MOVPE Growth of Semipolar GaN on Patterned Sapphire Wafers: Influence of Substrate Miscut

We describe epitaxial methods for two different semipolar GaN orientations on patterned sapphire substrates: With (101̄2) (r-plane) sapphire substrates we achieve planar (112̄2) GaN layers with smooth surfaces on a large scale. In the case of (112̄3) (n-plane) patterned wafers the growth of (101̄1) GaN is possible. We optimized the growth conditions for (112̄2) GaN (especially the growth temperature) yielding a coalesced, planar semipolar surface. Thereafter we transferred the knowledge from (112̄2) oriented growth to (101̄1) oriented growth and investigated the general influence of substrate miscuts on surface and crystal qualities, respectively. Due to the fact that the angle between (101̄1) and (0001) in the case of GaN and the angle between (112̄3) and (0001) in the case of sapphire are slightly different, we detected an imperfect surface. Choosing the right substrate miscut angle the crystal and / or the surface quality of GaN could be improved. The third important point is the non-homogeneous defect density distribution in the crystal. The right miscut could help to push the growth of the areas with less defects over the areas with a high defect density to improve the total crystal quality.