Recombination at the interface between silicon and stoichiometric plasma silicon nitride

The injection level dependence of the effective surface recombination velocity (S_eff) for the interface between crystalline silicon and stoichiometric silicon nitride, prepared by high-frequency direct plasma enhanced chemical vapour deposition (PECVD), has been comprehensively studied. A wide variety of substrate resistivities for both n-type and p-type dopants have been investigated for minority carrier injection levels (Δn) between 10¹² and 10¹⁷ cm⁻³. Effective lifetimes of 10 ms have been measured for high resistivity n-type and p-type silicon, the highest ever measured for silicon nitride passivated wafers, resulting in S_eff values of 1 cm s⁻¹ being unambiguously determined. The S_eff(Δn) dependence is shown to be constant for n-type silicon under low injection conditions, while for p-type silicon, there is a clear minimum to S_eff for injection levels close to the doping density. Further, the S_eff(Δn) dependence for these stoichiometric silicon nitride films appears to be weaker than that for other high-quality, silicon-rich silicon nitride films prepared by remote PECVD.