Observation of multicharged excitons and biexcitons in a single InGaAs quantum dot

The effects of excess electron occupation on the optical properties of excitons (X) and biexcitons $(2X)$ in a single self-assembled InGaAs quantum dot are investigated. The behavior of X and $2X$ differ strongly as the number of excess electrons is varied with the biexciton being much more weakly perturbed as a result of its filled s-shell ground state, a direct manifestation of shell-filling effects. Good correlation is found between charging thresholds observed from s-shell recombination perturbed by p-shell occupation, and direct observation of p-shell recombination.