Formation of epitaxial Si1−yCysubstitutional alloy layers on monocrystalline silicon surfaces withy≊1 at. % is reported. The preparation method was carbon ion implantation, followed by KrF excimer laser annealing. Results of Rutherford backscattering (RBS), secondary ion mass spectrometry (SIMS) and infrared absorption analyses are compared. The authors concluded that, up to ∼1 at. % carbon content, the dominant process is nonequilibrium trapping of carbon in substitutional lattice sites upon fast resolidification. Above this concentration the complex carbon redistribution processes are influenced by silicon carbide precipitation in the melt and segregation effects in the near‐surface region. ©1996 American Institute of Physics.