Choices between SiC, GaN and Si Forecast to Get more Difficult

January 12, 2015 by Power Pulse1595211359

The Power Devices Special Focus Session at the recent IEEE International Electron Devices Meeting, included an invited paper titled, "Application-Specific Trade-offs for WBG SiC, GaN and High-End Si Power Switch Technologies" by a team of authors from Infineon Technologies AG. The paper noted that there is an increasing choice of power switches in the 600V to 1700V range. Besides the well-established Si SJ (Super Junction) MOSFETs and IGBTs, there are now also SiC and GaN power switches available for new designs. Completely new system optimizations are possible driven by totally different trade-off options such as between static and dynamic losses and their temperature dependencies.

Dr. Roland Rupp, who presented the paper, opened by commenting, “In the last decade the competition of power semiconductor switch technologies was enriched by two new members: SiC-FETs (MOSFETs and JFETs) and lateral GaN-HEMTs. In parallel to these new semiconductor switch solutions, the traditional Si-based technologies of IGBT (like Trench Fieldstop) and Super Junction MOSFETs (like CoolMOS) have improved continuously.”

He stated that no clear long-term winner can be identified today. “The race will be decided individually depending on the target application,” Rupp commented. The paper then presented a detailed technical analysis of the competitive strengths and weaknesses of the various power switch technologies. It concluded with a comparison of technology and performance parameters for key power devices.

“The most interesting voltage class is around 600V as this is a market segment with very high volumes, where all the technologies compete,” Rupp observed. “Neglecting the cost differences between the various technologies would lead to a clear champion, the SiC FET. But the high SiC material cost dims this picture and limits market acceptance,” he continued. Still, he expects that “SiC power switches will continue to increase their market share in the next few years."

Turning to GaN, the market penetration is expected to depend strongly on application relevant demonstration of long-term reliability, minimized derating of use-voltage versus breakdown voltage and, of course, cost. On the other hand, the Infineon researchers see that both SJ and IGBT technologies are getting closer to their technological limits. “There are still new ideas to further improve the trade-off between static and switching losses and keeping short circuit ruggedness, but they are fighting with the fact that performance improvements are counter balanced by increasing processing costs coming with the more sophisticated processing and reduced process tolerances,” stated Rupp.

The paper concluded: “In sum, the race is getting tighter with respect to device cost and application-specific differentiation is more and more important. In the opinion of the authors, this will lead to a co-existence of all the mentioned power switch technologies in the coming years with possibly even fluctuating market shares depending on application trends and ‘carbon footprint reduction’ driven legal regulations.”