Rare-Earth Adatoms On Gan (0001)

Several oxides, including those of rare-earth metals such as Gd2O3, have been used to passivate the GaN (0001) surface and are being considered as possible gate oxides in metal-oxide-semiconductor high electron mobility transistor applications. One of the problems in heteroepitaxy of rare-earth oxides (REOs) on GaN is poor wetting related to the unfavorable interface and film surface energy balance. The use of Zintl and Zintllike intermetallic compounds can offer a solution to overcome this problem. Using density-functional theory, we investigate the bare (0001)-oriented surface of wurtzite GaN and rare-earth Eu, Gd, and Ce adatoms on it including surface mobility, wetting, and electronic structure. We also explore the possibility of forming a Zintl-like transition layer, EuGa2. Our results provide a microscopic understanding of the intermetallic layer formation and its potential role in the heteroepitaxy of REOs on GaN.