NEWS ANALYSIS
weighting in its $27 million SWITCHES program, Strategies for Wide Bandgap, Inexpensive Transistors for Controlling High Efficiency Systems.
And as Timmerman highlights only last month, the Department of Defense opened up solicitations for projects on GaN Technology for GPS L-band space power amplification, as part of its Small Business Innovation Research program. “GaN really has a good fit for our overall research and commercialisation of different products,” he adds.
However, Fairfield Crystal is no stranger to US government interest in crystal growth. Preceding 2010, it had won just over $1 million from the National Science Foundation to develop ZnS, CdS, ZnSe and AlN crystals.
Then come 2010, it received $200,000 from the independent government agency to develop a novel approach, and demonstrate and sample 1-inch diameter free-standing GaN wafers for III-Nitride light emitters and detectors. Three years on, NSF funds run into the millions of dollars with the company working on pilot production of 2-inch GaN.
But what exactly is the novel approach? Timmerman remains tight-lipped; when asked if the process is based on either HVPE or ammonothermal methods, he confirms it is not based on the latter.
“It is the current state of the art. We know some folks are using ammonothermal, Kyma has been using a HVPE process, and others are looking at a combination of the two. But ours is different,” he says. “It’s using a combination of expertise from other crystal growth, be it AlN or ZnO, or even just some of the techniques we’ve gleaned from growing our optical crystals.”
One such technique entails a novel method for growing a ZnO single crystal boule from a ZnO seed within an iridium crucible placed inside an induction-heated physical vapour transport (PVT) furnace system. According to Timmerman, the technique overcomes inadequacies in hydrothermal, CVT and melt growth techniques, but ‘is a distinct technology differing from Fairfield’s GaN technologies’.
The top surface of a GaN single crystal of about 1-inch in diameter produced at Fairfield Crystal; the company has achieved a dislocation density of 1 X 107
cm-2
“However, we have found that having a very very clean source material is a priority [for the GaN process],” he adds. “And we’ve developed an in-house process with high quality source material.
With this in hand, the team now intends to drive GaN substrate costs down by growing longer boules and slicing more wafers per growth run. And of course, a crucial part of the ARPA-E grant, is to grow 3-inch GaN crystals, within the next three years.
“The time frames are very aggressive, especially since in a number of years other organisations have also been trying,” admits Timmerman. “We’re cautious but confident we can get there, although we are not dismissive of the challenges.”
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The team now intends to drive GaN substrate costs down by growing longer boules and slicing more wafers per growth run. And of course, a crucial part of the ARPA-E grant, is to grow 3-inch GaN crystals, within the next three years
January / February 2014
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