/ZnO/GaN ferroelectric-semiconductor heterostructure studied by X-ray photoelectron spectroscopy*

Knowledge of the band offsets at the interfaces in the PbZr_0.2Ti_0.8O₃/ZnO/GaN heterostructure are necessary for the insight-driven design and development of corresponding ferroelectric-semiconductor based electronic devices. We have directly measured the valence band offset (VBO) at the ZnO/GaN and PbZr_0.2Ti_0.8O₃/ZnO heterointerfaces using X-ray photoelectron spectroscopy. For this, ZnO and PbZr_0.2Ti_0.8O₃ (PZT) films of different thicknesses were deposited on GaN/(0001) Al₂O₃ and ZnO/GaN/(0001) Al₂O₃, respectively, by RF sputtering to be able to monitor core level positions upon interface formation in order to access changes in band bending at the interface. The derived interface-induced band bending and the positions of the valence band maxima (VBM) were used to derive the VBO. The gained information provides detailed insights into the underlying mechanisms explaining the electrical properties of ferroelectric-semiconductor heterostructures opening a knowledge-based route to explore new approaches to engineer functional nanomaterials.