Onset of implant-related recombination in self-ion implanted and annealed crystalline silicon

The impact of residual recombination centers after low-energy self-implantation of crystalline silicon wafers and annealing at 900 °C has been determined by bulk carrier lifetime measurements as a function of implant dose. Doses below 10(exp 13) cm-2 resulted in no measurable increase in recombination, while higher doses caused a linear increase in the recombination center density. This threshold value corresponds to the known critical dose required for the formation of relatively stable dislocation loops during high temperature annealing. Deep level transient spectroscopy revealed a decrease in the vacancy-related defect concentration in the high-dose samples, which we interpret as reflecting an increase in the silicon interstitial concentration. This suggests that silicon interstitials, arising from the slowly dissolving dislocation loops, may be responsible for the increased recombination deep within the samples.