LED light bulbs have always promised to be a highly efficient, nontoxic, long-lasting alternative to today's incandescent, CFL or halogen bulbs. However, lighting entire rooms using LEDs has, proved both technically challenging and expensive. As such, LEDs which contain a semiconducting material that lights up when current passes through it, have more commonly been used for low-light applications such as illuminating computer screens.
California-based 2008 start-up, Soraa, claims to have a solution with its new type of LED that it says generates 10 times more light from the same quantity of active material used in other LEDs. The company's first product is a 12-watt bulb that uses 75 percent less energy than a similarly illuminating 50-watt halogen bulb. Details around the cost are sketchy, but those kind of numbers would suggest an payback less than one year through energy savings.
Soraa has however shared some of its innovative technology. Where LEDs are usually made by growing a thin layer of gallium nitride (GaN) on top of a dissimilar substrate of sapphire, silicon carbide or silicon, Soraa also uses gallium nitride for the substrate. This reduces a mismatch in the crystal structure between the two layers, which apparently diminishes the performance of LEDs as current densities increase to. Soraa officials claim that by reducing such mismatches, essentially 'dislocations' within the crystal structure by a factor of 1,000, they can push 10 times more current through a given area of active layer material. The increase in current density results in a ten-fold increase in LED brightness.
GaN is significantly more expensive than either sapphire- or silicon-based materials, with some competitors noting that growing GaN in bulk is difficult and time-consuming. I can't attest to the numbers, but the price of a one-inch diameter gallium-nitride wafer is in the order of $500, whereas a six-inch diameter silicon wafer or a two-inch diameter sapphire wafer goes for approximately $30. Soraa claims that its novel method of fabrication significantly reduces the cost of GaN production, adding that the cost of substrate is only a 'single digit percent' of the total cost of the Soraa bulbs.
Soraa company executives also counter competitor arguments stating that the increased output more than makes up for the added cost, particularly noting that other 50-watt-equivalent LED lights typically combine multiple LEDs in a single bulb. The increased brightness of its new LED design uses a single chip or diode.
Soraa has apparently received more than $100 million in start-up funding, and plans to ship its first bulbs for commercial applications by the end of this quarter.
If you would like to read more, just click on http://www.technologyreview.com/energy/39726/?p1=A1 or visit the Company's website at www.soraa.com.