Direct evidence for the type-II character of In0.52Al0.48As/AlAs0.56Sb0.44 multiple quantum well structures

The type-II nature of the energy gap has been identified in In_0.52Al_0.48As/AlAs_0.56Sb_0.44 multiple quantum well structures through cw and time-resolved photoluminescence (PL) measurements. Direct evidence for the type-II character of the energy gap in this material system are the energetic position of the PL, the by more than two orders of magnitude prolonged PL decay time in comparison to the substrate and the directgap buffer layers, as well as the increase of the decay time with increasing Ino.52Alo.48As layer thickness.