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Bookham to Acquire VCSEL Maker, Avalon Photonics |
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Commentary & Perspective...
Foxes Prefer the Lights Be Less BrightMarch 1, 2006...Does the brightness of our compound semi (CS) and solid state lighting (SSL) industries' blue LED indicator lights on computers and on the little black or gray boxes strewn around your home office ever bother you at night? Do you find yourself putting duct tape over them so you don't feel like they're doing something they shouldn't be when they're supposed to be "resting?" Do those intense violet/white LEDs in "modern" decorative and architectural lighting make you feel like a fox caught in an auto's headlights on a country highway? High brightness LEDs have their obvious and very applaudable applications, but what about the softer, more subtle blue and white lights? Who's producing those... and how are they doing it? And who's making a serious attempt at commercializing UV LEDs these days? I really liked the original blue LEDs made in pre-GaN days. I saw them first
in elevators. Nice color. Soft. Subtle. They helped make you patient, which
comes in handy when in an elevator. Everything seems to have gone high intensity
lately (including the business scene), with an emphasis on squeezing as much
of the light out of the die as possible while eliminating most of the profit
on the other end, transferring even more squeeze onto the suppliers. And there
doesn't seem to be nearly as much focus on UV LEDs as I thought there'd be by
this time. Perhaps if there'd been more production of more subtle blue, white
and efficient UV LEDs, the market revenue numbers might still be in double digits.
We'd also have more of those gentle blues and whites warming our nights, and
more UV LEDs fielded into medical, curing, and purification applications. On the occasion of the release of news that their 15mm epi-ready AlN substrates are on the market (ref: March 1, 2006 coverage), I had the pleasure of getting to know The Fox Group better. They're obviously really into aluminum. In addition to their new aluminum nitride (AlN) substrates, which are moving out of their Deer Park, New York doors in the USA, The Fox Group has AlGaN-based emitters in production in their Canadian facility. These are then being packaged in Asia. Seems that, if you want to make your blue spectrum LEDs really bright, you use indium (In) and you grow them, exacting layer by careful layer, in MOCVD reactors. If you want to make them less expensively and grow the die faster... and you're after color consistency rather than brightness, you turn to the method called HVPE. Principals from The Fox Group and Technologies and Devices International Inc. (TDI) in Silver Springs, Maryland USA wrote a paper about the HVPE process, which TDI licenses to The Fox Group, back in Dec. of 2004 for IOP's CS magazine. You can access it online under the title: HVPE offers alternative route to AlGaN-based UV emitters. Note the heavy-hitting author names of: TDI's Vladimir Dmitriev and Alexander Usikov, and Heikki Helava and Barney O'Meara of The Fox Group. While The Fox Group has been putting their R&D team to work for five long years, they only recently came on my radar screen. Typical of teams spread over various physical locations, they've been doing excellent, creative R&D, but they weren't really very proactive... until now. Then again, when you're in R&D mode for longer than you may have originally anticipated, it's not a bad idea to stay "below the radar" until you're actually shipping products. The Fox Group was cofounded by Heikki Helava, who serves now as CTO. Many of you may know Heikki from his years at AXT in the 1990s. He's a great technologist, writer, and cheerleader for all things nitride related. Not only is Fox licensing the LED growth technology from Vladimir Dmitriev's group at TDI, but Fox also has other outstanding Russians on their strategic team who originally hailed from Ioffee Institute. Vladimir was one of the original three group leaders at Ioffee, and his team became Cree's Eastern European division before forming TDI. Note that the names, headed by Yury Alexandrovich Vodakov, are listed on the key USA patents cited in the March 1, 2006 coverage. What I like best about Fox's approach to blue LEDs is that they're not competing with the big guns who are going after the usual SSL holy grails. They're focusing on the not-so-bright blues and are setting their sights towards the mainstream UV-LED applications, using what they feel is a practical, aluminum-based production method. HVPE, as championed for years by TDI, stands for Hydride Vapor Phase Epitaxy. Like MOCVD, it sometimes goes by other names (in the case of MOCVD, "OMVPE" and "MOVPE" are also used). HVPE is sometimes called Chloride Hydride Vapor Phase Epitaxy. It's a mature, low-cost epitaxial technique that uses HCl (hydrogen chloride) gas flowing over hot Group III metals to form metal chlorides. The metal chlorides react with Group V metal hydrides to form III-V compounds. In the case of GaN (gallium nitride) the "metal" hydride is NH3 (ammonia). I'm told HVPE isn't as precisely controllable as MOCVD, but when you're not going for the high brightness, MOCVD isn't all that necessary. What you get with HVPE, according to the experts, is excellent color consistency and color stability. Vladimir gave a presentation of the process at one of our 101 workshops, which is still available on video. The Fox Group's key is in the use of aluminum instead of indium, and according to Fox, aluminum is what gets you to UV's desired wavelengths of 350 to 365nm. I wrote about the UV opportunities in a McD Report last March, titled "Water Water Everywhere" following an inspiring presentation by GE's Michael Sutsko at our Wide Bandgap Business Opportunities Workshop in December at CS Outlook (the precursor to CS Vision, which we'll be holding in April 27/28 2006 in Vancouver BC). I encourage you to re-read Water Water Everywhere where you can learn more about this promising field. And then, like The Fox Group, give me a call and let me know if your team is climbing on the not-so-bright blue and/or the UV LED bandwagon. If you have news or
views to share about the compound semiconductor, LED or solid
state lighting industries |
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