The Influence of Optical Absorption Saturation on Transient Performance of SiC Photoconductive Semiconductor Switch

The influence of optical absorption saturation on transient performance of silicon carbide (SiC) photoconductive semiconductor switch (PCSS) is investigated. Under both single pulse and burst mode laser conditions, experiments are conducted on the PCSS. The PCSS is subjected to laser irradiation with a pulse width of 8 ns, with an energy range of 0.1 mJ to 63 mJ. It is observed that as the laser energy increases, the on-state resistance of the device progressively decreases until it reaches saturation, and the pulse width expands from 8 ns to 17 ns. Under the condition of a burst mode laser with a pulse width of 25 ns, the laser energy increases from 1 mJ to 20 mJ, the modulation depth ratio diminishes and the output power gradually reaches saturation. A comprehensive internal physical model is developed, which elucidates that with increasing laser energy, the device experiences optical absorption saturation. This phenomenon leads to an increase of the pulse width and a saturation of the electron concentration.