Single-dot spectroscopy of low density GaAs quantum dots grown by modified droplet epitaxy

Low density GaAs/AlGaAs quantum dots (QDs) have been fabricated using Modified Droplet Epitaxy (MDE) [11 for the spectroscopic study of single QDs using microphoto-luminescence (muPL). In muPL measurements, the excitation/observation area is focused by a 50 x objective to a spot size of approximately 0.6 mum. Thus, a low density sample was necessary to limit the number of QDs in such a spot size to no more than one. This work made possible the first broad-spectrum single QD spectroscopy of GaAs/AlGaAs QDs fabricated by MDE. The excitation intensity dependence of the muPL spectrum of this sample shows multiple spectral lines which appear at higher excitation intensities. These lines appear from the recombination of electrons and holes from higher energy levels.