Redistribution of localised excitons in CdSe/ZnSe quantum dot structures

Population processes and recombination mechanisms of excitons localised in CdSe/ZnSe quantum dot structures are investigated. The photoluminescence (PL) properties are governed by lateral energy transfer within a dense ensemble of quantum dots, which differ in size and Cd concentration, providing for a complex potential landscape with localisation sites of widely varying depth for excitons. At low temperatures, lateral transfer by tunnelling leads to a mobility edge at 2.561 eV. Thermally activated escape and recapture of excitons cause a strong redshift of the PL maximum and the mobility edge.