Surface-passivating properties of hydrogenated amorphous silicon carbide films (a-SiCx:H) deposited by plasma-enhanced chemical-vapor deposition on both p- and n-type crystalline silicon (c-Si) have been extensively studied by our research group in previous publications. We characterized surface recombination by measuring the dependence of the effective lifetime (τeff) on excess carrier density (Δn) through quasi-steady-state photoconductance technique. Additionally, we fitted the measured τeff(Δn) curves applying an insulator/semiconductor model which allows us to determine the surface recombination parameters. In this paper, this model is analyzed in detail focusing on the accuracy in the determination of the fitting parameters and revealing uncertainties not detected up to now. Taking advantage of this analysis, the dependence of surface passivation on film deposition conditions is revised including intrinsic a-SiCx:H films on both p- and n-type c-Si and phosphorus-doped a-SiCx:H films on p-type c-Si. As a consequence, a broad view of this passivation scheme is obtained.