Ultrahigh Gain of a Vacuum-Ultraviolet Photodetector Based on a Heterojunction Structure of AlN Nanowires and NiO Quantum Dots

Abstract

Aluminum nitride ($\mathrm{Al}\mathrm{N}$) is a promising candidate for the manufacture of vacuum ultraviolet (VUV) photodetectors. However, its poor electrical conductivity limits its applications. Herein, a high-performance $\mathrm{Al}\mathrm{N}$ nanowire (NW)-$\mathrm{Ni}\mathrm{O}$ quantum dot (QD) based VUV photodetector is constructed via a mixed-dimensional strategy. The formation of isolated nanoscale p-n heterojunctions greatly increases the concentration of photogenerated electrons, resulting in an ultrahigh photoconductive gain (9.96) in the $\mathrm{Al}\mathrm{N}$ NW-$\mathrm{Ni}\mathrm{O}$ QD material, which is about 27-fold higher than that of $\mathrm{Al}\mathrm{N}$ NW (0.368). In addition, the significant improvement in both photocurrent and response speed convincingly suggest the great potential of $\mathrm{Al}\mathrm{N}$ NW-$\mathrm{Ni}\mathrm{O}$ QD based VUV photodetectors. Furthermore, the properties of these photodetectors in an irradiation environment are also evaluated here. It is found that $\mathrm{Al}\mathrm{N}$ NW exhibits excellent anti-irradiation characteristics towards both electron and proton irradiation, while the $\mathrm{Al}\mathrm{N}$ NW-$\mathrm{Ni}\mathrm{O}$ QD material also presents promising potential under low-dose electron irradiation. This study can be used as a guideline to design and fabricate high-performance VUV photodetectors based on wide-band-gap semiconductors coupled with other nanostructured systems.