Carrier dynamics in a vanadium-doped 4H-SiC photoconductive semiconductor switch at different photon injection rates

The transient photoconductivity of a silicon carbide photoconductive semiconductor switch (SiC PCSS) mainly depends on optical excitation to generate an electron–hole plasma in the semiconductor substrate. As an important parameter of the laser pulse, the photon injection rate has a significant impact on the generation and transport of photogenerated carriers within a PCSS. In this work the effect of the photon injection rate on the output characteristics of a vanadium-doped 4H-SiC PCSS under 532 nm extrinsic laser triggering is experimentally studied. Experiments show that the turn-on time and output amplitude of a PCSS can be effectively regulated by changing the photon injection rate at the same energy. A physical model of a SiC PCSS is constructed based on the finite element method, and the effects of different photon injection rates on the distribution of transient electric field and current density are investigated. Simulation results show that a high-current-density plasma channel is rapidly formed within the PCSS based on two-photon absorption and electric field enhancement at a higher photon injection rate.