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Acosta L.,University of New Mexico | Klein B.,University of New Mexico | Tian Z.-B.,University of New Mexico | Frantz E.,University of Cincinnati | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The objective of this study is to optimize the absorption in the active region of InAs/GaSb T2SL photodetectors for the realization of high-performance MWIR devices. Two sets of MWIR (Î100% cut-off ~ 5.5Î=m at 77K) T2SL detectors were realized; one set with varied detector absorber thickness, the other set with varied T2SL period. The T2SL material quality was evaluated on the basis of room temperature photoluminescence (RTPL) and the high-resolution X-ray diffraction (HRXRD) data. Then the device performance was compared using spectral response, dark current and responsivity measurements. Finally, quantum efficiency was calculated and employed as a metric for the definition of the optimal T2SL period and active region thickness. For the first part of the study, a homojunction pin architecture based on 8 monolayers (MLs) InAs/8MLs GaSb T2SL was used. The thickness of the non-intentionally doped absorber layers were 1.5Î=m, 2.5Î=m, and 3.5Î=m. For the second part of the study, unipolar barrier (pBiBn) devices were grown. The thickness of the absorber region and the T2SL constituent InAs layer thicknesses were kept the same (1.5 Î=m and 8 MLs, respectively) whereas the T2SL constituent GaSb thickness was varied as 6 MLs, 8 MLs, and 10 MLs. We have found that the pin detector with 2.5 Î=m thick absorber and the pBiBn detector with 8 ML InAs/ 8 ML GaSb T2SL composition are, within the scope of this study, optimal for the realization of MWIR single-element devices and FPAs with corresponding architectures. © 2014 SPIE. Source


Zamiri M.,University of New Mexico | Plis E.,University of New Mexico | Kim J.O.,University of New Mexico | Lee S.C.,University of New Mexico | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Detectivity of mid-wave infrared (MWIR) detectors based on InAs/GaSb type II strained layer superlattices (T2SLs) can be significantly enhanced at select wavelengths by integrating the detector with a back-side illuminated plasmonic coupler. The application of a simple metal-T2SL structure directly on the GaSb substrate can result in radiation losses into the substrate due to the low refractive index of T2SL layer. However, insertion of a higher refractive index material, such as germanium (Ge), into the metal-SLS structure can confine the surface plasmon waveguide (SPW) modes to the surface. In this work, metal (Au)-Ge-T2SL structures are designed with an approximately 100 nm thick Ge layer. The T2SL layer utilized a p-i-n detector design with 8 monolayers (MLs) InAs/8 MLs GaSb. A plasmonic coupler was then realized inside the 300 μm circular apertures of these single element detectors by the formation of a corrugated metal (Au) surface. The T2SL single element detector integrated with an optimized plasmonic coupler design increased the quantum efficiency (QE) by a factor of three at an operating temperature of 77 K and 3 to 5 μm illumination wavelength, compared to a reference detector structure, and each structure exhibited the same level of dark current. © 2014 SPIE. Source


Ramirez D.A.,University Blvd | Plis E.A.,University Blvd | Myers S.A.,University Blvd | Morath C.P.,Air Force Research Lab | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

The realization of high operating temperature (HOT) midwave infrared (MWIR) photodetectors would significantly relax the requirements imposed on the cooling system, which would lead to a reduction in the size, weight, and cost of the detection system. One of the most attractive material systems to develop HOT photodetectors is InAs/GaSb Type II Superlattice (T2SL). This is due the ability of T2SL materials to engineer the band structure of the device, which can be exploited to make devices with unipolar barriers. It has been shown that the use of unipolar barriers can dramatically reduce the dark current levels of the device, which is essential to realize HOT photodetectors. In this work, we report on the performance of a unipolar barrier mid wave infrared detector based on type-II InAs/GaSb strained layer superlattice for high operating temperatures. The device architecture is the double-barrier heterostructure, pBiBn design. Under an applied bias of -10 mV and an operating temperature of 200 K, the best performing devices show a dark current density of 4.9×10-4 A/cm2. At 200 K, the measured zero-bias specific detectivity was 4.4×1010 Jones. © 2015 SPIE. Source


Rotter T.J.,Actoprobe LLC | Busani T.,Actoprobe LLC | Rathi P.,Actoprobe LLC | Jaeckel F.,Actoprobe LLC | And 9 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

We propose to utilize confocal Raman spectroscopy combined with high resolution atomic force microscopy (AFM) for nondestructive characterisation of the sidewalls of etched and passivated small pixel (24 μm×24 μm) focal plane arrays (FPA) fabricated using LW/LWIR InAs/GaSb type-II strained layer superlattice (T2SL) detector material. Special high aspect ratio Si and GaAs AFM probes, with tip length of 13 μm and tip aperture less than 7°, allow characterisation of the sidewall morphology. Confocal microscopy enables imaging of the sidewall profile through optical sectioning. Raman spectra measured on etched T2SL FPA single pixels enable us to quantify the non-uniformity of the mesa delineation process. © 2015 SPIE. Source


Plis E.,University Blvd | Myers S.,University Blvd | Ramirez D.,University Blvd | Smith E.P.,Raytheon Co. | And 4 more authors.
Infrared Physics and Technology | Year: 2015

We report on the design, growth, fabrication and characterization of dual-band (long-/long-wave infrared) type-II InAs/GaSb strained layer superlattice (T2SL) detectors with pBp architecture. Under operating the bias of -200 mV and +100 mV, quantum efficiencies of 37% (∼11 μm band) and 25% (∼9 μm band) were realized, respectively. To reduce the dark current in a dual-band T2SL detector, the effect of a "restoration" chemical etch treatment and ZnTe passivation on device performance were investigated. © 2014 Elsevier B.V. All rights reserved. Source

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