Electronic structure of GeO2-passivated interfaces of (100)Ge with Al2O3 and HfO2

Analysis of internal photoemission and photoconductivity in Ge/thermal germanium oxide/high-dielectric constant oxide (HfO2,Al2O3) structures reveals that the bandgap of the germanium oxide interlayer is significantly lower (4.3±0.2eV) than that of stiochiometric GeO2 (5.4–5.9eV). As a result, the conduction and valence band offsets at the interface appear to be insufficient to block electron and hole injection leading to significant charge trapping in the GeOx∕high-κ oxide stack. Formation of a hydroxyl-rich Ge oxide phase is suggested to be responsible for the modification of the oxide properties.