Structural, optical, and surface science studies of 4H-SiC epilayers grown by low pressure chemical vapor deposition

A series of epitaxial 4H-SiC thin films grown by low pressure chemical vapor deposition (LPCVD) were characterized using various techniques, including xray diffraction (XRD), Fourier transform infrared (FTIR) reflectance, Raman scattering, and x-ray photoelectron spectroscopy (XPS). The epilayers were grown on heavily doped n-type 4H-SiC substrates using different gas compositions. XRD showed that the thin films were single crystal. Raman scattering identified the films to be 4H polytype. FTIR reflectivity spectra indicated improvement in the film quality over that of the substrate and atmospheric pressure-grown epilayers. XPS scans revealed the existence of Si, C, and O along with C-contaminant species in the form of CH and carbon oxides. Variations in crystalline quality, optical, and surface properties with the growth conditions were studied. This study also provides an important comparison between low and atmospheric pressure-grown 4H-SiC epilayers.