Investigation on the surface flashover of high gain SI-GaAs PCSS

The GaAs photoconductive semiconductor switch (PCSS) is generally recognized currently as a leading power electronic device for its unique advantages. A major limitation of PCSS has been its surprisingly low voltage threshold for the surface flashover found when PCSS works at the high gain mode. In this paper, the surface flashover of high gain PCSS is studied by experiments. We propose that the non-uniform distribution of the surface field that resulted from the photo-activated charge domain (PACD) and the gas desorption is the key cause of such reducing of the SF field. SF6 ambient dielectric is efficient in increasing the surface field, and the experiment results show that the PCSS we developed could resist a voltage as high as 20 kV/cm when the ambient dielectric is 3 atmospheric SF6. This conclusion has the practical application of significance to improve the performance of the high gain PCSS, which is severely limited by the premature breakdown effects.