Study On Photoelectric Characteristics Of Photoconductive Switches In High Field

Photoconductive semiconductor switches,abbreviated as PCSS,have high power capacity and fast switching speed,which have evident prospect for applications in the field of pulsed power and ultra-wideband electronics.After the discovery of the non-linear mode of GaAs PCSS,the switches can be triggered by laser diode because of the small excitation energy they required,which make the miniaturizing applications possible.However,the life of switches working in the non-linear mode is limited.There are three main ways to improve the life of switches,the first is to improve the manufacturing technique of switches,the second is to use engineering methods such as multi-current channel triggering,the third is to analyze the non-linear mechanism of switches so as to avoid damaging.This paper reviews the development of PCSS,summarizes the characteristics of different modes of switches and existing theoretical models,and outlines the theories of GaAs PCSS.Because TCAD software has the advantages of friendly user interface and good convergence in calculation,in this paper,TCAD software is used to conduct the device modeling and circuit mixed model simulation of switches.The simulation results include electrical characteristics such as current or voltage curves,and the distribution of physical quantities inside the PCSS at a certain time during it works.The simulation calculations can predict the optoelectronic characteristics of the device and provide a basis for the analysis of the working principle of the PCSS.For the application of TCAD software,this paper adopts the improved drift velocity equations of electrons and holes which is in better agreement with the experimental data.The effects of different carrier mobility models for the output of non-linear mode are obtained by comparing the simulation results based on improved and old drift models under different illumination intensities and bias voltages.In order to test and study for GaAs PCSS,two generations of test system were built independently,and tests have been done by a new generation of test system.In the test system,the Blumlein pulse forming line before the switch is charged by a pulsed high voltage charging power supply,and the PCSS is triggered by a laser diode.The voltages at the both ends of the switch and the signal outputs through the formation line are attenuated and read out by the oscilloscope.The two switches are tested,and the system is stable during the test.The measured output RF waveform is clean,the pulse width is larger than the designed value,and the output voltage efficiency needs to be strengthened.The building and continuous improvement of the test system also provide convenience for the experimental research of PCSS.