Si₃ N₄ Passivation and Side Illumination of High-Power Photoconductive Semiconductor Switch Based on Free-Standing SI-GaN

To meet the needs of wide band gap (WBG) gallium nitride (GaN)-based photoconductive semiconductor switch (PCSS) in high-voltage and high-power microwave systems. Herein, silicon nitride (Si3N4) dielectric films were deposited on GaN PCSS using plasma-enhanced chemical vapor deposition (PECVD) and illuminated from the side of the device. A high refractive index of 2.03 and a high permittivity of 7.97 were obtained from Si3N4 films, which are characterized by high optical and dielectric properties. According to the electrostatic field simulation, Si3N4’s high permittivity minimizes the peak electric field at the electrode boundary of GaN PCSSs. When the 532-nm incident light is side illuminated for the device, the output peak power and rise time are 59.8 kW and 0.52 ns, respectively. At a future date, the proposed GaN-based PCSS will have a practical application for radio frequency microwave systems.