Study On GaN Photoconductive Switch And Pulse Drive Circuit

Photoconductive semiconductor switches(PCSS),due to their small trigger jitter,small structure,high repetition rate,fast response,and good photoelectric insulation,have been widely used in medical facilities,military weapons,communications.Traditionally,the pulsed laser beam is the primary trigger source for the PCSS,owing to coherent,monochromatic and high peak power light pulses.However,pulsed lasers are generally expensive,bulky,unmovable,and frequently maintained,these disadvantages resulting in limiting inhibit the use of PCSS.Therefore,it is very important to study low-cost,compact,high-stability light trigger source for the promotion of the application of PCSS.The main work of this thesis is as follows:1.Based on the avalanche effect of high-frequency and low-power transistors,in this thesis we design a high-power nanosecond pulse driving circuit that can achieve higher power,narrower pulse width,smaller rising edge,and higher repetition frequency.High-power narrow pulse drive circuit was simulated by PSPICE software.The results show that the circuit generates an analog electrical pulse signal with an amplitude of 57 A,a pulse width of4 ns,and a frequency of 1 kHz at a supply voltage of 300 V.In the experiment,the rising edges from 4.4 ns to 7 ns and pulse width of approximately 5 ns to 10 ns were obtained by a LED light source.Therefore,the LED light source,as pulse signal source,can meet the need of the photoconductive switch experiment.2.We chose GaN,with a band gap of 3.39 eV,a bandgap type of direct band gap,and a thermal conductivity of 1.3 W/cm-K,to prepared photoconductive switching.The performance of GaN photoconductive switch has been studied.When using a blue LED to illuminate it,a pulse signal with a rising edge of 0.95 ns,falling edge of 6.4ns and a conduction current of 18.6 mA and withstand voltage of 3.5kV can be obtained.