Thermal carrier escape and capture in CdTe quantum dots

We studied optical properties of CdTe quantum dots (QDs) by steady-state an d time-resolved photoluminescence spectroscopy. By changing the excitation power at high temperatures (about T = 70K) we can significantly influence t he distribution of excitons within the quantum dot ensemble. The effect man ifests 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 dis cuss these effects in the frame of a model of thermally induced redistribut ion of carriers between the zero-dimensional electronic states within the q uantum dot ensemble. Moreover, we found that the exciton decay time of the QD emission increases dramatically when the number of excitons injected int o the system is reduced.