Output Characteristics of Side-Illuminated Photoconductive Semiconductor Switch Based on High Purity Semi-Insulating 4H-SiC

Abstract

Photoconductive semiconductor switch (PCSS) allowing side illumination was fabricated on high purity semi-insulating (HPSI) 4H-SiC. A 532-nm pulsed laser with variable optical energy was used to trigger the PCSS. The performance of the PCSS was characterized under the two different load conditions, 50-Ω load and 0.05-Ω, with a current viewing resistor (CVR). The PCSS exhibited significantly different output characteristics for the two different loads. The equivalent resistance of the PCSS with the 50-Ω load, which was calculated from the output voltage and current, was inversely proportional to the optical energy, but the one with a 0.05-Ω load exhibited saturation behavior with the optical energy. While the times at peak output with the 50-Ω load were similar at various optical energies, the times at peak output with the 0.05-Ω load were dependent on the optical energy. Output current oscillation was also observed after the PCSS was turned off in the case of 0.05-Ω load condition. The different output characteristics for the different load resistances were analyzed using the transient response of the equivalent circuits. The PCSS exhibited a minimum on-state resistance of 0.27 Ω with the optical energy of 8 mJ and a maximum output current of 657 A at the bias voltage of 4.8 kV. The operating voltage of the PCSS was limited by surface flashover, which caused an additional output pulse following the first output pulse.