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This article addresses the impact of the buffer doping on the critical performance issues of current-collapse and dynamic RON in GaN high electron mobility transistors. It focusses on the effect of carbon, either incorporated deliberately in GaN-on-Si power switches, or as a background impurity in iron doped RF GaN-on-SiC devices. The commonality is that carbon results in the epitaxial buffer becoming p-type and hence electrically isolated from the two-dimensional electron gas by a P-N junction. Simulations which incorporate a model for leakage along dislocations are used to show that a remarkably wide range of experimental observations can be explained including dynamic RON and the complex time dependence of drain current transients in power switches. In RF GaN-on-SiC devices, the current-collapse, the drain current dynamics, kink effect, pulse-IV and electric field distribution in the gate-drain gap can all be explained.
Bibliographical noteFunding Information:
This work was in part supported by the Engineering and Physical Sciences Research Council (EPSRC) under EP/ N031563/1 and EP/R022739/1, and by Innovate UK under SLOGAN-M4. We would like to thank the many members of the University of Bristol CDTR group who have contributed to this study. The model could not have been developed without close collaboration with Peter Moens of ON Semiconductor, Mark Gajda of Nexperia, Trevor Martin of IQE, Ahmed Nejim and Stephen Wilson of Silvaco, and Paul Tasker and the team at CHFE, Cardiff University.
© 2021 The Japan Society of Applied Physics.
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