The band-gap (Egp) and valence band offset (ΔEv) energies of pseudomorphic GaAsSb layers on GaAs substrate are determined from temperature-dependent photoluminescence measurements on GaAsSb/GaAs and GaAsSb/GaAlAs quantum wells grown by molecular beam epitaxy. A clear evidence of staggered type-II band alignment of GaAsSb relative to GaAs and a value of 1.05 for the valence band offset ratio (Qv) are proposed. Finally, through a detailed comparison of these values with those published previously, we have shown that the scatter in Qv found in the literature (<1 to 2.1) is closely dependent on the exact determination of Egp. Particularly, we have shown that the strain dependence of the deformation potential is important in the calculation of the strain energy contribution to Egp.

Quantum cascade lasers (QCLs) emitting at wavelengths as short as 2.63–2.65 μm are demonstrated. The InAs/AlSb QCL design was optimized to weaken carrier leakage into the L-valley by reducing coupling between the active InAs quantum wells. The lasers with HR-coated facets operated up to 175 K.