Technology to grow GaN substrates may lead to cheaper lighting LEDs

April 04, 2013 // By Christoph Hammerschmidt
A new facility for growing Gallium Nitride – the key material needed to make energy-saving light-emitting diodes (LEDs) – has opened at the university of 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. They are normally grown on expensive substrates, which pushes up the price of LED luminaires. The new Gallium Nitride growth reactor at Cambridge will allow researchers to improve a method of growing low-cost LED materials on silicon substrates, reducing their cost by more than 50% and opening them up for more general use.

Researchers are developing colour-tunable LED lighting, which would have the quality of natural sunlight, bringing considerable health benefits to users.The same substrates may be sutiable for power-device fabrication and other areas of electronics where power savings are sought.
The reactor, which is funded by the Engineering and Physical Sciences Research Council (EPSRC), was opened on March 28 by David Willetts, the Minister for Universities and Science. It marks the latest chapter in a decade-long research project to make LEDs the automatic choice 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 developed a successful process, and in 2012 this was picked up semiconductor 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.

LEDs are noted for being a more efficient technology for lighting; gallium nitride LEDs are already 30% energy efficient and 60% efficiency has been achieved in laboratory research.

“At the moment, a 48-watt LED lightbulb, made from GaN on sapphire LEDs, costs about £15,” Humphreys said. “That’s a