High power ultrawideband short pulse (UWBSP) electromagnetics (EM) application for wide band gap (WBG) photoconductive semiconductor switches (PCSS)

UWBSP EM systems typically rely on spark gap or vacuum tube-based devices because of the significant current and voltage magnitudes involved. Historically, solid-state devices have not been able to resist dielectric breakdown and the subsequent catastrophic failure modes that result in device damage when the large, pulsed bias voltages associated with UWBSP applications are applied. Recent advances in semi-insulating WBG materials have the potential to create switches that relieve the breakdown problem, while also allowing for more predictable, controllable, stable, and efficient switching at a reduced size and weight than what has been possible with traditional high power switching technologies. These WBG switches are operated by virtue of optical excitation of charge carriers from dopants deep within the band gap, also known as extrinsic photoconduction. This paper presents a hybrid computational approach for investigating a PCSS-based UWBSP system, focusing on the source and accompanying antenna radiation. The PCSS is simulated through Synopsys Sentaurus, using an array of fundamental and user-defined solid-state physics models. Both conventional and WBG materials are examined, and compared to published data in existing literature on comparable spark gap and PCSS systems. The results of the PCSS are used to excite two lossy UWB antenna designs, and the radiated output signals are compared both to each other and to existing literature. The results indicate that PCSS possess very high potential for not only matching but also exceeding the performance of spark gap based devices. The thick dipole UWB antenna appears to be a better suited design for radiating the transient signal switched by the PCSS than the bow tie antenna, with a higher amplitude of radiated power and far electric field. The magnitude of the radiation presents a compelling case for further investigation into the prospect of further developing solid-state driving sources for high power electromagnetic radiating systems. More advanced material measurement and characterization of the physical process involved with critical aspects of the switch, such as extrinsic photoconduction, are required in order to produce a higher fidelity model for future research.