An intrinsic, carbon- rich a- SiCx: H thin film, prepared by the plasma- enhanced chemical vapour deposition ( PECVD) technique, has been studied mainly by AC admittance and small- pulse deep- level transient spectroscopy ( DLTS) measurements on an Al/ a- SiCx: H/ p- Si metal - insulator - semiconductor ( MIS) structure. The effects of measurement temperature, voltage and small- signal AC modulation frequency on the MIS capacitor are qualitatively and quantitatively described. The kinetics of charge injection from the silicon substrate into the a- SiCx: H film, as a function of temperature and voltage bias stresses, are reported. Nearest-neighbour and variable- range hopping mechanisms are considered. An activation energy of similar to 0.09 eV, and a density of states ( DOS) of about 10(19) cm(-3)/ eV were found. The value of the DOS is in agreement with the effective interface DOS of above 10(12) cm(-2)/ eV assessed by both capacitance and DLTS measurements. The frequency ( or temperature) dependence of the MIS capacitor over the whole DC voltage range is considered in detail. Single- and double- step carrier exchange mechanisms between the a- SiCx: H film and the silicon substrate, in the accumulation and depletion voltage regimes, respectively, are proposed.