Kyma aims to plug 'green gap' in DoE project
Scientists at Rensselaer Polytechnic Institute (RPI) will develop high-brightness LEDs based on native GaN substrates from materials company Kyma Technologies in a bid to plug the so-called green gap .
While highly-efficient blue and red emitters based on GaN or AlInGaP are routinely made using sapphire, SiC or GaAs substrates, the development of green emitters has not been quite so successful.
Now, under the US Department of Energy's solid-state lighting core technologies program, RPI and Kyma will work together to produce improved materials and develop better processes that should lead to higher-performance green emitters.
The improvement should result from use of Kyma's low-defect-density native GaN substrates. Both polar and cutting-edge non-polar materials will feature in the development program.
Because they do not suffer from electric fields in the crystal lattice that can degrade device performance, non-polar LEDs should have much better performance characteristics than the conventional polar GaN devices that are the mainstay of today's high-brightness LED industry.
However, initial results with devices grown on r-plane sapphire substrates have suffered from relatively low power output that is thought to result from high defect densities in the crystal lattice.
"Use of Kyma's native GaN substrates should enable reduction of such defects by a factor of over ten thousand compared with such non-native approaches," claims the Raleigh, NC, company.
Kyma CTO and co-founder Drew Hanser will work closely with Christian Wetzel and Fred Schubert from RPI's Future Chips Constellation on the new program. They will focus on developing improved, commercially-viable green emitters that should help to fulfill the promise of solid-state lighting for general lighting applications.
• Kyma is also working with the Air Force Research Laboratory (AFRL) under a cooperative research and development agreement (CRADA), aiming to improve the reliability of GaN-based transistors through the use of native nitride substrates.
John Blevins at AFRL and Kyma's Drew Hanser are leading the three-year effort, which will focus on characterization techniques such as X-ray and Hall analysis, among others.
Field-effect transistors grown on GaN substrates will be characterized all the way through to high-frequency reliability testing as part of the effort.