Influence of carbon incorporation in amorphous hydrogenated silicon

Glow-discharge a-Si1−x, Cx: H films prepared from mixtures of SiH4, and CH4 have been studied in the low carbon concentration range. The density of states at mid-gap, determined by measuring the space-charge limited current, was found to depend quadratically on the carbon concentration in the film. This suggests that the density of states increases because of the pairing of diluted defect precursors in the network. A tentative model is described and discussed in terms of the present knowledge of the structure of SiC alloys. Data on the composition dependence of the optical gap and the refractive index are also presented.