Impurity doping using B2H6 gas using hot-wire CVD has been tried for hydrogenated amorphous silicon-carbon (a-SiCX:H) alloy films including hydrogenated microcrystalline silicon (muc-Si:H) with carbon content, C/(Si+C), of about 28%. The dark- and photoconductivities of B-doped samples are larger than those of undoped samples. The activation energy for dark conductivity of the B-doped sample with the doping gas ratio, B2H6/(SiH4+CH4), of about 0.054% is 0.17 eV. This value is smaller than that of the undoped sample. The P-doped samples also show larger dark- and photoconductivities and smaller activation energy than the undoped samples. (C) 2002 Elsevier Science B.V. All rights reserved.