Multi-Exciton Spectroscopy of a Single Self Assembled Quantum Dot
  We apply low temperature confocal optical microscopy to spatially resolve, and spectroscopically study a single self assembled quantum dot. By comparing the emission spectra obtained at various excitation levels to a theoretical many body model, we show that: Single exciton radiative recombination is very weak. Sharp spectral lines are due to optical transitions between confined multiexcitonic states among which excitons thermalize within their lifetime. Once these few states are fully occupied, broad bands appear due to transitions between states which contain continuum electrons. 
E. Dekel, D. Gershoni, E. Ehrenfreund, D. Spektor J.M. Garcia and P.M.   Petroff