attracted significant attention, which has a vast and growing number of military and civilian applications such as fire detection, missile interception, ozone hole monitoring, bioaerosol detection, astronomical imaging, and so on. [1][2][3] As the continuous improvement of devices integration, environment complexity, and interference technology, BUV photodetectors can effectively reduce false alarm rates in early warning, searching, and tracking systems, to improve the accuracy and versatility of detection systems in various situations. Many heterojunction structures based on wide-band-gap semiconductors have been reported to achieve the BUV photodetectors such as AlGaN/GaN, MgZnO/ZnO, and Ga 2 O 3 /GaN heterojunction. [4][5][6][7][8][9][10] However, AlGaN/GaN heterojunction has a high conduction band discontinuity which impedes the flow of photogenerated electrons and reduces the performance of photodetectors. [11] And high Mg-content MgZnO with high crystal quality is difficult to achieve by epitaxial growth due to the phase segregation in single wurtzite phase MgZnO. [12] β-Ga 2 O 3 with an ultrawide bandage of 4.9 eV is considered as a promising candidate for UV detection. [13,14] It has great thermal and chemical stability, determining its possibility of working at high temperatures and strong radiations. Moreover, there is a small lattice mismatch and a low conduction band offset at the interface between Ga 2 O 3 and GaN. These characteristics mean that Ga 2 O 3 /GaN heterojunction could be a potential for BUV photodetectors. Kalra et al. [6] demonstrated epitaxial β-Ga 2 O 3 /GaN-based vertical metal-heterojunctionmetal multiband UV photodetectors with the responsivity (R) of 3.7 A W −1 at 256 and 365 nm. For saving energy and broadening the application prospects of UV photodetectors, Guo et al. [15] fabricated a super-high-performance self-powered UV photodetector based on the GaN/Sn:Ga 2 O 3 p-n junction generated by depositing a Sn-doped n-type Ga 2 O 3 thin film onto a p-type GaN thick film. The responsivity at 254 nm reached up to 3.05 A W −1 without consuming external power. Lin et al. [16] used graphene as the transparent conductive layer to form graphene/β-Ga 2 O 3 /GaN heterojunction. With the help of largearea transparent electrode, a typical "sandwich" structure UV photodetector with low dark current density (1.25 × 10 −8 A cm −2 ) and high sensitivity (12.8 A W −1 ) was successfully assembled. Broadband ultraviolet (BUV) photodetectors responding to the multiband spectrum can effectively reduce false alarm rates and improve the accuracy and versatility of detection systems in various situations. A high-responsivityBUV photodetector based on vertical Ga 2 O 3 /GaN nanowire array is proposed and demonstrated. Ga 2 O 3 /GaN nanowires are obtained by partially thermally oxidizing GaN nanowires grown by molecular beam epitaxy and used to combine with a monolayer graphene film to form graphene/Ga 2 O 3 /GaN heterojunction. Moreover, the oxidation mechanism of GaN nanowires is further investigated by ...

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