On the effects of double-step anneal treatments on light emission from Er-doped Si-rich silicon oxide

We have studied photoluminescence (PL) from an Er-doped Si-rich Si oxide (SRSO) film thermally annealed under different conditions. Compared to the case of annealing in N2 alone, double-step annealing the film at 875 °C in N2 and then at ∼850 °C in O2 or vice versa increases Er PL intensities by 10%-15%; while double-step annealing in N2 +5% H2 (FG) and then in O2 or vice versa yields significant enhancements of the PL from the SRSO matrix and the Er PL intensity decreases differently by exchanging the processing order. Fourier transform infrared spectroscopy indicates that silicon oxynitride forms after annealing in FG ambient, and for the samples initially oxidized, the increase of Er PL intensity after secondary annealing in N2 (or FG) is due to more Si nanoclusters being formed. The PL spectra exhibit different annealing behavior with increasing the FG annealing temperature and the processing order. Weak oxygen bonds and silicon oxynitrides are believed to form upon O2 and FG annealing, respectively, and play important roles in the PL.