共面型GaAs光导开关的击穿特性研究

Research on breakdown character of coplanar GaAs photoconductive switch

用ANSYS软件对暴露在空气中共面型GaAs光导开关进行了模拟仿真,根据其电场分布在X方向和Y方向的剖面图可以看出:在GaAs表面、电极、空气隙3种介质的交界面是极易发生击穿的区域,特别在电极的拐角部位。对用空气和Si3N4介质包覆开关表面时的电流分布进行了模拟比较,给出了X方向剖面图,结果表明:经Si3Ni4薄膜保护的GaAs光导开关的耐压能力可提高2个数量级。对设计制作的3 mm间隙共面型GaAs光导开关进行了耐压试验研究,分别采用绝缘油、绝缘胶对光导开关进行了绝缘保护,并结合介质击穿理论对试验结果进行了分析。模拟和试验结果表明:适当的绝缘保护可以有效提高耐压特性,使绝缘强度达4 kV/mm。

The simulation of coplanar electrodes GaAs photoconductive semiconductor switch（PCSS） exposed in air is done using ANSYS. Based on the electric field results cross-section in X and Y directions, the most breakdown region is the interface among GaAs surface, electrode and air space, especially at the corner. The current distribution of GaAs PCSS covered with of air and Sis Ni4 in X direction is given, it shows that the Sis Ni4 protection can improve the breakdown voltage almost 2 magnitude. Withstand voltage experiments are done with fabricated 3 mm gap coplanar GaAs PCSS. Different insulation techniques for surface protection of high-voltage are tested and different protection materials are coated on the surface of the GaAs switch. Combined with medium insulation and the surface breakdown theory, the experiment datum are analyzed. The simulation and experiment results show that approriate insulation technique can improve the voltage resistance of GaAs PCSS efficiently, and the hold-off field strength reaches 4 kV/mm.