Research on current filament mechanism of nonlinear semi-insulation GaAs photoconductive semiconductor switches*

   With the rapid development of pulsed power technology, the GaAs photoconductive semiconductor switch (PCSS) with power and band width arouses broad attention. On the nonlinear mode, the current filament phenomena will occur in the GaAs PCSS. Because the phenomena are so complicated and uncertain, up to now the latent mechanism is not very clear.

   The paper proposes a new streamer model to explain current filament phenomenon. The model includes three aspects: the streamer generation, the streamer development and the streamer flowing through PCSS. There are two conditions for streamer formation: one is the carrier density which should be not less than 10¹⁷cm^-3, and another is the electric field which should be much higher than 250 kV/cm. Avalanche ionization and compound radiation are the physical factors of the streamer development. When the current filament flows through PCSS, Lock-on effect is caused by dynamic distribution of transient voltages of PCSS and the load. On a micro level, Lock-on effect is caused by dynamic change of production rate and recombination rate of carries. Based on this streamer mode, the current filament velocity is calculated as about 2×10⁸cm/s. Then the current filament phenomenon is explained by Franz-Keldysh effect.