Quantum dots of InAs/GaSb type II superlattice for infrared sensing
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Quantum dots of InAs/GaSb type II superlattice for infrared sensing (Invited paper) M. Razeghi a), Y. Wei, A. Gin Northwestern University, Center for Quantum Devices, ECE Department Evanston, IL 60208 G. J. Brown Air Force Research Laboratory, Materials & Manufacturing Directorate, AFRL/MLPS, Wright-Patterson AFB, OH 45433-7707 ABSTRACT Throughout the past years, significant progress has been made in Type II (InAs/GaSb) photovoltaic detectors in both LWIR and VLWIR ranges. BLIP performance at 60K for 16µm photovoltaic type II detectors has been successfully demonstrated for the first time. The detectors had a 50% cut-off wavelength of 18.8 µm and a peak current responsivity of 4 A/W at 80K. A peak detectivity of 4.5×1010cm·Hz1/2/W was achieved at 80K at a reverse bias of 110mV. Detectors of cutoff wavelength up to 25µm have been demonstrated at 77K. The great performance of single element detectors appeals us to lower dimensional structures for both higher temperature performance and possible wavelength tunability. Simple calculations show that quantum effects will become significant when the lateral confinement is within tens of nanometers. The variation of applied gate voltage will move the electron and hole energy levels unevenly. The cutoff wavelength of the superlattice will vary accordingly. Auger recombination will also decrease and higher temperature operation becomes possible. In this talk, the latest results will be discussed. INTRODUCTION In recent years, extensive research has been done on infrared photodetectors for use throughout the mid to very long wavelength (3-25µm) range. These detectors have a wide variety of military, medical, and industrial applications. Uncooled infrared (IR) detectors are required for low-cost, lightweight sensor applications. Commercially available uncooled IR devices use ferroelectric or microbolometer detectors. These sensors are inherently slow and cannot detect rapid signal changes needed for many applications. Some of the applications which require a fast detector response time (τ < 30 msec) are: free-space communication, proximity fuses, active infrared countermeasure systems, non-invasive medical monitoring, and LIDARs. Although photon detectors have frequency responses in the megahertz range, their high temperature detectivity is severely degraded due to physical limitations. The existing infrared photon detectors can be categorized as interband, which are mostly HgCdTe and InAsSb, or intersubband quantum well infrared detectors (QWIP)[1]. Unfortunately, fast Auger recombination rate in such interband detectors[2] and high thermal generation rate in the a)
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intersubband detectors decrease their performance for room temperature operation drastically. As another alternative for infrared photodetectors, type-II superlattices have been studied which were originally suggested by Sai-Halasz and L. Esaki[3]. In order to realize Auger suppression at room temperature, we have developed a new type-II superlattice detector
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