Electron energy band alignment at interfaces of (100)Ge with rare-earth oxide insulators

Energy diagrams of interfaces between (100)Ge and several rare-earth oxide insulators deposited from a molecular beam are determined using a combination of internal photoemission and photoconductivity measurements. For the wide band gap (5.9eV) oxides Gd2O3 and LaHfOx, the band alignment at the interface is found to be close to that of HfO2 and is characterized by conduction/valence band offsets of ∼2∕∼3eV. In contrast, CeO2 which has a much narrower band gap (3.3eV) does not provide a band alignment diagram corresponding to sufficient insulation.