Thermal stability of Si/Si1-x-yGexCy/Si heterostructures grown by rapid thermal chemical vapor deposition

High quality pseudomorphic Si1-x-yGexCy alloy layers were grown on (100) silicon substrates by rapid thermal chemical vapor deposition with 0 or 11 at% Ge and 0.5 or 1 at% C. The relaxation behavior of these strained layers was investigated using rapid thermal annealing between 1000 and 1130 degrees C. Substitutional C gradually precipitated out to form cubic silicon carbide (beta-SiC). The in-plane lattice constant remained constant after annealing, indicating that there was no mechanical strain relaxation by misfit dislocations. The perpendicular lattice constant increased due to the decreasing substitutional C concentration. The same behavior was observed for both SiC and SiGeC samples, showing that Ge did not influence C precipitation. C atoms diffused over very short distances before they precipitated. It appears that, once formed, the beta-SiC particles stayed put. Germanium out-diffusion was found to be somewhat higher than calculated with published diffusion coefficients.