SILICON AND GALLIUM ARSENIDE VACUUM SURFACE FLASHOVER

ABSTRACT Photoconductive semiconductor switches (PCSS) presently have the greatest potential fordramatic performance enhancements for high power pulsed applications. However, surface flashover severely limits the maximum stand off voltage in the open state. We report theuse of a novel technique to PCSS to overcome this limitation. The technique is anextension of the graded ring bushing idea from accelerator technology, but differs byreducing the thickness of the insulator (semiconductor) down to tens of micrometers. Recent results using this technique have yielded electric field values, before flashover, in the range of 70 kY/cm to 114 kVF/cm in silicon and 70 kY/cm to 84 kV/cm in gallium arsenide. 1. INTRODUCTION Photoconductive switch development is being pursued in several research programs.Results with GaAs switches capable of delivering 26 MW in 6Ons pulses, and current densities of up to 100 kA/cm2 have been obtained.' Research done at Los Alamosdemonstrated a 200MW silicon switch operating at 150 kV and a peak current of 3 kA,