Ga₂O₃ photodetectors with interdigitated electrodes have been designed and fabricated, and the Ga₂O₃ area exposed to illumination acts as the active layer of the photodetector, while the area covered by Au interdigital electrode provide an arena for carrier multiplication. The photodetectors show a maximum responsivity at around 255 nm and a cutoff wavelength of 260 nm, which lies in the solar-blind region. The responsivity of the photodetector reaches 17 A/W when the bias voltage is 20 V, which corresponds to a quantum efficiency of 8228%, amongst the best value ever reported in Ga₂O₃ film based solar-blind photodetectors.

Although nitrogen-doped zinc oxide has been fabricated as a light-emitting diode, the origin of its $p$-type conductivity remains mysterious. Here, by analyzing the surface reaction pathway of N in ZnO with first-principles density functional theory calculations, we demonstrate that the origin of $p$-type conductivity of N-doped ZnO can originate from the defect complexes of ${\mathrm{N}}_{\mathrm{Zn}}\mathrm{\text{−}}{V}_{\mathrm{O}}$ and ${\mathrm{N}}_{\mathrm{O}}\mathrm{\text{−}}{V}_{\mathrm{Zn}}$. Favored by the Zn-polar growth, the shallow acceptor of ${\mathrm{N}}_{\mathrm{O}}\mathrm{\text{−}}{V}_{\mathrm{Zn}}$ actually evolves from the double-donor state of ${\mathrm{N}}_{\mathrm{Zn}}\mathrm{\text{−}}{V}_{\mathrm{O}}$. While ${\mathrm{N}}_{\mathrm{Zn}}\mathrm{\text{−}}{V}_{\mathrm{O}}$ is metastable, the $p$-doping mechanism of ${\mathrm{N}}_{\mathrm{Zn}}\mathrm{\text{−}}{V}_{\mathrm{O}}\to {\mathrm{N}}_{\mathrm{O}}\mathrm{\text{−}}{V}_{\mathrm{Zn}}$ in ZnO will be free from the spontaneous compensation from the intrinsic donors. The results may offer clearer strategies for doping ZnO $p$-type more efficiently with N.