Investigations on phonon-assisted relaxation mechanisms in CdSe/ZnSe quantum islands using time-resolved near-field spectroscopy

We report on relaxation studies of excitons in quantum islands using time-resolved near-field photoluminescence (n-TRPL). This new method allow us to follow the temporal evolution of an ensemble of localized states with a spatial resolution of about 200 nm. The temporal and spectral resolutions are 5 ps and 1.7 meV, respectively. We study the relaxation mechanisms of excitons in two samples containing CdSe/ZnSe quantum islands. In the first sample, where the excitons are weaker localized, the sharp lines of the n-TRPL are repeated at a constant distance of 25 meV. This is not the case in the second sample, where the excitons are stronger localized. We discuss the origin of this correlation, comparing the dynamics of the lines.