Photon Absorption Effects on the Transient Carrier Dynamics in High-Purity 4H-SiC PCSS

Photon absorption is a key factor for the transient output characteristics of silicon carbide photoconductive semiconductor switch (SiC PCSS), which is determined by the effective photo flux in the substrate. A high-purity 4H-SiC PCSS with a 1 mm gap is excited by a 532 nm laser pulse from different laser incidence planes. The results show that the output amplitude of the PCSS under the side trigger at 70 kV/cm is about 3.1 kV, which is 1.82 and 1.26 times higher than that of the front and back, respectively. Furthermore, 3D simulation indicates that the number of photo-generated carriers under the side trigger is one order of magnitude higher than that of the front and back. The efficient utilization and rapid enhancement of the electric fields make it exhibit better spatio-temporal characteristics during carrier transport processes.