Influence of interlayer GeOx thickness on band alignment of Al2O3/GeOx/Ge structure

Energy band lineup at hetero-interface and its physical origin have been always a fascinating issue, and are being intensely investigated. The understanding of the influence of an interlayer on the band lineup of hetero-interface provides a view of studying the band lineup of hetero-interface. Thus in this paper, the Al2O3/GeOx/Ge structure is employed, and the effect of interlayer GeOx thickness on band lineup of Al2O3/GeOx/Ge structure is studied by X-ray photoelectron spectroscopy technique. The valence band offset of Al2O3/Ge hetero-interface is found to be nearly identical (3.5 eV) for different GeOx thicknesses (0.2 nm similar to 1.2 nm). The gap states model is employed to successfully explain these results. The interfacial dipole in Al2O3/GeOx/Ge structure is nearly unchanged with GeOx thickness based on the gap states model. This indicates that the band lineup of Al2O3/GeOx/Ge structure is independent on GeOx thickness. Thus these further verify that the gap state model is feasible in elucidating energy band lineup at hetero-interfaces.