The epitaxial quality of non-selective and selective deposition of Si1-x-yGexCy (0 less than or equal to x less than or equal to 0.30, 0 less than or equal to y less than or equal to 0.02) layers has been optimized by using high-resolution reciprocal lattice mapping (HRRLM). The main goal was to incorporate a high amount of substitutional carbon atoms in Si or Si1-xGex matrix without creating defects. The carbon incorporation behavior was explained by chemical and kinetic effects of the reactant gases during epitaxial process. Although high quality epitaxial Si1-yCy layers can be deposited, lower electron mobility compared to Si layers was observed. (C) 2003 Elsevier B.V. All rights reserved.