The conduction efficiency and reliability of photoconductive semiconductor switches (PCSSs) are strongly influenced by the resistivity of semi-insulating 4H-SiC substrates. In this work, PCSSs fabricated on four 4H-SiC substrates with resistivities ranging from 2.59 × 1011 to 1 × 1012 Ω cm were evaluated under intrinsic excitation (355 nm) and high-voltage, high-repetition operation. All devices exhibit similar optical saturation behavior and comparable switching speed, indicating consistent optical absorption and intrinsic response. In contrast, pronounced differences in conduction stability and degradation behavior emerge under high electric fields and high repetition rates. Under saturated excitation, the low-resistivity device achieves a voltage-conversion efficiency of 99.3%. It also delivers a stable 10 MW peak output for 35 min at 500 Hz, corresponding to more than 106 switching cycles. In comparison, devices fabricated on higher-resistivity substrates exhibit accelerated output decay and more severe electrode degradation. Technology Computer Aided Design simulations yield conduction characteristics consistent with the experimental observations. These results highlight the critical role of substrate resistivity of intrinsically triggered 4H-SiC PCSSs and provide guidance for material selection in high-voltage fast-pulse switching applications.
Yu et al. (Mon,) studied this question.