Experimental Investigations and Modeling of Auger Recombination in Silicon Nanocrystals

The Auger process provides one of the most important nonradiative recombination channels in semiconductors and strongly enhances in nanostructures. In this paper, we investigate Auger recombination for silicon nanocrystals embedded in a SiO2 matrix by transient-induced absorption. Past experience showed that such investigations are very difficult since, in contrast to nanocrystals of direct bandgap materials, exciton dynamics in silicon nanocrystals are dominated by efficient trapping and/or other fast nonradiative relaxation processes. Using a femtosecond pump-probe technique, we separate these processes and assign them to (i) very efficient nonradiative recombination in so-called dark nanocrystals and (ii) formation of a self-trapped excitonic state. Subsequently, we successfully measure the dynamics of Auger interaction between excitons and model this process in terms of exciton-exciton and 3-charge interaction. We find that the 3-charge interaction model provides a suitable framework to describe Auger recombination in silicon NCs.