Publications by    
Page 1  (23 Items)

1.  Type-II Binary Superlattices for Infrared Detector
M. Razeghi, H. Mohseni and G.J. Brown
Journal of the Korean Physical Society 39-- December 1, 2001
III-V quantum wells and superlattices based on InAs/GaSb/AlSb, and related compounds have attracted many attentions due to their unique band alignments and physical properties. Recently, novel electronic and optoelectronic heterostructures have been proposed from this material system for hundred gigahertz logic circuits, terahertz transistors, RTDs, infrared lasers, and infrared detectors. In this paper we will describe the ongoing research at the Center for Quantum Devices to develop the theory, modeling, growth, characterization, and device fabrication techniques for this material system. We have demonstrated the rst uncooled infrared detectors from type-II superlattices. The measured detectivity is more than 1 x 108 cm·Hz½/W at 10.6 μm at room temperature which is higher than the commercially available uncooled photon detectors at similar wavelength. In parallel, we have demonstrated the rst high-performance p-i-n type-II photodiode in the very long wavelength infrared (VLWIR) range operating at T = 80 K. The devices with cuto wavelength of 16 μm showed a responsivity of 3.5 A/W at 80 K leading to a detectivity of 1.51 x 1010 cm·Hz½/W. Similar devices with cutoff wavelengths up to 25 μm was demonstrated at 80 K. To enhance this technology further, we plan to move from quantum wells to quantum wire and quantum dots.
 
2.  Long Wavelength Type-II Photodiodes Operating at Room Temperature
H. Mohseni and M. Razeghi
IEEE Photonics Technology Letters 13 (5)-- May 1, 2001
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
 
3.  High Performance InAs/GaSb Superlattice Photodiodes for the Very Long Wavelength Infrared Range
H. Mohseni, M. Razeghi, G.J. Brown, Y.S. Park
Applied Physics Letters 78 (15)-- April 9, 2001
We report on the demonstration of high-performance p-i-n photodiodes based on type-II InAs/GaSb superlattices with 50% cut-off wavelength λc = 16 μm operating at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices show a current responsivity of 3.5 A/W at 80 K leading to a detectivity of ∼ 1.51×1010 cm·Hz½/W. The quantum efficiency of these devices is about 35% which is comparable to HgCdTe detectors with a similar active layer thickness. reprint
 
4.  Miniaturization: enabling technology for the new millennium
M. Razeghi and H. Mohseni
SPIE International Conference on Solid State Crystals, Zakopane, Poland, -- April 1, 2001
The history of semiconductor devices has been characterized by a constant drive toward lower dimensions in order to increase integration density, system functionality and performance. However, this is still far from being comparable with the performance of natural systems such as human brain. The challenges facing semiconductor technologies in the millennium will be to move toward miniaturization. The influence of this trend on the quantum sensing of infrared radiation is one example that is elaborated here. A new generation of infrared detectors has been developed by growing layers of different semiconductors with nanometer thicknesses. The resulted badgap engineered semiconductor has superior performance compared to the bulk material. To enhance this technology further, we plan to move from quantum wells to quantum wire and quantum dots. reprint
 
5.  High Performance Type-II InAs/GaSb Superlattice Photodiodes
H. Mohseni, Y. Wei, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 22, 2001
We report on the demonstration of high performance p-i-n photodiodes based on Type-II InAs/GaSb superlattices operating in the very long wavelength infrared (VLWIR) range at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices with a 50% cutoff wavelength of λc equals 22 μm show a peak current responsivity about 5.5 A/W at 80 K. The use of binary layers in the superlattice has significantly enhanced the uniformity and reproducibility of the energy gap. The 90% to 10% cut-off energy width of these devices is on the order of 2 kT which is about four times smaller compared to the devices based on InAs/Ga1-xInxSb superlattices. Similar photovoltaic devices with cut-off wavelengths up to 25 μm have been measured at 80 K. Our experimental results shows excellent uniformity over a three inch wafer area, indicating the possibility of VLWIR focal plane arrays based on Type-II superlattices. reprint
 
6.  Miniaturization: enabling technology for the new millennium
M. Razeghi and H. Mohseni
-- January 1, 2001
 
7.  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
 
8.  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
 
9.  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
 
10.  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
 
11.  High power asymmetrical InAsSb/InAsSbP/AlAsSb double heterostructure lasers emitting at 3.4 μm
D. Wu, B. Lane, H. Mohseni, J. Diaz and M. Razeghi
Applied Physics Letters 74 (9)-- March 1, 1999
Midinfrared lasers with an asymmetrical InPAsSb/InAsSb/AlAsSb double heterostructure are reported. Using the asymmetrical double heterostructure, p- and n-cladding layers are separately optimized; high energy-gap AlAsSb (Eg ≈ 1.5 eV) for the p-type cladding layer to reduce the leakage current, and thus to increase To, and low energy-gap InPAsSb (Eg ≈ 0.5 eV) for the n-cladding layer to have low turn-on voltage. 100-μm-width broad-area lasers with 1000 μm cavity length exhibited peak output powers of 1.88 W in pulse and 350 mW in continuous wave modes per two facets at T=80 K with To of 54 K and turn-on voltage of 0.36 V. Maximum peak output powers up to 6.7 W were obtained from a laser bar of total aperture of 400 μm width and cavity length of 1000 μm, with a differential efficiency of 34% and far-field beam divergence narrower than 40° at 80 K. reprint
 
12.  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
 
13.  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
 
14.  Interface-induced Suppression of the Auger Recombination in Type-II InAs/GaSb Superlattices
H. Mohseni, V.I. Litvinov and M. Razeghi
Physical Review B 58 (23)-- December 15, 1998
The temperature dependence of the nonequilibrium carriers lifetime has been deduced from the measurement of the photocurrent response in InAs/GaSb superlattices. Based on the temperature dependence of the responsivity and modeling of the transport parameters we have found that the carrier lifetime weakly depends on temperature in the high-temperature region. This indicates the temperature dependence of the Auger recombination rate with no threshold that differs it from that in the bulk material and can be attributed to the interface-induced suppression of the Auger recombination in thin quantum wells. reprint
 
15.  Growth and Characterization of InAs/GaSb Type-II Superlattice for 8–12 μm Room Temperature Detectors
H. Mohseni and M. Razeghi
-- November 5, 1998
 
16.  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
 
17.  Growth and characterization of InGaAs/InGaP quantum dots for mid-infrared photoconductive detector
S. Kim, H. Mohseni, M. Erdtmann, E. Michel, C. Jelen and M. Razeghi
Applied Physics Letters 73 (7)-- August 17, 1998
We report InGaAs quantum dot intersubband infrared photodetectors grown by low-pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The optimum growth conditions were studied to obtain uniform InGaAs quantum dots constructed in an InGaP matrix. Normal incidence photoconductivity was observed at a peak wavelength of 5.5 μm with a high responsivity of 130 mA/W and a detectivity of 4.74×107  cm· Hz½/W at 77 K. reprint
 
18.  Growth and characterization of InAs/GaSb Type-II superlattices for long-wavelength infrared detectors
H. Mohseni, E. Michel, M. Razeghi, W. Mitchel, and G. Brown
SPIE Conference, San Jose, CA, -- January 28, 1998
We report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi- insulating GaAs substrate for long wavelength IR detectors. Photoconductive detectors fabricated from the superlattices showed 80% cut-off at 11.6 μm and peak responsivity of 6.5 V/W with Johnson noise limited detectivity of 2.36 x 109 cm·Hz½/W at 10.7 μm at 78 K. The responsivity decreases at higher temperatures with a T-2 behavior rather than exponential decay, and at room temperature the responsivity is about 660 mV/W at 11 μm. Lower Auger recombination rate in this system provides comparable detectivity to the best HgCdTe detectors at 300K. Higher uniformity over large areas, simpler growth and the possibility of having read-out circuits in the same GaAs chip are the advantages of this system over HgCdTe detectors for near room temperature operation. reprint
 
19.  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
 
20.  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
 
21.  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
 
22.  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
 
23.  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
 

Page 1  (23 Items)