Band Alignment of β-Ga2O3 with BaTiO3, SrTiO3, and Related Composites

Integrating perovskite oxides BaTiO 3 (BTO), SrTiO 3 (STO) with β -Ga 2 O 3 is of great interest for developing β -Ga 2 O 3 power devices due to its promotion for improving uniformity in the electric field profile and breakdown characteristics. In this work, β -Ga 2 O 3 /BaTiO 3 (BTO), β -Ga 2 O 3 /SrTiO 3 (STO), β -Ga 2 O 3 /Ba 0.5 Sr 0.5 TiO 3 (BSTO) heterojunction were epitaxially grown on sapphire substrates by low-pressure chemical vapor deposition (LPCVD) and radio frequency physical vapor deposition (RF PVD). The energy band alignment of β -Ga 2 O 3 /BaTiO 3 , β -Ga 2 O 3 /SrTiO 3 , β -Ga 2 O 3 /Ba 0.5 Sr 0.5 TiO 3 (BSTO) heterojunction have been analyzed by X-ray photoemission spectroscopy and UV–visible transmittance spectrum. The conduction band offsets ( ∆E c ) of β -Ga 2 O 3 /BTO, β -Ga 2 O 3 /STO, β -Ga 2 O 3 /BSTO is found to be 0.32 ± 0.05, 1.15 ± 0.05, 0.78 ± 0.05 eV, respectively; and the valence band offsets ( ∆E v ) of these heterojunction is 0.76 ± 0.05 eV, 0.55 ± 0.05 eV, and 0.73 ± 0.05 eV, respectively. Our results indicate that type-I band alignment respectively form at these heterojunction, in which the valence and conduction bands of β -Ga 2 O 3 are concomitantly higher than those of BTO, STO, and BSTO. The accurate determination of ∆E c and ∆E v is important for the design of β -Ga 2 O 3 /ferroelectric heterojunction multifunctional devices.