Substitutional C fraction and the influence of C on Si dimer diffusion in Si1-yCy alloys grown on (001) and (118) Si

The dependence of substitutional C fraction on growth temperature and subst rate orientation is measured for Si1-yCy alloy films grown on (001) and (11 8) Si by molecular-beam epitaxy. Secondary ion mass spectrometry and high-r esolution x-ray diffraction were used to measure the total C and the substi tutional C concentrations, respectively, in several samples prepared at tem peratures between 450 and 650 degrees C. The substitutional C fraction decr eased rapidly with increasing temperature in this range, regardless of orie ntation, and was slightly lower for growth on (118) Si. Cross-sectional tra nsmission electron microscopy on (118)-oriented samples revealed a tendency for C to concentrate periodically on (001) facets which formed immediately after initiation of Si1-yCy growth. A kinetic Monte Carlo simulation based upon enhanced diffusion of Si dimers in the presence of subsurface C predi cted a step instability leading to step bunching and the formation of perio dic surface features, as well as the accumulation of high C concentrations on nearly (001) planes. (C) 2000 American Institute of Physics. [S0003-6951 (00)00831-7].