MULTIEXCITON SPECTROSCOPY OF A SINGLE SELF-ASSEMBLED QUANTUM-DOT

We apply low temperature confocal optical microscopy to spatially reso lve, and spectroscopically study, a single self-assembled quantum dot. By comparing the emission spectra obtained at various excitation leve ls to a theoretical many body model, we show that (a) single exciton r adiative recombination is very weak, and (b) sharp spectral lines are due to optical transitions between confined multiexcitonic states amon g which excitons thermalize within their lifetimes. Once these few sta tes are fully occupied, broadbands appear due to transitions between s tates which contain electrons in the continuum.