People would think of GaN (gallium nitride) when talking about high frequency or very high frequency switching. However, a study published by scientists from Stanford University showed that SiC can also be extremely fast.
The scientists demonstrated that DC-RF efficiency higher than 86% can be realized with a 17MHz class E inverter using SiC MOSFET. There is one characteristic that commercial SiC MOSFETs are superior to GaN HEMTs: the output capacitance (Coss) related loss (Ediss) of SiC MOSFET is independent of switching frequency. In the meantime, the Ediss of GaN HEMTs tends to increase with increasing frequency (due to increased dV/dt) which deteriorates GaN’s performance at very high frequency.
Of course, SiC MOSFET does not come with no shortcomings for high frequency or very high frequency switching operations. SiC MOSFET is a vertical device while GaN HEMT is a lateral device, therefore the input capacitance (Ciss) of SiC MOSFET is inherently higher than that of GaN HEMT. Also, the Rds(on)*Co(eq.) figure-of-merit for today’s commercial SiC MOSFETs is still larger than that of GaN HEMT. However, should the performance of SiC MOSFET be continuously improved, it will not be surprising to see more multi-MHz converters implemented by SiC MOSFETs.
