Band Offsets of the MOCVD-Grown beta-(Al0.21Ga0.79)(2)O-3/beta-Ga2O3 (010) Heterojunction

The band offsets for the beta-(Al0.21Ga0.79)(2)O-3/beta-Ga2O3 (010) heterojunction have been experimentally measured by X-ray photoelectron spectroscopy. High-quality beta-(Al0.21Ga0.79)(2)O-3 films were grown by metal-organic chemical vapor deposition for characterization. The indirect band gap of beta-(Al0.21Ga0.79)(2)O-3 was determined by optical transmission to be 4.69 +/- 0.03 eV with a direct transition of 5.37 +/- 0.03 eV, while beta-Ga2O3 was confirmed to have an indirect band gap of 4.52 +/- 0.03 eV with a direct transition of 4.94 +/- 0.03 eV. The resulting band alignment at the heterojunction was determined to be of type II with the valence and conduction band edges of beta-(Al0.21Ga0.79)(2)O-3 being -0.26 +/- 0.08 and 0.43 +/- 0.08 eV, respectively, above those of beta-Ga2O3 (010). These values can now be used to help better design and predict the performance of beta-(AlxGa1-x)(2)O-3 heterojunction-based devices.