Investigation of high electric fields at the electrode-SiC interface in photo-switches

Photoconductive semiconductor switches (PCSSs) have also been used for sometime in systems for generating high power microwaves. As a switch material, SiC offers certain advantage over Si and GaAs, the other known PCSS materials [1] [2]. In the existing SiC photo-switch, however, electric field blocking performance is mainly limited by the switch packaging. No packaging method exists to effectively address electric field crowding at the location where the copper electrode leaves the SiC substrate. Electric field crowding causes premature breakdown in the photo-switch at an applied electric field of less than 300 kV/cm, even though the bulk dielectric strength of SiC is 3MV/cm [3]. This paper reports on our investigation of inserting contoured electrodes into the bulk material to reduced field enhancement. Approaches and simulations for the grinding and etching of SiC to insert the electrodes will also be presented. Simulation results incorporating contoured electrodes into the bulk materials show that the electric field enhancement can be reduced by one order of magnitude compared to existing electrode configurations.