Surface passivation of n-type crystalline Si by plasma-enhanced-chemical-vapor-deposited amorphous SiCx:H and amorphous SiCxNy:H films

Abstract

Excellent passivation of n-type crystalline silicon surface is demonstrated by means of intrinsic amorphous silicon carbide (a-SiCx:H) thin films. An optimum CH4/SiH4 ratio is determined, leading to an effective surface recombination velocity, Seff, lower than 54 cm s−1. By adding a constant flow of N2 to the precursor gases, the surface passivation is improved to Seff⩽16 cm s−1. From infrared spectroscopy measurements of these films, it can be deduced that the N2 flow increases the carbon content of the layers for a constant CH4/SiH4 ratio. The dependence of the effective lifetime, τeff, on the excess charge carrier density, Δn, is measured using the quasisteady-state photoconductance technique, and these curves are simulated through an electrical model based on an insulator/semiconductor structure.