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Defect density reduction in InAs/GaSb type II superlattice focal plane array infrared detectors

: Walther, M.; Rehm, R.; Schmitz, J.; Niemasz, J.; Rutz, F.; Wörl, A.; Kirste, L.; Scheibner, R.; Wendler, J.; Ziegler, J.


Razeghi, M. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Quantum sensing and nanophotonic devices VIII : 23 - 27 January 2011, San Francisco, California, United States; Part of SPIE photonics west
Bellingham, WA: SPIE, 2011 (Proceedings of SPIE 7945)
ISBN: 978-0-8194-8482-6
Paper 79451N
Conference "Quantum Sensing and Nanophotonic Devices" <8, 2011, San Francisco/Calif.>
Fraunhofer IAF ()
infrared camera; focal plane array; bispectral; dual-color; InAs/GaSb type II superlattice; GaSb substrate; thermal imaging; missile approach warning

InAs/GaSb short-period superlattices (SL) have proven their large potential for high performance focal plane array infrared detectors. Lots of interest is focused on the development of short-period InAs/GaSb SLs for mono- and bispectral infrared detectors between 3 - 30 µm. InAs/GaSb short-period superlattices can be fabricated with up to 1000 periods in the intrinsic region without revealing diffusion limited behavior. This enables the fabrication of InAs/GaSb SL camera systems with very high responsivity, comparable to state of the art CdHgTe and InSb detectors. The material system is also well suited for the fabrication of dual-color mid-wavelength infrared InAs/GaSb SL camera systems. These systems exhibit high quantum efficiency and offer simultaneous and spatially coincident detection in both spectral channels.
An essential point for the performance of two-dimensional focal plane infrared detectors in camera systems is the number of defective pixel on the matrix detector. Sources for pixel outages are manifold and might be caused by the dislocation in the substrate, the epitaxial growth process or by imperfections during the focal plane array fabrication process. The goal is to grow defect-free epitaxial layers on a dislocation free large area GaSb substrate. Permanent improvement of the substrate quality and the development of techniques to monitor the substrate quality are of particular importance. To examine the crystalline quality of 3'' and 4''GaSb substrates, synchrotron white beam X-ray topography (SWBXRT) was employed. In a comparative defect study of different 3'' GaSb and 4'' GaSb substrates, a significant reduction of the dislocation density caused by improvements in bulk crystal growth has been obtained. Optical characterization techniques for defect characterization after MBE growth are employed to correlate epitaxially grown defects with the detector performance after hybridization with the read-out integrated circuit.