The one-dimensional nanoarray heterostructure exhibits multiple advantages, including direct charge transport channels and an inherent electric field, making it an ideal structure for manufacturing high-performance optoelectronic devices. In this work, the ZnO/α-Ga₂O₃ nanorod arrays (NRAs) heterostructures on titanium substrates are fabricated via the hydrothermal method, and then applied as the photoanodes of photoelectrochemical (PEC) ultraviolet detectors. The built-in electric field generated by the ZnO/α-Ga₂O₃ heterojunction enhances the separation efficiency of photogenerated carriers. Moreover, the Ga₂O₃ coating reduces surface states on the ZnO NRAs, further boosting the response rate, while also acting as a barrier layer to minimize carrier recombination at the solid-liquid interface. Under UV irradiation of 200 μW/cm², the ZnO/α-Ga₂O₃ NRAs photoanode detector achieved a photocurrent density of 38.4 μA/cm² and a responsivity of 0.17 A/W—1.55 times higher than that of the detector based on ZnO NRAs photoanode. Additionally, the wire-shaped detector demonstrates excellent linear response across the UV line irradiation angle range from 0° to 360°. This work provides insights for enhancing photogenerated carrier separation efficiency and reducing solid-liquid interface recombination in PEC ultraviolet detectors.