Bridgelux Sets a New Record in Highest Lumen-per-Watt Achieved with GaN-ON-Silicon Technology
Aug 10, 2011 Bridgelux has officially announced an exciting breakthrough result for highest Lumen per Watt values for Gallium Nitride on Silicon (GaN-on-Si). Using its proprietary buffer layer technology, the company has demonstrated growth of crack-free GaN layers on 8-inch silicon wafers, without bowing at room temperature, extending the company’s lead in driving the performance and manufacturability of GaN LEDs on silicon substrate.
Bridgelux is demonstrating LED performance levels comparable to today’s state-of-the-art sapphire-based LEDs. Cool white LEDs showed efficiencies as high as 160 Lm/W at a CCT of 4350K. Warm white LEDs constructed from the GaN on Si chips delivered 125 Lm/W at a color temperature of 2940K and CRI of 80.
Conventional LEDs are made using sapphire or silicon carbide substrates as the starting material. Both are more expensive than silicon. As a result, production costs have inhibited the widespread adoption of LED lighting in homes and commercial buildings. But growing GaN on larger, low-cost silicon wafers that are compatible with modern semiconductor manufacturing can deliver a 75% improvement in cost over current approaches. Bridgelux’s technology process has the potential to significantly drive down the cost of manufacturing LEDs and make them competitive to conventional white lighting technology.
“The performance levels that we announced today are the highest Lm/W values yet published for GaN-on-Si and rival the best commercial LEDs grown on sapphire or silicon carbide (SiC),” stated Dr. Steve Lester, Bridgelux chief technology officer. “These achievements are a direct result of our investment in building a world-class team of Bridgelux materials scientists and chip design engineers with a strong focus on driving industry-leading epitaxial process technology. We are very pleased with the pace of our progress in this area, and we will continue to aggressively develop our GaN-on-Si processes in order to drive the migration of LED commercial production from sapphire to silicon substrates. Our first commercially available GaN-on-Si products remain on schedule for delivery to the market within the next two years.”
The thermal expansion coefficient of GaN is considerably larger than that of silicon. This mismatch can cause the epitaxial films to crack, or the wafers to bow, either during epitaxial growth or at room temperature. Bridgelux’s proprietary buffer layer process produces crack-free wafers that are virtually flat at room temperature.
Encapsulated 1.5mm blue LEDs emit 591mW with wall plug efficiencies as high as 59% at 350mA, exceeding any published values. The LEDs have very low forward voltages, 2.85V at 350mA, making them ideal for use at high current densities. At a drive current of 1 amp the LEDs emitted 1.52 Watts of blue power at a forward voltage of 3.21V, resulting in a wall plug efficiency of 47%. Wavelength uniformity of sigma 6.8nm has been demonstrated for 8-inch LED wafers with median wavelength of 455nm.
“This new technological breakthrough is a direct result of Bridgelux’s continued investment in Research and Development combined with a singular focus on the needs of the solid state lighting market,” said Bill Watkins, Bridgelux CEO. “This key innovation is a game-changer for the industry, delivering dramatic reductions in the up-front capital investment required for solid state lighting and thereby significantly increasing the rate of market adoption. Bridgelux, which maintains an asset-light operating model, is uniquely well-positioned to benefit from the transition to silicon substrates. Leveraging our R&D and Intellectual Property position in LED epitaxy will allow the Company to pursue partnerships with existing semiconductor manufacturers. Leveraging existing semiconductor fabs via partnerships with established semiconductor manufacturers has the potential to favorably impact production costs, margins and returns on invested capital.”
Author: Alice Jones
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