Excited states and selection rules in self-assembled InAs/GaAs quantum dots

High-pumping-intensity photoluminescence (PL) studies of InAs self-assembled quantum dots (SAQD) have been performed under high pressure P up to 70 kbar. The origin of the higher-energy PL lines that appear in the spectra with increasing pumping intensity is determined by using the Γ-X crossover effect in the conduction band. With increasing P, these lines are sequentially quenched at particular values of P. From this we unambiguously conclude that the lines correspond to the transitions from different excited conduction electron states in the SAQD. This indicates the existence of strong selection rules for the electron-hole recombination in the SAQD.