11 June 2013 Defects and noise in Type-II superlattice infrared detectors
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To examine defects in InAs/GaSb type-II superlattices we investigated GaSb substrates and epitaxial InAs/GaSb layers by synchrotron white beam X-ray topography to characterize the distribution of threading dislocations. Those measurements are compared with wet chemical etch pit density measurements on GaSb substrates and InAs/GaSb type-II superlattices epitaxial layer structures. The technique uses a wet chemical etch process to decorate threading dislocations and an automated optical analyzing system for mapping the defect distribution. Dark current and noise measurements on processed InAs/GaSb type-II superlattice single element photo diodes reveal a generation-recombination limited dark current behavior without contributions by surface leakage currents for midwavelength infrared detectors. In the white noise part of the noise spectrum, the extracted diode noise closely matches the theoretically expected shot noise behavior. For diodes with an increased dark current in comparison to the dark current of generation-recombination limited material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre’s noise model for avalanche multiplication processes fits the data quite well. We suggest that within high electric field domains localized around crystallographic defects, electrons initiate avalanche multiplication processes leading to increased dark current and excess noise.
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Martin Walther, Martin Walther, Andreas Wörl, Andreas Wörl, Volker Daumer, Volker Daumer, Robert Rehm, Robert Rehm, Lutz Kirste, Lutz Kirste, Frank Rutz, Frank Rutz, Johannes Schmitz, Johannes Schmitz, "Defects and noise in Type-II superlattice infrared detectors", Proc. SPIE 8704, Infrared Technology and Applications XXXIX, 87040U (11 June 2013); doi: 10.1117/12.2015926; https://doi.org/10.1117/12.2015926

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