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GaN LEDs set record for highest luminous efficacy

Posted: 15 Aug 2011 ?? ?Print Version ?Bookmark and Share

Keywords:solid-state lighting? luminous efficacy? GaN-on-Si?

Lumen per Watt (Lm/W) values for Gallium Nitride on Silicon (GaN-on-Si) has reached a new high, according to Bridgelux Inc. Using its proprietary buffer layer technology, the company has demonstrated growth of GaN layers on silicon wafers in room temperature, without exhibiting any crack. The performance of the LEDs is comparable to today's modern sapphire-based LEDs with cool white LEDs showing efficiencies as high as 160Lm/W at a color correlated temperature (CCT) of 4350K, Bridgelux noted. Warm white LEDs built from GaN-on-Si chips showed 125Lm/W at a CCT of 2940K and CRI of 80.

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. Growing GaN on larger, low-cost silicon wafers that are compatible with modern semiconductor manufacturing can deliver a 75 percent improvement in cost over current approaches, the company stated.

"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)," said Steve Lester, Bridgelux CTO. "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."

Encapsulated 1.5mm blue LEDs emit 591mW with wall plug efficiencies as high as 59 percent at 350mA, exceeding any published values. The LEDs have very low forward voltages, 2.85V at 350mA, making them ideal at high current densities, Bridgelux said. At a drive current of one ampere, the LEDs emitted 1.52W of blue power at a forward voltage of 3.21V, resulting in a wall plug efficiency of 47 percent. Wavelength uniformity of sigma 6.8nm has been demonstrated for eight-inch LED wafers with median wavelength of 455nm.

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