Lifetime and Longevity of an Intense, Photoconductivity - Switched Stacked Blumlein Modulator for Ultra - Wideband HPM Applications

摘要

In this work, experiments with the stacked Blumlein prototype pulsers were conducted under different conditions of operation at power levels bypassing 100 MW. Special attention was placed on broadening of the current channels in the avalanche photoconductive switch in order to improve lifetime. The mechanical and semiconductor properties of amorphic diamond were employed to improve the lifetime by coating the switch cathode or anode areas or both. Issues concerning the switch longevity were studied by fabrication and testing the GaAs photoconductive switches treated with the amorphic diamond under different switch configuration, gap settings, and diamond coating thickness. When the switch cathode was coated, the tunneling of electrons from amorphic diamond to GaAs provided pre-avalanche sites that diffused conduction current upon switch activation. On the other hand, the diamond coating of the switch anode resulted in increased hold-off characteristics and longer switch lifetimes by blocking leakage current during off-state stage of operation. A significant improvement in switch lifetime was demonstrated by coating the cathode and anode areas of a GaAs photoconductive switch with amorphic diamond and testing its performance in a high power operation with a prototype stacked Blumlein pulser. In addition, elementary processes involved in conduction of a diamond-treated photoconductive switch were extensively examined.