The impact of carbon doping on electrical properties of epitaxial Gd2O3 grown on Si substrates has been studied. The doping with low concentration of carbon into epitaxial Gd2O3 shows strong influence on dielectric properties especially to the reduction of leakage current behavior. The structural quality of the oxide layer is merely influenced by small amount of carbon incorporation. The most critical observation of this study is that the very often found adverse effect of oxygen vacancy induced defects in oxides grown at higher temperature could be eliminated by moderate amount of carbon doping during growth.