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626.  The Center for Quantum Devices - extending the scope of photonics
M. Razeghi
-- October 1, 1997
627.  Photoresponse of InGaAsP-based p-doped quantum well infrared photodetectors
M. Tadic, C. Jelen, S. Slivken, and M. Razeghi
-- September 14, 1997
628.  In-plane electron dynamics and hot electron effects in a quantum cascade laser
M. Tadic, C. Jelen, S. Slivken, and M. Razeghi
-- September 14, 1997
629.  Growth and characterization of InAs/GaSb photoconductors for long wavelength infrared range
H. Mohseni, E. Michel, J. Sandven, M. Razeghi, W. Mitchel, and G. Brown
Applied Physics Letters 71 (10)-- September 8, 1997
In this letter we report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi-insulating GaAs substrates for long wavelength infrared detectors. Photoconductive detectors fabricated from the superlattices showed photoresponse up to 12 µm and peak responsivity of 5.5 V/W with Johnson noise limited detectivity of 1.33 × 109 cm·Hz½/W at 10.3 µm at 78 K. reprint
630.  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
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
631.  Schottky barrier heights and conduction-band offsets of In1-xGaxAs1-yPy lattice matched to GaAs
J.K. Lee, Y.H. Cho, B.D. Choe, K.S. Kim, H.I. Jeon, H. Lim and M. Razeghi
Applied Physics Letters 71 (7)-- August 18, 1997
The Schottky barrier heights of Au/In1−xGaxAs1−yPy contacts have been determined as a function of y by the capacitance–voltage and temperature dependent current–voltage characteristics measurements. The barrier height is observed to increase as y is increased for both n- and p-type materials, with a more rapid increase for the p-type material. The compositional variation of the barrier heights for Au/n-In1−xGaxAs1−yPy is found to be identical to that of the conduction-band offsets in In1−xGaxAs1−yPy/GaAs heterojunctions. A possible cause of this phenomenon is also discussed. reprint
632.  Generalized k·p perturbation theory for atomic-scale superlattices
H. Yi and M. Razeghi
Physical Review B 56 (7)-- August 15, 1997
We present a generalized k⋅p perturbation method that is applicable for atomic-scale superlattices. The present model is in good quantitative agreement with full band theories with local-density approximation, and approaches results of the conventional k⋅p perturbation method (i.e., Kane’s Hamiltonian) with the envelope function approximation for superlattices with large periods. The indirect band gap of AlAs/GaAs superlattices with short periods observed in experiments is explained using this method. reprint
633.  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
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
634.  GaN Grown Using Trimethylgallium and Triethylgallium
A. Saxler, P. Kung, X. Zhang, D. Walker, J. Solomon, W.C. Mitchel and M. Razeghi
-- July 1, 1997
635.  GaN Doped with Sulfur
A. Saxler, P. Kung, X. Zhang, D. Walker, J. Solomon, M. Ahoujja, W.C. Mitchel, H.R. Vydyanath, and M. Razeghi
-- July 1, 1997
636.  Electroluminescence of III-Nitride Double Heterostructure Light Emitting Diodes with Silicon and Magnesium Doped InGaN
A. Saxler, K.S. Kim, D. Walker, P. Kung, X. Zhang, G.J. Brown, W.C. Mitchel and M. Razeghi
-- July 1, 1997
637.  Localized Epitaxy for Vertical Cavity Surface Emitting Laser Applications
M. Erdtmann, S. Kim and M. Razeghi
-- July 1, 1997
638.  The Long Wavelength Luminescence Observation from the Self-Organized InGaAs Quantum Dots Grown on (100) GaAs Substrate by Metalorganic Chemical Vapor Deposition
S. Kim, M. Erdtmann, and M. Razeghi
-- July 1, 1997
639.  Structural and Microstructural Characterization of GaN Thin Films and GaN-based Heterostructures Grown on Sapphire Substrates
M. Razeghi, P. Kung, X. Zhang, D. Walker, A. Saxler, K.Y. Lim and K.S. Kim
-- June 30, 1997
640.  Stability of far fields in double heterostructure and multiple quantum well InAsSb/InPAsSb/InAs midinfrared lasers
H. Yi, A. Rybaltowski, J. Diaz, D. Wu, B. Lane, Y. Xiao, and M. Razeghi
Applied Physics Letters 70 (24)-- June 16, 1997
Far fields in perpendicular direction to the junction are investigated in double heterostructure (DH) and multiple quantum well (MQW) midwave-infrared InAsSb/InPAsSb/InAs lasers (λ = 3.2–3.6 μm). Strong broadening of the far fields in the DH lasers was observed with increases in temperature and/or current. On the contrary, MQW lasers with otherwise identical structure exhibit very stable far fields as narrow as 23° for all the operating conditions investigated. Our experiment and theoretical modeling suggest that these different behaviors of far fields in DH and MQW lasers are attributed to the refractive index fluctuation in the InAsSb laser active region. reprint
641.  Growth and characterization of InSbBi for long wavelength infrared photodetectors
J.J. Lee, J.D. Kim, and M. Razeghi
Applied Physics Letters 70 (24)-- June 16, 1997
The epitaxial growth of InSbBi ternary alloys by low-pressure metalorganic chemical vapor deposition is reported on. X-ray diffraction spectra showed well resolved peaks of InSbBi and InSb films. Bi incorporation was confirmed by energy dispersive x-ray analysis. Photoresponse spectrum up to 9.3 μm which corresponds to 0.13 eV energy band gap has been measured in a sample with Bi composition of 5.8 at.% at 77 K. Electron mobility at room temperature ranges from 44 100 to 4910 cm²/V·s as Bi composition increases. reprint
642.  Quantum Hall liquid-to-insulator transition in In1-xGaxAs/InP heterostructures
W. Pan, D. Shahar, D.C. Tsui, H.P. Wei, and M. Razeghi
Physical Review B 55 (23)-- June 15, 1997
We report a temperature- and current-scaling study of the quantum Hall liquid-to-insulator transition in an In1-xGaxAs/InP heterostructure. When the magnetic field is at the critical field Bc, ρxx=0.86h/e². Furthermore, the transport near Bc scales as |B- Bc|T with κ=0.45±0.05, and as |B- Bc|I-b with b=0.23±0.05. The latter can be due to phonon emission in a dirty piezoelectric medium, or can be the consequence of critical behavior near Bc, within which z=1.0±0.1 and ν=2.1±0.3 are obtained from our data. reprint
643.  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
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
644.  AlxGa1-xN (0 ≤ x ≤ 1) Ultraviolet Photodetectors Grown on Sapphire by Metal-organic Chemical-vapor Deposition
D. Walker, X. Zhang, A. Saxler, P. Kung, J. Xu, and M. Razeghi
Applied Physics Letters 70 (8)-- February 24, 1997
AlxGa1–xN (0 ≤ x ≤ 1) ultraviolet photoconductors with cutoff wavelengths from 365 to 200 nm have been fabricated and characterized. The maximum detectivity reached 5.5 × 108 cm·Hz1/2/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in AlxGa1–xN materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 ms. The frequency-dependent noise spectrum shows that it is dominated by Johnson noise at high frequencies for low-Al-composition samples. reprint
645.  AlGaN ultraviolet detectors
M. Razeghi and A. Rogalski,
SPIE Conference, San Jose, CA, -- February 12, 1997
Hitherto, the semiconductor ultraviolet (UV) detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main efforts are currently directed to anew generation of UV detectors fabricated from wide-band-gap semiconductors between them the most promising are diamond and AlGaN. The latest progress in development of AlGaN UV detectors is described in detail. reprint
646.  Intrinsic AlGaN photodetectors for the entire compositional range
D. Walker, X. Zhang, A. Saxler, P. Kung, J. Xu, and M. Razeghi
SPIE Conference, San Jose, CA, -- February 12, 1997
AlxGa1-xN ultraviolet photoconductors with cut- off wavelengths from 365 nm to 200 nm have been fabricated and characterized. Various characteristics of the devices, such as photoresponse, voltage-dependent responsivity, frequency-dependent responsivity and noise spectral density, were measured and cross-referenced with optical, electrical and structural characteristics of the material to provide information about the mechanisms taking place during detection. The maximum detectivity reached 5.5 X 108 cm·Hz½/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in AlxGa1-xN materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 msec. The frequency-dependent noise-spectrum shows that it is dominated by Johnson-noise at high frequencies for low Al-composition samples. reprint
647.  Very Long Wavelength GaAs/GaInP Quantum Well Infrared Photodetectors
C. Jelen, S. Slivken, G.J. Brown, and M. Razeghi
SPIE Conference, San Jose, CA, -- February 12, 1997
We demonstrate long wavelength quantum well infrared photodetectors with GaAs quantum wells and GaInP barriers grown using gas-source molecular beam epitaxy. Wafers were grown with varying well widths. The optimum well width was 75 angstrom, which resulted in a detection peak at 13 μm and a cutoff wavelength of 15 μm. Dark current measurements of the samples with 15 μm cutoff wavelength show low dark current densities. The dark current characteristics have been investigated as a function of temperature and electron density in the well and compared to a model which takes into account thermionic emission and thermally assisted tunneling. The model is used to extract a saturation velocity of 1.5 x 105 cm/s for electrons. The photoelectron lifetime before recapture has been deduced from this carrier velocity and photoconductive gain measurements. The lifetime is found to be approximately 5 ps. Preliminary focal plane array imaging is demonstrated. reprint
648.  Sb-based infrared materials and photodetectors for the near room temperature applications
J.D. Kim, E. Michel, H. Mohseni, J. Wojkowski, J.J. Lee and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 2999, pp. 55-- February 12, 1997
We report on the growth of InSb, InAsSb, and InTlSb alloys for infrared photodetector applications. The fabrication and characterization of photodetectors based on these materials are also reported. Both photoconductive and photovoltaic devices are investigated. The materials and detector structures were grown on (100) and (111)B semi-insulating GaAs and GaAs coated Si substrates by low pressure metalorganic chemical vapor deposition and solid source molecular beam epitaxy. Photoconductive detectors fabricated from InAsSb and InTlSb have been operated in the temperature range from 77 K to 300 K. The material parameters for photovoltaic device structures have been optimized through theoretical calculations based on fundamental mechanisms. InSb p-i-n photodiodes with 77 K peak responsivities approximately 103 V/W were grown on Si and (111) GaAs substrates. An InAsSb photovoltaic detector with a composition of x equals 0.85 showed photoresponse up to 13 micrometers at 300 K with a peak responsivity of 9.13 X 10-2 V/W at 8 micrometers . The RoA product of InAsSb detectors has been theoretically and experimentally analyzed. reprint
649.  Growth models of GaN thin films based on crystal chemistry: Hexagonal and cubic GaN on Si substrates
H. Ohsato and M. Razeghi
-- February 12, 1997
650.  Temperature insensitivity of the Al-free InGaAsP/GaAs lasers for λ = 808 and 908 nm
M. Razeghi, H. Yi, J. Diaz, S. Kim, and M. Erdtmann
SPIE Conference, San Jose, CA; Proceedings 3001-- February 12, 1997
n this work, we present our recent achievements for the reliability of the Al-free lasers at high temperatures and high powers. Laser operations up to 30,000 hours were achieved without any degradation in the lasers characteristics from 7 randomly selected InGaAsP/GaAs diodes for λ = 808 nm. The test were performed for lasers without mirror-coating for optical power of 0.5 to 1 W CW at 50 approximately 60 °C. To the best of our knowledge, this is the first direct demonstration of the extremely high reliability of Al-free diodes operations at high powers and temperatures for periods of time much longer than practical need (approximately 3 years). The characteristics during the tests are discussed in detail. reprint

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