Near band edge photoluminescence (PL) is observed from about 100-nm-thick pseudomorphicSi1−yCyepilayers, which were grown by molecular beam epitaxy on a Si substrate. Different pieces of one wafer were annealed at temperatures between 500 and 800 °C, and it is shown that annealing leads to increased PL intensities and reduced linewidths. The smallest achieved full width at half maximum was 8.6 meV. We also observe a blueshift of the PL lines after annealing, which does not correspond to the minor changes in the amount of substitutional carbon deduced from x-ray measurements. Temperature dependent PL measurements suggest that the recombination involves electrons localized at alloy fluctuations. ©1997 American Institute of Physics.