Study of optical and passivation properties of hydrogenated silicon carbide thin films deposited by reactive magnetron sputtering for c-Si solar cell application

Abstract

In this paper, optical and passivating properties of hydrogenated silicon carbide synthesized by reactive magnetron sputtering for c-Si solar cell application were studied. SiC:H films were synthesized by sputtering a SiC target in an argon-hydrogen ambient at a Radio Frequency (RF) power of 100–250 W. The thickness, density, and roughness of the films were measured by X-ray reflectometry. The optical properties of the films were studied by UV–visible spectroscopy. It is shown that with an increase in RF power, the refractive index increases from 1.53 to 2.32 (at λ = 633 nm), and the extinction coefficient does not exceed 0.009 in most of the visible and near-IR spectrum. Based on the measured optical constants using computer simulation the optimal thicknesses were calculated to maximize antireflection effect. IR spectroscopy showed correlation between the structure and physical properties of the films. It has been established that, at a lower RF power (100–150 W), particles are deposited instead of atoms. This leads to the formation of voids at the particle boundaries, which are subsequently filled with oxygen. Using the non-contact microwave photoconductance decay method, it was shown that the maximum effective lifetime (τeff) is achieved at RF power of 250 W. In addition, influence of preliminary surface cleaning procedure and post-annealing in vacuum on the τeff was considered.