Thermal carrier processes in bimodal-sized quantum dots with different lateral coupling strength

In this paper, we have studied the thermal carrier process in bimodal-sized In(Ga)As/GaAs quantum dots (QDs) via temperature dependent photoluminescence (PL). The PL intensity ratio of low energy modal to high energy modal is observed to be temperature sensitive and show different trends for QDs with weak and strong lateral coupling strength, i.e., rise and drop with increasing temperature, respectively. The experimental results are explained by two competing processes: (i) carrier thermal escape from each modal to wetting layer state and (ii) direct carrier coupling between two modals. An improved carrier rate equation model is developed to further demonstrate the importance of process ii in strong lateral coupled QDs system. (C) 2011 American Institute of Physics. [doi:10.1063/1.3614433