Energy-band alignments at ZnO/Ga2O3 and Ta2O5/Ga2O3 heterointerfaces by X-ray photoelectron spectroscopy and electron affinity rule

Wide bandgap oxide semiconductors have been a hot topic in electronic and optoelectronic technologies. The oxide heterojunctions provide many significant favorable properties in devices. The energy-band alignments at the heterointerfaces between oxides play a key role in the functional electronics. In this work, we studied the band alignments of ZnO/Ga2O3 and Ta2O5/Ga2O3 heterojunctions. The valence band offsets of Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions were determined by X-ray photoelectron spectroscopy. The Ta2O5/Ga2O3 heterojunction exhibits a type II band alignment with a valence band offset of - 0.24 +/- 0.02 eV and a conduction band offset of 1.06 +/- 0.02 eV, while the ZnO/Ga2O3 heterojunction has a type I band alignment accompanied with a valence band offset of 0.14 +/- 0.05 eV and a conduction band offset of 1.47 +/- 0.05 eV, which has no obvious difference with results by the electron affinity rule. The investigation for Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions could provide a useful guidance of design and physical analysis of their further applications in corresponding heterogeneous structured devices.