Fabrication and Design Issues of Bulk Photoconductwes~tchesusedfor Ul Tra-wideband, High-power Microwave Generation

The Army Research Laboratory (ARL), in collaboration with the Air Force Phillips Laboratory, has been developing the fabrication process for lateral topology, highpower photoconductive semiconductor switches (PCSS) used in phased-array, ultrawideband (UWB) sources. This work presents issues associated with the development of these switches. First-generation devices (1.0 em gap spacing) have been shown to achieve sub-nanosecond risetimes, working hold-off voltages of 50 kV, switched currents of 333 A into a 75 Q load, and lifetimes in excess of 2 X l(f shots at 10Hz. Later-generation devices (0.25 gap spacing) operate at 20 kV and 1 kHz, with improved risetimes, jitter characteristics, and trigger requirements.