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To: John Finley who wrote (104)	12/7/1999 10:46:00 PM
From: kinkblot	of 565

I'm wondering about GaN substrates because of Nakamura. He's going that route, after a fashion. Since he's the guy who found the holy grail, the enabling technology, whatever he does is worth paying attention to. ttec.org This is something called Int'l Tech Research Institute, Tech Transfer Division. ? Judging by the sponsors, our tax dollars are once again at work. <g> see: Site Report ---> Nichia Chemical (6/98) In the section GaN Blue Laser Diodes, they give a slightly different description of ELOG: A key development in obtaining reliable CW laser performance has been defect reduction by using an epitaxial lateral overgrowth GaN (ELOG) substrate. In this technique a silicon dioxide mask is propagated by block dislocation, and a "defect free" film is achieved in the laterally overgrown region. After 100 microns of growth, a fully coalesced GaN thin film is achieved, and a proprietary process removes the sapphire substrate. see: Panel Presentation ---> Status of Japan and U.S. GaN Materials Tech (12/98) About 10 slides in is a cartoon of the overgrowth technique, showing that defects are blocked by a silicon dioxide layer. This is a lot like what Kopin does (used to do) with their CLEFT and ISE techniques. I thought they might be using a selective etching technique to release the 100 micron layer. I'm not so sure the EETimes article has it right about the polishing; maybe they just polish after cleaving? The slide "Size of GaN Technology Effort in Japan" shows what we're up against. Some of the other Presentations are also worth looking at, though they're about a year old now. WT

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