Time-resolved photoluminescence of type-II quantum dots and isoelectronic centers in Zn-Se-Te superlattice structures

Spectrally and time-resolved photoluminescence of a ZnTe/ZnSe superlattice reveals a smooth transition of the photoluminescence (PL) lifetime from similar to 100 ns at 2.35 eV to less than a few nanoseconds at 2.8 eV. The significant increase of the lifetime in the low energy region is strong evidence to support the formation of type-II quantum dots (QDs), since in these nanostructures the spatial separation of carriers is increased. The shorter lived emission above 2.5 eV is attributed to excitons bound to Te isoelectronic centers in the ZnSe matrix. The smooth transition of the PL lifetime confirms that clusters of these Te atoms evolve into type-II ZnTe/ZnSe QDs. (c) 2008 American Institute of Physics.