On effective surface recombination parameters

This paper examines two effective surface recombination parameters: the effective surface recombination velocity Seff and the surface saturation current density J0s. The dependence of Seff and J0s on surface charge Q, surface dopant concentration Ns, and interface parameters is derived. It is shown that for crystalline silicon at 300 K in low-injection, Seff is independent of Ns only when Q2/Ns 1900 cm in accumulation and Q2/Ns 1600 cm in depletion; otherwise Seff increases with Ns. 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, J0s is independent of Ns when Q2/Ns 1.5 × 107 cm for accumulation and Q1.85/Ns 1.5 × 106 cm for inversion. These conditions are commonly satisfied in undiffused wafers but rarely in diffused wafers. We conclude that for undiffused silicon, J0s is superior to the conventional Seff as a metric for quantifying the surface passivation, whereas for diffused silicon, the merit in using J0s or Seff (or neither) depends on the sample. Experimental examples are given that illustrate the merits and flaws of J0s and Seff.