Three-Modal Size Distribution of Self-assembled InAs Quantum Dots

Abstract

We report a photoluminescence study of self-assembled InAs/GaAs quantum dots (QDs) in which excitation intensity and temperature were varied. The power-dependent photoluminescence spectra reveal three peaks associated with the ground-state transitions of QDs in three branches of different sizes. Thermal carrier redistribution among the three branches of QDs is observed and investigated in terms of the temperature dependence of their relative photoluminescence peak energy, linewidth and intensity. It is found that the optical properties are rather different and unexpected among the three branches of QDs with increasing temperature, which originate from the thermally activated carrier transfer from QDs in the smaller size group to those in the larger size group. We propose a model in which carrier transfer between QDs is facilitated by the wetting layer and which explains the unusual photoluminescence behavior.