Research On The Characterisitic Of Time Jitter Of GaAs Photoconductive Conductor Switches Under Synchronous Laser Triggering

GaAs photoconductive semiconductor switch(PCSS)is a kind of critical device for ultrafast pulse power device,which has features of quick response speed,low trigger jitter,large power capacity,MHz repetition frequency,photoelectric isolation characteristics and adjustable current conduction time.In recent years,with the wide application in areas such as compact pulsed power system,fine synchronization control device,large current ignition device and THz radiation source,etc.,PCSS is required not only just to get stable pulses from single channel,but also to improve output power by connecting several switches in parallel by array and to realize the addition or even the coherent synthesis of pulses among multi-channels by turning-on at same time or certain order precisely.These demands enhance the requirement for higher switches synchronization and lower time jitter.Based on theoretical analysis,mathematical calculation and experimental analysis,the paper analyzed the mechanism of trigger light on the carrier generation and electric field on the carrier transport,GaAs PCSS time jitter theoretical formula interrelated with trigger light,electric field and switch characteristics were presented.The systematic research and conclusions on GaAs PCSS are as follows:(?)The mechanism of optical carrier generation and transition was studied;the relationship between the distribution of carrier in valleys and the transition model of carrier were established;the influence of trigger light,electric field and material properties on the switch conduction and shutoff were discussed;and the characteristic of different switch structure and performance under different models was compared.(?)On the basis of the band structure of GaAs,the scattering mechanism of GaAs carrier and their effect on mobility were analyzed;the relationship between electric field and GaAs electronic temperature,drift velocity,high-energy valley probability were achieved respectively;the influence of high-energy valley probability on carrier drift velocity was discussed.(?)Based on the error theory and the features of pulse in time domain,the inner logic between the synchronization precision of multi-switch and time jitter of single switch was defined;the conception of testing the single switch jitter with the time lag between the binary channels and the experimental measurement method on time jitter of GaAs PCSS were proposed,which effectively eliminated the influence of system error(laser delay for an example)on measurement accuracy;The time jitter theoretical formula interrelated with trigger light,electric field and switch characteristics was deduced;the influences of pulse width,the stability of electric field and trigger pulse on time jitter were discussed systematically and the influence coefficient was set as well;Based on the characteristics of velocity field for GaAs material,the subregional discussion on the characteristics of GaAs PCSS time jitter under linear model was conducted,acquiring the fact that time jitter varying along with the electric field.(?)Equal output amplitude of pulses from GaAs PCSS was realized by the application of multi-channel synchronization trigger circuit scheme that stored energy in each channel;The experiment verified the formula obtained from trigger light and electric field and that from characteristic of carrier transport properties and switch structure;The experiments showed that time jitter of GaAs PCSS measured by different time samples were consistent,indicating that the divergent of time lag at dual channel was one of the reasons that led to the time jitter of GaAs PCSS.(?)The experimental rules dedicated that time jitter of 3mm-gap GaAs PCSS were triggered by laser pulse with 500 ps pulse width and 1053 nm wavelength under two kinds of beam splitting models.The time jitter rule with electric field showed that time jitter of GaAs had maximum value in differential mobility region,while minimum value at its beginning.The pulse width broadening resulted from the fiber dispersion was the factor that caused larger time jitters in Fiber-splitter-method measurement.The relationship between time jitter and electric field,influenced by the variance ratio of carrier high-energy valley probability that is the main factor of time jitter,was deduced.Taking advantage of time jitter theoretical formula derived from this paper,the relationship between electrode gap on GaAs PCSS and time jitter was theoretically analyzed.The changes of drift velocity and differential mobility of carrier at different electric fields were the factors that causing the change of time jitter along with electric field.The relationship between the change of time jitter and displacement distance during the movement of trigger light spot from anode to cathode was verified,which were in agreement with the experiment results held by American Air Force Research Laboratory(AFRL)and Sandia National Laboratories(SNL).In view of the difference of carrier distribution in valleys caused by different transition modes,the paper theoretically analyzed the GaAs PCSS time jitter under different scattering mechanism.Triggered by 1064 nm wavelength of light pulse,the variation of carrier mobility caused by the inter-valley scattering mechanism of carriers between high-energy and low-energy was the reason why the time jitter increased firstly and then decreased in differential mobility region of electric field.Triggered by light pulse of 532 nm wavelength,the intra-valley scattering mechanism and saturated drift velocity were the reasons why time jitter kept constant even when electric field changed.The inter-valley scattering of little carrier that located in lower energy valley was the reason why time jitter decreased in 1 to 3kV/cm region.