Investigation of the relaxation behavior of Si1−xCx alloys during epitaxial UHV-CVD growth

In this work, the epitaxial growth of Si1−xCx alloys using an Ultra High Vacuum Chemical Vapor Deposition (UHV-CVD) system was studied. Si1−xCx layers were grown in a temperature range of 550-650 °C and characterized using rocking curve X-ray diffraction (XRD), atomic force microscopy (AFM) as well as Fourier transform infrared spectroscopy (FT-IR). It was found that with increasing carbon precursor flow (Methylsilane) the amount of substitutional carbon rises up to a critical value. After a maximum in substitutional carbon content is reached, a further increase of carbon fraction leads to a reduction of the strain. By FT-IR, the non-substitutional carbon was determined to form 3C-SiC precipitates already during growth. A strong correlation between the increase of Methylsilane flow and the formation of coherent precipitates even at low carbon fractions was observed. A low deposition temperature was found to promote the precipitation of 3C-SiC.