Investigation of p-NiO/N-Ga₀.₃Zn₀.₇O Heterojunction Photodiodes for Ultraviolet-B Detection

A p-NiO/N-Ga _0.3 Zn _0.7 O heterojunction photodiode was fabricated and investigated in this study. p-type NiO and n-type Ga _0.3 Zn _0.7 O thin films were deposited using mist atmospheric pressure chemical vapor deposition to form the pN heterojunction. This study also characterizes the crystallinity, oxygen deficiency, and energy bandgap of the NiO and Ga _0.3 Zn _0.7 O thin films. The p-NiO/N-Ga _0.3 Zn _0.7 O heterojunction photodiode exhibits significant rectification I-V characteristics. Compared with a Ga _0.3 Zn _0.7 O metal-semiconductor-metal photodetector, the p-NiO/N-Ga _0.3 Zn _0.7 O heterojunction photodiode shows a smaller dark current (~7.94 nA at −1 V), more significant UV-to-visible rejection ratio ( $\sim 9 \times 10 ^{3}$ ), and higher specific detectivity ( $\sim 1.67 \times 10 ^{{11{ }}}$ Jones). Additionally, the p-NiO/N-Ga _0.3 Zn _0.7 O heterojunction photodiode does not have internal photoconductive gain, so the p-NiO/N-Ga _0.3 Zn _0.7 O heterojunction photodiode shows a shorter response time than the Ga _0.3 Zn _0.7 O metal-semiconductor-metal photodetector.