Effects of tail states on the conduction mechanisms in silicon carbide thin films with high carbon content

Hydrogenated amorphous silicon carbide (a-SiCx:H) films of different carbon content (x) were deposited by radio frequency plasma enhanced chemical vapor deposition (PECVD) system. Apart from the X-ray photoelectron spectroscopy (XPS) and UV-Visible transmission analyses, the resistivity measurements between 293 K and 450 K were emphasized to assess the eventual transport mechanisms. The film resistivities are unexpectedly found relatively low, especially for high carbon content. In the frame of exclusive band conduction, the apparent thermal activation energies, evaluated from Arrhenius type plot remain too low compared to half values of the optical gaps.