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1.  
Ultra-broadband quantum cascade laser, tunable over 760 cm−1, with balanced gain
Ultra-broadband quantum cascade laser, tunable over 760 cm−1, with balanced gain
N. Bandyopadhyay, M. Chen, S. Sengupta, S. Slivken, and M. Razeghi
Opt. Express 23, 21159-21164 -- August 10, 2015
A heterogeneous quantum cascade laser, consisting of multiple stacks of discrete wavelength quantum cascade stages, emitting in 5.9-10.9 µm, wavelength range is reported. The broadband characteristics are demonstrated with a distributed-feedback laser array, emitting at fixed frequencies at room temperature, covering an emission range of ~760 cm−1, which is ~59% relative to the center frequency. By appropriate choice of a strained AlInAs/GaInAs material system, quantum cascade stage design and spatial arrangement of stages, the distributed-feedback array has been engineered to exhibit a flat threshold current density across the demonstrated range. reprint
 
2.  
InAs/InAs<sub>1-X</sub>Sb<sub>x</sub> Type-II Superlattices for High-Performance Long-Wavelength Infrared Medical Thermography
InAs/InAs1-XSbx Type-II Superlattices for High-Performance Long-Wavelength Infrared Medical Thermography
Manijeh Razeghi, Abbas Haddadi, Guanxi Chen, Romain Chevallier and Ahn Minh Hoang
ECS Trans. 2015 66(7): 109-116-- June 1, 2015
We present the demonstration of a high-performance long-wavelength infrared nBn photodetectors based on InAs/InAs1-xSbx type-II superlattices on GaSb substrate. The photodetector’s 50% cut-off wavelength was ~10 μm at 77K. The photodetector with a 6 μm-thick absorption region exhibited a peak responsivity of 4.47 A/W at 7.9 μm, corresponding to a quantum efficiency of 54% at -90 mV applied bias voltage under front-side illumination and without any anti-reflection coating. With an R×A of 119 Ω·cm² and a dark current density of 4.4×10-4 A/cm² under -90 mV applied bias voltage at 77 K, the photodetector exhibited a specific detectivity of 2.8×1011 Jones. This photodetector opens a new horizon for making infrared imagers with higher sensitivity for medical thermography.
 
3.  
High power frequency comb based on mid-infrared quantum cascade laser at λ ~9μm
High power frequency comb based on mid-infrared quantum cascade laser at λ ~9μm
Q. Y. Lu, M. Razeghi, S. Slivken, N. Bandyopadhyay, Y. Bai, W. J. Zhou, M. Chen, D. Heydari, A. Haddadi, R. McClintock, M. Amanti, and C. Sirtori
Appl. Phys. Lett. 106, 051105 (2015)-- February 2, 2015
We investigate a frequency comb source based on a mid-infrared quantum cascade laser at λ ∼9 μm with high power output. A broad flat-top gain with near-zero group velocity dispersion has been engineered using a dual-core active region structure. This favors the locking of the dispersed Fabry-Pérot modes into equally spaced frequency lines via four wave mixing. A current range with a narrow intermode beating linewidth of 3 kHz is identified with a fast detector and spectrum analyzer. This range corresponds to a broad spectral coverage of 65 cm−1 and a high power output of 180 mW for ∼176 comb modes. reprint
 
4.  
Bias-selectable dual-band mid-/long-wavelength infrared photodetectors based on InAs/InAs<sub>1−x</sub>Sb<sub>x</sub> type-II superlattices
Bias-selectable dual-band mid-/long-wavelength infrared photodetectors based on InAs/InAs1−xSbx type-II superlattices
A. Haddadi, R. Chevallier, G. Chen, A. M. Hoang, and M. Razeghi
Applied Physics Letters 106 , 011104 (2015)-- January 8, 2015
A high performance bias-selectable mid-/long-wavelength infrared photodetector based on InAs/InAs1−xSbx type-II superlattices on GaSb substrate has been demonstrated. The mid- and long-wavelength channels' 50% cut-off wavelengths were ∼5.1 and ∼9.5 μm at 77 K. The mid-wavelength channel exhibited a quantum efficiency of 45% at 100 mV bias voltage under front-side illumination and without any anti-reflection coating. With a dark current density of 1 × 10−7 A/cm² under 100 mV applied bias, the mid-wavelength channel exhibited a specific detectivity of 8.2 × 1012 cm·Hz½·W-1 at 77 K. The long-wavelength channel exhibited a quantum efficiency of 40%, a dark current density of 5.7 × 10−4 A/cm² under −150 mV applied bias at 77 K, providing a specific detectivity value of 1.64 × 1011 cm·Hz½·W-1. reprint
 
5.  
Demonstration of type-II superlattice MWIR minority carrier unipolar imager for high operation temperature application
Demonstration of type-II superlattice MWIR minority carrier unipolar imager for high operation temperature application
Guanxi Chen, Abbas Haddadi, Anh-Minh Hoang, Romain Chevallier, and Manijeh Razeghi
Optics Letters Vol. 40, Iss. 1, pp. 29–32 (2015)-- December 18, 2014
An InAs/GaSb type-II superlattice-based mid-wavelength infrared (MWIR) 320×256 unipolar focal plane array (FPA) using pMp architecture exhibited excellent infrared image from 81 to 150 K and ∼98% operability, which illustrated the possibility for high operation temperature application. At 150 K and −50  mV operation bias, the 27 μm pixels exhibited dark current density to be 1.2×10−5  A/cm², with 50% cutoff wavelength of 4.9 μm, quantum efficiency of 67% at peak responsivity (4.6 μm), and specific detectivity of 1.2×1012 Jones. At 90 K and below, the 27 μm pixels exhibited system limited dark current density, which is below 1×10−9  A/cm², and specific detectivity of 1.5×1014 Jones. From 81 to 100 K, the FPA showed ∼11  mK NEDT by using F/2.3 optics and a 9.69 ms integration time. reprint
 
6.  
InAs/InAs<sub>1-x</sub>Sb<sub>x</sub> type-II superlattices for high performance long wavelength infrared detection
InAs/InAs1-xSbx type-II superlattices for high performance long wavelength infrared detection
A. Haddadi , G. Chen , R. Chevallier , A. M. Hoang , and M. Razeghi
Appl. Phys. Lett. 105, 121104 (2014)-- September 22, 2014
High performance long-wavelength infrared nBn photodetectors based on InAs/InAs1−xSbx type-II superlattices on GaSb substrate have been demonstrated. The photodetector's 50% cut-off wavelength was ∼10 μm at 77 K. The photodetector with a 6 μm-thick absorption region exhibited a peak responsivity of 4.47 A/W at 7.9 μm, corresponding to a quantum efficiency of 54% at −90 mV bias voltage under front-side illumination and without any anti-reflection coating. With an R × A of 119 Ω·cm² and a dark current density of 4.4 × 10−4 A/cm² under −90 mV applied bias at 77 K, the photodetector exhibited a specific detectivity of 2.8 × 1011 cm·Hz1/2·W-1. reprint
 
7.  
Antimonide-Based Type II Superlattices:  A Superior Candidate for the Third Generation of Infrared Imaging Systems
Antimonide-Based Type II Superlattices: A Superior Candidate for the Third Generation of Infrared Imaging Systems
M. Razeghi, A. Haddadi, A.M. Hoang, G. Chen, S. Bogdanov, S.R. Darvish, F. Callewaert, P.R. Bijjam, and R. McClintock
Journal of ELECTRONIC MATERIALS, Vol. 43, No. 8, 2014-- August 1, 2014
Type II superlattices (T2SLs), a system of interacting multiquantum wells,were introduced by Nobel Laureate L. Esaki in the 1970s. Since then, this material system has drawn a lot of attention, especially for infrared detection and imaging. In recent years, the T2SL material system has experienced incredible improvements in material growth quality, device structure design, and device fabrication techniques that have elevated the performance of T2SL-based photodetectors and focal-plane arrays (FPAs) to a level comparable to state-of-the-art material systems for infrared detection and imaging, such as mercury cadmium telluride compounds. We present the current status of T2SL-based photodetectors and FPAs for imaging in different infrared regimes, from short wavelength to very long wavelength, and dual-band infrared detection and imaging, as well as the future outlook for this material system. reprint
 
8.  
High performance photodiodes based on InAs/InAsSb type-II superlattices for very long wavelength infrared detection
High performance photodiodes based on InAs/InAsSb type-II superlattices for very long wavelength infrared detection
A. M. Hoang, G. Chen, R. Chevallier, A. Haddadi, and M. Razeghi
Appl. Phys. Lett. 104, 251105 (2014)-- June 23, 2014
Very long wavelength infrared photodetectors based on InAs/InAsSb Type-II superlattices are demonstrated on GaSb substrate. A heterostructure photodiode was grown with 50% cut-off wavelength of 14.6 μm. At 77 K, the photodiode exhibited a peak responsivity of 4.8 A/W, corresponding to a quantum efficiency of 46% at −300 mV bias voltage from front side illumination without antireflective coating. With the dark current density of 0.7 A/cm², it provided a specific detectivity of 1.4 × 1010 Jones. The device performance was investigated as a function of operating temperature, revealing a very stable optical response and a background limited performance below 50 K. reprint
 
9.  Evaluating the size-dependent quantum efficiency loss in a SiO2-Y2O3 hybrid gated type-II InAs/GaSb long-infrared photodetector array
G. Chen , A. M. Hoang , and M. Razeghi
Applied Physics Letters 104 , 103509 (2014)-- March 14, 2014
Growing Y2O3 on 20 nm SiO2 to passivate a 11 μm 50% cut-off wavelength long-wavelength infrared type-II superlattice gated photodetector array reduces its saturated gate bias (VGsat ) to −7 V. Size-dependent quantum efficiency (QE) losses are evaluated from 400 μm to 57 μm size gated photodiode. Evolution of QE of the 57 μm gated photodiode with gate bias and diode operation bias reveals different surface recombination mechanisms. At 77 K and VG,sat , the 57 μm gated photodiode exhibits QE enhancement from 53% to 63%, and it has 1.2 × 10−5 A/cm² dark current density at −200 mV, and a specific detectivity of 2.3 × 1012 Jones. reprint
 
10.  Effect of sidewall surface recombination on the quantum efficiency in a Y2O3 passivated gated type-II InAs/GaSb long-infrared photodetector array
G. Chen, A. M. Hoang, S. Bogdanov, A. Haddadi, S. R. Darvish, and M. Razeghi
Appl. Phys. Lett. 103, 223501 (2013)-- November 25, 2013
Y2O3 was applied to passivate a long-wavelength infrared type-II superlattice gated photodetector array with 50% cut-off wavelength at 11 μm, resulting in a saturated gate bias that was 3 times lower than in a SiO2 passivated array. Besides effectively suppressing surface leakage, gating technique exhibited its ability to enhance the quantum efficiency of 100 × 100 μm size mesa from 51% to 57% by suppressing sidewall surface recombination. At 77 K, the gated photodetector showed dark current density and resistance-area product at −300 mV of 2.5 × 10−5 A/cm² and 1.3 × 104 Ω·cm², respectively, and a specific detectivity of 1.4 × 1012 Jones. reprint
 
11.  Investigation of impurities in type-II InAs/GaSb superlattices via capacitance-voltage measurement
G. Chen, A. M. Hoang, S. Bogdanov, A. Haddadi, P. R. Bijjam, B.-M. Nguyen, and M. Razeghi
Applied Physics Letters 103, 033512 (2013)-- July 17, 2013
Capacitance-voltage measurement was utilized to characterize impurities in the non-intentionally doped region of Type-II InAs/GaSb superlattice p-i-n photodiodes. Ionized carrier concentration versus temperature dependence revealed the presence of a kind of defects with activation energy below 6 meV and a total concentration of low 1015 cm−3. Correlation between defect characteristics and superlattice designs was studied. The defects exhibited a p-type behavior with decreasing activation energy as the InAs thickness increased from 7 to 11 monolayers, while maintaining the GaSb thickness of 7 monolayers. With 13 monolayers of InAs, the superlattice became n-type and the activation energy deviated from the p-type trend. reprint
 
12.  Advances in antimonide-based Type-II superlattices for infrared detection and imaging at center for quantum devices
M. Razeghi, A. Haddadi, A.M. Hoang, E.K. Huang, G. Chen, S. Bogdanov, S.R. Darvish, F. Callewaert, R. McClintock
Infrared Physics & Technology, Volume 59, Pages 41-52 (2013)-- July 1, 2013
Type-II InAs/GaSb superlattices (T2SLs), a system of multi-interacting quantum wells, was introduced by Nobel Laureate L. Esaki in the 1970s. Since then, this material system has drawn a lot of attention especially for infrared detection. In recent years, T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process which elevated the performances of T2SL-based photo-detectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). In this paper, we will present the current status of T2SL-based photo-detectors and focal plane arrays for imaging in different infrared regions, from SWIR to VLWIR, and the future outlook of this material system. reprint
 
13.  High-performance bias-selectable dual-band Short-/Mid-wavelength infrared photodetectors and focal plane arrays based on InAs/GaSb/AlSb Type-II superlattices
M. Razeghi; A.M. Hoang; A. Haddadi; G. Chen; S. Ramezani-Darvish; P. Bijjam; P. Wijewarnasuriy; E. Decuir
Proc. SPIE 8704, Infrared Technology and Applications XXXIX, 87041W (June 18, 2013)-- June 18, 2013
We report a bias selectable dual-band Type-II superlattice-based short-wave infrared (SWIR) and mid-wave infrared (MWIR) co-located photodetector capable of active and passive imaging. A new double-layer etch-stop scheme is introduced for back-side-illuminated photodetectors, which enhanced the external quantum efficiency both in the SWIR and MWIR spectral regions. Temperature-dependent dark current measurements of pixel-sized 27 μm detectors found the dark current density to be ∼1×10-5 A/cm2 for the ∼4.2 μm cut-off MWIR channel at 140 K. This corresponded to a reasonable imager noise equivalent difference in temperature of ∼49 mK using F/2.3 optics and a 10 ms integration time (tint), which lowered to ∼13 mK at 110 K using and integration time of 30 ms, illustrating the potential for high-temperature operation. The SWIR channel was found to be limited by readout noise below 150 K. An excellent imagery from the dual-band imager exemplifying pixel coincidence is shown. reprint
 
14.  High-performance bias-selectable dual-band mid-/long-wavelength infrared photodetectors and focal plane arrays based on InAs/GaSb Type-II superlattices
M. Razeghi; A. Haddadi; A.M. Hoang; G. Chen; S. Ramezani-Darvish; P. Bijjam
Proc. SPIE 8704, Infrared Technology and Applications XXXIX, 87040S (June 11, 2013)-- June 11, 2013
We report a bias selectable dual-band mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector's electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature's 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective. reprint
 
15.  High performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices
A.M. Hoang, G. Chen, A. Haddadi and M. Razeghi
SPIE Proceedings, Vol. 8631, p. 86311K-1, Photonics West, San Francisco, CA-- February 5, 2013
Active and passive imaging in a single camera based on the combination of short-wavelength and mid-wavelength infrared detection is highly needed in a number of tracking and reconnaissance missions. Due to its versatility in band-gap engineering, Type-II InAs/GaSb/AlSb superlattice has emerged as a candidate highly suitable for this multi-spectral detection. In this paper, we report the demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm and 4 μm. Taking advantages of the high performance short-wavelength and mid-wavelength single color photodetectors, back-to-back p-i-n-n-i-p photodiode structures were grown on GaSb substrate by molecular beam epitaxy. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0x10-9 A/cm² at -50 mV bias voltage, providing an associated shot noise detectivity of 3.0x1013 Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6x10-5 A/cm² at 300 mV bias voltage, resulting in a detectivity of 4.0x1011 Jones. The operations of the two absorber channels are selectable by changing the polarity of applied bias voltage. reprint
 
16.  Demonstration of high performance bias-slectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices
A.M. Hoang, G. Chen, A. Haddadi and M. Razeghi
Applied Physics Letters, Vol. 102, No. 1, p. 011108-1-- January 7, 2013
High performance bias-selectable dual-band short-/mid-wavelength infrared photodetector based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm and 4 μm was demonstrated. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0 × 10−9 A/cm² at −50 mV bias voltage, providing an associated shot noise detectivity of 3.0 × 1013 Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6 × 10−5 A/cm² at 300 mV bias voltage, resulting in a detectivity of 4.0 × 1011 Jones. The spectral cross-talk between the two channels was also discussed for further optimization. reprint
 
17.  Active and passive infrared imager based on short-wave and mid-wave type-II superlattice dual-band detectors
E.K. Huang, A. Haddadi, G. Chen, A.M. Hoang, and M. Razeghi
Optics Letters, Vol. 38, no. 1, p. 22-24-- January 1, 2013
A versatile dual-band detector capable of active and passive use is demonstrated using short-wave (SW) and midwave(MW) IR type-II superlattice photodiodes. A bilayer etch-stop scheme is introduced for back-side-illuminated detectors, which enhanced the external quantum efficiency both in the SWIR and MWIR spectral regions. Temperature-dependent dark current measurements of pixel-sized 27 μm detectors found the dark current density to be ~1 × 10-5 A/cm² for the ∼4.2 μm cutoff MWIR channel at 140 K. This corresponded to a reasonable imager noise equivalent difference in temperature of ∼49 mK using F∕2.3 optics and a 10 ms integration time (tint), which lowered to ∼13 mK at 110 K using tint  30 ms, illustrating the potential for high-temperature operation. The SWIR channel was found to be limited by readout noise below 150 K. Excellent imagery from the dual-band imager exemplifying pixel coincidence is shown. reprint
 
18.  Surface leakage investigation via gated type-II InAs/GaSb long-wavelength infrared photodetectors
G. Chen, E.K. Huang, A.M. Hoang, S. Bogdanov, S.R. Darvish, and M. Razeghi
Applied Physics Letters, Vol. 101, No. 21, p. 213501-1-- November 19, 2012
By using gating technique, surface leakage generated by SiO2 passivation in long-wavelength infrared type-II superlattice photodetector is suppressed, and different surface leakage mechanisms are disclosed. By reducing the SiO2 passivation layer thickness, the saturated gated bias is reduced to −4.5 V. At 77 K, dark current densities of gated devices are reduced by more than 2 orders of magnitude, with 3071 Ω·cm² differential-resistance-area product at −100 mV. With quantum efficiency of 50%, the 11 μm 50% cut-off gated photodiode has a specific detectivity of 7 × 1011 Jones, and the detectivity stays above 2 × 1011 Jones from 0 to −500 mV operation bias. reprint
 
19.  Highly selective two-color mid-wave and long-wave infrared detector hybrid based on Type-II superlattices
E.K. Huang, M.A. Hoang, G. Chen, S.R. Darvish, A. Haddadi, and M. Razeghi
Optics Letters, Vol. 37, No. 22, p. 4744-4746-- November 15, 2012
We report a two-color mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector’s electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature’s 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective. reprint
 
20.  Demonstration of shortwavelength infrared photodiodes based on type-II InAs/GaSb/AlSb superlattices
A.M. Hoang, G. Chen, A. Haddadi, S. Abdollahi Pour, and M. Razeghi
Applied Physics Letters, Vol. 100, No. 21, p. 211101-1-- May 21, 2012
We demonstrate the feasibility of the InAs/GaSb/AlSb type-II superlattice photodiodes operating at the short wavelength infrared regime below 3  μm. An n-i-p type-II InAs/GaSb/AlSb photodiode was grown with a designed cut-off wavelength of 2 μm on a GaSb substrate. At 150  K, the photodiode exhibited a dark current density of 5.6 × 10−8 A/cm² and a front-side-illuminated quantum efficiency of 40.3%, providing an associated shot noise detectivity of 1.0 × 1013 Jones. The uncooled photodiode showed a dark current density of 2.2 × 10−3 A/cm² and a quantum efficiency of 41.5%, resulting in a detectivity of 1.7 × 1010 Jones reprint
 
21.  High operability 1024 x 1024 long wavelength Type-II superlattice focal plane array
A. Haddadi, S.R. Darvish, G. Chen, A.M. Hoang, B.M. Nguyen and M. Razeghi
IEEE Journal of Quantum Electronics (JQE), Vol. 48, No. 2, p. 221-228-- February 10, 2012
Electrical and radiometric characterization results of a high-operability 1024 x 1024 long wavelength infrared type-II superlattice focal plane array are described. It demonstrates excellent quantum efficiency operability of 95.8% and 97.4% at operating temperatures of 81 K and 68 K, respectively. The external quantum efficiency is 81% without any antireflective coating. The dynamic range is 37 dB at 81 K and increases to 39 dB at 68 K operating temperature. The focal plane array has noise equivalent temperature difference as low as 27 mK and 19 mK at operating temperatures of 81 K and 68 K, respectively, using f/2 optics and an integration time of 0.13 ms. reprint
 
22.  Low frequency noise in 1024 x 1024 long wavelength infrared focal plane array base on Type-II InAs/GaSb superlattice
A. Haddadi, S.R. Darvish, G. Chen, A.M. Hoang, B.M. Nguyen and M. Razeghi
SPIE Proceedings, Vol. 8268, p. 82680X-- January 22, 2012
Recently, the type-II InAs/GaSb superlattice (T2SL) material platform is considered as a potential alternative for HgCdTe technology in long wavelength infrared (LWIR) imaging. This is due to the incredible growth in the understanding of its material properties and improvement of device processing which leads to design and fabrication of better devices. In this paper, we report electrical low frequency noise measurement on a high performance type-II InAs/GaSb superlattice 1024×1024 LWIR focal plane array. reprint
 
23.  Suppresion of surface leakage in gate controlled Type-II InAs/GaSb mid-Infrared photodetectors
G. Chen, B.M. Nguyen, A.M. Hoang, E.K. Huang, S.R. Darvish and M. Razeghi
SPIE Proceedings, Vol. 8268, p. 826811-- January 22, 2012
One of the biggest challenges of improving the electrical performance in Type II InAs/GaSb superlattice photodetector is suppressing the surface leakage. Surface leakage screens important bulk dark current mechanisms, and brings difficulty and uncertainty to the material optimization and bulk intrinsic parameters extraction such as carrier lifetime and mobility. Most of surface treatments were attempted beyond the mid-infrared (MWIR) regime because compared to the bulk performance, surface leakage in MWIR was generally considered to be a minor factor. In this work, we show that below 150 K, surface leakage still strongly affects the electrical performance of the very high bulk performance p-π-M-n MWIR photon detectors. With gating technique, we can effectively eliminate the surface leakage in a controllable manner. At 110K, the dark current density of a 4.7 μm cut-off gated photon diode is more than 2 orders of magnitude lower than the current density in SiO2 passivated ungated diode. With a quantum efficiency of 48%, the specific detecivity of gated diodes attains 2.5 x 1014 cm·Hz1/2/W, which is 3.6 times higher than that of ungated diodes. reprint
 
24.  Suppression of surface leakage in gate controlled type-II InAs/GaSb mid-infrared photodetectors
G. Chen; B.-M. Nguyen; A.M. Hoang; E.K. Huang; S.R. Darvish; M. Razeghi
Proc. SPIE 8268, Quantum Sensing and Nanophotonic Devices IX, 826811 (January 20, 2012)-- January 20, 2012
One of the biggest challenges of improving the electrical performance in Type II InAs/GaSb superlattice photodetector is suppressing the surface leakage. Surface leakage screens important bulk dark current mechanisms, and brings difficulty and uncertainty to the material optimization and bulk intrinsic parameters extraction such as carrier lifetime and mobility. Most of surface treatments were attempted beyond the mid-infrared (MWIR) regime because compared to the bulk performance, surface leakage in MWIR was generally considered to be a minor factor. In this work, we show that below 150K, surface leakage still strongly affects the electrical performance of the very high bulk performance p-π-M-n MWIR photon detectors. With gating technique, we can effectively eliminate the surface leakage in a controllable manner. At 110K, the dark current density of a 4.7 μm cut-off gated photon diode is more than 2 orders of magnitude lower than the current density in SiO2 passivated ungated diode. With a quantum efficiency of 48%, the specific detecivity of gated diodes attains 2.5 x 1014 cm·Hz1/2/W, which is 3.6 times higher than that of ungated diodes. reprint
 
25.  High operability 1024 x 1024 long wavelength infrared focal plane array base on Type-II InAs/GaSb superlattice
A. Haddadi, S.R. Darvish, G. Chen, A.M. Hoang, B.M. Nguyen and M. Razeghi
AIP Conference Proceedings, Vol. 1416, p. 56-58_NGS15 Conf_Blacksburg, VA_Aug 1-5, 2011-- December 31, 2011
Fabrication and characterization of a high performance 1024×1024 long wavelength infrared type‐II superlattice focal plane array are described. The FPA performs imaging at a continous rate of 15.00 frames/sec. Each pixel has pitch of 18μm with a fill factor of 71.31%. It demonstrates excellent operability of 95.8% and 97.4% at 81 and 68K operation temperature. The external quantum efficiency is ∼81% without any antireflective coating. Using F∕2 optics and an integration time of 0.13ms, the FPA exhibits an NEDT as low as 27 and 19mK at operating temperatures of 81 and 68K respectively. reprint
 

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