Control growth orientation of semipolar GaN layers grown on 3C-SiC/(001) Si

Heteroepitaxial growth of GaN buffer layers on 3C-SiC/(001) Si substrates (4°-miscut towards [110]) by metalorganic vapour phase epitaxy has been investigated. High-temperature grown Al_xGa_1-xN/AlN interlayers were employed to control GaN surface orientations. Semipolar GaN layers with (101¯1), (202¯3) and (101¯2) surface orientations were achieved, as confirmed by X-ray diffraction. Due to the substrate miscut, the growth of (101¯1) layers was twinned along [11¯0]_3C-SiC/Si and [1¯10]_3C-SiC/Si while the growth of (202¯3) and (101¯2) layers was only along [110]_3C-SiC/Si. The (101¯1) layers have rough surface morphology while the (202¯3) and (101¯2) 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.