Improved quality a-SiC:H films prepared by photo chemical vapour decomposition of silane and acetylene

Abstract

Hydrogenated amorphous and microcrystalline silicon carbon alloy films have been grown by photo-CVD using C₂H₂ as a source gas of carbon. The hydrogenated amorphous silicon carbon (a-SiC:H) film with a band gap of ~2.0 eV prepared at a very low hydrogen (LD) concentration exhibits better photo-electronic properties compared to that at high hydrogen dilution (HD) having a similar optical gap. Notwithstanding a high deposition rate, the high photosensitivity (~10⁶), the low density of the defect states ( ~6 × 10¹⁶cm^-3) and the Urbach energy parameter (72 meV) for the a-SiC:H film prepared at low hydrogen dilution and pressure are impressive. On the other hand, low pressure along with high hydrogen dilution have been found to be conducive to microcrystalline silicon carbon alloy (μc-Si:H) formation. Interestingly, crystallites are of silicon while carbon remains in the amorphous and grain boundary regions.