Simulation And Fabrication Of 4H-SiC PCSS With Transparent Electrode

In new Century,with the development of military and industry.The technical requirements of high power switching devices become diversified.The switches should not only meet the requirement of high power,but also should be able to work in the high frequency field.Low jitter and small in size are also in demand.PCSS?Photoconductive Semiconductor Switches?,which own all adventages above have been studied for more than thirty years.Especially in the 21st century,Preparation Process of SiC and GaN become mature.In this dissertation,analysis was conducted with experiments and simulation data from do-mestic and overseas.Research on the silicon carbide photoconductive switches with oppos-ing contact structure.This Research based on the newest experiment conducted by Penhui Cao and Wei Huang in 2017^[1].The 4H-SiC PCSS with AZO transparent conductive window and silver mirror was comprehensively studied and simulated.With the purpose to enhance the abilities of voltage withstanding properties and quantum efficiency.An 2D 1:1 model and an 3D 1:1 model were built.Advantages and disadvantages of PCSSs with different structures on voltage withstanding properties and quantum efficiency was discussed in de-tail.1.The phenomenon of the distribution of electric field and photogeneration rate were ex-plained in theory.We got the conclusion that the maximum working voltage would decrease if PCSSs were excited by light.Because the nonequilibrium carrier made the change of elec-tric field more sensitive.The maximum electric field strength firstly appeared on the inner side of the annular electrode-anode,then the outside of annular electrode-anode.If anode was protected properly,the maximum electric field strength would appear on the edge of cathode.With the bias voltage increasing,it moved from cathode to anode.This phenomenon showed a law of the distribution of electric field.2.Two new methods were offered to improve the performance of pressure resistance.One was increasing the strength of electric field on the radial direction,another was covering the transparent electrode-AZO on all of the area of metal electrode.Especially the later one,the performance of PCSSs got 100%improvement during the off-state and 300%improvement during the on-state.3.The the performance of the quantum efficiency of different structures were also simulated.Diffuse reflection was first introduced to the simulation of PCSSs.The results showed that the diffuse reflection could effectively improve the distribution of electric field,thus the breakdown voltage would rise.The diffuse reflection could also increase the density of photon-generated carriers under the metal electrode.It was useful to reduce the resistance of PCSSs,but it would also reduce the efficiency of the transparent electrode-AZO and increase the resistance of the PCSSs with such structure.It is a double-edged sword.After finishing the simulation of PCSSs,a circuit without load resistor was built to get the performance of devices.Devices with four different structures were tested.The results of experiment and simulation were analysed detailedly.The results of simulation qualitatively conformed to the results we got from experiment.Unexpectedly,the simulation and the experiment results of the PCSSs with AZO deposited on cathode was inconsistent.According to the phenomenon we observed from the past experiments.Finally,we got the conclusion that the AZO worked as a subconnect layer would reduce the quantum efficiency of PCSSs,but it could also improve the performance of adhesion between the layers of 4H-SiC and Ag.Taken together,the adventage AZO subconnect layer brought palyed a more important role.