Diffusion-enhanced preferential growth of m-oriented GaN micro-domains on directly grown graphene with a large domain size on Ti/SiO2/Si(001)

A graphene film with a domain size larger than 100 mu m was grown on a Ti/SiO2/Si(001) template. To make a comparative investigation of the effect of a domain size of graphene on the growth behavior of GaN micro-domains, GaN micro-domains were grown on either directly grown graphene with a large domain size or transferred graphene. The unusual dominance of m-oriented GaN domains over c-oriented ones was observed when grown at 985 degrees C on graphene directly grown on Ti/SiO2/Si. Unlike the preferential formation of m-oriented GaN, c-oriented GaN domains dominated over m-oriented ones when grown at 935 degrees C on directly grown graphene or at 985 degrees C on transferred graphene. The dependence of the preferred orientation of GaN domains on growth temperature and the type of graphene was explained by the distinct diffusion barrier of adatoms under different conditions. In addition, the aspect ratio of individual domains and the surface morphology of c-facet of each of m- and c-oriented GaN domains also suggest that the growth behavior was significantly influenced by diffusion on both graphene and the different facets of GaN. The enhanced diffusion on directly grown graphene was associated with a large domain size.