Multiexcitonic effects in the carrier dynamics in single quantum dot

We report on a detailed experimental study of multiexcitonic effects in the carrier dynamics in single GaAs/Al0.3Ga0.7As quantum dot (QD) obtained by means of molecular beam droplet epitaxy. The PL spectrum shows large modifications with the time delay and the excitation power density. During the early stages after pulse excitation the QD ground-state emission consists in a broad band. Increasing the delay time (or decreasing the excitation power) the low energy tail of the PL band rapidly decreases and the PL bandwidth is reduced, eventually collapsing with well-resolved sharp lines (FWHM < 0.5 meV). We attribute the different contributions to emissions from single exciton, few exciton and many exciton levels inside the QD.