Large conduction band offset at SiO₂/β-Ga₂O₃ heterojunction determined by X-ray photoelectron spectroscopy

We evaluated the band offsets at the SiO2/β-Ga2O3 (010) interface by X-ray photoelectron spectroscopy (XPS). Plasma chemical vapor deposition with a liquid tetraethyl orthosilicate source for SiO2 was used to prepare an SiO2(40 nm)/Ga2O3 sample and an SiO2(3 nm)/Ga2O3 sample for XPS analyses. The bandgap of SiO2 was determined to be 8.7 ± 0.2 eV. A large conduction band offset of 3.1 ± 0.2 eV and a corresponding valence band offset of 1.0 ± 0.2 eV were determined for the SiO2/Ga2O3 interface. These results suggest that an SiO2 gate insulator is favorable for Ga2O3 field effect transistors operating under high temperatures.