Integration of Ultrawide Bandgap Photoconducting Semiconductor Switches into High-Voltage, High-Current Pulser Systems

Project Overview

In this feasibility study we will evaluate the viability of integrating ultrawide bandgap (UWBG) photoconducting semiconductor switches (PCSS) in high-voltage pulser systems capable of driving low-impedance dynamic loads critical for next-generation accelerator and radio frequency (RF)-source applications. The project consisted of developing modelling tools that would inform design of UWBG PCSS packages that could be mounted onto conventional circuit boards. Specifically, we are interested in evaluating the following through simulation software: (1) resistance to electrical breakdown (2) proximity effects due to high-frequency skin effect (3) transient behavior from switching (4) effective transmission of RF signals (5) thermal dynamics of the switch under operation (6) sensitivity to inhomogeneities in optical excitation of the material (7) cross-talk effects from parallel switching structures, and (8) susceptibility of system to damaged components. The project resulted in the development of a special-purpose circuit code that implements photoconductivity physics. This code was used to evaluate objectives 1-6 above, identifying a critical requirement associated with the need for fine control of dopant concentrations in the UWBG material to reach an optimal solution for voltage standoff and laser light responsivity requirements. In addition, we identified that the temperature dependence of the electrical conductivity of this material was typically not well-measured and developed a platform for measuring both the "dark" and "illuminated" conductivity on real physical switches in the lab to better inform our models.

Mission Impact

The conclusions of this research provide target bounds for UWBG fabrication that would be usable in future high voltage pulser application. Further development of this technology may be dependent on other programs at the laboratory finding ways to meet these requirements. This feasibility study supports multiple laboratory goals including development of accelerators for stockpile stewardship applications as well as enabling compact, low-cost technologies for improving national defense and national infrastructure's resiliency again drone-based and electronic-based attacks, relevant to the Mission areas of Nuclear Deterrence and Threat Preparedness and Response.