Polarity control of ammonia-MBE grown GaN{0001} film

摘要

Epitaxial wurtzite GaN{0001}, which is a promisining material for optoelectronic, high-temperature and high-power device applications, has a polar structure whose c axis is parallel to the growth direction (Fig.1). In the wurtzite GaN films, lattice polarity is one of the key issues which affect the optical and electrical properties of grown films[1-3]. In metalorganic chemical vapor deposition (MOCVD), there are many reports about the polarities of grown films [4] and high quality films are revealed to have Ga-face. however, in molecular beam epitaxy (MBE), there are only few reports about the plarities of heteroepitaxial GaN films.[5, 6] Regarding the plasma-assisted MBE films, the polarity is assumed to be N-Face, which is inferior to Ga-face in quality, though the growth parameters which determine the polarities of the films are not so clear.