Soraa Aims for Better Light Quality with Gallium Nitride Tech

Photo: Soraa

In the LED lighting industry, it’s an all-out race to lower costs and drive adoption. But LED company Soraa is betting that people will also purchase LEDs for the quality of light, as much as for efficiency and long life.

The Fremont, Calif.-based company said it intends to release a set of lamps later this year based on its third-generation LEDs, which use gallium nitride on a gallium nitride substrate. Soraa’s LED technology is different than most. The bulk of LEDs are made with GaN on a substrate of sapphire, while LED company Cree uses a silicon carbide substrate. A number of companies, including Bridgelux, are seeking to lower costs by manufacturing LEDs on larger silicon wafers.

Sapphire and silicon carbide substrates are less expensive and have mature production methods. By contrast, manufacturing on GaN substrates is far more challenging technically. Sorra was co-founded by LED pioneer, Professor Shuji Nakamura, in 2008 to commercialize GaN-on-GaN LEDs. The company began selling its first product, the MR16 lamp, in 2012. 

The advantage of having the same material for the active component and substrate is that there are fewer defects, so the LEDs can withstand high power, says Mike Krames, Soraa's chief technology officer. That translates into a relatively efficient conversion of current to light and good color rendering, he says.

Soraa makes LED lamps designed to replace halogen spot lights, which are often used in places where very good light quality is important, such as retail displays and museums. Light quality is measured by its color rendering index (CRI), or how accurately artificial lights display colors. Incandescent lamps, which include halogens, have a CRI of 100, and bulbs must have a CRI of 80 to meet the EnergyStar rating. Soraa’s lamps have a color rendering index (CRI) of 95.

In an effort to match the quality of halogen lights, Soraa starts with a violet LED and uses three phosphors to create a full spectrum of visible light, and thus a higher color rendering index, Krames says. Producing a wider spectrum of light requires more energy, but because it's an LED, its lights still have a big efficiency advantage over halogens with similar light quality, he says.

“Once people get more familiarity with their options, quality of light will be a bigger deal and a bigger driver of adoption than people believe,” Krames predicts.

Krames worries that consumers could be turned off by LEDs if manufacturers sacrifice light quality. Granted, Soraa’s entire business is centered on producing premium, high-CRI products so he has a clear bias. But light quality has not been the highest priority for LED manufacturers as they seek to replace other forms of lighting.

A report by the Department of Energy’s solid-state lighting program noted that LED prices have dropped dramatically and efficiency has improved over the past four years, but the quality has remained about the same. The majority of the bulbs surveyed by the DOE have a CRI between 80 and 85, which is the typical rating for compact fluorescent lamps.

Instead, LED lighting companies have focused on bringing down price—something they've been successful at. When Philips started selling a 60-watt equivalent LED bulb with omnidirectional light in 2010, it cost almost $40. Last week, Cree cut prices by 23 percent so that a 60-watt equivalent now costs under $10. It also introduced a 100-watt equivalent priced under $20.

Cree designed its bulbs with a vertical “tower” that gives off light from the center of the bulb to mimic the way an incandescent bulb glows. The CRI of its products are about 83, which is good enough for the majority of uses, says Mike Watson, the vice president of product strategy at Cree. “What we really care most about is what consumers see. Having done many demonstrations for consumers in stores, I’m stunned at the number of people who think an LED at 83 CRI is better than an incandescent at 100,” he says.  

New lighting labels require manufacturers to indicate CRI, which could draw more consumer attention to light quality. In addition, California put in place a voluntary specification for LEDs that sets a minimum of 90 CRI. The standard was put in place to avoid a flood of low-quality LEDs, which occurred when compact fluorescent bulbs were introduced, souring many consumers’ opinions on efficient lighting.

Higher quality light does mean a more expensive product, but Krames says there's potential to improve the economics of GaN-on-GaN LEDs. Soraa's third-generation LEDs improve energy efficiency by 30 percent and, since GaN-on-GaN is relatively new, there’s more room for improvement than existing technologies, Krames says.

Premium, high-CRI bulbs are now mainly used by commercial customers, but perhaps consumers will eventually buy in, too. “Once people start to get a taste for higher CRI lamps, they’re not going to want to go back,” says Krames. 

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