Structure and electrical properties of hydrogenated amorphous silicon carbide prepared by plasma CVD method

Abstract

The XPS and AC conductivities of a-Si_xC_1-x: H films prepared by the plasma CVD method from silane and methane gases were measured. The separation of the XPS spectra into several peaks revealed the nature of the chemical bonds of silicon and carbon atoms. The coordination of the carbon atom was fourfold in the silicon-rich films, while the threefold coordination was dominant in carbon-rich films. Films prepared from hydrogen-diluted gas contained more carbon atoms with fourfold coordination than those prepared from argon-diluted gas. AC conductivities of the films with silicon content 0.7<x<0.9 were explained in terms of the correlated barrier hopping (CBH) model, the densities of hopping sites were estimsted to be 10¹⁷-10¹⁸cm^-3. AC conductances of the films with x>0.9 above 300K were discussed in terms of the trap-released model. The densities of states at the Fermi level were estimsted at-10¹⁶cm^-3eV^-3 and the Fermi level was in the midgap.