Graphoepitaxy of High-Quality GaN Layers on Graphene/6H-SiC

The implementation of graphene layers in gallium nitride (GaN) heterostructure growth can solve self-heating problems in nitride-based high-power electronic and light-emitting optoelectronic devices. In the present study, high-quality GaN layers are grown on patterned graphene layers and 6H-SiC by metalorganic chemical vapor deposition. A periodic pattern of graphene layers is fabricated on 6H-SiC by using polymethyl methacrylate deposition and electron beam lithography, followed by etching using an Ar/O-2 gas atmosphere. Prior to GaN growth, an AlN buffer layer and an Al0.2Ga0.8N transition layer are deposited. The atomic structures of the interfaces between the 6H-SiC and graphene, as well as between the graphene and AlN, are studied using scanning transmission electron microscopy. Phase separation of the Al0.2Ga0.8N transition layer into an AlN and GaN superlattice is observed. Above the continuous graphene layers, polycrystalline defective GaN is rapidly overgrown by better quality single-crystalline GaN from the etched regions. The lateral overgrowth of GaN results in the presence of a low density of dislocations (approximate to 10(9) cm(-2)) and inversion domains and the formation of a smooth GaN surface.