Electronic band structure of InAs/InAsSb type-II superlattice for HOT LWIR detectors

Abstract

The InAs/InAs1−xSbx type-II superlattices (T2SLs) grown on GaSb buffer layer and GaAs substrates have recently been applied for detectors for long wavelength infrared (LWIR) range and high operating temperature (HOT) conditions. The detailed modeling of T2SLs minibands structure required for detector’s design optimization process relies on accurate knowledge of the InAs1−xSbx bandgap and band edge position. The k∙p (8 × 8 method) was used to analyze the valence band offset (VBO) between InAs and InAs1−xSbx, and hence the InAs1−xSbx band edge position at required xSb composition. An increase of the VBO leads to the structure transformation from type-IIb to type-II superlattices. The required energy bandgap can be reached by changing the conduction band offset (CBO) and the energy bandgap bowing parameter. The temperature dependence of the experimental results of InAs/InAs1−xSbx T2SLs energy bandgap was found to be comparable with theoretical one when energy bandgap bowing parameter is dependent on temperature. The proper fitting of theoretically calculated and experimentally measured spectral response characteristics was shown. Keywords: InAs/InAs1−xSbx type-II superlattice, T2SLs, Energy-band offset, Infrared detectors, LWIR