Nature of optical transitions in self-organized InAs/GaAs quantum dots

Electronic transitions in nm-scale pyramid-shaped InAs/GaAs quantum dots feature only ground-state electrons. Allowed optical transitions involving excited hole states in addition to the ground-state transition are revealed in absorption and photoluminescence spectra. The experimental data agree with detailed theoretical calculations of the electronic structure, including strain, piezoelectric, and excitonic effects, and lead to unambiguous assignment of the transitions. We find as upper bound for the relative standard deviation of the size fluctuation $\xi <~0.04$. The hole sublevel separation is consistent with a pyramid shape fluctuation between {101} and {203} side facets.