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

Photoconductive semiconductor switches (PCSS) can be applied in pulsed high power systems and microwave techniques.Reducing the damage and increasing the lifetime of silicon carbide (SiC) PCSS are important research trends.PCSSs with various structures were prepared on 4-inch diameter, 500 μm thick high-purity semiinsulating 4H-SiC substrates.The on-state resistance and damage mechanisms were investigated.It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950 ℃ had a minimum on-state resistance of 6.0 Ω at 1 kV bias with a 532 nm, 170 mJ pulsed laser by backside illumination trigger.The backside trigger can reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot is 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 is 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 ℃, 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.