Heteroepitaxial integration of α-Ga2O3/p-NiO by mist-CVD for solar-blind UV detection

Solar-blind ultraviolet (SBUV) photodetection is critically demanded in military and civil fields thanks to its near-zero background radiation. Gallium oxide (Ga2O3) emerges as an ideal wide-bandgap semiconductor for SBUV and power devices thanks to its suitable bandgap and compatibility with substrates. Up to now, the lack of stable p-type Ga2O3 has become a bottleneck, restricting its application. Consequently, p–n heterojunction formation is one possible solution, where p-type nickel oxide appears as a promising p-type semiconductor. Here, we employ mist chemical vapor deposition technology to demonstrate epitaxial integration of single-crystal α-Ga2O3/NiO heterojunctions on c-plane sapphire, featuring a distinct interface with an epitaxial relationship of α-Al2O3(0006) || α-Ga2O3(0006) || NiO(111). The as-grown Li+-doped NiO film shows a high hole mobility (88.32 cm2/V s) and low resistivity (0.09 Ω cm) and exhibits a type-II band alignment with α-Ga2O3, consequently enabling efficient carrier separation. The fabricated α-Ga2O3/NiO p–n junction photodetector exhibits rectification effects and self-powered detection capability, achieving high-performance UV detection with a responsivity of 43.86 A/W, detectivity of 1.64 × 1012 Jones, rejection ratio of 177.3, and fast response (17/16 ms). This work demonstrates a low-cost epitaxial approach to realize high-quality α-Ga2O3/NiO p–n heterojunction integration for fast UV detection applications.