Numerical investigation of the postgrowth intermixing effects on the optical properties of InAs/GaAs quantum dots

We report on a simple theoretical model allowing to investigate the rapid thermal annealing induced quantum dots intermixing and consequent inhomogeneous broadening. In this model, where the 3D Schrödinger equation has been solved, by the orthonormal wave function expansion method, for strained InAs QD, we assume a lens-shaped QD with a uniform indium composition and a constant aspect ratio during the intermixing process. The size and aspect ratio for as-grown InAs QD, have been estimated by matching the calculated interband optical transition energies to the experimental photoluminescence emission peaks from ground and excited states. The simulated results were correlated with photoluminescence data at various annealing temperatures. Keeping constant the QD aspect ratio, a good agreement has been found between experimental and calculated emission energies for different indium atomic diffusion lengths. Small QDs are found to be more sensitive to the intermixing than larger QDs. This study allows also to calculate the full width at half maximum (FWHM) and compare it with the experimental value. The theoretical calculations suggest that the origin of the inhomogeneous broadening is mainly related to the variation of the QDs size.