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24 August 2006


SSL Program awards $1.8m to boost green LEDs

Under the US Department of Energy’s Solid State Lighting Core Technologies Program, $1.8m has been awarded to a team of researchers led by professors Christian Wetzel and E. Fred Schubert of Rensselaer Polytechnic Institute’s Future Chips Constellation for the three-year project “High Performance Green LEDs by Homoepitaxial MOVPE” (one of 16 projects chosen for funding in March’s Funding Opportunity Announcement, but starting in August).  

The team plans to develop improved III-nitride materials and processes to boost green LEDs efficiencies by a factor of 2-3, to fill the ‘green gap’ in white solid-state lighting sources combining red, green and blue LEDs. The subcontract partners are Kyma Technologies Inc of Raleigh, NC, USA, which makes bulk GaN-based substrates and epiwafers (with Dr Drew Hanser, co-founder and chief technology officer, as principal investigator) and Crystal IS Inc, which developes bulk AlN substrates.

Kyma says that key materials improvements are expected to arise from the use of its low-defect-density native GaN substrates. Such materials and process improvements must be realized to fully capitalize on solid-state lighting, generally considered to be the largest nitride device market opportunity.  According to Strategies Unlimited, the commercial market for nitride devices should grow from $3.2bn in 2004 to $7.2bn in 2009. The SSL program targets the development, by 2025, of advanced solid-state lighting technologies that, compared to conventional lighting technologies, are much more energy efficient, longer lasting, and cost competitive, aiming for a product system efficiency of 50% with lighting that accurately reproduces sunlight spectrum."

Under the program, Kyma will continue to develop their patented native crystalline GaN materials manufacturing technology and will also provide both polar and non-polar native GaN substrates to the Rensselaer researchers for epitaxial growth, device fabrication and device performance testing. The addition of native non-polar GaN substrates to Kyma’s product line was announced earlier this year and represents the highest-quality non-polar GaN commercially available, claims Kyma.

Kyma says that nitride materials and devices experts, including University of Cailfornia Santa Barbara professor Shuji Nakamura, have touted the potential of non-polar GaN to enable LED performance improvements, but the efficiency of initial devices made from non-polar GaN-based materials has been limited by defects resulting from a non-native fabrication approach. Use of Kyma’s native GaN substrates should enable reduction of such defects by a factor of over 10,000 compared to non-native approaches, claims Kyma.

“While much progress has been made in developing blue and green LEDs on sapphire and silicon carbide substrates, much more progress is required, especially in the green, before nitride LEDs can begin to realize their full commercialization potential,” says Hanser. “We believe that Kyma’s native GaN substrates have the potential to enable the development of green LEDs with the kind of price point and operating characteristics that fulfill the promise of solid-state lighting for general illumination.”

Visit Rensselaer: http://www.rpi.edu

Visit U.S. Department of Energy: http://www.netl.doe.gov/ssl

Visit Kyma: http://www.kymatech.com

Visit Crystal IS: http://www.crystal-is.com