| Due to the intrinsic characteristics of wide frequency band and high power capability, Semi-insulating material GaAs, Photoconductive Semiconductor Switches (PCSS’s), can be widely used in ultrahigh speed electronics, field of high power microwave generation and pulse shaping, especially, in nonlinear mode used in high voltage big power and ultrafast pulses systems. Although the great importance was attached to the device research and application of GaAs PCSS’s, up to the present, there are no reliable theories that can correctly account for the observed transient characteristics produced by the nonlinear mode. In addition, the nonlinear mode stability and value of bias electric field thresholds, irradiated energy and laser wavelength chosen are serious and urgent problems in the applications.In this thesis, the characteristic of nonlinear mode of GaAs PCSS’s is analysised deeply. The working principle of nonlinear waveform is point out. Not only a big bias electric field, but also asymmetric distribution of electric field and monopole charge domain forming are needed. When the monopole charge domain is formed and the electric field strength is near or equal to the avalanche intensity, the carriers increase exponentially due to impact ionization. The delay time between linear and nonlinear mode is decided by the time of monopole charge domain forming.The nonlinear mode is deduced from system experiments of PCSS’s work mode. YAG laser with wavelength of 1064nm and 532nm, and pulse duration of 5ns is used to trigger the PCSS’s. The PCSS’s gap is 4mm. The working mode of PCSS’s are studied with various bias electric field and laser energy. After nonlinear mode occurs, nonlinear waveform vs time are observed by multiple experiments. Under 1064nm laser irradiation, delay effect of the PCSS’s nonlinear mode is obvious, while under 532nm laser irradiation, the delay time is very short. The quantitative stability conditions of PCSS’s nonlinear mode are deduced from experiments. |
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