Time-Resolved Photoluminescence from nm-Sized Silicon Crystallites In SiO2

Time resolved photoluminescence (PL) decays have been measured for Si nanocrystals embedded in silicon dioxide. The nanocrystals were formed by Si implantation followed by thermal annealing at 800 - 1200 °C. The observed PL peaked in the wavelength range 640 - 850 nm and the PL decay exhibited a stretched exponential lineshape, characterized by a relatively large time constant. A nonlinear dose dependence of the PL yield and an observed redshifting for increasing doses and/or higher annealing temperatures is discussed in terms of a nucleation and growth mechanism for the nanocrystals. Finally, we argue that Auger recombination is effective at high excitation densities explaining a wavelength dependent saturation of the PL intensity.