Biexciton Emission as a Probe of Auger Recombination in Individual Silicon Nanocrystals

Biexciton emission from individual silicon nanocrystals was detected at room temperature by time-resolved, single-particle luminescence measurements. The efficiency of this process, however, was found to be very low, about 10–20 times less than the single exciton emission efficiency. It decreases even further at low temperature, explaining the lack of biexciton emission line observations in silicon nanocrystal single-dot spectroscopy under high excitation. The poor efficiency of the biexciton emission is attributed to the dominant nonradiative Auger process. Corresponding measured biexciton decay times then represent Auger lifetimes, and the values obtained here, from tens to hundreds of nanoseconds, reveal strong dot-to-dot variations, while the range compares well with recent calculations taking into account the resonant nature of the Auger process in semiconductor nanocrystals.