Time jitter characteristics of GaAs photoconductive semiconductor switch in linear mode

Abstract

Time precision switching is crucial to a high-precision synchronization control system with several synchronized sources. Compared with the other high-power switches, a GaAs photoconductive semiconductor switch (PCSS) with a litter time jitter has been widely used in a precision synchronization control system. There is little work on the time jitter of a GaAs PCSS. In this paper, a formula of GaAs PCSS time jitter is derived by the qualitative theoretical derivation through using the probability distribution of the output electrical pulse and the corresponding relation between the time and electrical waveform of GaAs PCSS, and combining the carrier transport process. In experiment, a neodymium-doped yttrium aluminum garnet nanosecond laser beam is split by a semipermeable half mirror into two optical beams, and then these two beams simultaneously trigger two identical GaAs PCSSs in two parallel circuits. As the energy of a triggering laser pulse is fixed at 0.35 mJ, four different laser pulse widths, namely 30 ns, 22 ns, 16 ns and 11 ns, respectively, are used to trigger the GaAs PCSSs. The bias voltage changes from 0.1 kV to 1 kV in steps of 0.1 kV, and it is used in the above-mentioned experiment. The PCSSs are triggered 20 times at each of the bias voltage values. The time jitter of the GaAs PCSS with a 3-mm gap can be measured. By analyzing the experimental data, we conclude that the time jitter of the GaAs PCSS decreases with the triggering laser pulse width decreasing under the condition of different bias voltage. In the linear mode, the GaAs PCSS illuminated by a photon with a proper wavelength creates an electron-hole pair. The characteristic of the triggering laser pulse determines that of the output electrical pulse. With the energy of triggering laser pulse fixed, the fluctuation of electrical pulse increases fast with its pulse width decreasing. Moreover, according to the derived formula for a time jitter, the GaAs PCSS time jitter decreases with triggering laser pulse width narrowing, under the different externally applied bias voltages. It is demonstrated that the theoretical and experimental results of the relationship between the triggering laser pulse width and the GaAs PCSS time jitter are consistent. The obtained results provide a basis for further reducing the GaAs PCSS time jitter, which is important for a next-generation fusion research facility and laser trigger antenna array of generating short pulse sequence.