A Backward-Triggered 4H-SiC Photoconductive Semiconductor Switch With Planar Electrode Structure

The power capacity of a photoconductive semiconductor switch with the planar electrode is limited by surface breakdown voltage. In this work, an efficient thinned 4H-SiC PCSS with a planar electrode backward-triggered structure was fabricated. Comparison simulations on the photocurrent density and electric field showed that the distribution of photogenerated carriers was homogenized, and the maximum electric field declined. By thinning and polishing, photoconductive semiconductor switch (PCSS) devices with thicknesses of 50 and 500 $\mu $ m were obtained for experiments. Triggered by a 355-nm laser, it demonstrated that the photocurrent of the backward-triggered PCSS device was basically equivalent to the origin planar structure. Meanwhile, the withstand voltage of PCSS devices significantly increased from 5.5 to 8 kV. The results proved that the backward-triggered structure can optimize the photocurrent of PCSS devices from 37 to 41 A while ensuring the photoelectric output efficiency. The failure mechanisms were also investigated with several analysis methods. Under a strong electric field, the devices were damaged due to the thermal stress caused by local field concentration. The characterization analysis results further demonstrated the importance of optimizing electrode configuration to decrease the electric field distribution at the electrode edge. This work is of great significance for PCSS devices on high-power applications.