There is a Tremendous Interest in the market today for GaN based power conversion technology. Over the last decade or so, the international research community and corporate researchers have published performance results that clearly demonstrate device figure of merit superiority of GaN based power transistors over conventional silicon based power MOSFETs1. Several companies have demonstrated in circuit application performance benefits of GaN based power transistors2,3 across the voltage range from 12V to 600V and beyond. And most recently, during APEC 2010, International Rectifier became the first company to publicly announce production release of a GaN based power transistor device: the iP20104. The future is bright for this new technology.
Why is GaN performance superior to Silicon? GaN HEMT (high electron mobility transistor) devices, with a wider bandgap than silicon have much higher critical field. Together with high carrier concentration and high mobility, GaN devices offer a superior trade off of specific RDS(ON) (think conduction losses) vs. breakdown voltage rating. With very high mobility, fewer carriers are required to achieve these low conduction losses which translates into low charge and low switching losses as well. Overall, there is a virtuous combination of material properties adding to superior efficiency, density and (with commercialization hurdles conquered) cost for power conversion solutions.
LOW VS HIGH VOLTAGE GAN
Note from Figure 1 that GaN FOM (Figure of Merit) has been demonstrated superior to silicon across a wide range of voltage. When faced with such a large opportunity for commercialization, development resources must be prioritized. There is an urgent mandate in the low voltage point of load application space for high efficiency and high density which is best met by GaN power devices. As this represents a large market opportunity with rapid adoption rates, IR has chosen to focus in this area first.
In addition, IR has already demonstrated excellent 600V device switching performance based on the cost effective GaNpowIR manufacturing platform (Figure 2)5. Further, IR has announced a planned 600V product release before the end of calendar year 20116.
Ultimately, as industry further develops the technology, GaN based power FETs should widely displace their silicon counterparts from the range 20 to 1200V.
Moving from mere technology demonstration to commercialization and market adoption requires application performance per cost ratio (P/C) competitive with silicon MOSFETs. This makes mandatory a manufacturing platform that is capable of delivering consistent output, high quality and reliability at cost low enough to reach the required P/C.
The iP2010 provides cost effective point of load power conversion where space is a premium and efficiency is a must. Likewise, adoption of 600V GaN based solutions will occur when P/C is compelling and ease of use issues such as assembly and product robustness is demonstrated.
GAN VS SIC
As Figure 1 shows, GaN has almost an order of magnitude better material limited performance potential compared to SiC. But, as stated above, it is P/C that drives market adoption and so the cost factor plays an equal role to performance. GaN on silicon based power conversion benefits from more than 10x lower substrate costs compared with SiC. Additionally, Si substrates are easily available in larger wafer diameters which can be used to drive down wafer fabrication costs. Putting together both performance and cost, P/C of GaN is much, much more than 2x that of SiC.
REFERENCES
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N. Ikeda et.al. ISPSD 2008 p.289
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“GaN Based Power Conversion,” Dr. Michael A. Briere, Power Electronics Europe, 2009 Issue 5, pp 23-27: http://www.power-mag.com/pdf/issuearchive/30.pdf
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http://www.irf.com/whats-new/nr100223.html, and also APEC 2010 Proceedings, Professional Education Seminar: Current State and Future Improvements of GaN Based Power Conversion
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APEC 2010 Proceedings, Professional Education Seminar: “Current State and Future Improvements of GaN Based Power Conversion”