Photoluminescence (PL) spectroscopy has been used to study the incorporation of C in several samples consisting of strained Si(1-x-y)Ge(x)C(y) epilayers lattice matched to Si (001). To obtain the total C concentration, these samples were characterized by both SIMS and Auger emission spectroscopy, and X-ray diffraction data was analyzed to obtain the substitutional C concentration. The difference of the total and substitutional C concentrations, i.e., the non-substitutional carbon fraction, was found to be directly correlated with specific spectral lines in both the room-temperature Raman and low-temperature PL spectra. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.