Optical transitions and band gap discontinuities of GaInAsSb/AlGaAsSb quantum wells emitting in the 3 μm range determined by modulation spectroscopy

Modulation spectroscopy, in a form of photoreflectance (PR), has been used to study the electronic structure properties of Ga0.55 In0.45 Asx Sb1-x / Al0.30 Ga0.70 Asy Sb1-y quantum wells (QWs) designed for the 3 μm emission range at room temperature. A number of spectral features related to QW transitions have been revealed. With the support of energy level calculations they could be identified unambiguously for the unstrained (chemical) conduction band offset of 85%, almost independent of a small As/Sb content change in both the well and the barrier. This has been recalculated into the band discontinuities of the realistic (strained) structure, which have been found to be in a good agreement with the values obtained based on the first principles method.