Heteroepitaxial growth of GaN buffer layers on 3C-SiC/(001) Si substrates (4 degrees-miscut towards [110]) by metalorganic vapour phase epitaxy has been investigated. High -temperature grown AlxGa1-xN/AlN interlayers were employed to control GaN surface orientations. Semipolar GaN layers with (1011), (2073) and (1012) surface orientations were achieved, as confirmed by X-ray diffraction. Due to the substrate miscut, the growth of (1011) layers was twinned along 11I013c-ncin and [I10]3c-ncin while the growth of (2073) and (1012) layers was only along [110]3c-ncis, The (1011) layers have rough surface morphology while the (2023) and (1012) layers have mirror-like smooth surface. For all samples with various surface orientations, different photoluminescence peak emission energies were observed at -3.45 eV, 3.78 eV and 3.27 eV at 10 K. These emissions are attributed to the near -band edge of hexagonal GaN, basal -plane stacking faults and partial dislocations, respectively. The dominant luminescence intensity of stacking faults indicates their high density in the GaN layers.