Short-period InAsSb-based strained layer superlattices for high quantum efficiency long-wave infrared detectors

Infrared detector barrier heterostructures with strained layer superlattice (SLS) absorbers with different periods were compared. The first was a reference using a conventional barrier heterostructure with a low temperature energy gap corresponding to a wavelength of 10 μm in a 2-μm-thick undoped absorber using a 10.9 nm period with InAs/InAsSb0.36 compositions grown directly on a GaSb substrate. The second structure, in contrast, used a significantly shorter 4.3 nm period absorber with InAsSb0.3/InAsSb0.55 compositions, similar energy gap, and absorber thickness, which were grown on a 6.2 Å lattice constant GaIn0.3Sb virtual substrate on GaSb. It was found that in the short period SLS, the vertical hole mobility and minority carrier lifetime in the temperature range of 80–150 K were a factor on 2–3 greater than in the reference structure. The improvement of the vertical hole mobility was attributed to the effect of hole delocalization. The latter results in an increase in the optical absorption coefficient and the quantum efficiency.