Transient Characteristics Of A Nonlinear GaAs Photoconductive Semiconductor Switch Based On Spark Gap

This paper induced a high gain quench mode of photoconductive semiconductor switch (PCSS) achieve by reducing the bias electric field based on the insufficiency in PCSS which works under high gain mode and generates high power and high repetition rate electrical pulse. PCSS began to restore high-impedance state due to the reduced field promptly, so the lock-on phenomenon of the final output pulse waveform did not present itself obviously. There were two methods including spark gap in series with the PCSS and spark gap parallel connected with PCSS in this paper. The series circuit distributed voltage dynamically, high gain mode PCSS provided an ultra-fast high voltage pulse to the spark gap switch which was over-voltage discharge. Biased electric field of PCSS reduced under the lock-on threshold quickly when the voltage of capacitor was constant, while the spark gap switch was recovery, so the resistance of PCSS increased rapidly. The PCSS generated oscillate electrical pulses waveform which was closedown in the 320ns finally, the main reason of oscillation waveform was the load impedance was less than the transmission line impedance. Using laser-induced spark gap switch breakdown discharge in the parallel circuit mainly, PCSS worked in controlled pre-breakdown high gain mode because the laser-induced spark gap discharge existed 160ns time delay, and the spark gap switch generated electron avalanche breakdown discharge due to multi-photon ionization and cascade ionization after the time delay. Spark gap switch was turned-on and its resistance was ohm order of magnitude, so the capacitor voltage delivered from the spark gap switch rapidly, leading to biased field of PCSS less than the threshold, and then the entire circuit was in close state, the capacitor was re-charging finally. Compared with the traditional single PCSS, the rising edge and the amplitude of the output pulse waveform were the same, but the capacitor residual voltage method did not appear typical lock-on phenomenon of high gain mode while recovery the high-impedance state rapidly. Therefore PCSS could work in high-gain quench mode by means of laser-induced spark gap discharge effectively.