On effective surface recombination parameters

Abstract

This paper examines two effective surface recombination parameters: the effective surface recombination velocity Seff and the surface saturation current density J0 s . The dependence of Seff and J0 s 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, J0 s is independent of Ns when Q 2/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, J0 s is superior to the conventional Seff as a metric for quantifying the surface passivation, whereas for diffused silicon, the merit in using J0 s or Seff (or neither) depends on the sample. Experimental examples are given that illustrate the merits and flaws of J0 s and Seff .