Fireset applications of improved longevity optically activated GaAs photoconductive semiconductor switches

The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) for fireset applications operating at 1 kV/1 kA levels and higher has been greatly improved by multiple filament triggering and improved contacts. While longevity operating at /spl sim/100A or below has been greatly increased by doping the semi-insulating GaAs underneath the contact metal to improve the ohmic contacts, this technique has not yet improved PCSS longevity for firesets. This paper will compare various approaches to optical triggering of the switches and methods of establishing electrical connection to the devices with regard to switch longevity at kA current levels. Data on device performance and lifetime will also be presented for different structures. The device characterization also includes examination of the switch behavior due to neutron irradiation. This irradiation provides an enhancement of DC voltage holdoff, improvement of radiation hardness, and modification of switching behavior. To improve lifetime at 1 kV-1 kA and above, we employ multi-filament operation and InPb solder/Au ribbon wirebonding. These studies have resulted in the demonstration of fireset switches that have >400 shot lifetime at nominally 1 kA operating current.