Temperature dependence of the photoluminescence of ZnSe/ZnS quantum-dot structures

Following the previous work on formation of quantum-dot structures in ultrathin ZnSe/ZnS quantum wells, we investigate the temperature dependence of the photoluminescence spectra in a temperature range from 20 to 100 K. The quantum-dot structure exhibits an intense but broadened photoluminescence line at low temperature. However, the emission quenches rapidly when temperature rises to around 60 K, suggesting the existence of defect-related states either in the ZnSe well layer or in the vicinity of ZnSe/ZnS interfaces. It was found that the thermal activation energy that characterizes the quench process is strongly dependent on the energy position inside the broadened emission lines, which is interpreted as originating from the different extent of lateral quantum confinement of each individual quantum dot.