Description: Power electronic components with high operating voltages are desirable in NASA Power Management and Distribution (PMAD) systems since they can lead to reduced mass and higher efficiency at the system architecture level, and serve as an enabling technology for solar electric propulsion systems. Gallium nitride (GaN) offers significant advantages over silicon (Si) technologies for power applications including higher breakdown voltage and power density, rapid switching, lower switching losses, and higher temperature tolerance. Enhancement mode GaN-on-Si high electron mobility transistors (HEMTs) are a rapidly advancing technology that are scalable with voltage, offer superior electrical performance, and also demonstrate high tolerance to displacement damage and total ionizing dose (TID). However, prior tests have shown that heavy ion (HI) induced leakage currents and catastrophic damage may occur well below rated voltages. A thorough investigation of the HI response of emerging, higher voltage GaN HEMTs and underlying mechanisms is essential to develop radiation tolerant devices for space applications. CFDRC, in collaboration with Vanderbilt University and EPC, proposes to use an integrated experimental and physics-based modeling approach to address this challenge. In Phase I, we will perform heavy ion testing of commercial EPC GaN HEMTs to generate response data. Detailed TCAD models will be developed for the HEMT structure to investigate physical mechanisms behind measured radiation response. In Phase II, we will perform additional heavy ion and TID testing as a function of temperature and bias. Extensive TCAD and higher-fidelity modeling will be performed to determine radiation and temperature-dependent mechanisms, and to investigate device design modifications for improved radiation tolerance. Promising solutions will be prototyped and characterized via testing. Participation by EPC in Phase II and beyond will ensure advanced space-qualified, GaN power devices.

Benefits: As described in the NASA Space Power and Energy Storage Roadmap-Technology Area (TA) 03, space qualified high voltage/high temperature power electronics are directly aligned with science and exploration missions including missions using electric propulsion, robotic surface missions to Venus and Europa, Mars polar and lunar polar science missions, crewed exploration vehicles, crewed surface habitats, and others. A higher operating voltage can yield a lower distribution system weight for the same power level and is highly desirable across many areas of PMAD. GaN devices offer high breakdown voltage and power densities, fast switching times and lower switching losses, and increased temperature tolerance, all crucial features for NASA space power applications. The hardened GaN designs from this project will add to the NASA components library. The physics-based models and predictive tools developed in this project to characterize the performance of power-related components are a cross-cutting technology applicable to all NASA missions that require power electronics. They also support the requirements specified in TA 11.2.4 (Science Modeling) and TA 11.3.7 (Multiscale, Multiphysics, and Multifidelity Simulation). The simulations tools will help NASA evaluate device performance under radiation and high temperature at an early stage, and design space qualified power electronics with better understanding of design margins, thereby reducing the development time and cost.

Space qualified GaN power electronics will find applications in power systems in all space-based platforms, including DoD space systems (communication, surveillance, missile defense), and commercial satellites. Other DoD/national defense applications include unmanned underwater vehicles and soldier portable power systems. Applications in the terrestrial energy sector (electric grid) include PMAD system components such as solid�\state transformers, inverters, fault current limiters, high�\voltage direct current, and power flow controllers. GaN HEMT devices are also attractive for high-temperature electronics and smart power applications. Specifically, enhancement mode operation of GaN HEMTs will deliver higher performance in circuit and system levels in power applications such as envelope tracking (converters and power amplifiers), wireless power (high speed switches), light distancing and ranging (LiDAR �C high speed switches), power inverters (high speed switches with lower losses), and others. Other commercial applications of GaN include high temperature (> 200 C) power and control systems in electric vehicles and hybrid vehicle engines. For all the applications listed above, physics-based predictive and accurate modeling and design tools reduce the amount of required radiation/temperature testing, thus decreasing their cost, and time to market or field application.