Theoretical Investigation on Lanthanide Ad-atoms on Wurzite GaN

Several oxides including rare earth oxide (REO) such as Gd₂O_3, have been used to passivate the GaN surface as well as to serve as the gate oxide in metal-oxide-semiconductor (MOS) applications. One of the problems in heteroepitaxy with REO on GaN is poor wetting related to the interface and film surface energy balance. The use of Zintl and Zintl-like intermetallic compounds can be a possible solution to overcome poor wetting. Using density functional theory, we investigate electronic structures of bare (0001)-oriented surface of wurzite GaN and lanthanide Eu and Gd ad-atoms on it. We also explore the possibility of forming a Zintl-like transition layer, EuGa₂. Our results provide the microscopic understanding of the intermetallic layer formation and its role in the growth of REO on GaN. We validate our theoretical results through a comparison with the in-situ x-ray photoelectron spectroscopy data.