All-oxide p–n heterojunction diodes comprising p-type NiO and n-type β-Ga₂O₃

Abstract NiO/β-Ga 2 O 3 all-oxide p–n heterojunction diodes were fabricated for the first time using p-type NiO epitaxial layers grown on n-type β-Ga 2 O 3 substrates. The fabricated diodes exhibited good rectifying current–voltage characteristics, with a rectifying ratio greater than 10 8 at ±3 V. The capacitance–voltage measurements showed that the built-in voltage was 1.4 V. These results were discussed in terms of the energy band diagram of a type-II heterojunction, where the conduction band and valence band discontinuities were estimated to be 2.2 and 3.4 eV, respectively.