RAPID CARRIER RELAXATION IN SELF-ASSEMBLED INXGA1-XAS GAAS QUANTUM DOTS/

Carrier capture and relaxation processes in self-assembled 15-Mm In0.5 Ga0.5As/GaAs quantum dots are investigated by means of time-resolved p hotoluminescence spectroscopy. In a systematic study of photoluminesce nce rise times and barrier decay times (variation of temperature, exci tation energy, and excitation density) we aim to identify the physical mechanisms responsible for fast carrier capture and relaxation in qua ntum dots. Both processes are separated by using appropriate excitatio n energies. Carrier capture and relaxation are shown to proceed with r ates as high as similar to 2x10(10) s(-1) at low temperature even if l ess than one electron-hole pair per dot and excitation pulse is create d. We interpret our results in terms of multiphonon processes at low e xcitation densities and in terms of Auger processes at high excitation densities.