Evaluation of band alignment of α-Ga 2 O 3 /α-(Al x Ga 1− x ) 2 O 3 heterostructures by X-ray photoelectron spectroscopy

The band alignment at an α-Ga 2 O 3 /α-(Al x Ga 1− x ) 2 O 3 heterointerface, with different Al compositions ( x ), grown on a c -plane sapphire substrate was evaluated by X-ray photoelectron spectroscopy. The experimental results show that the heterointerface has the type-I band discontinuity with the valence band offsets of 0.090, 0.12, and 0.14 eV, and the conduction band offsets of 0.34, 0.79, and 1.87 eV, for x values of 0.1, 0.4, and 0.8, respectively. The small band offset for the valence band is attributed to the fact that the valence band of oxides is constituted by the localized O 2p level, which is dominated by the nature of oxygen atoms. The type-I band discontinuity is desirable for a variety of heterostructure devices.