The effect of grain boundary on electrical characteristics in B- and P-doped polycrystalline (poly) Si1-x-yGexCy films was investigated. Poly-Si1-xGexCy films were deposited on thermally oxidized Si(100) at 500-650 degrees C in a SiH4-GeH4-SiH3CH3-H-2 gas mixture by an ultraclean hot-wall low-pressure chemical vapor deposition. B and P were doped into the films by ion implantation and diffusion by heat-treatment. The electrical properties are characterized by grain size, width of disordered region near grain boundaries, carrier trap density and the amount of impurity segregation at grain boundaries. in the B-doped poly-Si1-x-yGexCy films heat-treated at 900 degrees C, the increase of carrier concentration n(poly) and the decrease of resistivity rho(poly) with Ge addition are caused by the narrowing of the width of disordered regions, i.e., crystallization of disordered regions induced by Ge atoms. The decrease of n(poly) and the increase of rho(poly) with C addition are explained by the suppression of crystallization of disordered region due to C atom segregation at grain boundaries. In the P-doped poly-Si1-x-yGexCy films, it is found that n(poly) and rho(poly) are influenced by P atom segregation at grain boundaries due to lowering solid solubility of P in grain by the existence of Ge. (c) 2005 Elsevier B.V. All rights reserved.