Transmission electron microscopy study of ultra-thin SiC layers obtained by rapid thermal carbonization of Si wafers

A structural multitechnique study of beta-SiC/Si(111) and beta-SiC/Si(100) wafers is reported in this paper. SiC thin layers have been developed in a Rapid Thermal Chemical Vapor Deposition (RTCVD) system by Si carbonization with propane. The study was carried out by High Resolution and Conventional Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), Spectroscopic Ellipsometry (SE), Fourier Transform Infra-Red Spectroscopy (FTIR) and Single Wave Length Multiple Angle (SWLMA) measurements. The thickness variations of the carbonized layer are determined along radial directions in both wafers by High Resolution Transmission Electron Microscopy (HRTEM). The latter are compared with average thickness determinations obtained by SE. The analyses confirm the existence of beta-SiC layers with thicknesses of few nanometers in 3 inch SiC/Si wafers. Plan-view SAED evidences the existence of good structural quality and well aligned (111) and (001) beta-SiC layers. Compositional and structural homogeneity indicates a self-limiting conversion mechanism of the Si surface into SiC. These are encouraging results in order to use the Si carbonization to grow stoichiometric crystalline III-N thin layers on Si. In fact, the obtained substrates in this work are actually used for a further GaN overgrowth.