LED lighting has long been viewed as a superior alternative to compact flourescent bulbs. Although flourescents are more electrically efficient than old-fashioned incandescent bulbs, producing them requires a complex procedure that uses a little mercury—a big environmental and health no-no. Indeed many are questioning whether CFLs are actually an environmentally-friendly choice at all.
So why aren't we using LEDs in our homes already? The problem is that CFLs are still cheaper to manufacture than LEDs. But now scientists at Cambridge University haved invented a process that promises to make the lighting technology even more energy efficient and cheaper to produce.
The new manufacturing process is identical to commercially-used systems for making other chips, which is why the cost is phenomenally low. In fact a 15cm wafer will cost around $15, and can fit in 150,000 GaN LEDs: making the core component of the device (before it gets wrapped in the familiar plastic bubble, and given conducting connections) a mere $0.0001.
LEDs are little slices of layered semiconductor, carefully arranged so that electrical current flowing through them excites the material into producing light. They work instantly, requiring no warm-up, they're small, easy to manufacture, and are very efficient at turning electrical power into light without generating waste heat.
Current gallium nitride (GaN) LEDs are limited however by the complexity and cost of manufacturing them. Unlike other semiconductor devices, they can't be fabricated on silicon—after being deposited in layers the GaN physically contracts twice as fast at the silicon base, leading to deformed and cracked devices that won't work. Current solutions to this problem involve growing GaN LEDs on saphhire, which has the same rate of shrinkage after the 1000ºC manufacturing process. But, of course, including sapphire in the devices pushes their cost much higher.
The Cambridge team worked out that by incorporating thin layers of another material—aluminum gallium nitride—into the structure of GaN LEDs, the resulting devices can tolerate the shrinkage and still work as light sources.
This will certainly ring the death knell of the compact fluorescent light bulb that's just recently arrived—and that governments are aggressively pushing as an environmentally friendly solution.
In contrast LEDs are easier to make, potentially more electrically efficient, smaller—and thus more design-customizable—and last up to 10 times longer than CFLs. The new invention means we'll see them lighting our homes and offices before you know it (the image is of the Clifton Suspension Bridge in the U.K., which is lit by white GaN LEDs already.) Doing so will apparently drop the amount of electrical energy needed nationally for lighting from 20% to 5%.
[via New Scientist, Physorg]