Two-step preparation of 6H–SiC(0001) surface for epitaxial growth of GaN thin film

A scratch-free and atomically flat 6H–SiC(0001) surface has been successfully prepared by a two-step method which combines atmospheric hydrogen treatment and ultrahigh vacuum Si etching. On this surface, a high-quality GaN(0001) thin film is obtained by radio frequency nitrogen plasma assisted molecular beam epitaxy. Its surface exhibits a typical terrace-plus-step morphology, which enables us to study various GaN(0001) surface superstructures and hollow-core defects with atomic resolution by scanning tunneling microscopy.