Ultrawide Bandgap AlGaN Power Electronics - Transforming Solid-State Circuit Breakers (ULTRAlGaN)

There is an urgent need for new power electronic technologies to underpin the transition to net zero. The imminent risks for our planet have been highlighted by UN's Intergovernmental Panel on Climate Change calling our current status 'code red' for human driven global heating in its scientific report published in 2021. Deploying power electronics in renewable generation systems enables smart control of grid networks and efficient energy utilization. This is also true of transportation, which in turn will support a dramatic reduction of the 72% of global primary energy consumption currently wasted world-wide. In this programme grant (PG), we develop a transformative next generation of Aluminium Gallium Nitride (AlGaN) Solid-State Circuit Breakers (SSCBs), with greatly improved efficiency and greater voltage range, to many kVs, enabling anticipated global energy savings >20% compared to continuing with current technologies. Circuit breakers are critical components for safe, reliable electrical power systems, including for power-electronics-dense grids, but a step-change in performance is needed. According to the major power electronics company ABB / Hitachi Energy, SSCBs are 'the weakest link in next-generation electricity infrastructure'. The slow response time of existing mechanical circuit breakers available on the market risks damaging sensitive equipment. The alternative use of Silicon (Si) - based SSCBs, although providing superior switching speed ( 100 microseconds), and offering the fast circuit protection critically needed for high-performance power distribution, presently suffer from high conduction losses and are often limited at best to 4-5 kV safe operation for a single chip. Higher voltage ranges are required in increasingly more complex and varied application areas including electric planes and ships. For example, Si-based SSCB inefficiencies would contribute up to an additional 600 Mtons of CO2 emissions per year if implemented in the global cruise liner industry alone. The vision and ambition is to address current roadblocks in power electronics by developing new SSCBs. The limitations in existing technologies can be largely eliminated using ultrawide bandgap AlGaN SSCBs, which conservatively have a 100x improvement in efficiency compared to existing commercial high-voltage devices such as Si insulated-gate bipolar transistors and Silicon Carbide (SiC) metal oxide semiconductor field effect transistors, to enable efficient, compact SSCBs with minimal cooling requirements. In 20 years, it is expected that these highly efficient ultrawide bandgap AlGaN power electronic components will have displaced all other technologies such as Si and SiC for high-current high-voltage uses, e.g. in power distribution and transportation such as in trains, maritime and planes, helping enable a carbon neutral society. The underlying physical reason for the great benefit of using AlGaN is its much greater bandgap (up to 6.2 eV) compared to Si (1.1 eV) and SiC (3.2 eV). The commonly used power electronics Baliga Figure of Merit, i.e. the suitability of a material for power electronics, of AlGaN is nearly 1,800 compared to 1 for Si and 340 for SiC, enabling a revolution in what power electronics will be able to deliver. Many interlinked technological challenges need to be addressed, including AlGaN materials growth, and methods to enable large enough layer thicknesses, alongside the development and fabrication of new device concepts to achieve high performance and reliable AlGaN SSCBs. The PG will be driven by the realization of transformative device prototypes, with ever increasing complexity, challenge and innovation during the course of the PG, ultimately driving UK research in this area towards end-application prototypes. The high-power application space is huge, and developments will be steered by involving end-users in a co-creation role for the SSCB prototypes.