Development Of Semiconductor Photoconductive Switch Testing System And Study Of Its Electrical Properties

Photoconductive switch(PCSS)is a kind of semiconductor switch which uses semiconductor materials to generate photogenerated carriers by laser radiation energy to realize rapid impedance conversion,so that the circuit can be turned off or turned on.It has many advantages,such as photoelectric separation,fast response,high repetition frequency,high voltage withstand,picosecond time accuracy,small parasitic parameters and compact structure.In order to study and test the actual performance of the photoconductive switch samples,firstly some semiconductor materials suitable to the photoconductive switch were compared,secondly the requirements of the working environment of the semiconductor photoconductive switch were analyzed.Then,a test platform for the photoconductive switch was built,and the working state of the photoconductive switch was simulated.Finally,the working parameters of the photoconductive switch are tested and studied.On the other hand,the performance of the test system for photoconductive switches is further optimized through solving the technical problems encountered in the construction of the experimental platform.The working characteristics and technology of silicon carbide and gallium arsenide photoconductive switch materials are main subjects of study in this paper.The mainstream design scheme of photoconductive switch was outlined,and the functional requirements and structural design of the test platform for photoconductive switch were analyzed.Semiconductor laser diode is used as trigger device,Blumlein transmission line is used as load-bearing structure of system output and photoconductive switch.The design of circuit components of experimental platform and the process of solving problems are discussed in detail.Nowadays the traditional YAG laser has been replaced by the semiconductor laser diode as the triggering device.The laser diode has the advantages of low cost and small volume.The laser pulse generated by semiconductor laser diode is enough to make the photoconductive switch turn on.The driving circuit consists of two parts: energy storage and control.The driving and controlling function is realized by metal oxide semiconductor switch(MOSFET).In order to realize the functions of fast switching on MOSFET to control capacitor discharge and circuit protection,several schemes and components are selected and analyzed,and optimized through simulation and experimental comparison.The principle of voltage doubling for Blumlein transmission line is analyzed.The parasitic parameters of the output structure of the photoconductive switch are simulated.The differences of experimental results and output efficiency between different material substrates and different sizes are analyzed by using the CST software.Considering the influence of parasitic parameters,substrate material and structure size on the output,a single-layer double-voltage microstrip Blumlein line is designed,and the transmission line is drawn by Altium Designer.After processing and assembling the circuit system and transmission line structure,the platform was properly tested from two sides including stability and operability,by using several photoconductive switch samples.According to the problems encountered in the experiment,the platform structure is further optimized.The stable output waveforms of the photoconductive switch samples under linear and non-linear working conditions were obtained.The performance and appearance of the photoconductive switch samples were measured and analyzed at different repetition frequencies.The the test platform for photoconductive switches achieves the design targets,and the experimental data are credible.