Soraa Inc of Fremont, CA, USA, which develops solid-state lighting technology built on 'GaN on GaN' (gallium nitride on gallium nitride) substrates, has been selected by the US Department of Energy's (DOE) Advanced Research Projects Agency-Energy (ARPA-E) to lead a project on the development of bulk gallium nitride (GaN) substrates.
Currently, this is the only ARPA-E funded LED substrate project, says Soraa. Specifically, Soraa will continue development of ammonothermal technology for bulk GaN substrates.
Soraa says that such an advance in a commercially viable new substrate technology promises higher efficiency and performance. GaN-on-GaN LEDs are of interest because they have demonstrated much higher performance than traditional lighting technologies and hence offer the potential for major energy savings.
Most white, blue and green LEDs are made by depositing GaN on non-native substrates, typically sapphire or silicon carbide (SiC). In contrast, Soraa claims to be the only LED maker shipping products based on GaN-on-GaN LEDs. To date, the adoption of native-substrate GaN-on-GaN technology for large-scale applications has been inhibited by high costs due partly to the absence of inexpensive native GaN substrates. Soraa reckons that creating a US-made solution to the challenges of bulk GaN production will benefit the firm, the LED industry, and the US consumer with more energy-efficient, less expensive and more readily available components.
LEDs lend themselves well to the new substrate because it greatly enhances performance - in terms of the quality of light - in addition to benefiting energy efficiency. Because of innate physical properties of the compound, GaN-on-GaN LEDs can withstand higher power densities than diodes made with other substrates, leading to a much brighter diode and allowing the use of just one LED light emitter per lamp. Other substrates necessitates the use of three, four or more LEDs to achieve the same brightness, claims Soraa. Multiple sources of light within a lamp produce fuzzy shadows instead of the crisp light required of an MR-16 lamp for best use in commercial, museum or high-end consumer applications. The MR-16 bulb represents Soraa's first commercially available product.
ARPA-E, which invests exclusively in transformational energy technologies, began funding Soraa as a consortium member for the project in 2011. ARPA-E's recent decision to make the firm the lead organization on the project means that Soraa will become the prime contractor working with ARPA-E to commercialize GaN substrate technology. The firm says that applications for GaN substrates have the potential to reduce US energy consumption by over 30%. These applications represent potential markets (including laser diodes and power electronics) of more than $50bn annually, according a DOE study.
"Soraa's system design and capabilities represent a breakthrough path toward the development of high-quality, low-cost GaN substrates," says ARPA-E program director Mark Johnson, who adds that the project is supporting Soraa's process development, crystal quality improvements, and device characterization.
"DOE's recognition and support of this transformational technology is expected to accelerate a more energy-efficient, higher-performing US-based technology for LEDs and a host of additional applications," comments Mark D'Evelyn, Soraa's principal investigator on the project.
"This level of funding, combined with the vote of confidence from the Department of Energy, is a significant step forward to a future of lighting technology based on large-area, high-quality, low-cost GaN substrates," reckons the firm's chief technology officer Mike Krames.
