The noise behavior of InAs/GaSb superlattice photodiodes for high-performance thermal imaging in the mid- and longwavelength infrared atmospheric windows at 3-5 μm and 8-12 μm is complex and up to now not very well understood. In order to characterize these devices we have developed a noise measurement setup with a noise current resolution in the femtoampère range. First, we show that, when sidewall leakage is absent, InAs/GaSb superlattice photodiodes with a low dark current very close to the generation-recombination limited dark current level of the bulk behave according to the well-known shot noise expression. Next, we investigate a set of 18 large-area diodes with a bandgap in the midwavelength infrared regime, which show an increased dark current depending linearly on the applied reverse bias. For these diodes the common shot noise model generally fails to describe the noise experimentally observed in the white part of the noise spectrum. Instead, we find that McIntyre’s excess noise model for electron-initiated avalanche multiplication processes fits our data remarkably well for the entire set of diodes, which covers about three orders of magnitude in dark current and a wide range of reverse bias voltage. Thus, to explain the mechanism leading to the increased reverse dark current and observed excess noise we tentatively suggest that primary electrons originating from Shockley-Read-Hall states within the space charge region might initiate avalanche multiplication processes within high electric field domains localized around sites of macroscopic crystallographic defects.

Date Published: 4 February 2013
PDF: 9 pages
Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X, 86311M (4 February 2013); doi: 10.1117/12.2013854

Published in SPIE Proceedings Vol. 8631:
Quantum Sensing and Nanophotonic Devices X
Manijeh Razeghi, Editor(s)