The growth of GaN films on Si substrates is very attractive work because of irreplaceable merits of Si wafer such as low cost, high surface quality, large area wafer availability, high conductivity and well-established processing techniques.
In this work, we studied the effect of buffer layers to grow high quality GaN films on 3C- SiC/Si(111) substrates. GaN films were grown on 3C-SiC/Si(111) by metalorganic chemical vapor deposition (MOCVD) using various buffer layers (GaN, AlN, and superlattice). The surface morphology and structural and optical properties of GaN films were investigated with atomic force microscopy (AFM), x-ray diffraction (XRD), Raman spectroscopy, and Photoluminescence (PL), respectively. GaN films grown using superlattice buffer layer showed only c-oriented (0002) plane of GaN from the XRD analysis. Raman spectra showed that the E2 high mode agreed with the selection rule was well observed in all GaN films. The A1(TO) and E1(TO) mode were appeared for GaN grown without buffer layer, whereas the E1(TO) mode was additionally appeared in the GaN films grown with GaN buffer layer. In the PL spectra at low temperature, the peaks associated with band edge emission and donor-accepter pair (D0A0) were observed in GaN films grown without buffer layer or with GaN buffer layer and AlN buffer layer. GaN films grown with superlattice buffer layer showed band edge and very weak D0A0 emission. The root mean square (RMS) roughness of the GaN film grown on superlattice buffer layer was only 4.21 Å Our experimental results indicated that the buffer layer affects crucially the qualities of GaN films grown on the 3C-SiC/Si substrate. Superlattice buffer layer improved the surface morphology as well as structural and optical properties of GaN films.