Biexciton versus exciton lifetime in a single semiconductor quantum dot

The decay characteristics of excitons and biexcitons in one single semicond uctor quantum dot (QD) are directly monitored using time- and spatially res olved photoluminescence spectroscopy. The experiments are performed on a Cd Se/ZnSe QD, occupied by either one or two excitons at a time, allowing a di rect comparison between the radiative lifetime of a biexciton and an excito n confined in the same QD. The rather surprising result of comparable recom bination rates for both states is related to the spatial wave function dist ribution and the spin structure of the particles and their coupling to the photon field, i.e., the superradiance effect.