Research On The Characteristics Of Charge Domain And Optimization Design Of Electrode Structure Of GaAs Photoconductive Semiconductor Switches

Photoconductive switches have good application value in microwave,ultrafast electronics,and national defense,including microwave and millimeter wave generation,pulsed and ultra-wideband radars,particle accelerators and directional energy systems.Due to the complex dynamic behavior of the electric field domains generated in the high multiplication mode,so far,there is no unified theory on the generation mechanism of the high multiplication mode.Based on Gunn effect electronics theory,the numerical simulation software(silvaco.Inc)was used to simulate the formation characteristics of avalanche domains and multi-domains and the influence of the structure change of the GaAs photoconductive switch electrode on its withstand voltage in the dark state.The following conclusions can be drawn.(1)By researching the effects of bias electric field,carrier concentration,device length on the electric field distribution of charge domains,and the dynamic changes of domain peak electric field and domain width with time,the mechanism and conditions of avalanche domain formation are analyzed.The results show that the impact ionization has little effect on the domain width,which will cause the domain peak electric field to increase nonlinearly and irregularly,and the threshold conditions for impact ionization and avalanche ionization are 200 kV/cm and 380 kV/cm,respectively.With the increase of time,the bias electric field and carrier concentration will increase the domain peak electric field,which tends to saturate at about 30 ps,and the domain width will increase slightly.(2)By reasearching the influence of bias voltage and light intensity on the formation of multi-domains and the dynamic changes of multi-domains,the formation conditions and laws of multi-domains are analyzed.The results show that both light intensity and bias voltage contribute to the formation of multiple domains,and the threshold conditions of light intensity and bias voltage are 150 W/cm2 and 500 V,respectively.When the electrode gap,doping concentration,bias voltage and light intensity are fixed,the number of domains increases with time,the peak electric field of the domain increases,and the domain width decreases.(3)By studying the internal electric field and current density distribution of the photoconductive switch with different electrode contact modes and electrode geometric shapes,the voltage resistance characteristics of the photoconductive semiconductor switch were analyzed.The results show that the embedded electrode has a circular shape with a small peak electric field and current density,which is helpful to improve the withstand voltage.