journal of Applied Physics 76 (2)-- July 15, 1994 ...[Visit Journal]
Special double‐ and separate‐confinement InGaAsP/GaAs heterostructures intended for photoluminescence measurements have been grown by low‐pressure metal‐organic chemical‐vapor deposition. The band gap of the active region quaternary material was close to 1.5 eV, and the waveguide of the separate‐confinement structures was near 1.8 eV. Measurement of the integrated luminescence efficiency at 300 K has shown that over a wide range of excitation level (10–103 W/cm²) radiative transitions are the dominant mechanism for excess carrier recombination in the active region of the structures studied. As determined by spectral measurements, the excess carrier concentration in the waveguide of the separate‐confinement heterostructures and the intensity of the waveguide emission band correspond to a condition of thermal equilibrium of the excess carrier populations in the active region and the waveguide. The ratio of the intensity of the waveguide emission to the active region emission fits a model which assumes that the barrier height for minority carriers (holes) is equal to the difference in band gaps between the active region and the waveguide region. [reprint (PDF)]
 
3.  High quality AlN and GaN epilayers grown on (00*1) sapphire, (100) and (111) silicon substrates
P. Kung, A. Saxler, X. Zhang, D. Walker, T.C. Wang, I. Ferguson, and M. Razeghi
Applied Physics Letters 66 (22)-- May 29, 1995 ...[Visit Journal]
The growth of high quality AlN and GaN thin films on basal plane sapphire, (100), and (111) silicon substrates is reported using low pressure metalorganic chemical vapor deposition. X-ray rocking curve linewidths of about 100 and 30 arcsec were obtained for AlN and GaN on sapphire, respectively. Room‐temperature optical transmission and photoluminescence (of GaN) measurements confirmed the high quality of the films. The luminescence at 300 and 77 K of the GaN films grown on basal plane sapphire, (100), and (111) silicon was compared. [reprint (PDF)]
 
3.  Intermixing of GaInP/GaAs Multiple Quantum Wells
C. Francis, M.A. Bradley, P. Boucaud, F.H. Julien and M. Razeghi
Applied Physics Letters 62 (2)-- January 11, 1993 ...[Visit Journal]
The intermixing of GaInP‐GaAs superlattices induced by a heat treatment is investigated as a function of the annealing temperature and duration. Photoluminescence experiments reveal a large red shift of the effective band gap of the annealed quantum wells thus indicating a dominant self‐diffusion of the group III atoms which is confirmed by secondary ion mass spectroscopic measurements. For long enough annealing durations, the red shift saturates and even decreases due to the competing slower self‐diffusion of the group V atoms. Experiments are well understood based on a simple diffusion model. [reprint (PDF)]
 
3.  A Review of III-Nitride Research at the Center for Quantum Devices
M. Razeghi and R. McClintock
Journal of Crystal Growth, Vol. 311, No. 10-- May 1, 2009 ...[Visit Journal]
In this paper, we review the history of the Center for Quantum Devices’ (CQD) III-nitride research covering the past 15 years. We review early work developing III-nitride material growth. We then present a review of laser and light-emitting diode (LED) results covering everything from blue lasers to deep UV LEDs emitting at 250 nm. This is followed by a discussion of our UV photodetector research from early photoconductors all the way to current state of the art Geiger-mode UV single photon detectors. [reprint (PDF)]
 
3.  High performance focal plane array based on type-II InAs/GaSb superlattice heterostructures
P.Y. Delaunay and M. Razeghi
SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000M-1-10.-- February 1, 2008 ...[Visit Journal]
Recent progress in growth techniques, structure design and processing has lifted the performances of Type-II InAs/GaSb superlattice photodetectors. A double heterostructure design, based on a low band gap (11 µm) active region and high band gap (5 µm) superlattice contacts, reduced the sensitivity of the superlattice to surface effects. The heterodiodes with an 11 µm cutoff, passivated with SiO2, presented similar performances to unpassivated devices and a one order of magnitude increase of the resistivity of the sidewalls, even after flip-chip bonding and underfill. Thanks to this new design and to the inversion of the polarity of the devices, a high performance focal plane array with an 11 µm cutoff was demonstrated. The noise equivalent temperature difference was measured as 26 mK and 19 mK for operating temperatures of 81 K and 67 K. At an integration time of 0.08 ms, the FPA presented a quantum efficiency superior to 50%. [reprint (PDF)]
 
3.  Investigation of MgZnO/ZnO heterostructures grown on c-sapphire substrates by pulsed laser deposition
D. J. Rogers ; F. Hosseini Teherani ; P. Bove ; A. Lusson ; M. Razeghi
Proc. SPIE 8626, Oxide-based Materials and Devices IV, 86261X (March 18, 2013)-- March 18, 2013 ...[Visit Journal]
MgZnO thin films were grown on c-sapphire and ZnO-coated c-sapphire substrates by pulsed laser deposition from a ZnMgO target with 4 at% Mg. The MgZnO grown on the ZnO underlayer showed significantly better crystal quality than that grown directly on sapphire. AFM studies revealed a significant deterioration in surface morphology for the MgZnO layers compared with the ZnO underlayer. Optical transmission studies indicated a MgZnO bandgap of 3.61eV (compared with 3.34eV for the ZnO), which corresponds to a Mg content of about 16.1 at%. The MgZnO/ZnO heterojunction showed an anomalously low resistivity, which was more than two orders of magnitude less than the MgZnO layer and an order of magnitude lower than that for the ZnO layer. It was suggested that this may be attributable to the presence of a 2D electron gas at the ZnMgO/ZnO heterointerface. [reprint (PDF)]
 
3.  III-Nitride photon counting avalanche photodiodes
R. McClintock, J.L. Pau, K. Minder, C. Bayram and M. Razeghi
SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000N-1-11.-- February 1, 2008 ...[Visit Journal]
In order for solar and visible blind III-Nitride based photodetectors to effectively compete with the detective performance of PMT there is a need to develop photodetectors that take advantage of low noise avalanche gain. Furthermore, in certain applications, it is desirable to obtain UV photon counting performance. In this paper, we review the characteristics of III-nitride visible-blind avalanche photodetectors (APDs), and present the state-of-the-art results on photon counting based on the Geiger mode operation of GaN APDs. The devices are fabricated on transparent AlN templates specifically for back-illumination in order to enhance hole-initiated multiplication. The spectral response and Geiger-mode photon counting performance are analyzed under low photon fluxes, with single photon detection capabilities being demonstrated in smaller devices. Other major technical issues associated with the realization of high-quality visible-blind APDs and Geiger mode APDs are also discussed in detail and solutions to the major problems are described where available. Finally, future prospects for improving upon the performance of these devices are outlined. [reprint (PDF)]
 
3.  High Carrier Lifetime InSb Grown on GaAs Substrates
E. Michel, H. Mohseni, J.D. Kim, J. Wojkowski, J. Sandven, J. Xu, M. Razeghi, R. Bredthauer, P. Vu, W. Mitchel, and M. Ahoujja
Applied Physics Letters 71 (8-- August 25, 1997 ...[Visit Journal]
We report on the growth of near bulklike InSb on GaAs substrates by molecular beam epitaxy despite the 14% lattice mismatch between the epilayer and the substrate. Structural, electrical, and optical properties were measured to assess material quality. X-ray full widths at half-maximum were as low as 55 arcsec for a 10 µm epilayer, peak mobilities as high as ~ 125 000 cm2/V s, and carrier lifetimes up to 240 ns at 80 K. [reprint (PDF)]
 
3.  InTlSb alloys for infrared detection
E. Bigan, Y.H. Choi, G. Labeyrie, and M. Razeghi
Proceedings, SPIE Nonlinear Optics for High-Speed Electronics and Optical Frequency Conversion, Vol. 2145-- January 24, 1994 ...[Visit Journal]
InTISb alloys have been grown by low-pressure metalorganic chemical vapor deposition, and characterized. Photoconductors exhibit a cutoff wavelength that can be tailored from 5.5 μm up to 9 μm by varying the thallium content. Experimental observations suggest that this can be further extended by increasing the thallium content. An InTISb photoconductor having a 9 μm cutoff wavelength exhibited a D* of 109 cm·Hz½·W-1 at 7 μm operating wavelength. [reprint (PDF)]
 
3.  Determination of of Band Gap Energy of Al1-xInxN Grown by Metal Organic Chemical Vapor Deposition in the High Al Composition Regime
K.S. Kim, A. Saxler, P. Kung, M. Razeghi, and K.Y. Lim
Applied Physics Letters 71 (6)-- August 11, 1997 ...[Visit Journal]
Ternary AlInN was grown by metal–organic chemical-vapor deposition in the high Al composition regime. The band-gap energy of AlInN ternary was measured by optical absorption spectroscopy at room temperature. The band-gap energy of Al0.92In0.08N is 5.26 eV. The potential application of AlInN as a barrier material for GaN is also discussed. [reprint (PDF)]
 
3.  Cavity Length Effects of High-Temperature High-Power Continuous Wave Characteristics in Quantum-Cascade Lasers
J.S. Yu, A. Evans, J. David, L. Doris, S. Slivken, and M. Razeghi
Applied Physics Letters, 83 (25)-- December 22, 2003 ...[Visit Journal]
We report the cavity-length dependent high-temperature high-power cw characteristics in λ=6 µm quantum-cascade lasers with a thick electroplated Au top contact layer. For a high-reflectivity (HR) coated 15 µm wide and 3 mm long laser, the cw operation is achieved up to 313 K (40 °C) with an output power of 17 mW. At 298 K, a very high cw output power of 213 mW is obtained for a HR coated 15 µm wide and 4 mm long laser. Thermal resistance is analyzed at temperatures above 283 K for HR coated lasers with different cavities. [reprint (PDF)]
 
3.  Photoluminescence study of InAsSb/InAsSbP heterostructures grown by low-pressure metalorganic chemical vapor deposition
S. Kim, M. Erdtmann, D. Wu, E. Kaas, H. Yi, J. Diaz, and M. Razeghi
Applied Physics Letters 69 (11)-- September 9, 1996 ...[Visit Journal]
Photoluminescence has been measured for double‐ and separate‐confinement InAsSb/InAsSbP heterostructures grown by low‐pressure metalorganic vapor deposition. A measurement of the integrated luminescence intensity at the temperature range of 77–300 K shows that over a wide range of excitation level (1–5×10² W/cm²) the radiative transitions are the dominant. mechanism below T∼170 K. Auger recombination coefficient C=C0 exp(−Ea/kT) with C0≊5×10−27 cm6/s and Ea≊40 meV has been estimated. [reprint (PDF)]
 
3.  GaInAsP/InP 1.35 μm Double Heterostructure Laser Grown on Silicon Substrate by Metalorganic Chemical Vapor Deposition
K. Mobarhan, C. Jelen, E. Kolev, and M. Razeghi
Journal of Applied Physics 74 (1)-- July 1, 1993 ...[Visit Journal]
A 1.35 μm GaInAsP/InP double heterostructure laser has been grown on a Si substrate using low‐pressure metalorganic chemical vapor deposition. This was done without the use of a superlattice layer or a very thick InP buffer layer, which are used to prevent the dislocations from spreading into the active layer. Pulsed operation with output power of over 200 mW per facet was achieved at room temperature for broad area lasers with 20 μm width and 170 μm cavity length. The threshold current density of a 350 μm cavity length device was 9.8 kA/cm². The characteristic temperature was 66 K. [reprint (PDF)]
 

Page 23 of 23:  Prev << 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23    (567 Items)