X-ray photoelectron spectroscopy study for band alignments of BaTiO3/Ga2O3 and In2O3/Ga2O3 heterostructures

Abstract

The energy-band alignments of BaTiO3/Ga2O3 and In2O3/Ga2O3 heterostructures are investigated by x-ray photoelectron spectroscopy (XPS). All of the samples used in this experiment are deposited by pulsed laser deposition method. The optical bandgaps of BaTiO3, In2O3, and Ga2O3 are derived to be 3.59, 3.71, and 4.9 eV, respectively, by ultraviolet-visible absorption spectrum measurement. In detail, the valence band offsets at BaTiO3/Ga2O3 and In2O3/Ga2O3 interfaces are calculated to be 1.19 and 1.13 eV by using the XPS data based on Kraut’s equation, while, correspondingly, the conduction band offsets are 0.11 and 0.07 eV, respectively. Both BaTiO3/Ga2O3 and In2O3/Ga2O3 heterojunctions exhibit type-I alignments. From the view of applications of these two fabricated heterojunctions, fortunately and interestingly, both BaTiO3 and In2O3 are certified as excellent materials to inject electrons into Ga2O3 and may well be beneficial to the contact resistance reduction, for Ga2O3, as interlayers between metals and Ga2O3. Overall, this work is valuable and instructional for device designing and development by right of the relative heterojunctions in further investigations.