The effect of grain boundary on electrical characteristics in B- and P-doped polycrystalline (poly) Si1−x−yGexCy films was investigated. Poly-Si1−x−yGexCy films were deposited on thermally oxidized Si(100) at 500 to 650C in a SiH4–GeH4–SiH3CH3–H2 gas mixture by an ultra-clean hot-wall low-pressure chemical vapour deposition. B and P were doped into the films by ion implantation and diffusion by heat-treatment. The electrical properties were 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 900C, the increase of carrier concentration npoly and the decrease of resistivity ρpoly with Ge addition were caused by the narrowing of the width of disordered regions, i.e., crystallization of disordered regions induced by Ge atoms. The decrease of npoly and the increase of ρpoly with C addition were 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 was found that npoly and ρpoly were influenced by P atom segregation at grain boundaries due to lowering solid solubility of P in grain by the existence of Ge.

Effect of Grain Boundary on Electrical Characteristics in B- and P-Doped Polycrystalline Si1−x−yGexCy Film Deposited by Ultra-Clean LPCVD. H.Shim, M.Sakuraba, J.Murota: Thin Solid Films, 2006, 508[1-2], 36-9