Thermal Carrier Escape and Capture in CdTe Quantum Dots

Abstract

We studied optical properties of CdTe quantum dots (QDs) by steady-state and time-resolved photoluminescence spectroscopy. By changing the excitation power at high temperatures (about T = 70 K) we can significantly influence the distribution of excitons within the quantum dot ensemble. The effect manifests itself by a large (100 meV) red shift of the PL emission energy when the excitation power decreases by five orders of magnitude. This red shift is accompanied by a decrease of the linewidth of the emission band. We discuss these effects in the frame of a model of thermally induced redistribution of carriers between the zero-dimensional electronic states within the quantum dot ensemble. Moreover, we found that the exciton decay time of the QD emission increases dramatically when the number of excitons injected into the system is reduced.