Lattice distortions induced by carbon in silicon

X-ray double-crystal diffractometry has been used to investigate the lattice distortions in silicon crystals containing carbon impurities. Precise lattice-spacing measurements have been carried out with a double-source double-crystal transmission technique. A linear correlation between the absolute value of lattice spacing and the carbon concentration was observed. X-ray double-crystal reflection topography was used to measure residual minute lattice strains also as a function of the carbon atom number density. A similar relationship was found. A comparison of the results of the lattice-spacing measurements and of the topographic investigations indicates that the lattice consists of consecutive layers which are alternately more and less carbon enriched. The observed lattice deformations arise from the substitutional exchange of silicon and carbon atoms.