Excess Noise in Long-Wavelength Infrared InAs/GaSb type-II Superlattice pin-Photodiodes

We present investigations of the noise behavior of InAs/GaSb superlattice infrared pin-photodiodes for the long-wavelength infrared regime at 8-12 mu m. In diodes with an increased dark current compared to the generation-recombination limited bulk value, the standard shot-noise model fails to describe noise which we observe experimentally in the white part of the spectrum. Instead we find that McIntyre's noise model for avalanche multiplication processes fits our data well. We thus suggest that avalanche multiplication processes within high electric field domains localized around macroscopic defects lead to increased dark current and excess noise.