An optical controlled AlGaN/GaN semiconductor power transistor with a low on-resistance normally off high electron mobility two-dimensional electron gas (2DEG) channel is numerically proposed. The device consists of a p-GaN region sandwiched between undoped GaN over which n-AlGaN (Al 20%) is formed. The 2DEG channel is formed at the n-AlGaN/GaN heterojunction due to photogenerated electron jumps from the valance band to the conduction band, when a beam of light having energy greater than the band gap (3.4 eV) of GaN at a wavelength of 350 nm falls on the SiO₂ and TiO₂ Bi-layers antireflecting structure and light penetrates deeper into the p-GaN region and generates e-h pairs. The device current can be optically controlled by varying the power intensity of the incident beam of light; this device exhibits very low (<1 Ω) on-resistance, which yields a very low conduction loss. The switching characteristics of the device are also investigated, and the device attains low rise and fall times.