AN X-RAY-DIFFRACTION STUDY OF THE STRAIN AND STRUCTURE OF SIGEC (100)SI ALLOYS/

High resolution X-ray diffraction studies were conducted on samples of Si1-x-yGexCy grown on (100)Si by chemical vapor deposition. The measu rements were made with the diffractometer in its triple-axis configura tion to produce reciprocal space maps. Films with compositions of appr oximately Si0.78Ge0.21C0.01 and thicknesses ranging from 120 nm to 750 nm were found to be pseudomorphic with a tetragonal distortion strain , epsilon(T), near 1%. The tetragonal strain was found to be independe nt of sample thickness. The strain in samples with compositions near S i0.47Ge0.50C0.03 and thicknesses ranging from 61 to 115 nm were found to have tetragonal strain values greater than 2%. These strain measure ments correlated well with ion channeling measurements. The experiment al perpendicular lattice parameters were used to estimate the relaxed film lattice constants. These values fell midway between predicted val ues using Vegard's law for complete strain compensation by the carbon and no compensation by the carbon.