Nucleation and growth mode of GaN on vicinal SiC surfaces

Nucleation and growth mode of GaN during molecular beam epitaxy on vicinal SiC surfaces, consisting of a pair of self-ordered periodic nanofacets, (0001) and (112̄n), are investigated. Well-defined surface nanostructures on SiC enable us to understand growth physics. Here, the Ga-adsorption process on SiC is noticed in particular, and its effects on initial GaN growth stages are examined using reflection high-energy electron diffraction (RHEED) and atomic force microscopy (AFM). With the presence of a Ga-adlayer on a SiC surface, GaN nucleation occurs at step sites on (112̄n) facets, followed by step-flow growth. In contrast, without a Ga-adlayer, GaN nucleation is predominantly observed on (0001) terraces. Interestingly, the crystal structure of the resultant film differs in each case from a typical wultzite (2H) to a 6H-polytype, without and with a Ga-adlayer, respectively.