The problem of leakage current limits the application of traditional semi-insulated gallium nitride (GaN) photoconductive semiconductor switches (PCSSs) in high-voltage applications. Therefore, a n-type epitaxial layer is grown on the semi-insulated GaN∶Fe substrate (as a laser-triggered region), in which a cell array of vertical double-diffusion-field-effect transistors (as a voltage-triggered region) is constructed. In other words, a reverse pn junction controlled by the gate voltage is introduced into the traditional vertical PCSS structure for restraining the leakage current of the semi-insulated GaN due to the carrier depletion effect of the pn-junction space-charge region. The device simulation results show that the 10-kV bias voltage is reasonably shared by the laser- and voltage-triggered regions and the leakage current of the device is two orders of magnitude less than that of the traditional PCSS with the same bias electric field. Moreover, the results show that the bias voltage of the voltage-triggered region can be transferred to the laser-triggered region quickly with the gate opening; thus, the laser energy efficiency is heightened because the dynamic bias electric field increment across the laser-triggered region brings a high photocurrent peak. Moreover, the relationships between the laser parameters and the device output characteristics are calculated and analyzed to ensure high laser energy efficiency.