Relaxation of localized excitons in CdSe/ZnSe heterostructures containing quantum islands of different sizes

We report on localization dynamics of excitons in ensembles of self-organiz ed CdSe islands embedded in ZnSe. The experimental methods employed are tem perature dependent, spatially-resolved photoluminescence (mu -PL), spatiall y-integrated PL (macro-PL), as well as time-resolved PL (TRPL). We see the often observed non-monotonous shift of the FL maximum with temperature whic h we can explain by a redistribution of the excitons amongst the islands. T he measured shift is compared with the exact shift of the bandgap deduced f rom mu -PL measurements and is found to depend strongly on island size and distribution. These transport processes are recovered in the temporal evolu tion of the FL. The decay time of the spectrally integrated PL reaches its maximum at exactly the same temperature at which the redshift of the macro- FL turns into a blueshift.