Bimodal size distribution of self-assembled InxGa1-xAs quantum dots -: art. no. 125309

We investigate quantization of energy levels in self-assembled InxGa1-xAs quantum dots that are embedded in a GaAs matrix. We use capacitance and photoluminescence spectroscopies to analyze the evolution of the energy levels with varying amounts of deposited InxGa1-xAs. These techniques suggest that the size distribution of the quantum dots contains two well-separated peaks. Transmission electron microscopy confirms a bimodal size distribution and further shows that the big and the small quantum dots have different shapes. In addition, we use an effective-mass based method to calculate the lowest energy states of quantum dots with the physical dimensions obtained by transmission electron and atomic force microscopies. Our results allow us to construct the energy-level diagrams of the two kinds of quantum dots.