Cheap, super-efficient LEDs

''Gallium nitride (GaN) LEDs have many advantages over compact fluorescent lamps (CFLs) and incandescent bulbs. They switch on instantly, with no gradual warm-up, and can burn for an average of 100,000 hours before they need replacing - 10 times as long as fluorescent lamps and some 130 times as long as an incandescent bulb. CFLs also contain small levels of mercury, which makes environmentally-friendly disposal of spent bulbs difficult.
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Now Colin Humphreys's team at the University of Cambridge has discovered a simple solution to the shrinkage problem.

They included layers of aluminium gallium nitride in their LED design. These layers shrink at a much slower rate during cooling and help to counteract the fast-shrinkage of pure gallium nitride. These LEDs can be grown on silicon as so many other electronics components are.
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A 15-centimetre silicon wafer costs just $15 and can accommodate 150,000 LEDs making the cost per unit tiny. That levels the playing field with CFLs, which many people only ever saw as a stopgap solution to the lighting problem.
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