Microstructure and ion beam characterization of heteroepitaxial Si 1- x- yGe xC y

Si _{1- x- y}Ge _xC _y is a novel group IV semiconductor alloy with interesting possibilities for strain modification and bandgap engineering. To investigate the growth kinetics of this new semiconductor, heteroepitaxial Si _{1- x- y}Ge _xC _y films were grown on 4 in. Si(100) wafers by combined ion and molecular beam deposition at temperatures between 450 and 560°C. Transmission electron microscopy (TEM) combined with diffraction show that the films, 1000 ± 220 Å thick, are single phase heteroepitaxial cubic diamond solid solutions. For films with a Si:Ge ratio of 7:3 the defect density is low for carbon concentrations less than 1%. The <110> minimum yield increases from 0.13 to 0.89 as the carbon concentration increases from 0.5 to 3%. For low C concentrations, the channeling yield increases with depth indicating that the defect density increases near the film substrate interface, which is characteristic of partial film relaxation. For C concentrations of 2% and higher the defect density is uniformly high throughout the films indicating that defects are uniformly nucleated throughout the film during growth. Infrared spectroscopy measurements show that the SiC bond length distribution broadens as the carbon concentration increases and also shows that carbon exhibits a higher substitutionality for a growth temperature of 450°C than for 560°C. A possible interpretation of these results is that the high local strain associated with the SiC bonds deteriorates the elastic properties of Si _{1- x-y}Ge _xC _y, making it more susceptible to relaxation and defect nucleation than Si _{1- x}Ge _x under similar strain and growth temperatures.