Self-trapped exciton recombination in silicon nanocrystals

Abstract

In this paper we investigate the time-resolved and stationary photoluminescence (PL) of silicon nanocrystals fabricated in a silicon oxide matrix. The PL intensity reveals a nonexponential decay for all temperatures which can be fitted by a ``stretch''-exponential function. From 60 down to 5 K an increase of decay time is observed going along with a decrease of the PL intensity. In addition the PL spectra show a shape change during the decay. The experimental data are interpreted in the model of self-trapped excitons (STE) which are localized in a Si-Si dimer. A numerical simulation of this model provides the radiative and nonradiative recombination times of the STE transition, the energy of the STE singlet-triplet splitting and the height of the self-trapped barrier.