Observation of Si out-diffusion related defects in SiC growth on Si(001)

Good quality epitaxial β-SiC growth on Si(001) substrates is conventionally obtained by various chemical vapour deposition process using the reaction of carbon and silicon-containing gases at high temperature (around 1300°C). We explore here an alternative route, at lower sample temperature, where SiC growth is obtained by molecular beam epitaxy evaporation of Si with C2H4 cracking on a surface held at 850°C. Preliminary IR analyses show the expected absorption band at 794 cm−1 of β-SiC with a damping coefficient of 0.02 close to the theoretical value (0.01). Moreover, cross-sectional transmission electron microscopy and in-situ X-ray photoelectron spectroscopy studies revealed the presence of elemental Si on the SiC surface, related to out-diffusion of Si atoms from the substrate. This on-top diffusion generates large pyramid-shaped defects in the substrate along 〈011〉 directions and contributes to the formation of strong SiC islands emerging above other SiC regions presenting more regular two-dimensional growth. High resolution figures obtained by zooming on these islands allows us to probe their local polycrystalline atomic structure. These defects are not characteristic of our growth process as they were observed previously using other growth methods. Investigations are under way to determine a growth procedure which suppresses the formation of these defects.