Startup Soraa thinks it can make LEDs cheap enough to replace regular bulbs

Soraa, a startup based in Fremont, California, has developed a new type of LED that it says generates 10 times more light from the same quantity of active material used in other LEDs. (Technology Review) The company’s first product is a 12-watt bulb that uses 75 percent less energy than a similarly illuminating 50-watt halogen bulb. Company officials would not disclose the cost of the bulb, but say it will pay for itself in less than one year through energy savings. 

LEDs are usually made by growing a thin layer of gallium nitride on top of a sapphire, silicon carbine, or silicon substrate. Soraa takes a different approach. It uses gallium nitride for the substrate. This reduces a mismatch in the crystal structure between the two layers, which causes the performance of LEDs to diminish as current densities increase. By reducing such mismatches, or “dislocations,” by a factor of 1,000, Soraa officials say they can push 10 times more current through a given area of active layer material. The increase in current density results in a tenfold increase in LED brightness. 

Soraa’s LEDs could prove to be expensive, however. Colin Humphreys, director of research at the University of Cambridge’s Department of Materials Science and Metallurgy, says growing gallium nitride in bulk is difficult and time-consuming.

“I pay about $30 for a six-inch-diameter silicon wafer or a two-inch-diameter sapphire wafer, and about $500 for a one-inch-diameter gallium-nitride wafer,” he says.