With the development of semiconductor technology, ultraviolet light-emitting diodes (UV-LEDs) had been widely used in lighting, sterilisation, biological medical and other fields, which had broad market application prospects. The p-CuO/i-Ga2O3/n-GaN heterojunction diode was fabricated by radio frequency (RF) magnetron sputtering technology. The influence of ambient temperature on the electrical characteristics of diodes was studied, which exhibited typical diode rectification characteristics with high rectification ratios at different ambient temperatures. It was found that the temperature sensitivity of the forward current was greater than that of the reverse current when the driving voltage were ±3 V. Moreover, two luminescence peaks could be detected by the electroluminescence (EL) measurement, one was a strong ultraviolet (UV) luminescence peak at ∼370 nm, and the other was a wide deep-level luminescence peak at ∼500 nm. Eventually, the luminescence mechanism was discussed from the aspect of the energy band diagram of the heterojunction diode.