Excited states in InAs self-assembled quantum dots

摘要

Abstract: We use capacitance and photoluminescence spectroscopy to study the energy splitting of electron and hole states in InAs self assembled quantum dots embedded in GaAs bulk material. In our photoluminescence spectra, measured with high excitation, we observe five peaks below the wetting layer transition which we attribute to electron hole recombination from quantum dot levels of the same quantum number. Resonant excited photoluminescence experiments show clearly the existence of phonon enhanced carrier relaxation if the energy splitting between two different quantum dot levels matches a multiple of the available phonon energies. Therefore a maximum in the intensity of the resonantly excited photoluminescence does not necessarily occur when most of the dots are pumped resonantly into an excited state, the main criterion, however, is that the energy distance between the pumped levels and the levels below matches a multiple of the available phonon energies. !17