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GaN-on-Diamond RF Device Milestones

Technology achievements with respect to gallium nitride (GaN) continue to propel this material toward new horizons in the realm of RF devices. Its relatively high electron mobility (440 cm2 /(V-s) at room temperature) elevates its footing for more switching and RF power applications at higher breakdown voltages, lower leakage currents, and higher frequencies than competitive semiconductors such as silicon and silicon carbide (SiC). Many research groups have been focusing on improving the heat dissipation properties of GaN through SiC substrates in order to increase its overall efficiency in high-power device applications, and positive developments have benefitted this technical field over the last year.

 

(Image: Element Six)

US defense contractors such as Raytheon and TriQuint Semiconductor have been leading the race in GaN-on-diamond device fabrication in order to improve the heat-spreading properties of GaN. GaN-on-diamond transistors can achieve areal power densities of nearly four times that of GaN-on-SiC substrate based devices, along with a 50% reduction in thermal barrier resistance between the gate junction and substrate. Ultimately, these properties bolster the commercialization potential of GaN via reduced material costs and cooling architecture for fabrication of GaN-on-diamond transistors in future military radar and commercial cellular and satellite products. GaN-on-diamond has been especially targeted for high-power-density RF devices such as high-electron mobility transistors (HEMTs).

Over the last three years, the GaN-on-diamond technology has been funded by the Defense Advanced Research Projects Agency under the US Department of Defense (DOD) Near Junction Thermal Transport (NJTT) program. Raytheon and TriQuint received millions in funding to enhance their capabilities in this area to develop devices that they could sell to branches of the DOD. Thus, it’s a win-win for all parties involved. Last year, these companies announced reductions of nearly 45% in operating junction temperature, along with a 300% increase in the areal RF power density using GaN-on-diamond instead of SiC. In addition, TriQuint reported output power exceeding 5 W/mm with a power-added efficiency of 55% at a 28V drain voltage, which was another impressive accomplishment. These companies have been closing in on NJTT goals of minimizing the thermal boundary resistance between GaN and diamond by eliminating the AlGaN/AlN buffer layers under the GaN electrical transport layer in order to reduce costs and boost performance.

However, for GaN-on-diamond technology to reach its full potential, the quality, mass production, and manufacturing cost of diamond substrates or wafers must meet the challenge. One company in particular is rising to the occasion. A synthetic diamond materials firm called Element Six, a member of the De Beers Family of Companies, is the leader in the growth of diamond substrates. It has supplied the wafers for TriQuint and Raytheon to achieve GaN-on-diamond device milestones.

This past month, Element Six said it has developed a new thermal grade of diamond grown by chemical vapor deposition (CVD). The product, which has been given the trade name Diafilm TM130, has a thermal conductivity of at least 1,300 W/mK and isotropic heat spreading in both planar and through-plane directions, which is well beyond the capacity of materials such as copper. Element Six’s solid thermal products are available up to 3 mm thick and in diameters up to 140 mm. They can be laser cut to any required size for customization. Metallization product solutions have enabled die bonding with low thermal barrier resistance that is compatible with soldering and brazing used in standard microelectronic packaging processes.

A robust diamond wafer supply chain is critical for the success of this technology, but very few players have been willing to take the risk to enter this market. The situation is similar to the initial landscape for SiC wafers, which was dominated for decades by Cree. GaN-on-diamond transistors can operate at lower temperatures to enhance overall electrical performance, leading to longer device lifetimes and enhanced reliability. This will inevitably foster more RF device-related defense and commercial applications over the next decade.

25 comments on “GaN-on-Diamond RF Device Milestones

  1. bjcoppa
    October 27, 2014

    Currently, this technology is essentially being subsidized indirectly by US DOD funds since many customers purchasing the diamond substrates, are government contractors and universities conducting funded research. Manufacturing costs will have to fall in line with SiC to really gain traction in the marketplace, while wafer sizes will eventually need to be expanded for a wider range of device applications.

  2. samicksha
    October 28, 2014

    I have been reading about GaN devolopment for while now, but this blog bring new education to me. GaN is a promising magnetic semiconductors with same i realize this can be injurious to health and safety, i read report published by some Safety institute wherein they claim that GaN dust can be irritant to skin or lungs.

  3. bjcoppa
    October 28, 2014

    GaN waste is generally no worse than other materials used commonly in standard semiconductor processing. It has been in production for 20 years so major health issues would have likely been vetted out already. 

  4. Netcrawl
    October 30, 2014

    @samicksha the growing demand for high speed, high temperature and power handling capabilities have forced the entire semiconductor industry rethink about the desgins and materials used in semiconductors, as various and smaller computing devices coming forth, the use of silicon in semiconductors industry is making it difficult to sustain Moore's Law.

    GaN poses to be a unique material of choice for semiconductors and numerous applications because of its unique charcteristics- superior noise factor, high maximum current, high breakdown voltage, high oscillation frequency and many more. Growing application areas as well as increased demand from aerospace and military are the major driving force for the growth of GaN market, the increase in demand is mainly due to significant reduction in weight and size of devices obtained by th eusage of GaN.

  5. Netcrawl
    October 30, 2014

    @analoging Thanks for a great post, very informative! GaN has turned out to be the material of choice for most of the semiconductor applications and is quickly replacing the old technology (the silicon). GaN's properties such as wider bandgap, high-breakdown voltage, larger critical electric field, and higher thermal conductivity, enable the GaN devices operate at higher voltages, handle higher power density and offer enhanced power efficiency than the pure Si devices, I think these are the main reason why the military like it. 

  6. bjcoppa
    October 30, 2014

    Thanks for the comments. You reiterated many of the points made in the article. Its properties dictate increased usage for LED and high-power, high-frequency applications however supply chain and cost issues have tempered the transition and momentum, as GaAs still reigns supreme in price-sensitive consumer electronics where high-frequency is needed.

  7. geek
    October 31, 2014

    “i realize this can be injurious to health and safety, i read report published by some Safety institute wherein they claim that GaN dust can be irritant to skin or lungs.”

    @Samicksha: I think that risk is there with a large number of industrial materials. However, there are standards for health and safety that guide the way these materials should be used. The same goes for GaN as well. If those standards are strictly followed then there's not a lot of chance that any great health damages will occur.

  8. geek
    October 31, 2014

    “Manufacturing costs will have to fall in line with SiC to really gain traction in the marketplace, while wafer sizes will eventually need to be expanded for a wider range of device applications.”

    @analoging: I think cost alone is never a concern in industrial or millitary applications where quality and reliability is essential. As long as the application requires the performance, designers don't give a lot of importance to cost unless there are budget constraints.

  9. geek
    October 31, 2014

    “I think these are the main reason why the military like it. “

    @Netcrawl: While this may be the main reason, the reason why it is being used in military applications can also be due to the fact that it has been used for ages. Mostly military application designers do not want to take unnecessary risk and as long as something is working without any major issues, they'd rather let it continue than to intervene and experiment.

  10. samicksha
    October 31, 2014

    Not sure though but i believe GaN dust is little injurious but bulk GaN is biocompatible.

  11. bjcoppa
    November 4, 2014

    Thanks for the comments. GaN has the beneficial path of having many defense-funded military communications device applications that facilitate its eventual growth in the commercial sector as performance is enhanced and costs come down which is also a good thing for the other app in LED lighting.

  12. bjcoppa
    November 12, 2014

    High power electronics and semiconductors are a fast growing segment of the industry. SiC wafers are critical to sustaining that growth. Diamond wafers may be just as important in the next decade unless heat dissipation issues are addressed other ways.

  13. bjcoppa
    November 12, 2014

    High power electronics and semiconductors are a fast growing segment of the industry. SiC wafers are critical to sustaining that growth. Diamond wafers may be just as important in the next decade unless heat dissipation issues are addressed other ways.

  14. Davidled
    November 15, 2014

    A very expensive raw material such as Gold, Silver and Diamond is gettting more indispensable material in electronic industry. In consequence, performance is increased while cost goes to up. Well, researcher might develop the synthesized raw material for diamond and any required raw material. Therefore, device could be more competitive in the market.

  15. nasimson
    November 18, 2014

    > Mostly military application designers do not want to take
    > unnecessary risk and as long as something is working
    > without any major issues, they'd rather let it continue
    > than to intervene and experiment.

    Simply, if its not broke, why fix it? If its working fine, why replace it?

  16. bjcoppa
    November 21, 2014

    Believe it or not, the defense industry is willing to risk on less developed, higher return materials to boost device performance well in advance of commercial readiness. The DOD is designed to fund less mature microelectronic process technology and then capitalize on its own investment by purchasing the devices years down the road once enhanced by universities, national labs and companies. A good example is the hundreds of millions invested by DOD-DARPA into SiC and GaN over the last decade before the materials were ready for prime time.  Companies such as TriQuint Semi and Cree received millions in government contracts to boost the performance of these materials and now are selling various high-power and high-frequency transistors to other DOD agencies. The same is happening with diamond.

  17. chirshadblog
    November 23, 2014

    @nasimson: Well I guess they are a bit scared to go ahead with the latest technology. It surely will put them way behind their competitors for sure. 

  18. nasimson
    November 26, 2014

    > @nasimson: Well I guess they are a bit scared to go ahead with the latest
    > technology. It surely will put them way behind their competitors for sure.

    @chrishadblog: Since its Dept of Defense and its mega contractors like Raytheon we are talking about, I dont see how can they be left behind competitors. They dont have active competition as such.

  19. dassa.an
    November 27, 2014

    @chris: You have a valid point here but that does not apply for this isn't it ? 

  20. dassa.an
    November 27, 2014

    @analoging: Yes its growing very fast but we also must find out an alternative to make sure things do improve by the force of competition itself. 

  21. PAKIKO
    November 9, 2016

    I know every thing growing fast than other just to find an alternative.

  22. jessepkm
    July 8, 2017

    I believe that hardly costs may represent problems size of benefits that can be obtained, soon someone will look this with your eyes certain.

  23. etooner
    July 11, 2017

    Hi, thank you for your great article, I have been reading about GaN devolopment for while now, but this blog bring new education to me. GaN is a promising magnetic semiconductors with same i realize this can be injurious to health and safety, i read report published by some Safety institute wherein they claim that GaN dust can be irritant to skin or lungs.

  24. Steve Taranovich
    July 20, 2017

    @etooner—please share your source of infomation with us regarding GaN dust and health/safety

  25. TimTonne
    January 8, 2018

    Thanks for your great message, this post was posted in 2017 but still very useful today, you are the expert!

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