Transition from the conventional scheme of manufacturing circuits using discrete components to that of a fully integrated power system-on-chip is anticipated to be a prerequisite to take advantage of the high-frequency power switching benefits offered by GaN devices. High slew rates, in the presence of parasitic inductance (device/package/circuit) can result in over-voltage transients, which can seriously impair the functionality of a GaN device. Even with the most innovative packaging approaches, a finite residual inductance is present. Monolithic integration of gate drive circuitry with power devices on a single technology platform is considered as an essential approach to minimize parasitic inductance in the circuitry and therefore enable stable high-frequency operation, efficiency and power densities unachievable by existing techniques. The fundamental requirement of a semiconductor technology platform that enables simultaneous development of a wide range of high voltage and low voltage N and PMOS devices as required for integration is served by the Polarisation Super Junction (PSJ) platform in GaN. Recent reports on the performance of vertical devices fabricated on bulk GaN substrates have shown performance close to the theoretical limits. However, marginal improvement in performance over Silicon Carbide (SiC) and the high cost of bulk GaN substrates will make market adoption difficult. However, the scenario can be transformed by implementing super junction architectures in GaN that can then enable ultra-high efficiency and reduction in on-state losses by orders of magnitude, thus making the solution highly competitive. A reduction of almost two orders of magnitude in RON.A can be achieved using vertical PSJ (VI-PSJ) structures for breakdown voltage of 1kV, which could extend to three orders of magnitude improvement for 10kV devices, in comparison to conventional SiC devices.
Prof Shankar Ekkanath Madathil @ EM Sankara Narayanan was a Royal Society Industry Fellow in Rolls-Royce where he worked on the systems impact of next generation power electronics technologies; prior to that he was a Royal Academy of Engineering Chair in Power Electronics from 2007-2013. His team has proven world leading design-2-manufacture expertise in Silicon and GaN. Presently, his work is focussed on ultra-high power density power conversion solutions, which ranges from materials to circuits and thermal management with a focus on effective use of high value materials and manufacturing techniques for aerospace applications, through direct support from Rolls-Royce. He is an editor of IEEE – TDMR, IEEE-TED, and Proceedings of the Royal Society A and an associated editor of IET – PEL and holds 40 patents/applications and published in excess of 250 articles.