Near bandgap absorption and carrier transport in InAs/InAsSb superlattice devices

In mid-wavelength infrared detectors built with the InAs/InAsSb superlattice, a study of the absorption behavior near the cutoff wavelength was conducted. Two results are, first, an accurate method for determining the bandgap energy from the spectral response of a fabricated device, and second, an analysis of the Urbach tail of the absorption showing that its characteristic energy is consistent with the dominant phonon of InAs. Additionally, a temperature-dependent measurement of the transport of photo-generated holes in nBn devices can be used to identify the effects of localization due to layer nonuniformities, and to measure the energy step at hole-blocking features.