Jan. 30, 2009 A new way of making LEDs could see household lighting bills reduced by up to 75% within five years. Gallium Nitride (GaN), a man-made semiconductor used to make LEDs (light emitting diodes), emits brilliant light but uses very little electricity. Until now high production costs have made GaN lighting too expensive for wide spread use in homes and offices.
However the Cambridge University based Centre for Gallium Nitride has developed a new way of making GaN which could produce LEDs for a tenth of current prices.
GaN, grown in labs on expensive sapphire wafers since the 1990s, can now be grown on silicon wafers. This lower cost method could mean cheap mass produced LEDs become widely available for lighting homes and offices in the next five years.
Based on current results, GaN LED lights in every home and office could cut the proportion of UK electricity used for lights from 20% to 5%. That means we could close or not need to replace eight power stations.
A GaN LED can burn for 100,000 hours so, on average, it only needs replacing after 60 years. And, unlike currently available energy-saving bulbs GaN LEDs do not contain mercury so disposal is less damaging to the environment. GaN LEDs also have the advantage of turning on instantly and being dimmable.
Professor Colin Humphreys, lead scientist on the project said: “This could well be the holy grail in terms of providing our lighting needs for the future. We are very close to achieving highly efficient, low cost white LEDs that can take the place of both traditional and currently available low energy light bulbs. That won’t just be good news for the environment. It will also benefit consumers by cutting their electricity bills.”
GaN LEDs, used to illuminate landmarks like Buckingham Palace and the Severn Bridge, are also appearing in camera flashes, mobile phones, torches, bicycle lights and interior bus, train and plane lighting.
Parallel research is also being carried out into how GaN lights could mimic sunlight to help 3m people in the UK with Seasonal Affective Disorder (SAD).
Ultraviolet rays made from GaN lighting could also aid water purification and disease control in developing countries, identify the spread of cancer tumours and help fight hospital ‘super bugs’.
Funding was provided by the Engineering and Physical Sciences Research Council (EPSRC).
About GaN LEDs
A light-emitting diode (LED) is a semiconductor diode that emits light when charged with electricity. LEDs are used for display and lighting in a whole range of electrical and electronic products. Although GaN was first produced over 30 years ago, it is only in the last ten years that GaN lighting has started to enter real-world applications. Currently, the brilliant light produced by GaN LEDs is blue or green in colour. A phosphor coating is applied to the LED to transform this into a more practical white light.
GaN LEDs are currently grown on 2-inch sapphire. Manufacturers can get 9 times as many LEDs on a 6-inch silicon wafer than on a 2-inch sapphire wafer. In addition, edge effects are less, so the number of good LEDs is about 10 times higher. The processing costs for a 2-inch wafer are essentially the same as for a 6-inch wafer. A 6-inch silicon wafer is much cheaper to produce than a 2-inch sapphire wafer. Together these factors result in a cost reduction of about a factor of 10.
Possible Future Applications
- Cancer surgery. Currently, it is very difficult to detect exactly where a tumour ends. As a result, patients undergoing cancer surgery have to be kept under anaesthetic while cells are taken away for laboratory tests to see whether or not they are healthy. This may need to happen several times during an operation, prolonging the procedure extensively. But in the future, patients could be given harmless drugs that attach themselves to cancer cells, which can be distinguished when a blue GaN LED is shone on them. The tumour’s edge will be revealed, quickly and unmistakably, to the surgeon.
- Water purification. GaN may revolutionise drinking water provision in developing countries. If aluminium is added to GaN then deep ultra-violet light can be produced and this kills all viruses and bacteria, so fitting such a GaN LED to the inside of a water pipe will instantly eradicate diseases, as well as killing mosquito larvae and other harmful organisms.
- Hospital-acquired infections. Shining a ultra-violet GaN torch beam could kill viruses and bacteria, boosting the fight against MRSA and C Difficile. Simply shining a GaN torch at a hospital wall or trolley, for example, could kill any ‘superbugs’ lurking there.
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The above story is based on materials provided by Engineering and Physical Sciences Research Council (EPSRC).
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