Electric-Field Dependence of Photocurrent Performance Characterization of Gallium Nitride Photoconductive Semiconductor Switch for Pulse Power Applications

The gallium nitride photoconductive semiconductor switch (GaN PCSS) is a promising switching device for high power density and high-efficiency pulse power source systems, owing to its superior material properties. Nevertheless, the development of the higher resistivity and lower defect density of semi-insulated (SI) GaN has been constrained by the epitaxial technology, which poses challenges in achieving high-voltage devices. To enhance the operating voltage range of PCSS, this study adopts fast pulse biasing, electric insulating oil, devices in series, side illumination, and thick substrate. Despite their apparent commonality and simplicity, they are highly effective in achieving the negative resistance effect of GaN PCSS under high electric field circumstances, representing novel experimental findings for GaN PCSS. The negative differential photoresponse of GaN PCSS at a high field is elucidated by considering the relationship between electron velocity field and resistivity-dependence on temperature. A photocurrent generated by device #1 is 10.8 A with a rise time of 475 ps at a laser energy of $90~\mu $ J and a voltage of 85.7 kV/cm. These results obtained in high-electric fields will provide new concepts and approaches for further research and applications in high-power GaN PCSSs.