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1.  
Advances in mid-infrared detection and imaging: a key issues review
Advances in mid-infrared detection and imaging: a key issues review
Manijeh Razeghi and Binh-Minh Nguyen
Rep. Prog. Phys. 77 (2014) 082401-- August 4, 2014
It has been over 200 years since people recognized the presence of infrared radiation, and developed methods to capture this signal. However, current material systems and technologies for infrared detections have not met the increasing demand for high performance infrared detectors/cameras, with each system having intrinsic drawbacks. Type-II InAs/GaSb superlattice has been recently considered as a promising candidate for the next generation of infrared detection and imaging. Type-II superlattice is a man-made crystal structure, consisting of multiple quantum wells placed next to each other in a controlled way such that adjacent quantum wells can interact. The interaction between multiple quantum wells offers an additional degree of freedom in tailoring the material's properties. Another advantage of type-II superlattice is the experimental benefit of inheriting previous research on material synthesis and device fabrication of bulk semiconductors. It is the combination of these two unique strengths of type-II superlattice—novel physics and easy manipulation—that has enabled unprecedented progress in recent years. In this review, we will describe historical development, and current status of type-II InAs/GaSb superlattice for advanced detection and imaging in the mid-infrared regime (λ = 3–5 µm). reprint
 
2.  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
 
3.  Thermal Conductivity of InAs/GaSb Type II Superlattice
C. Zhou, B.M. Nguyen, M. Razeghi and M. Grayson
Journal of Electronic Materials, Vol. 41, No. 9, p. 2322-2325-- August 1, 2012
The cross-plane thermal conductivity of a type II InAs/GaSb superlattice(T2SL) is measured from 13 K to 300 K using the 3x method. Thermal conductivity is reduced by up to two orders of magnitude relative to the GaSb bulk substrate. The low thermal conductivity of around 1 W/m K to 8 W/m K may serve as an advantage for thermoelectric applications at low temperatures, while presenting a challenge for T2SL interband cascade lasers and highpower photodiodes. We describe a power-law approximation to model nonlinearities in the thermal conductivity, resulting in increased or decreased peak temperature for negative or positive exponents, respectively. reprint
 
4.  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
 
5.  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
 
6.  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
 
7.  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
 
8.  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
 
9.  Elimination 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
Applied Physics Letters, Vol. 99, No. 18, p. 183503-1-- October 31, 2011
The electrical performance of mid-infrared type-II superlattice M-barrier photodetectors is shown to be limited by surface leakage. By applying gate bias on the mesa sidewall surface, leakage current is significantly reduced. Qualitatively IV modeling shows diffusion-dominated behavior of dark current at temperatures greater than 120 K. At 110 K, the dark current of gated device is reduced by more than 2 orders of magnitude, reaching the measurement system noise floor. With a quantum efficiency of 48% in front side illumination configuration, a 4.7μm cut-off gated device attains a specific detectivity of 2.5 × 1014 cm·Hz½·W-1 at 110 K, which is 3.6 times higher than in ungated devices. reprint
 
10.  Effect of contact doping on superlattice-based minority carrier unipolar detectors
B.M. Nguyen, G. Chen, A.M. Hoang, S. Abdollahi Pour, S. Bogdanov, and M. Razeghi
Applied Physics Letters, Vol. 99, No. 3, p. 033501-1-- July 18, 2011
We report the influence of the contact doping profile on the performance of superlattice-based minority carrier unipolar devices for mid-wave infrared detection. Unlike in a photodiode, the space charge in the p-contact of a pMp unipolar device is formed with accumulated mobile carriers, resulting in higher dark current in the device with highly doped p-contact. By reducing the doping concentration in the contact layer, the dark current is decreased by one order of magnitude. At 150 K, 4.9 μm cut-off devices exhibit a dark current of 2 × 10−5A/cm² and a quantum efficiency of 44%. The resulting specific detectivity is 6.2 × 1011 cm·Hz1/2/W at 150 K and exceeds 1.9 × 1014 cm·Hz1/2/W at 77 K. reprint
 
11.  Type-II superlattice dual-band LWIR imager with M-barrier and Fabry-Perot resonance
E.K. Huang, A. Haddadi, G. Chen, B.M. Nguyen, M.A. Hoang, R. McClintock, M. Stegall, and M. Razeghi
OSA Optics Letters, Vol. 36, No. 13, p. 2560-2562-- July 1, 2011
We report a high performance long-wavelength IR dual-band imager based on type-II superlattices with 100% cutoff wavelengths at 9.5 μm (blue channel) and 13 μm (red channel). Test pixels reveal background-limited behavior with specific detectivities as high as ∼5×1011 Jones at 7.9 μm in the blue channel and ∼1×1011 Jones at 10.2 μm in the red channel at 77 K. These performances were attributed to low dark currents thanks to the M-barrier and Fabry–Perot enhanced quantum efficiencies despite using thin 2 μm absorbing regions. In the imager, the high signal-to-noise ratio contributed to median noise equivalent temperature differences of ∼20 mK for both channels with integration times on the order of 0.5 ms, making it suitable for high speed applications. reprint
 
12.  Type-II InAs/GaSb photodiodes and focal plane arrays aimed at high operating temperatures
M. Razeghi, S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi, and B.M. Nguyen
Opto-Electronics Review (OER), Vol. 19, No. 3, June 2011, p. 46-54-- June 1, 2011
Recent efforts to improve the performance of type-II InAs/GaSb superlattice photodiodes and focal plane arrays (FPA) have been reviewed. The theoretical bandstructure models have been discussed first. A review of recent developments in growth and characterization techniques is given. The efforts to improve the performance of MWIR photodiodes and focal plane arrays (FPAs) have been reviewed and the latest results have been reported. It is shown that these improvements has resulted in background limited performance (BLIP) of single element photodiodes up to 180 K. FPA shows a constant noise equivalent temperature difference (NEDT) of 11 mK up to 120 K and it shows human body imaging up to 170 K. reprint
 
13.  Growth and Characterization of Long-Wavelength Infrared Type-II Superlattice Photodiodes on a 3-in GaSb Wafer
B.M. Nguyen, G. Chen, M.A. Hoang, and M. Razeghi
IEEE Journal of Quantum Electronics (JQE), Vol. 47, No. 5, May 2011, p. 686-690-- May 11, 2011
We report the molecular beam epitaxial growth and characterization of high performance Type-II superlattice photodiodes on 3” GaSb substrates for long wavelength infrared detection. A 7.3 micron thick device structure shows excellent structural homogeneity via atomic force microscopy and x-ray diffraction characterization. Optical and electrical measurements of photodiodes reveal not only the uniformity of the Type-II superlattice material but also of the fabrication process. Across the wafer, at 77 K, photodiodes with a 50% cut-off wavelength of 11 micron exhibit more than 45% quantum efficiency, and a dark current density of 1.0 x 10-4 A/cm² at 50 mV, resulting in a specific detectivity of 6x1011 cm·Hz1/2/W. reprint
 
14.  Surface leakage current reduction in long wavelength infrared type-II InAs/GaSb superlattice photodiodes
S. Bogdanov, B.M. Nguyen, A.M. Hoang, and M. Razeghi
Applied Physics Letters, Vol. 98, No. 18, p. 183501-1-- May 2, 2011
Dielectric passivation of long wavelength infrared Type-II InAs/GaSb superlattice photodetectors with different active region doping profiles has been studied. SiO2 passivation was shown to be efficient as long as it was not put in direct contact with the highly doped superlattice. A hybrid graded doping profile combined with the shallow etch technique reduced the surface leakage current in SiO2 passivated devices by up to two orders of magnitude compared to the usual design. As a result, at 77 K the SiO(2) passivated devices with 10.5 μm cutoff wavelength exhibit an R0A of 120 Ω·cm², RmaxA of 6000 Ω·cm², and a dark current level of 3.5×10−5 A·cm−2 at −50 mV bias. reprint
 
15.  High operating temperature MWIR photon detectors based on Type II InAs/GaSb superlattice
M. Razeghi, S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi and B.M. Nguyen
SPIE Proceedings, Infrared Technology and Applications XXXVII, Orlando, FL, Vol. 8012, p. 80122Q-1-- April 26, 2011
Recent efforts have been paid to elevate the operating temperature of Type II superlattice Mid Infrared photon detectors. Using M-structure superlattice, novel device architectures have been developed, resulting in significant improvement of the device performances. In this paper, we will compare different photodetector architectures and discuss the optimization scheme which leads to almost one order of magnitude of improvement to the electrical performance. At 150K, single element detectors exhibit a quantum efficiency above 50%, and a specific detectivity of 1.05x10(12) cm.Hz(1/2)/W. BLIP operation with a 300K background and 2π FOV can be reached with an operating temperature up to 180K. High quality focal plane arrays were demonstrated with a noise equivalent temperature difference (NEDT) of 11mK up to 120K. Human body imaging is achieved at 150K with NEDT of 150mK. reprint
 
16.  Recent advances in high performance antimonide-based superlattice FPAs
E.K. Huang, B.M. Nguyen, S.R. Darvish, S. Abdollahi Pour, G. Chen, A. Haddadi, and M.A. Hoang
SPIE Proceedings, Infrared technology and Applications XXXVII, Orlando, FL, Vol. 8012, p. 80120T-1-- April 25, 2011
Infrared detection technologies entering the third generation demand performances for higher detectivity, higher operating temperature, higher resolution and multi-color detection, all accomplished with better yield and lower manufacturing/operating costs. Type-II antimonide based superlattices (T2SL) are making firm steps toward the new era of focal plane array imaging as witnessed in the unique advantages and significant progress achieved in recent years. In this talk, we will present the four research themes towards third generation imagers based on T2SL at the Center for Quantum Devices. High performance LWIR megapixel focal plane arrays (FPAs) are demonstrated at 80K with an NEDT of 23.6 mK using f/2 optics, an integration time of 0.13 ms and a 300 K background. MWIR and LWIR FPAs on non-native GaAs substrates are demonstrated as a proof of concept for the cost reduction and mass production of this technology. In the MWIR regime, progress has been made to elevate the operating temperature of the device, in order to avoid the burden of liquid nitrogen cooling. We have demonstrated a quantum efficiency above 50%, and a specific detectivity of 1.05x1012 cm·Hz1/2/W at 150 K for 4.2 μm cut-off single element devices. Progress on LWIR/LWIR dual color FPAs as well as novel approaches for FPA fabrication will also be discussed. reprint
 
17.  High operating temperature midwave infrared photodiodes and focal plane arrays based on type-II InAs/GaSb superlattices
S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi, B.M. Nguyen and M. Razeghi
Applied Physics Letters, Vol. 98, No. 14, p. 143501-1-- April 4, 2011
The dominant dark current mechanisms are identified and suppressed to improve the performance of midwave infrared InAs/GaSb Type-II superlattice photodiodes at high temperatures. The optimized heterojunction photodiode exhibits a quantum efficiency of 50% for 2 μm thick active region without any bias dependence. At 150 K, R0A of 5100 Ω·cm² and specific detectivity of 1.05×1012 cm·Hz0.5·W-1 are demonstrated for a 50% cutoff wavelength of 4.2 μm. Assuming 300 K background temperature and 2π field of view, the performance of the detector is background limited up to 180 K, which is improved by 25 °C compared to the homojunction photodiode. Infrared imaging using f/2.3 optics and an integration time of 10.02 ms demonstrates a noise equivalent temperature difference of 11 mK at operating temperatures below 120 K. reprint
 
18.  Growth and characterization of long wavelength infrared Type-II superlattice Photodiodes on a 3
B.M. Nguyen, G. Chen, M.A. Hoang, and M. Razeghi
SPIE Proceedings, San Francisco, CA (January 22-27, 2011), Vol. 7945, p. 79451O-- January 23, 2011
One of the great advantages of Type-II InAs/GaSb superlattice over other competing technologies for the third generation infrared imagers is the potential to have excellent uniformity across a large area as the electronic structure of the material is controlled by the layer thicknesses, not by the composition of the materials. This can economize the material growth, reduce the fabrication cost, and especially allow the realization of large format imagers. In this talk, we report the molecular beam epitaxial growth of Type-II superlattices on a 3-inch GaSb substrate for long wavelength infrared detection. The material exhibits excellent structural, optical and electrical uniformity via AFM, Xray, quantum efficiency and I-V measurements. At 77K, 11μm cutoff photodiodes exhibit more than 45% quantum efficiency, and a dark current density of 1.0x10-4 A/cm² at 50 mV, resulting in a specific detectivity of 6 x 1011 cm·Hz1/2/W. reprint
 
19.  Photovoltaic MWIR type-II superlattice focal plane array on GaAs substrate
E.K. Huang, P.Y. Delaunay, B.M. Nguyen, S. Abdoullahi-Pour, and M. Razeghi
IEEE Journal of Quantum Electronics (JQE), Vol. 46, No. 12, p. 1704-1708-- December 1, 2010
Recent improvements in the performance of Type-II superlattice (T2SL) photodetectors has spurred interest in developing low cost and large format focal plane arrays (FPA) on this material system. Due to the limitations of size and cost of native GaSb substrates, GaAs is an attractive alternative with 8” wafers commercially available, but is 7.8% lattice mismatched to T2SL. In this paper, we present a photovoltaic T2SL 320 x 256 focal plane array (FPA) in the MWIR on GaAs substrate. The FPA attained a median noise equivalent temperature difference (NEDT) of 13 mK and 10mK (F#=2.3) with integration times of 10.02 ms and 19.06 ms respectively at 67 K. reprint
 
20.  High performance long wavelength infrared mega-pixel focal plane array based on type-II superlattices
P. Manurkar, S.R. Darvish, B.M. Nguyen, M. Razeghi and J. Hubbs
Applied Physics Letters, Vol. 97, No 19, p. 193505-1-- November 8, 2010
A large format 1k × 1k focal plane array (FPA) is realized using type-II superlattice photodiodes for long wavelength infrared detection. Material growth on a 3 in. GaSb substrate exhibits a 50% cutoff wavelength of 11 μm across the entire wafer. The FPA shows excellent imaging. Noise equivalent temperature differences of 23.6 mK at 81 K and 22.5 mK at 68 K are achieved with an integration time of 0.13 ms, a 300 K background and f/4 optics. We report a dark current density of 3.3×10−4 A·cm−2 and differential resistance-area product at zero bias R0A of 166 Ω·cm² at 81 K, and 5.1×10−5 A·cm−2 and 1286 Ω·cm², respectively, at 68 K. The quantum efficiency obtained is 78%. reprint
 
21.  Type-II Antimonide-based Superlattices for the Third Generation Infrared Focal Plane Arrays
Manijeh Razeghi, Edward Kwei-wei Huang, Binh-Minh Nguyen, Siamak Abdollahi Pour, and Pierre-Yves Delaunay
SPIE Proceedings, Infrared Technology and Applications XXXVI, Vol. 7660, pp. 76601F-- May 10, 2010
In recent years, the Type-II superlattice (T2SL) material platform has seen incredible growth in the understanding of its material properties which has lead to unprecedented development in the arena of device design. Its versatility in band-structure engineering is perhaps one of the greatest hallmarks of the T2SL that other material platforms are lacking. In this paper, we discuss advantages of the T2SL, specifically the M-structure T2SL, which incorporates AlSb in the traditional InAs/GaSb superlattice. Using the M-structure, we present a new unipolar minority electron detector coined as the p-M-p, the letters which describe the composition of the device. Demonstration of this device structure with a 14 μm cutoff attained a detectivity of 4x1010 Jones (-50 mV) at 77 K. As device performance improves year after year with novel design contributions from the many researchers in this field, the natural progression in further enabling the ubiquitous use of this technology is to reduce cost and support the fabrication of large infrared imagers. In this paper, we also discuss the use of GaAs substrates as an enabling technology for third generation imaging on T2SLs. Despite the 7.8% lattice mismatch between the native GaSb and alternative GaAs substrates, T2SL photodiodes grown on GaAs at the MWIR and LWIR have been demonstrated at an operating temperature of 77 K reprint
 
22.  Band gap tunability of Type-II Antimonide-based superlattices
M. Razeghi and B.M. Nguyen
Physics Procedia, Vol. 3, Issue 2, p. 1207-1212 (14th International Conference on Narrow Gap Semiconductors and Systems NGSS-14, Sendai, Japan, July 13-17, 2009)-- January 31, 2010
Current state-of-the art infrared photon detectors based on bulk semiconductors such as InSb or HgCdTe are now relatively mature and have almost attained the theoretical limit of performance. It means, however, that the technology can not be expected to demonstrate revolutionary improvements, in terms of device performances. In contrasts, low dimensional quantum systems such as superlattices, quantum wells, quantum dots, are still the development stage, yet have shown comparable performance to the bulk detector family. Especially for the Type-II Antimony-based superlattices, recent years have seen significant improvements in material quality, structural design as well as fabrication techniques which lift the performance of Type-II superlattice photodetectors to a new level. In this talk, we will discuss the advantages of Type-II-superlattices, from the physical nature of the material to the practical realisms. We will demonstrate the flexibility in controlling the energy gap and their overall band alignment for the suppression of Auger recombination, as well as to create sophisticated hetero-designs. reprint
 
23.  High operating temperature MWIR photon detectors based on Type-II InAs/GaSb superlattice
M. Razeghi, B.M. Nguyen, P.Y. Delaunay, S. Abdollahi Pour, E.K.W. Huang, P. Manukar, S. Bogdanov, and G. Chen
SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7608, p. 76081Q-1-- January 22, 2010
Recent efforts have been paid to elevate the operating temperature of Type-II InAs/GaSb superlattice Mid Infrared photon detectors. Optimized growth parameters and interface engineering technique enable high quality material with a quantum efficiency above 50%. Intensive study on device architecture and doping profile has resulted in almost one order of magnitude of improvement to the electrical performance and lifted up the 300 K-background BLIP operation temperature to 166 K. At 77 K, the ~4.2 µm cut-off devices exhibit a differential resistance area product in excess of the measurement system limit (106 Ω·cm²) and a detectivity of 3x1013 cm·Hz½·W−1. High quality focal plane arrays were demonstrated with a noise equivalent temperature of 10 mK at 77 K. Uncooled camera is capable to capture hot objects such as soldering iron. reprint
 
24.  Minority electron unipolar photodetectors based on Type-II InAs/GaSb/AlSb superlattices for very long wavelength infrared detection
B.M. Nguyen, S. Abdollahi Pour, S. Bogdanov and M. Razeghi
SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7608, p. 760825-1-- January 22, 2010
The bandstructure tunability of Type-II antimonide-based superlattices has been significantly enhanced since the introduction of the M-structure superlattice, resulting in significant improvements of Type-II superlattice infrared detectors. By using M-structure, we developed the pMp design, a novel infrared photodetector architecture that inherits the advantages of traditional photoconductive and photovoltaic devices. This minority electron unipolar device consists of an M-structure barrier layer blocking the transport of majority holes in a p-type semiconductor, resulting in an electrical transport due to minority carriers with low current density. Applied for the very long wavelength detection, at 77K, a 14µm cutoff detector exhibits a dark current 3.3 mA·cm−2, a photoresponsivity of 1.4 A/W at 50mV bias and the associated shot-noise detectivity of 4x1010 Jones. reprint
 
25.  Minority electron unipolar photodetectors based on Type-II InAs/GaSb/AlSb superlattices for very long wavelength infrared detection
B.M. Nguyen, S. Bogdanov, S. Abdollahi Pour, and M. Razeghi
Applied Physics Letters, Vol. 95, No. 18, p. 183502-- November 2, 2009
We present a hybrid photodetector design that inherits the advantages of traditional photoconductive and photovoltaic devices. The structure consists of a barrier layer blocking the transport of majority holes in a p-type semiconductor, resulting in an electrical transport due to minority carriers with low current density. By using the M-structure superlattice as a barrier region, the band alignments can be experimentally controlled, allowing for the efficient extraction of the photosignal with less than 50 mV bias. At 77 K, a 14 µm cutoff detector exhibits a dark current 3.3 mA·cm−2, a photoresponsivity of 1.4 A/W, and the associated shot noise detectivity of 4×1010 Jones. reprint
 

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