Vertical transport in InAs/GaSb type-II strained-layer superlattices for ...

Vertical transport in InAs/GaSb type-II strained-layersuperlattices for infrared focal plane array applicationsG.A. Umana-Membreno a,† , B. Klein b , H. Kala a , J. Antoszewski a , G. Gautam b ,M.N. Kutty b , E. Plis b , J.M. Dell a , S. Krishna b , L. Faraone aa School of Electrical, Electronic and Computer Engineering, The University of Western Australia,Crawley WA 6009, Australiab Department of Electrical and Computer Engineering, University of New Mexico,Albuquerque NM 87106, USAABSTRACTIn this work, we report on the measurement of vertical transport parameters in p-doped InAs/GaSb type-IIsuperlattices for long-wavelength infrared detectors. Variable magnetic field geometrical magnetoresistance measurementshave been employed to extract the vertical transport parameters, since the Hall-effect technique cannotbe employed in the vertical transport configuration. The room-temperature magnetoresistance measurementswere performed employing a kelvin-mode set up, at electric fields not exceeding 25 V/cm and at magnetic fieldintensities up to 12 T. The measured magnetoresistance, shown to exhibit multiple-carrier conduction characteristics,were analyzed using a high-resolution mobility spectrum analysis technique. It is shown that, at roomtemperature, the electrical conductivity of the sample is due to four distinct carriers, associated with the majoritycarrier holes, sidewall inversion layer electrons, and two minority carrier electrons likely associated with twodistinct conduction band levels.Keywords: Magneto-transport, Type-II superlattices, Infrared detectors, Mobility Spectrum Analysis1. INTRODUCTIONThe use of infrared sensors has rapidly grown from predominantly military applications to widespread usein applications raging from medical diagnostics and scientific instrumentation, to agriculture, environmentalmonitoring and mineral exploration, a well as in areas related to homeland security, and search and rescue.Among the infrared (IR) detector technologies available today, photonic detectors are still pre-eminent in termsof performance, with Mercury Cadmium Telluride (HgCdTe) technology dominatig the high performance defenceand aerospace arena for decades. However, HgCdTe is a very difficult semiconductor material technology withrelatively low pixel uniformity that renders it a very high-cost option for modern large IR focal plane arrayapplications. Consequently, other material systems have been investigated as a replacement for HgCdTe. Ofparticular interest were GaAs/AlGaAs quantum well infrared detectors (QWIPs) and quantum dot infrareddetectors (QDIPs). Unfortunately, both suffer from poor optical absorption and low quantum efficiency, andhave never surpassed HgCdTe in performance. Recently, international research attention has been focusedon InAs/GaSb type-II strained layer superlattices (SLS). The strong optical absorption characteristics of thismaterial system has already enabled the demonstration of IR detectors with performance levels approachingthose of HgCdTe-based devices, and theoretical calculations predict that InAs/GaSb SLS based IR detectorshould significantly outperform state-of-the-art HgCdTe devices available today. 1In spite of a rapid progress in recent years, detectors based on InAs/GaSb SLS have yet to reach their fullpotential. Further development may demand better understanding of fundamental carrier transport mechanismsand, in particular, in obtaining electronic transport parameters in the vertical direction (i.e., perpendicularto the superlattice growth plane) which is the typical mode of operation of infrared photon detectors. Theinformation on vertical minority carrier mobility and lifetime is of critical importance since they impact onquantum efficiency and are directly related to device structure design and material quality and, hence, directly† Corresponding author, email: umana-ga@ee.uwa.edu.auInfrared Technology and Applications XXXVII, edited by Bjørn F. Andresen, Gabor F. Fulop, Paul R. Norton,Proc. of SPIE Vol. 8012, 80120Y · © 2011 SPIE · CCC code: 0277-786X/11/$18 · doi: 10.1117/12.883755Proc. of SPIE Vol. 8012 80120Y-1Downloaded from SPIE Digital Library on 14 Mar 2012 to 64.106.37.191. Terms of Use: http://spiedl.org/terms

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