On effective surface recombination parameters

This paper examines two effective surface recombination parameters: the effective surface recombination velocity S_eff and the surface saturation current density J_0s. The dependence of S _eff and J_0s on surface charge Q, surface dopant concentration N_s, and interface parameters is derived. It is shown that for crystalline silicon at 300K in low-injection, S_eff is independent of N_s only when Q²/N_s<1900cm in accumulation and Q²/N_s<1600cm in depletion; otherwise S_eff increases with N_s. These conditions are rarely satisfied in undiffused wafers but sometimes satisfied in heavily diffused wafers when coated with lowly charged films. Under the same conditions, J _0s is independent of N_s when Q ²/N_s>1.5×10⁷cm for accumulation and Q^1.85/N_s>1.5×10⁶cm for inversion. These conditions are commonly satisfied in undiffused wafers but rarely in diffused wafers. We conclude that for undiffused silicon, J_{0 s} is superior to the conventional S_eff as a metric for quantifying the surface passivation, whereas for diffused silicon, the merit in using J_0s or S_eff (or neither) depends on the sample. Experimental examples are given that illustrate the merits and flaws of J_0s and S_eff.