High-power photoconductive semiconductor switches treated with amorphic diamond coatings

The mechanical and semiconductor properties of amorphic diamond can be employed to improve the photoconductive semiconductor switch longevity by coating the switch cathode or anode areas or both. In this paper, issues concerning the switch longevity were studied by fabrication and testing the GaAs photoconductive switches treated with the amorphic diamond under different switch configurations, gap settings, and diamond coating thickness. The tunneling of electrons from amorphic diamond to GaAs during the off-state stage of operation provided preavalanche sites that diffused conduction current upon switch activation. A significant improvement in switch lifetime was demonstrated by testing the diamond-coated switch performance in a prototype pulser. Elementary processes involved in conduction of diamond treated switch and other design options such as coating of switch anode area are examined and discussed.