Publications by    
Page 1  (13 Items)

1.  Very Long Wavelength Infrared Type-II Detectors Operating at 80K
H. Mohseni, A. Tahraoui, J. Wojkowski, M. Razeghi, G.J. Brown, W.C. Mitchel, and Y.S. Park
Applied Physics Letters 77 (11)-- September 11, 2000
We report a demonstration of very long wavelength infrared detectors based on InAs/GaSb superlattices operating at T = 80 K. Detector structures with excellent material quality were grown on an optimized GaSb buffer layer on GaAs semi-insulating substrates. Photoconductive devices with 50% cutoff wavelength of λc = 17  μm showed a peak responsivity of about 100 mA/W at T = 80  K. Devices with 50% cutoff wavelengths up to λc = 22  μm were demonstrated at this temperature. Good uniformity was obtained over large areas even for the devices with very long cutoff wavelengths. reprint
2.  Growth and Characterization of Very Long Wavelength Type-II Infrared Detectors
H. Mohseni, A. Tahraoui, J. Wojkowski, M. Razeghi, W. Mitchel, and A. Saxler
SPIE Conference, San Jose, CA, -- January 26, 2000
We report on the growth and characterization of type-II IR detectors with a InAs/GaSb superlattice active layer in the 15-19 μm wavelength range. The material was grown by molecular beam epitaxy on semi-insulating GaAs substrates. The material was processed into photoconductive detectors using standard photolithography, dry etching, and metalization. The 50 percent cut-off wavelength of the detectors is about 15.5 μm with a responsivity of 90 mA/W at 80 K. The 90 percent-10 percent cut-off energy width of the responsivity is only 17 meV which is an indication of the uniformity of the superlattices. These are the best reported values for type-II superlattices grown on GaAs substrates. reprint
3.  Growth and Characterization of Type-II Non-Equilibrium Photovoltaic Detectors for Long Wavelength Infrared Range
H. Mohseni, J. Wojkowski, A. Tahraoui, M. Razeghi, G. Brown and W. Mitche
SPIE Conference, San Jose, CA, -- January 26, 2000
Growth and characterization of type-II detectors for mid-IR wavelength range is presented. The device has a p-i-n structure is designed to operate in the non-equilibrium mode with low tunneling current. The active layer is a short period InAs/GaSb superlattice. Wider bandgap p-type AlSb and n-type InAs layers are used to facilitate the extraction of both electronics and holes from the active layer for the first time. The performance of these devices were compared to the performance of devices grown at the same condition, but without the AlSb barrier layers. The processed devices with the AlSb barrier show a peak responsivity of about 1.2 A/W with Johnson noise limited detectivity of 1.1 X 1011 cm·Hz½/W at 8 μm at 80 K at zero bias. The details of the modeling, growth, and characterizations will be presented. reprint
4.  Uncooled InAs/GaSb Type-II infrared detectors grown on GaAs substrate for the 8–12 μm atmospheric window
H. Mohseni, J. Wojkowski, M. Razeghi, G. Brown, and W. Mitchel
IEEE Journal of Quantum Electronics 35 (7)-- July 1, 1999
The operation of uncooled InAs-GaSb superlattice photodiodes with a cutoff wavelength of λc=8 μm and a peak detectivity of 1.2×108 cm·Hz½/W at zero bias is demonstrated. The detectivity is similar to the best uncooled HgCdTe detectors and microbolometers. However, the R0A product is more than two orders of magnitude higher than HgCdTe and the device is more than four orders of magnitude faster than microbolometers. These features combined with their low 1/f noise and high uniformity make these type-II photodiodes an excellent choice for uncooled high-speed IR imaging arrays reprint
5.  Growth of InAsSb Alloys on GaAs and Si Substrates for Uncooled Infrared Photodetector Applications
J.D. Kim, H. Mohseni, J.S. Wojkowski, J.J. Lee and M. Razeghi
SPIE Conference, San Jose, CA, -- January 27, 1999
In this paper, we report on the growth and characterization of InAsSb alloys on GaAs and Si substrates for uncooled infrared photodetector applications. The fabrication and characterization of photodetectors from the grown layers are also reported. The photovoltaic and photoconductive devices were grown on (100) GaAs and Si substrates, respectively, using molecular beam epitaxy (MBE). The composition of InAs>sub>1-xSbx layers was 0.95 in both cases and cut-off wavelength of 7-8 μm has been obtained. At 300 K, the photovoltaic detectors on GaAs substrates resulted in a sharp cut-off wavelength of 7.5 μm with a peak responsivity as high as 0.32 V/W at 6.5 micrometer. For the photoconductive detectors on Si substrates, cut-off wavelength of 8 μm has been observed with a responsivity of 6.3x10-2 V/W at 7 μm under an electric field of 420 V/m. reprint
6.  Demonstration of InAsSb/AlInSb Double Heterostructure Detectors for Room Temperature Operation in the 5–8 μm Wavelength Range
J.S. Wojkowski, H. Mohseni, J.D. Kim, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 27, 1999
We report the first demonstration of InAsSb/AlInSb double heterostructure detectors for room temperature operation. The structures were grown in a solid source molecular beam epitaxy reactor on semi-insulating GaAs substrate. The material was processed to 400x400 micrometer mesas using standard photolithography, etching, and metallization techniques. No optical immersion or surface passivation was used. The photovoltaic detectors showed a cutoff wavelength at 8 micrometer at 300 K. The devices showed a high quantum efficiency of 40% at 7 μm at room temperature. A responsivity of 300 mA/W was measured at 7 μm under a reverse bias of 0.25 V at 300 K resulting in a Johnson noise limited detectivity of 2x108 cm·Hz½/W. reprint
7.  Uncooled long-wavelength infrared photodetectors using narrow bandgap semiconductors
M. Razeghi, J. Wojkowski, J.D. Kim, H. Mohseni and J.J. Lee
-- October 12, 1998
8.  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
9.  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
10.  Infrared Imaging Arrays Using Advanced III-V Materials and technology
M. Razeghi, J.D. Kim, C. Jelen, S. Slivken, E. Michel, H. Mohseni, J.J. Lee, J. Wojkowski, K.S. Kim, H.I. Jeon, and J. X
IEEE Proceedings, Advanced Workshop on Frontiers in Electronics (WOFE), Tenerife, Spain;-- January 6, 1997
Photodetectors operating in the 3-5 and 8-12 μm atmospheric windows are of great importance for applications in infrared (IR) thermal imaging. HgCdTe has been the dominant material system for these applications. However, it suffers from instability and non-uniformity problems over large areas due to high Hg vapor pressure during the material, growth. There has been a lot of interest in the use of heteroepitaxially grown Sb-based alloys, its strained layer superlattices, and GaAs based quantum wells as alternatives to MCT. This interest has been driven by the advanced material growth and processing technology available for the III-V material system reprint
11.  InSb Detectors and Focal Plane Arrays on GaAs, Si, and Al2O3 Substrates
E. Michel, H. Mohseni, J. Wojkowski, J. Sandven, J. Xu, M. Razeghi, P. Vu, R. Bredthauer, W. Mitchel, and M. Ahoujja
-- December 2, 1996
12.  Long-Wavelength InAsSb Photoconductors Operated at Near Room Temperatures (200-300 K)
J.D. Kim, D. Wu, J. Wojkowski, J. Piotrowski, J. Xu, and M. Razeghi
Applied Physics Letters., 68 (1),-- January 1, 1996
Long-wavelength InAs1−xSbx photoconductors operated without cryogenic cooling are reported. The devices are based on p-InAs1−xSbx/p-InSb heterostructures grown on (100) semi-insulating GaAs substrates by low pressure metalorganic chemical vapor deposition (LP‐MOCVD). Photoreponse up to 14 μm has been obtained in a sample with x=0.77 at 300 K, which is in good agreement with the measured infrared absorption spectra. The corresponding effective lifetime of ≊0.14 ns at 300 K has been derived from stationary photoconductivity. The Johnson noise limited detectivity at λ=10.6 μm is estimated to be about 3.27×107 cm· Hz½/W at 300 K. reprint
13.  8-13 μm InAsSb heterojunction photodiode operating at near room temperature
J.D. Kim, S. Kim, D. Wu, J. Wojkowski, J. Xu, J. Piotrowski, E. Bigan, and M. Razeghi
Applied Physics Letters 67 (18)-- October 30, 1995
p+-InSb/π-InAs1−xSbx/n+-InSb heterojunction photodiodes operating at near room temperature in the 8–13 μm region of infrared (IR) spectrum are reported. A room‐temperature photovoltaic response of up to 13 μm has been observed at 300 K with an x≊0.85 sample. The voltage responsivity‐area product of 3×10−5 V· cm²/W has been obtained at 300 K for the λ=10.6 μm optimized device. This was close to the theoretical limit set by the Auger mechanism, with a detectivity at room temperature of ≊1.5×108 cm ·Hz½/W. reprint

Page 1  (13 Items)