Band alignment of In₂O₃/β-Ga₂O₃ interface determined by X-ray photoelectron spectroscopy

The energy band alignment of the atomic-layer-deposited In₂O₃/β-Ga₂O₃ ( 2 ¯ 01) interface is evaluated by X-ray photoelectron spectroscopy. The X-ray diffraction pattern reveals that the In₂O₃ film grown at 160 °C is amorphous, while it becomes polycrystalline at a higher deposition temperature of 200 °C. The bandgaps, determined by reflection electron energy loss spectroscopy, are 4.65, 3.85, and 3.47 eV for β-Ga₂O₃, polycrystalline In₂O₃, and amorphous In₂O₃, respectively. Both amorphous and polycrystalline In₂O₃/β-Ga₂O₃ interfaces have Type I alignment. The conduction and valence band offsets at the polycrystalline (amorphous) In₂O₃/β-Ga₂O₃ interface are 0.35 and 0.45 eV (0.39 and 0.79 eV), respectively. These observations suggest that polycrystalline In₂O₃ as an intermediate semiconductor layer is beneficial to the barrier reduction of metal/Ga₂O₃ contact.