ASCENT: Optically-Driven Ultra-Wide-Bandgap Power Electronics for Grid Energy Conversion

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Electricity generation is responsible for 30% of U.S. greenhouse gas emission. Integration of renewable energy sources in electricity grids is key to reaching the goal of zero carbon emission, which requires the increased deployment of power electronics that possesses superior power scalability and higher frequency beyond the state of the art. Currently, the scalability of grid power electronics is limited by the electromagnetic interference (EMI) between the power and driving stages, which makes it difficult to stack many devices in series and in parallel. On the other hand, the frequency is limited by the slow switching speed of high-voltage power semiconductor devices. This NSF projects aims to concurrently advance the switching frequency and power scalability of grid power electronics through the deployment of an emerging ultra-wide-bandgap (UWBG) semiconductor. This goal will be achieved by leveraging the unique electronic and optical properties of UWBG materials to develop a new generation of high-voltage, ultra-fast UWBG devices that are driven by optical signals, as well as synergetic innovations in auxiliary circuits, deep UV optical systems, and packaging techniques. The intellectual merits of the project include establishing the knowledge base regarding the nanomaterials, UWBG devices, optical systems, packaging, and circuitry to enable the envisioned optically-driven, EMI-immune grid power electronics. The broader impacts of the project include training future students in the fields of nanotechnology, semiconductors, microelectronics, and power electronics, as well as increasing diversity and supporting students from underrepresented groups, with an emphasis on promoting the education of women scientists and engineers. This project will also be utilized to support the outreach activities for K-12 students.The objective of this project is to address the fundamental knowledge gaps in nanomaterials, UWBG devices, optical systems, packaging and circuitry to enable an optically-driven, highly-integrated, ultrafast, EMI-immune, highly-efficient power electronics for grid applications. This system vision builds upon an emerging semiconductor, gallium oxide (Ga2O3), which has a bandgap of ~4.6 eV and a critical electric field twice that of gallium nitride or silicon carbide and ~20 times that of silicon, rendering it an ideal candidate for power and deep UV photonic devices. This project will focus on research activities in the following four aspects: (1) A new Ga2O3 optically-driven power switch will be developed, which allows for orders of magnitude higher switching frequency and lower optical power as compared to optical silicon thyristors. (2) An integrated DUV optical system including light sources, optical waveguide and fiber-to-chip coupling will be explored for UWBG devices. (3) An advanced packaging design will be explored to realize the electric field mitigation, low thermal resistance, and low inductance, while maintaining the integrity of the optical fiber connections. (4) A self-sustained auxiliary power supply will be developed that will feed the driving power from the device voltage and current, thus obviating any external auxiliary power supply. Finally, the functionalities of the optically-driven, external-auxiliary-power-free, highly-integrated UWBG system will be evaluated in inductive switching tests and a medium-voltage solid-state circuit breaker.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.