Effects of gas flow ratio on silicon carbide thin film growth mode and polytype formation during gas-source molecular beam epitaxy

Silicon carbide thin films have been grown on vicinal 6H-SiC(0001) substrates by gas-source molecular beam epitaxy at 1050 °C. The effect of gas flow ratios (C2H4Si2H6=1,2,10) on the growth mode was examined via cross-sectional high resolution transmission electron microscopy and in situ reflection high energy electron diffraction. Step flow, step bunching, and the deposition of 6H-SiC occurred at the outset of the exposure of the (1×1) surface to the reactants using any flow ratio. Subsequent deposition resulted in step flow and continued growth of 6H films or formation and coalescence of 3C-SiC islands using the gas flow ratio of one of the ethylene-rich ratios, respectively. The (3×3) surface reconstruction observed using the former ratio is believed to enhance the diffusion lengths of the adatoms which, in turn, promotes step flow growth.