Gallium oxide (Ga₂O₃), a promising candidate in ultraviolet (UV) photodetection, suffers significant limitations in its optoelectronic performance owing to the challenge of achieving p-type doping. To address this challenge, we designed a type-I heterostructure photodetector by depositing two-dimensional (2D) Bi films on Ga₂O₃ using the pulsed laser deposition (PLD) technique. Under the illumination intensity of 0.1 μW/cm², this photodetector exhibits a remarkable responsivity of up to 200 mA/W and a detectivity of 8.58×10¹¹ Jones, demonstrating its excellent low-light detection ability. In addition, due to the built-in electric field of the heterojunction, the device can effectively suppress the dark current and has the performance of self-powered detection.