Fireset applications of improved longevity optically activated GaAs photoconductive semiconductor switches

Summary form only given. The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) 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. For fireset applications operating at 1 kV/1 kA levels and higher, such doped contacts have not yet resulted in improved longevity. This paper will compare various approaches to optical triggering of the switches and methods of establishing electrical connection to the devices in regard to switch longevity at kA current levels. Data on device performance and lifetime will also be presented for different structures, including vertical switch geometries. 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 1kV/1 kA and above, we employ multi-filament operation and InPb solder/Au ribbon wire bonding. These studies have resulted in the demonstration of fireset switches that have >400 shot lifetime at nominally 1 kA operating current. This data is guiding the continuing refinement of device structures, configurations for optical triggering, and electrical contacts to meet the demands of fireset applications.