Gallium nitride has been described as “the most important semiconductor since silicon” and is used in energy-saving LED lighting. A new £1million (or US$1,530,700) growth facility will allow University of Cambridge researchers to further reduce the cost and improve the efficiency of LEDs, with potentially huge cost-saving implications.
A new facility for growing Gallium Nitride – the key material needed to make energy-saving light-emitting diodes (LEDs) – has opened in Cambridge, enabling researchers to expand and accelerate their pioneering work in the field.
Gallium Nitride LEDs are already used in traffic lights, bicycle lights, televisions, computer screens, car headlamps and other devices, but they are too expensive to be used widely in homes and offices. The main reason for this is that they are normally grown on expensive substrates, which pushes up the price of LED lightbulbs. The new Gallium Nitride growth reactor at Cambridge will allow researchers to further improve a method of growing low-cost LEDs on silicon substrates, reducing their cost by more than 50 percent and opening them up for more general use.
In addition, researchers are developing color-tunable LED lighting, which would have the quality of natural sunlight, bringing considerable health benefits to users.
University scientists are also starting to investigate the potential of Gallium Nitride in electronics, which it is thought could have similarly significant energy-saving consequences – perhaps cutting nationwide electricity consumption by a further 9 percent.
The reactor, which is funded by the Engineering and Physical Sciences Research Council (EPSRC), was opened March 28, 2013 by David Willetts MP, the Minister for Universities and Science. It marks the latest chapter in a decade-long research project to make LEDs the go-to technology for lighting, led by Professor Sir Colin Humphreys in the University’s Department of Materials Science and Metallurgy.
In 2003, Humphreys and his team began experimenting with the possibility of growing Gallium Nitride (GaN) on silicon instead of costly sapphire and silicon carbide. After years of painstaking research, they finally developed a successful process, and in 2012 this was picked up by the British manufacturer, Plessey, which has already started to manufacture LEDs at its factory in Plymouth, based on the Cambridge technology. Plessey also hired three of Humphreys’ post-doctoral scientists to help transfer the process. It is the first time that LEDs have been manufactured in the UK.
Minister for Universities and Science David Willetts said: "LEDs are highly energy efficient but expensive to produce, meaning their domestic use is limited. This excellent new facility will enable researchers to look at more cost-efficient ways to produce LEDs, saving money and benefitting the environment. It will also help keep the UK research base at the very forefront of advanced materials, which is one of the eight great technologies."
Making Gallium Nitride LEDs more cost-effective could unlock benefits far beyond energy saving alone. Humphreys is investigating the possibility of “smart lighting” - a system in which LED lights coupled to a sensor would be able to switch themselves on and off, or alter their brightness, relative to a user’s presence or levels of natural daylight in a room.
As their use increases, the beams from LEDs could be used to transmit information, for example from traffic lights to cars.
“It’s conceivable that the two could be developed to talk to one another,” Humphreys said. “Traffic reports, such as information about a road accident, could be sent to traffic light systems. They could then relay the details to drivers by transmitting it through the headlamps.”
Researchers also believe that LEDs could be used to purify water supplies in the developing world. Deep ultraviolet (UV) radiation kills bacteria and viruses. By putting a ring of ultraviolet LEDs around a water pipe at the point where it enters a home, it might be possible to kill off bacteria in the water as well as other undesirable organisms, such as mosquito larvae.
Further energy-saving with LEDs may also be possible. Humphreys and his team are currently investigating the so-called “green gap” problem which could improve the way in which they make white light. The LEDs currently used to make white light are in fact blue - the color is changed using a phosphor coating. This phosphor is, however, not completely energy efficient, and a better way of making white light could be by mixing blue, red and green LEDs together instead.
This, however, depends on resolving lower efficiency in green light compared with the other two colors. If this can be addressed, and LEDs made the standard for lighting nationwide, then it is estimated that there would be an additional electricity saving of 5 percent - on top of the 10 percent likely to be engendered by switching to LED technology in the first place.
“If we can replicate devices with Gallium Nitride electronics, we believe that we could make them 40 percent more efficient,” he said. “That in itself would translate into a 9 percent electricity saving in the UK, if applied across the board.”
Gallium Nitride (GaN), grown on a silicon substrate, to manufacture light-emitting diodes. The material is critical to making LED lighting, which researchers and the Government agree could cut UK electricity consumption by 10-15 percent.
