Observation of band alignment transition from type-I to type-II in AlInAs/AlGaAs self-assembled quantum dots

We found that the AlInAs/AlGaAs self-assembled quantum dots (QDs) systematically changed from type-I to type-II band alignment in real and momentum space with increasing Al composition and QD coverage. A characteristic peak shift corresponding to the transition from type-I to type-II band alignment was observed when Al composition of AlGaAs matrix was increased. Time-resolved photoluminescence measurements revealed that there was a slow decay component corresponding to the type-II recombination as well as type-I-related fast component and that the slow component became dominant as Al composition of the matrix was increased. Samples containing only type-II QDs were successfully grown by optimizing the growth conditions and in these samples, a recombination lifetime of 30ns, which was determined by the strong Gamma-X mixing, was observed for the type-II transition.