Strong boron segregation to polycrystalline, Si1-x-yGexCy alloys from Si has previously been reported [MRS Symp. Proc. 669 (2001) J6.9]. In this study, we investigate potential mechanisms for this effect. We find that comparable segregation also occurs in both polycrystalline Si1-yCy and single-crystal Si1-x-yGexCy indicating neither Ge nor grain boundary effects are needed for it to occur. In addition, the stability of the electrical properties of polycrystalline Si1-x-yGexCy with annealing suggests that inactive B-C defects are not forming. Point defect gradients are presented as a mechanism consistent with the electrical data. (C) 2003 Elsevier B.V. All rights reserved.