Photoconductive semiconductor switche（PCSS）is used to generate high-power pulse.Increasing the hold-off voltage of PCSS can elevate output power effectively.Simulation is carried out on both coplanar and opposed contacts GaAs PCSS by using software SILVACO.Different breakdown voltage and distribution of impact ionization rate is obtained with the help of simulation tool mentioned above.The withstand voltage experiments are done using fabricated 3 mm gap coplanar and opposed contacts GaAs PCSS.Combined with simulation and experiment results

the withstand voltage characteristic of opposed contacts GaAs PCSS is analysed.Model analysis and experiment results show that in contrast to coplanar structure PCSS

opposed structure GaAs PCSS has higher withstand voltage

the breakdown voltage filed is up to 7.67 kV/mm.