The Critical State of GaAs Photoconductive Semiconductor Switch in a Capacitive Storage Loop

In this letter, the critical state of GaAs photoconductive semiconductor switch (PCSS) is discovered and investigated in a capacitive storage loop. The avalanche ionization of carriers is found to be influenced by the capacitance. When the capacitance is reduced to 16 pF, the GaAs PCSS starts to operate in linear mode when triggered at the anode edge but still switches on in avalanche mode with unchanged loop parameters when triggered at the cathode edge, which is defined as the critical state. The numerical simulation indicates that the ionized electrons from the cathode fail to induce the formation of initial avalanche ionization in anode-triggered PCSS before the bias voltage drops. The threshold capacitance for the critical state is found to be similar to 27 pF under the experimental conditions.