Time-resolved photoluminescence of type-II InAs/GaAs quantum dots covered by a thin GaAs_1-xSb_x layer

We investigate carrier lifetimes of InAs/GaAs quantum dots (QDs) covered by a thin GaAs_1-xSb_xlayer by time-resolved photoluminescence (PL). Both the power dependent PL peak shift and the longer decay time confirm the type-II band alignments. Different recombination paths have been identified by temperature dependent measurements. At low temperatures, the long-range recombination with holes trapped in the GaAsSb layer is significant, resulting in non-single-exponential decays. The short-range recombination with holes confined in the band-bending region surrounding the InAs QDs is important at higher temperatures. The variation in decay time across the ground-state and the temporal PL peak redshift further confirm the localization of holes in the GaAsSb layer.