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Thermoelectrically-Cooled InAs/GaSb Type-II Superlattice Detectors as an Alternative to HgCdTe in a Real-Time Mid-Infrared Backscattering Spectroscopy System

: Müller, Raphael; Härtelt, Marko; Niemasz, Jasmin; Schwarz, Klaus; Daumer, Volker; Flores, Yuri V.; Ostendorf, Ralf; Rehm, Robert

Volltext urn:nbn:de:0011-n-6245379 (6.2 MByte PDF)
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Micromachines 11 (2020), Nr.12, Art. 1124, 14 S.
ISSN: 2072-666X
European Commission EC
H2020; 688265; MIRPHAB
MidInfraRed PHotonics devices fABrication for chemical sensing and spectroscopic applications
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IAF ()
InAs/GaSb; T2SL; IR; photodetector; TE-cooled; spectroscopy; RoHS

We report on the development of thermoelectrically cooled (TE-cooled) InAs/GaSb type-II superlattice (T2SL) single element infrared (IR) photodetectors and exemplify their applicability for real-time IR spectroscopy in the mid-infrared in a possible application. As the European Union’s Restriction of Hazardous Substances (RoHS) threatens the usage of the state-of-the-art detector material mercury cadmium telluride (MCT), RoHS-compatible alternatives toMCT have to be established for IR detection. We use bandgap engineered InAs/GaSb T2SLs to tailor the temperature-dependent bandgap energy for detection throughout the required spectral range. Molecular beam epitaxy of superlattice samples is performed on GaAs substrates with a metamorphic GaAsSb buffer layer. Photolithographic processing yields laterally-operated T2SL photodetectors. Integrated in a TE-cooled IR detector module, such T2SL photodetectors can be an alternative to MCT photodetectors for spectroscopy applications. Here, we exemplify this by exchanging a commercially available MCT-based IR detector module with our T2SL-based IR detector module in a real-time mid-infrared backscattering spectroscopy system for substance identification. The key detector requirements imposed by the spectroscopy system are a MHz-bandwidth, a broad spectral response, and a high signal-to-noise ratio, all of which are covered by the reported T2SL-based IR detector module. Hence, in this paper, we demonstrate the versatility of TE-cooled InAs/GaSb T2SL photodetectors and their applicability in an IR spectroscopy system.