Performance of Lateral 4H-SiC Photoconductive Semiconductor Switches by Extrinsic Backside Trigger

Photoconductive semiconductor switch (PCSS) can be applied in pulsed high power systems and microwave techniques. However, reducing the damage and increasing the lifetime of silicon carbide (SiC) PCSS are still faced severe challenges. In this study, PCSSs with various structures were prepared on 4-inch diameter, 500 mu m thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated. It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950 degrees C had a minimum on-state resistance of 6.0 ohm at 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger. The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS. For the 200 s trigger test by a 10 Hz laser, the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers. Replacing metal Ni with boron gallium co-doped zinc oxide (BGZO) thin films annealed at 400 degrees C, black branch-like ablation was alleviated while concentric arc damage was obvious at the anode. The major causes of concentric arc are both pulsed laser diffraction and thermal effect.