IEEE Power Electronics Magazine Compendium - March 2018 - 50

Heat can be extracted
from a device from
both the front surface
and the back surface.

To determine the voltage acceleration of HTGB failure,
a matrix of tests was conducted at voltages between 6 and
7 V, all at a temperature of 150 cC. Note that this voltage
range is outside of the safe operating range of lower than
6 V for eGaN FETs. Each voltage leg consisted of 32 parts,
and parts were postscreened at three increments: 1) 24 h,
2) 100 h, and 3) 200 h.
These data were analyzed using the same methods as
described for the HTRB acceleration study. Raw TTF was
fit to a Weibull distribution for each voltage leg. Using the
MLE parameter (and confidence intervals), the MTTF and
FIT rate versus VGS was calculated. These are shown in Figure 7(a) and (b), respectively. The green line interpolating
the data is a best-fit exponential acceleration function. This
was not chosen on a priori theoretical grounds, but it does
provide a reasonable fit to the data.
With the use of this acceleration function, the MTTF
can be predicted at gate voltages within the normal safe
operating range. At 6 V (the data sheet limit), the MTTF
is well above ten years at 150 cC. To predict the TTF at a
specified probability level (e.g., 1% and 0.1%), further data
must be collected to refine the Weibull fits.
In summary, on-resistance, switching speed, thermal performance, size, and cost have all been examined, and GaN
transistors exceed the capability of the aging silicon-based
power MOSFET on all fronts. In addition, there is ample evidence that the reliability of this new technology is already
well beyond the requirements for commercial application.
Hence, designers who invest in the skills needed to extract
this superior performance from GaN technology for the
benefit of their power system designs have a proven advantage over the resistant players relying on the aging MOSFET
technology in their power conversion systems.

Alex Lidow (alex.lidow@epc-co.com) is the chief executive
officer and cofounder of Efficient Power Conversion Corp.
Johan Strydom (johan.strydom@epc-co.com) is the
vice president of applications engineering, Efficient Power
Conversion Corp.

IEEE PowEr ElEctronIcs MagazInE

References
[1] A. Lidow, J. Strydom, M. de Rooij, and D. Reusch, GaN Transistors for
Efficient Power Conversion, 2nd ed. Hoboken, NJ: Wiley, 2015.
[2] A. Lidow, D. Reusch, and J. Strydom. (2014, Oct.). How to GaN: Generation 4 eGaN FETs widening the performance gap with the aging MOSFET.
[Online]. Available: http://www.eeweb.com/blog/alex_lidow/how-to-gangen-4-egan-fets
[3] C. Blake, "Long-term reliability of 600 V GaN, test results and conclusions," presented at Darnell Power Forum, Dallas, TX, Sept. 11, 2013.
[4] EPC application note AN013. (2011). Second generation eGaN FETs
are lead free and offer improved performance. [Online]. Available:
http://epc-co.com/epc/documents/product-training/Characteristics_of_
Second_Generation_eGaN_FETs.pdf
[5] M. de Rooij and J. Strydom. (2014). EPC application note AN015. Introducing a family of eGaN FETs for multi-megahertz hard switching applications. [Online]. Available: http://epc-co.com/epc/documents/product-training/
AN015%20eGaN%20FETs%20for%20Multi-Megahertz%20Applications.pdf
[6] eGaN FET reliability reports. Efficient Power Conversion Corp., El
Segundo, CA. [Online]. Available: http://epc-co.com/epc/DesignSupport/
eGaNFETReliability.aspx
[7] S. C. Binari, P. Klein, and T. Kazior, "Trapping effects in GaN and SiC
microwave FETs," Proc. IEEE, vol. 90, no. 6, pp. 1048-1058, June 2007.
[8] D. Jin and J. del Alamo, "Mechanisms responsible for dynamic ONresistance in GaN high-voltage HEMTs," in Proc. 24th Int. Symp. Power
Semiconductor Devices ICs, Bruges, Belgium, June 3-7, 2012, pp. 333-336.
[9] W. Weibull, "A statistical distribution function of wide applicability," J.
Appl. Mech. Trans. ASME, vol. 18, no. 3, pp. 293-297, Sept. 1951.
[10] H. Hirose, "Maximum likelihood estimation in the 3-parameter Weibull

About the Authors

Robert Strittmatter (robert.strittmatter@epc-co.com)
is a member of technical staff, Efficient Power Conversion
Corp.
Chunhua Zhou (chunhua.zhou@epc-co.com) is a member of technical staff, Efficient Power Conversion Corp.

z March 2015

distribution: A look through the generalized extreme-value distribution,"
IEEE Trans. Dielectr. Electr. Insul., vol. 3, no. 1, pp. 43-55, Feb. 1996.
[11] W. J. Vigrass. (2012). Calculation of semiconductor failure rates.
[Online]. Available: http://www.intersil.com/content/dam/Intersil/quality/rel/
calculation_of_semiconductor_failure_rates.pdf

http://www.eeweb.com/blog/alex_lidow/how-to-gan-gen-4-egan-fets http://www.eeweb.com/blog/alex_lidow/how-to-gan-gen-4-egan-fets http://www.epc-co.com/epc/documents/product-training/Characteristics_of_Second_Generation_eGaN_FETs.pdf http://www.epc-co.com/epc/documents/product-training/AN015%20eGaN%20FETs%20for%20Multi-Megahertz%20Applications.pdf http://www.epc-co.com/epc/documents/product-training/AN015%20eGaN%20FETs%20for%20Multi-Megahertz%20Applications.pdf http://www.epc-co.com/epc/DesignSupport/eGaNFETReliability.aspx http://www.epc-co.com/epc/DesignSupport/eGaNFETReliability.aspx http://www.intersil.com/content/dam/Intersil/quality/rel/calculation_of_semiconductor_failure_rates.pdf http://www.intersil.com/content/dam/Intersil/quality/rel/calculation_of_semiconductor_failure_rates.pdf

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