The Study On Space Charge Waves Effect Of Semi-insulating GaAs Photoconductive Semiconductor Switches

Compared with the traditional switch,photoconductive semiconductor switch(PCSS)have many advantages,such as fast switching speed,low timing jitter,small parasitic inductance,capacitance small,and simple structure,especially its high voltage,large power storage capacity made it occupy a great application dominant position in the field of pulsed power and other technologies.PCSS fabricated with ?-? semiconductor compounds,such as:GaAs,InP,due to various phenomena appear in the locked mode,the areas of its application are wide.In this paper,through the in-depth study of space charge wave(SC W)effect and combining with typical experiment results of photoconductive switch,the conductivity transformation laws of photoconductive switch have been studied theoretically.The conclusions as follows:1.In the linear mode,the output current was all depended on photo-generated carriers.Phenomenon of switch current oscillation triggered by 532nm and 1064nm pulsed laser in linear mode and nonlinear mode have been studied experimentally.In linear mode,although the bias electric field is larger than Gunn electric field threshold,there is not any oscillation phenomenon for the output electric pulse when the triggering light energy is large.However,the output electrical pulses have a large amplitude pulse of electricity with a series of small damped oscillation amplitude pulses when the triggering light energy is small.In nonlinear mode,the current waveform always exhibits damped oscillation in some extent.2.Through the in-depth study the effect of space charge wave and combining with typical experiment results of photoconductive switch,the analytic expression of the conductivity and device transit angle of switch have been obtained.The fitting function lines of expressions under different gain figure have been given.The influence of different gain for the peak of electrical conductivity has been analyzed.The analysis shows the peak of output current increases with the increasement with the gain of SCW.3.Based on the space charge wave effect,the periodic and damped oscillation of electric current has been studied theoretically.Theoretical analysis shows that the growth and decay of SCW induced the oscillation of electric current.The decrease of device transit angle causes the decrease of the current oscillation amplitude.Theoretical analysis is identical with experiment results.