Relationship between impurity (B or P) and carrier concentration in Si1-x-yGexCy epitaxial films (0.22 less than or equal to x less than or equal to 0.7, 0 less than or equal to y less than or equal to 0.02) produced by thermal treatment has been investigated. In the case of the B-doped Si1-xGex films with B concentration of 10(21) cm(-3), the carrier concentration slightly decreases with increasing temperature up to 800 degreesC. Because the lattice constant of the film becomes larger with heat treatment, it is suggested that B clustering proceeds with heat treatment, in other words, the epitaxial film is grown in a non-equilibrium for B. In the case of the P-doped Si1-xGex, films with P concentration of 10(20) cm(-3), the carrier concentration scarcely changes with heat treatment for lower Ge fraction (x less than or equal to 0.44). For higher Ge fraction (x = 0.7), the carrier concentration becomes two times higher than that of as-deposited film after heat treatment at 800 degreesC. Because the lattice constant of the film becomes smaller with heat treatment, it is suggested that the solid solubility of electrically active P atoms becomes higher due to the generation of substitutional P atoms at higher temperature. In the P-doped Si0.54Ge0.44C0.02 film, it is considered that the generation of substitutional P atoms is enhanced by the localization of C atoms into the interstitial site due to heat treatment. (C) 2003 Elsevier B.V. All rights reserved.