Carrier Transport in the Valence Band of nBn III–V Superlattice Infrared Detectors

Abstract

Mid-wavelength infrared detectors have been fabricated in the nBn configuration using the InAs/InAsSb superlattice as the absorber. Possible impediments in the valence band can interfere with the transport of holes that represent the signal. We demonstrate that the thermal activation energy of the photocurrent density, as a function of the applied bias voltage, can be a very sensitive probe of the valence band features. We identify and measure two types of impediments, the hole-block due to a band misalignment and the localization sites formed by fluctuations in the superlattice layer thicknesses. The latter are found to dominate the temperature dependence of the hole mobility. Our inferred localization characteristics are consistent with published results obtained by other techniques.