Dr. Roger E. De Wames Profile

Dr. Roger E. De Wames

Consultant at QinetiQ Inc

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Author

Publications (24)

Proceedings Article | 31 January 2020 Presentation + Paper

Performance and limitations of NIR and extended wavelength eSWIR InP/InGaAs image sensors

Roger DeWames, Jonathan Schuster

Proceedings Volume 11288, 112880H (2020) https://doi.org/10.1117/12.2547616

KEYWORDS: Gallium, Diffusion, Diodes, Interfaces, Photodiodes, Quantum efficiency, Arsenic, Temperature metrology, Staring arrays, Absorption

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Proceedings Article | 7 May 2019 Presentation + Paper

Recombination processes in InAs/InAsSb type II strained layer superlattice MWIR nBn detectors

R. DeWames, J. Schuster, E. DeCuir, N. Dhar

Proceedings Volume 11002, 110020W (2019) https://doi.org/10.1117/12.2521907

KEYWORDS: Sensors, Quantum efficiency, Mid-IR, Heterojunctions, Temperature metrology, Absorption, Superlattices, Diodes, Diffusion, Solids

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There is great interest in MWIR Ga-free type II strained layer superlattice (T2SLS) nBn detectors for background limited photodetectors (BLIP) operating at temperatures higher than InSb (T ≥ 150K compared to T≈ 80-90K). Recently, Ting et al. [Proc. SPIE, Vol. 10624, 1062410-1 (2018)] reported on measurements of the dark current and quantum efficiency (QE) for e-SWIR (λ>1.7 μm), MWIR, and LWIR Ga-free nBn T2SLS detectors. Of particular interest is the reported MWIR nBn T2SLS data, since the measured dark current and QE provide the opportunity to analyze the measured detector optoelectronic characteristics using optical properties obtained separately from the hole minority carrier lifetime and optical absorption coefficient data, hence no adjustable parameters. The goal is to develop and utilize robust modeling techniques to explain real, measured nBn detector data to understand the technology limitations and the improvements needed to optimize performance and device designs. A notable result is the observation that the dark current data under reverse bias (-100 mV < bias ≤ 0 mV) obeys the ideal diode equation, where the saturation dark current is in agreement with the radiative recombination rate obtained from the measured absorption coefficient and a 9 μs Shockley-Read-Hall (SRH) lifetime obtained from the measured hole lifetime data. Most important is that the expected generation-recombination (G-R) space charge current based on the 9 μs SRH lifetime is not observed as expected for an ideal nBn heterojunction detector and that increasing excess dark currents are observed with decreasing temperature. The in-band external QE measured at 100K is in the range of 30% and is observed to increase with increasing operating temperature which indicates effects influenced by hole mobility anomalies. In contrast to the above listed observations, the Type II Ga-free nBn detector data reported by D. Ting et al. [Appl. Phys. Lett., 113, 021101, 2018] exhibits a hole energy barrier, G-R dark current like characteristics, and both temperature/voltage dependent QE.

Proceedings Article | 9 May 2018 Presentation + Paper

Shockley-Read-Hall (SRH) recombination dark current in planar diffused P+n heterostructure InP/In0.53Ga0.47As/InP high density small pitch Focal Plane Arrays (FPAs)

R. DeWames, E. DeCuir, J. Schuster, N. Dhar

Proceedings Volume 10624, 1062405 (2018) https://doi.org/10.1117/12.2315838

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Proceedings Article | 30 January 2017 Open Access

Accelerating technology innovations by early understanding of fundamental and technology limitations of material synthesis and device operation

Jagmohan Bajaj, Roger DeWames, Jonathan Schuster, Meredith Reed, Philip Perconti, Enrico Bellotti

Proceedings Volume 10111, 1011117 (2017) https://doi.org/10.1117/12.2261308

KEYWORDS: Laser sintering, Semiconductors, Instrument modeling, Infrared sensors, Long wavelength infrared, Sensors, Stereolithography, Mercury cadmium telluride, Semiconductor materials, Infrared technology

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Timely technology transition with minimal risk requires an understanding of fundamental and technology limitations of material synthesis, device operation and design controllable parameters. However, this knowledge-based approach requires substantial investment of resources in the Science and Technology (ST) stage of development. For low volume niche semiconductor technologies of Department of Defense (DoD) relevance, there is little drive for industry to expend their limited resources towards basic research simply because there is no significant return on investment. As a result, technology transition from ST to product development is often delayed, expensive and carries risks. The Army Research Laboratory (ARL) is addressing this problem by establishing a Center for Semiconductor Modeling of Materials and Devices (CSM) that brings together government, academia, and industry in a collaborative fashion to address research opportunities through its Open Campus initiative. This Center leverages combined core competencies of partner organizations, which include a broad knowledge base in modeling, and its validation; sharing of computational, characterization, materials growth and device processing resources; project continuity; and ‘extension of the bench’ via exchange of researchers between affiliated entities. A critical DoD technology is sensing in the infrared (IR) spectrum, where understanding of materials, devices and methods for sensing and processing IR information must continually improve to maintain superiority in combat. In this paper we focus on the historical evolution of IR technology and emphasize the need for understanding of material properties and device operation to accelerate innovation and shorten the cycle time, thereby ensuring timely transition of technology to product development and manufacturing. There are currently two competing IR technologies being pursued, namely the incumbent II-VI Hg₁- _xCd_xTe technology and the III-V Type 2 Superlattices (SLs) technology. A goal of the CSM is to develop physics based models for Type 2 SLs with the capability to timely understand the knowledge gap between what is built and what is designed.

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Proceedings Article | 20 May 2016 Paper

Review of an assortment of IR materials-devices technologies used for imaging in spectral bands ranging from the visible to very long wavelengths

Roger DeWames

Proceedings Volume 9819, 981924 (2016) https://doi.org/10.1117/12.2230550

KEYWORDS: Staring arrays, Photodiodes, Mercury cadmium telluride, Diffusion, Diodes, 3D modeling, Temperature metrology, Sensors, Neodymium, Mid-IR

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Proceedings Article | 28 August 2015 Paper

Heterojunction depth in P+-on-n eSWIR HgCdTe infrared detectors: generation-recombination suppression

J. Schuster, R. DeWames, E. DeCuir, E. Bellotti, N. Dhar, P. Wijewarnasuriya

Proceedings Volume 9609, 960904 (2015) https://doi.org/10.1117/12.2186043

KEYWORDS: Cadmium, Heterojunctions, Diffusion, Quantum efficiency, Mercury cadmium telluride, Arsenic, Sensors, Doping, Neodymium, Instrument modeling

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Proceedings Article | 24 June 2014 Paper

Three-dimensional numerical simulation of planar P+n heterojunction In0.53Ga0.47As photodiodes in dense arrays part II: modulation transfer function modeling

Adam Wichman, Roger DeWames, Enrico Bellotti

Proceedings Volume 9070, 907004 (2014) https://doi.org/10.1117/12.2050688

KEYWORDS: Modulation transfer functions, Indium gallium arsenide, 3D modeling, Spatial frequencies, Diodes, Diffusion, Sensors, Performance modeling, Numerical simulations, Neodymium

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Proceedings Article | 24 June 2014 Paper

Three-dimensional numerical simulation of planar P+n heterojunction In0.53Ga0.47As photodiodes in dense arrays part I: dark current dependence on device geometry

Adam Wichman, Roger DeWames, Enrico Bellotti

Proceedings Volume 9070, 907003 (2014) https://doi.org/10.1117/12.2050680

KEYWORDS: Diffusion, Diodes, Indium gallium arsenide, 3D modeling, Neodymium, Photodiodes, Numerical simulations, Quantum efficiency, Interfaces, Staring arrays

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Proceedings Article | 31 May 2012 Paper

Electrical characteristics of MOVPE grown MWIR N+p(As)HgCdTe heterostructure photodiodes build on GaAs substrates

Roger DeWames, Joseph Pellegrino

Proceedings Volume 8353, 83532P (2012) https://doi.org/10.1117/12.921093

KEYWORDS: Photodiodes, Diffusion, Gallium arsenide, Temperature metrology, Staring arrays, Mercury cadmium telluride, Data modeling, Mid-IR, Defense and security, Sensors

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Proceedings Article | 31 May 2012 Paper

HOT MWIR HgCdTe performance on CZT and alternative substrates

Joseph Pellegrino, Roger DeWames, Philip Perconti, Curtis Billman, Patrick Maloney

Proceedings Volume 8353, 83532X (2012) https://doi.org/10.1117/12.923836

KEYWORDS: Mid-IR, Mercury cadmium telluride, Staring arrays, Sensors, Diffusion, Infrared sensors, Gallium arsenide, Temperature metrology, Sensor technology, Data modeling

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Proceedings Article | 21 May 2011 Paper

Electro-optical characteristics of a MWIR and LWIR planar hetero-structure P+n HgCdTe photodiodes limited by intrinsic carrier recombination processes

R. DeWames, P. Maloney, C. Billman, J. Pellegrino

Proceedings Volume 8012, 801239 (2011) https://doi.org/10.1117/12.883757

KEYWORDS: Photodiodes, Long wavelength infrared, Mid-IR, Diffusion, Mercury cadmium telluride, Temperature metrology, Diodes, Sensors, Staring arrays, Electro optics

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Reported is a detailed analysis of the dark current versus voltage versus temperature data of planar hetero-structure P⁺n mid wavelength infrared MWIR photodiodes with band gap energy E_g(78K) = 0.243 eV, λ_g= 5.1 μm and long wavelength infrared LWIR photodiodes with E_g(78K) = 0.115 eV, λ_g= 10.8 μm. The purpose of the investigations is to identify the dominant carrier recombination mechanisms and in particular to determine at what temperature and voltage is the onset of Shockley Read Hall (SRH) space charge currents. The important finding is that the currents can mostly be explained by a combination of Auger (e-e) and radiative carrier recombination processes with no evidence of SRH recombination through near mid-gap states; a lower bound estimate of the SRH lifetime for LWIR photodiode is 100 μs. Intrinsic radiative recombination is found to be the dominant carrier recombination mechanisms for the MWIR photodiode with a carrier concentration N_d=10¹⁵ cm^-3, and Auger (e-e) being dominant for the LWIR photodiode. The LWIR Auger (e-e) lifetime data is well fitted with the Beattie, Landsberg and Blakemore (BLB) formulas with a constant overlap integral F1F2= 0.15, which is in accord with recent electronic band structure calculations. From the analysis of variable area LWIR photodiodes the minority carrier conductivity mobility and diffusion length at 80K are calculated to be 350 cm²/V-s and 23 μm respectively. The LWIR lifetime measured by the photoconductive decay method is in agreement with the expected intrinsic Auger (e-e) lifetime ≈ 2 μs at 80K and with the lifetimes obtained from device analysis. For T ≤ 40K, trap assisted tunneling is the dominant current in reversed bias LWIR photodiodes; forward bias currents are dominated by diffusion currents of origin in the n- layer. For the MWIR photodiode deviation from diffusion limited behavior to G-R is observed at T < 80K and, the SRH lifetimes ιn0 and ιp0 are estimated to be 50 ms. Measured and calculated external quantum efficiencies at the peak responsivity wavelength λpk for both MWIR and LWIR photodiodes are ≈ 70% at 78K. For imaging in the 3-5 μm spectral band scene temperature 300K, F/3 optics, the noise equivalent temperature difference NE▵T of MWIR photodiodes is calculated to be near background limited performance BLIP =12.4 mK for detector temperatures Td ≤ 150K.

Proceedings Article | 7 May 2009 Paper

Minority carrier lifetime characteristics in type II InAs/GaSb LWIR superlattice n+πp+ photodiodes

J. Pellegrino, R. DeWames

Proceedings Volume 7298, 72981U (2009) https://doi.org/10.1117/12.819641

KEYWORDS: Photodiodes, Diffusion, Long wavelength infrared, Sensors, Mercury cadmium telluride, Superlattices, Quantum efficiency, Data conversion, Solids, Temperature metrology

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Proceedings Article | 31 May 2005 Paper

Compositional variations in MBE grown InAs-GaSb superlattices for infrared detector applications

G. Sullivan, A. Ikhlassi, J. Bergman, R. DeWames, J. Waldrop, C. Grein, M. Flatte, K. Mahalingam, H. Yang, M. Zhong, M. Weimer

Proceedings Volume 5783, (2005) https://doi.org/10.1117/12.607360

KEYWORDS: Superlattices, Laser sintering, Gallium antimonide, Sensors, Indium arsenide, Gallium, Heterojunctions, Indium, Scanning tunneling microscopy, Mercury cadmium telluride

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Proceedings Article | 23 January 2003 Paper

Noise in large-area CrlS Hg1-xCdxTe photovoltaic detectors

Arvind D'Souza, Maryn Stapelbroek, Stacy Masterjohn, Priyalal Wijewarnasuriya, Roger DeWames, David Smith, John Ehlert

Proceedings Volume 4820, (2003) https://doi.org/10.1117/12.453567

KEYWORDS: Sensors, Photovoltaic detectors, Medium wave, Amplifiers, Mid-IR, Long wavelength infrared, Sensor performance, Diodes, Diffusion, Mercury

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Proceedings Article | 5 August 2002 Paper

1/f noise in Hg1-xCdxTe detectors

Arvind D'Souza, Maryn Stapelbroek, Stacy Masterjohn, Priyalal Wijewarnasuriya, Roger DeWames, G. Williams

Proceedings Volume 4721, (2002) https://doi.org/10.1117/12.478850

KEYWORDS: Sensors, Diffusion, Information operations, Temperature metrology, Diodes, Mercury cadmium telluride, Data modeling, Staring arrays, Infrared detectors, Photodetectors

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This paper investigates 1/f noise performance of Hg_1-xCd_xTe photovoltaic detectors when detector current is varied by changing detector area, bias, temperature and incident flux. Holding detector bias and temperature constant, measured 1/f noise current is proportional to the detector current. However for all detector areas measured, non-uniformity is observed in the noise current due to the varied quality of the detectors. Even for the λ_c=16μm , 4-μm-radius, diffusion-limited detectors at 78K held at reverse bias, the average and standard deviation in dark current is I_d=9.76+/- 1.59x10^-8A while the average and standard deviation in noise current at 1 Hz in a 1 Hz bandwidth is i_n=1.01+/- 0.63x10^-12A. For all detector areas measured at 100 mV reverse bias, the average and standard deviation in dark current to noise current ratio is α _D=i_n/I_d=1.39+/- 1.09x10^-5. Defects are presumed resident in the detectors that produce greater non- uniformity in the 1/f noise as compared to the dark current at 100 mV reverse bias. Noise was also measured as a function of temperature for two λ _c=16 micrometers detectors from 55 K to 100 K. The average and standard deviation in the noise current to dark current ratio is α_D=i_n/I_d=2.36+/- 0.83x10^-5 for the 26-micrometers -diameter detector and (alpha) _D=1.71+/- 0.69x10^-5 for the 16-micrometers -diameter detector. Dark and noise current were measured while changing the bias applied to a detector. In the diffusion-limited portion of the detector I-V curve, 1/f noise is independent of bias with α _D=i_n/I_d=1.51+/- 0.12x10^-5. When tunneling currents dominated, α_T=i_n/I_d=5.21+/- 0.83x10^-5. The 1/f noise associated with tunneling currents is a factor of three greater than the 1/f noise associated with diffusion currents. In addition, 1/f noise was measured on detectors held at -100 mV and 78 K under dark and illuminated conditions. The average noise to current ratio α_D was approximately 1.5 x 10^-5 for dark and photon-induced diffusion current. However, detector-to-detector variations exist even within a single chip. The two most important points are that non-uniformities in material/fabrication need to be addressed and that each individual type of current component has an associated 1/f noise current component, the magnitude of the relationship being different depending on the source current.

Proceedings Article | 12 November 2001 Paper

Advances in large-area Hg1-xCdxTe photovoltaic detectors for remote sensing applications

Priyalal Wijewarnasuriya, Majid Zandian, Jamie Phillips, Dennis Edwall, Roger DeWames, Gernot Hildebrandt, Jagmohan Bajaj, Jose Arias, Arvind D'Souza, Fergus Moore

Proceedings Volume 4454, (2001) https://doi.org/10.1117/12.448180

KEYWORDS: Sensors, Quantum efficiency, Long wavelength infrared, Short wave infrared radiation, Mid-IR, Mercury cadmium telluride, Semiconducting wafers, Photovoltaic detectors, Diffusion, Photovoltaics

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Proceedings Article | 10 October 2001 Paper

Cross-track infrared sounder FPA performance

Arvind D'Souza, Larry Dawson, Stacy Marsh, Richard Willis, Priyalal Wijewarnasuriya, Roger DeWames, Jose Arias, Jagmohan Bajaj, Gernot Hildebrandt, Fergus Moore

Proceedings Volume 4369, (2001) https://doi.org/10.1117/12.445336

KEYWORDS: Sensors, Staring arrays, Mid-IR, Long wavelength infrared, Quantum efficiency, Short wave infrared radiation, Infrared radiation, Photovoltaics, Amplifiers, Photovoltaic detectors

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Proceedings Article | 17 July 2000 Paper

VLWIR HgCdTe photovoltaic detectors performance

Arvind D'Souza, Larry Dawson, Craig Staller, John Reekstin, Priyalal Wijewarnasuriya, Roger DeWames, William McLevige, Jose Arias, Dennis Edwall, Gernot Hildebrandt

Proceedings Volume 4028, (2000) https://doi.org/10.1117/12.391747

KEYWORDS: Sensors, Quantum efficiency, Photovoltaic detectors, Black bodies, Mercury cadmium telluride, Temperature metrology, Diffusion, Resistance, Diodes, Interfaces

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Very Long Wavelength InfraRed (VLWIR; (lambda) _c approximately equals 15 to 17 micrometer at 78 K) photovoltaic detector operating in the 78 K range are needed for remote sensing applications. This temperature range permits the use of passive radiators in spacecraft to cool the detectors. VLWIR ((lambda) _c approximately equals 15 to 17 micrometer at 78 K) photovoltaic detectors in a range of sizes (8 micrometer diameter to 1000 micrometer diameter) have been fabricated and their performance measured as a function of temperature. Molecular Beam Epitaxy (MBE) was used to grow n-type VLWIR Hg_1-xCd_xTe on lattice matched CdZnTe. Arsenic was implanted and the wafer was annealed to provide the p-type regions. All the material was grown with wider bandgap cap layers and consequently the detector architecture is the Double Layer Planar Heterostructure (DLPH) architecture. I_d - V_d versus temperature curves for 8 and 1000 micrometer diameter, (lambda) _c equals 17 micrometer at 78 K detectors indicate that the 8 micrometer diameter detector is diffusion limited for temperatures greater than 63 K even at a -200 mV bias. There is no appreciable tunneling at T equals 50 K and at -200 mV applied bias. At T equals 40 K tunneling commences at a bias approximately equals -80 mV. Below T equals 30 K, the diode is tunneling limited. The 1000 micrometer diameter detector is diffusion limited at bias values less than -50 mV at 78 K. At zero bias, the detector impedance is comparable to the series/contact resistance. Interfacing with the low (comparable to the contact and series resistance) junction impedance detector is not feasible. Therefore a custom pre- amplifier was designed to interface with the large VLWIR detectors in reverse bias. The detector is dominated by tunneling currents at temperatures less than 78 K. The 1000 micrometer diameter, (lambda) _c approximately equals 17 micrometer at 78 K detectors have dark currents approximately equals 160 (mu) A at a -100 mV bias and at 78 K. Detector non-AR coated quantum efficiency > 60% was measured at -100 mV bias in these large detectors and the response was constant across the (lambda) equals 7 micrometer to 15 micrometer spectral band. With AR- coating the quantum efficiency will be > 70%. Response was measured and non-linearity < 0.15% was calculated for the 1000 micrometer detectors. The flux values were in the 10¹⁷ ph/cm²/sec range and were changed by varying the blackbody temperature. In addition, a linear response was measured while varying the spot size incident on the 1000 micrometer detectors. This excellent response uniformity measured as a function of spot size implies that, low frequency spatial response variations are absent, for the 1000 micrometer detectors.

Proceedings Article | 26 August 1997 Paper

Performance of HgCdTe, InGaAs and quantum well GaAs/AlGaAs staring infrared focal plane arrays

Lester Kozlowski, Kadri Vural, Jose Arias, William Tennant, Roger DeWames

Proceedings Volume 3182, (1997) https://doi.org/10.1117/12.280406

KEYWORDS: Staring arrays, Photovoltaics, Quantum wells, Indium gallium arsenide, Quantum well infrared photodetectors, Mercury cadmium telluride, Infrared radiation, Infrared detectors, Detector arrays, Silicon

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Proceedings Article | 27 June 1996 Paper

MBE flexible manufacturing for HgCdTe focal plane arrays

J. Benson, John Dinan, James Waterman, Christopher Summers, Rudolph Benz, Brent Wagner, S. Pearson, Ashesh Parikh, John Jensen, Owen Wu, Rajesh Rajavel, G. Kamath, Karl Harris, Steven Jost, Jose Arias, Lester Kozlowski, Majid Zandian, Jagmohan Bajaj, Kadri Vural, Roger DeWames, Charles Cockrum, G. Venzor, Scott Johnson, H.-D. Shih, M. Bevan, J. Dodge, Art Simmons

Proceedings Volume 2744, (1996) https://doi.org/10.1117/12.243457

KEYWORDS: Staring arrays, Manufacturing, Liquid phase epitaxy, Mercury cadmium telluride, Semiconducting wafers, Sensors, Detector arrays, Heterojunctions, Infrared radiation, Detector development

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Proceedings Article | 7 October 1994 Paper

MBE HgCdTe infrared focal plane array (IRFPA) flexible manufacturing

Jose Arias, Majid Zandian, John Pasko, Jagmohan Bajaj, Lester Kozlowski, William Tennant, Roger DeWames

Proceedings Volume 2274, (1994) https://doi.org/10.1117/12.189243

KEYWORDS: Long wavelength infrared, Mercury cadmium telluride, Diodes, Manufacturing, Staring arrays, Heterojunctions, Databases, Information operations, Mercury, Arsenic

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Proceedings Article | 13 July 1994 Paper

Molecular beam epitaxy (MBE) HgCdTe flexible growth technology for the manufacturing of infrared photovoltaic detectors

Jose Arias, John Pasko, Majid Zandian, Jagmohan Bajaj, Lester Kozlowski, Roger DeWames, William Tennant

Proceedings Volume 2228, (1994) https://doi.org/10.1117/12.179662

KEYWORDS: Mercury cadmium telluride, Molecular beam epitaxy, Manufacturing, Infrared detectors, Infrared photography, Infrared radiation, Photovoltaic detectors, Long wavelength infrared, Heterojunctions, Photovoltaics

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SPIE Journal Paper | 1 May 1994

Molecular beam epitaxy HgCdTe infrared photovoltaic detectors

Jose Arias, John Pasko, Majid Zandian, Lester Kozlowski, Roger DeWames

OE, Vol. 33, Issue 05, (May 1994) https://doi.org/10.1117/12.10.1117/12.165818

KEYWORDS: Mercury cadmium telluride, Diodes, Long wavelength infrared, Diffusion, Staring arrays, Heterojunctions, Arsenic, Photovoltaic detectors, Information operations, Infrared detectors

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Proceedings Article | 10 December 1992 Paper

Assessment of HgCdTe and GaAs/GaAlAs technologies for LWIR infrared imagers

Roger DeWames, Jose Arias, Lester Kozlowski, G. Williams

Proceedings Volume 1735, (1992) https://doi.org/10.1117/12.142561

KEYWORDS: Mercury cadmium telluride, Quantum well infrared photodetectors, Sensors, Detector arrays, Long wavelength infrared, Staring arrays, Gallium arsenide, Quantum wells, Infrared detectors, Quantum efficiency

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Showing 5 of 24 publications

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