Radiative Versus Nonradiative Decay Processes in Germanium Nanocrystals Probed by Time-resolved Photoluminescence Spectroscopy

Abstract

AbstractGe nanocrystals (NCs) of diameter 4–13 nm are grown embedded in a thermally grown SiO2 layer by Ge ion implantation and subsequent annealing. Steady state and time-resolved photoluminescence (PL) studies are performed on these embedded Ge nanocrystals to understand the origin of the PL emission at room temperature. Steady state PL spectra show a broad peak consisting of a peak at ∼2.1 eV originating from Ge NCs and another peak at ∼2.3 eV arising from ion-beam induced defects in the Ge/SiO2 interface. Time-resolved PL studies reveal double exponential decay dynamics of the PL emission on the nanoseconds time scale. The faster component of the decay with large amplitude and having a time constant τ1∼3.1 ns is attributed to the nonradiative lifetime, since the time constant reduces with increasing defect density. The slower component with time constant τ2∼10 ns is attributed to radiative recombination at the Ge NCs. These results are in close agreement with the theoretically predicted radiative lifetime for small Ge NCs.