with GaN (0001) and determination fundamental material properties*

As semiconductor technology moves beyond silicon, III-nitrides are strong candidates for high-power, high-temperature and high-frequency MOS applications. Rare-earth (RE) oxides are well suited as gate dielectrics on III-nitrides due to high dielectric constants, thermodynamic stability and large bandgaps. The RE oxide Eu2O3 was grown by MBE on the III-nitride GaN. The Eu2O3 film was characterized by in-situ RHEED, XPS, UPS and ex-situ XRD, STEM and inverse PES. The bandgap was extracted from XPS and inverse PES and the electron affinity determined from UPS, the band alignment with the GaN substrate from XPS. The correlated nature of the Eu 4f core-levels, overlapping the valence band states in binding energy, do not allow an interpretation of photoelectron spectra of the valence band in terms of initial (ground) state properties, hence a direct comparison with ab-initio theory DOS is not valid in this case. The combination of high- and low-energy excitations of XPS and UPS allow to probe matrix element effects in the photoemission process enabling the partial assignment of valence band structures to O 2p or Eu 4f emission hinting towards importance of hybridization between Eu 4f and O 2p.