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 Chem. Vapor Deposition (UHV-CVD) system was studied. Si1-xCx layers were grown in a temp. range of 550-650 DegC and characterized using rocking curve X-ray diffraction (XRD), at. force microscopy (AFM) as well as Fourier transform IR spectroscopy (FT-IR). It was found that with increasing carbon precursor flow (Methylsilane) the amt. of substitutional carbon rises up to a crit. value. After a max. in substitutional carbon content is reached, a further increase of carbon fraction leads to a redn. of the strain. By FT-IR, the non-substitutional carbon was detd. to form 3C-SiC ppts. already during growth. A strong correlation between the increase of Methylsilane flow and the formation of coherent ppts. even at low carbon fractions was observed. A low deposition temperature was found to promote the pptn. of 3C-SiC.