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The Sprout of a GaN Trend?

by Eric Higham | 4月 29, 2014

I have to admit that I am more of a summer person. When April comes around, I am reminded of how much I love April! Things begin growing again in the Northeast, the dreariness of winter starts to recede  and the possibilities seem endless.

 As the buds begin to sprout, so do the latest developments in the world of compound semiconductors. We still have the ongoing battle between GaAs and silicon, but let’s focus on GaN activity. As I have reported, GaN has finally caught on in commercial RF markets, with CATV applications leading the way. Wireless base station applications follow closely, even though it still is a bit challenging to find much volume production. We are even starting to see the buds of GaN usage in VSAT and point-to-point backhaul applications poking through the soil.

Of course, the big commercial application for GaN devices is the LED market, variously estimated in the $14 - $15B range. This market, characterized by high volume and price sensitivity was the obvious choice to drive the adoption of GaN-on-silicon technology. The argument is that the large diameter wafers, coupled with the existing infrastructure of high volume processing equipment make silicon substrates the best choice for cost. The technology is not without issues but challenges that include lattice and thermal mismatches have gotten the scrutiny of researchers, resulting in great strides in process and device development. Despite the large available market and substantial infrastructure advantages, the switch to silicon substrates is happening very slowly. Recently published reports, even the wildly optimistic ones indicate that more than 90% of LEDs will be manufactured with a GaN-on-sapphire process through the end of the decade.

Interestingly, a recent development in the RF market may signify the start of a trend toward GaN-on-silicon in that segment. M/A-COM Technology Solutions has been actively developing GaN products. They have released a family of GaN-on-SiC transistors for radar applications that handle up to 100W of pulsed power in plastic packages. While the plastic packaging adds an interesting dimension to future developments, it is a recent announcement that helps identify a potentially disruptive trend.

In the beginning of April, M/A-COM Tech and epitaxial substrate giant, IQE announced a license and supply agreement that will enable IQE to use M/A-COM’s technology to manufacture GaN-on-Si epitaxial wafers at 4-, 6- and 8-inch diameters. M/A-COM’s “technology” is the patent-protected IP portfolio of recently acquired GaN-on-silicon RF device manufacturer Nitronex. Speaking with their technologists, they feel the performance concerns about power handling, junction temperature, etc. have more to do with circuit design and issues they have solved in III-V manufacturing than any shortcoming of the GaN-on-silicon process. While solutions to the material and processing challenges mentioned earlier must evolve, they feel the Nitronex work in this area gives them a leg up on the competition.

While they don’t feel there is currently enough volume to support 8” manufacturing, they also feel that is not the right question. In their view, GaN-on-silicon becomes another solution, alongside GaN-on-SiC. Both will have their applications, but M/A-COM believes that the advantages of large diameter silicon will open up many new applications for GaN-on-silicon devices. They believe these applications will extend beyond power devices and this will increase the volume quickly. Their success with this strategy could signal a point of inflection with GaN adoption in general and more specifically GaN-on silicon. I’ll be keeping an eye on these developments, so stay tuned.

-Eric

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