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Ammonothermal Growth of GaN Substrates for LEDs

ARPA-E Award: 
Fremont, CA
Project Term: 
06/06/2012 to 01/31/2016
Project Status: 
Technical Categories: 
Critical Need: 
Gallium nitride (GaN)-based light-emitting diodes (LEDs) have demonstrated much higher efficiencies than traditional lighting technologies. However, adoption into large-scale applications has been inhibited by high costs, which are due in part to the absence of inexpensive native substrates. If highly efficient, low-cost LEDs fabricated on native substrates are deployed widely in both commercial and residential applications, the new substrate and native-substrate-based LED technologies could lead to savings of up to 300 terawatt-hours of electricity per year, roughly equivalent to the output of fifty 1000-megawatt power plants.
Project Innovation + Advantages: 
Soraa's new GaN crystal growth method is adapted from that used to grow quartz crystals, which are very inexpensive and represent the second-largest market for single crystals for electronic applications (after silicon). More extreme conditions are required to grow GaN crystals and therefore a new type of chemical growth chamber was invented that is suitable for large-scale manufacturing. A new process was developed that grows GaN crystals at a rate that is more than double that of current processes. The new technology will enable GaN substrates with best-in-world quality at lowest-in-world prices, which in turn will enable new generations of white LEDs, lasers for full-color displays, and high-performance power electronics.
Potential Impact: 
If successful, Soraa's advanced LEDs would improve the energy efficiency of buildings, substantially reducing greenhouse gas emissions and positioning the U.S. as a leader in the new substrate manufacturing industry.
Improving the energy efficiency of our buildings reduces pressure on the electrical grid, improving its stability.
Energy savings of up to 300 terawatt-hours per year corresponds to about 210 million metric tons of carbon greenhouse gases. In addition, replacing fluorescent lamps with LEDs will reduce environmental mercury exposures.
These applications represent markets of more than $50 billion per year and have the potential to reduce electricity consumption in the United States by 10% or more.
Innovation Update: 
(As of May 2016)
Through two ARPA-E-funded projects – one through OPEN 2009 and a later project through the SWITCHES program, Soraa has built and scaled a growth chamber capable of fabricating GaN wafers at least two inches in diameter. Using its growth method, Soraa has been able to fabricate GaN wafers to produce LEDs at a higher density without a significant decrease in efficiency. The company introduced its first commercial product, MR16 LED lamps, in 2012. Soraa will continue to improve their process to make GaN crystals for power electronics. Ultimately, the team seeks to build a commercial GaN growth facility. 
Semiconductor wafer sizes must continually increase in order to drive down costs. Soraa’s innovations will help the continuous scaling of GaN wafers, which is necessary to enable higher power LEDs and power electronics that will improve U.S. energy efficiency.
During Soraa’s OPEN 2009 project, the team built a six-inch diameter ammonothermal reactor and demonstrated that it could safely grow high-quality GaN crystals at a rate of at least 10 microns per hour. Through its subsequent work under the ARPA-E SWITCHES program, Soraa built a six-inch diameter reactor that is 350x larger than early prototypes. In order to do so, the team had to overcome various technical challenges to the reactor design and process. The resulting reactor design and growth process eliminates leaking, improves temperature uniformity, optimizes internal loading of seeds and polycrystalline raw material, increases heater lifetime, and improves growth uniformity at all locations throughout the capsule. 
For a detailed assessment of the Soraa team's project and impact, please click here.
ARPA-E Program Director: 
Dr. Timothy Heidel
Project Contact: 
Mark D'Evelyn
Release Date: