This study involves the design and simulation of a BGaN/GaN/ZnO/Al2O3 photodetector for UV/BLUE light with two different boron concentrations: 5% and 20%. The proposed photodetector structure exhibits an internal optical gain of 3.867 × 104 at 10 V and a wavelength of 250 nm for x = 0.05. Moreover, a gain of 1.006 × 104 at the same voltage and wavelength was obtained for a 20% boron concentration under an incidence of 0.01 × 104 cm2/W. A photocurrent peak of 0.31 mA at a wavelength of 0.455 µm, corresponding to an energy of 2.73 eV, was achieved for x = 0.05, which makes it a promising candidate for optoelectronic devices, such as light-emitting diodes (LEDs). A maximum photocurrent of 0.54 mA in the long-range deep UV range between 100 and 250 nm was obtained for x = 0.2. Based on the simulated spectral response, increasing the band gap (EG) improves the optical absorption, and higher absorption rates were found at x = 0.2 in the UV area. However, we also considered the impact of the BGaN active layer thickness on dark current and photocurrent at room temperature. Additionally, we studied the effect of temperature on current under illumination.