InAs/InxGa1-xSb Type II Strained Layer Superlattices for Long Wavelength Infrared Detection Applications

Abstract

AbstractShort period InAs/InxGa1−xSb superlattices (SLs) may allow strong optical transitions in the long wavelength infrared (> 10 μm) spectral region. Absorption calculations can be difficult, however, because of the strongly type - II interface and because of the large lattice mismatch. We propose that a long wavelength response can be achieved for substantially thinner layers of SLs if the In composition in InxGa1−xSb is properly chosen. This will misalign the bands through strain effects and further reduce the superlattice bandgap. Band structure calculations are reported for InAs/InxGa1−xSb type - II SLs grown on GaSb substrate by using an empirical tight-binding model (ETBM). All of the structures considered here are assumed to be well within the critical strain thickness. Particular care is taken to incorporate the strain effects accurately in the ETBM formalism by modifying the overlap integrals according to the bond lengths and bond angles. We compute the band structure and the cutoff wavelengths of InAs/InxGa1−xSb (001) SLs and compare the results with the existing magnetooptical and photo conductivity data. In addition, we compare the ETBM with the k.p and effective bond orbital models.