Band Offsets of the MOCVD-Grown β-(Al 0.21 Ga 0.79 ) 2 O 3 /β-Ga 2 O 3 (010) Heterojunction.

The band offsets for the β-(Al 0.21 Ga 0.79 ) 2 O 3 /β-Ga 2 O 3 (010) heterojunction have been experimentally measured by X-ray photoelectron spectroscopy. High-quality β-(Al 0.21 Ga 0.79 ) 2 O 3 films were grown by metal-organic chemical vapor deposition for characterization. The indirect band gap of β-(Al 0.21 Ga 0.79 ) 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 β-Ga 2 O 3 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 β-(Al 0.21 Ga 0.79 ) 2 O 3 being -0.26 ± 0.08 and 0.43 ± 0.08 eV, respectively, above those of β-Ga 2 O 3 (010). These values can now be used to help better design and predict the performance of β-(Al x Ga 1- x ) 2 O 3 heterojunction-based devices.