The Cambridge University materials scientist Colin Humphreys is on course to bring down the price of LEDs by growing gallium nitride LEDs on silicon wafers, rather than the far more expensive sapphire.

Humphreys has now overcome the problem of differential thermal expansion between gallium nitride and silicon, according to this article in The Guardian http://www.guardian.co.uk/technology/2009/oct/21/led-lamps-gallium-nitride.

Humphreys has a long-running interest in gallium nitride. The Cambridge Centre for Gallium Nitride http://www.msm.cam.ac.uk/GaN, based in the Department of Materials Science and Metallurgy Cambridge University, UK, which he heads, is one of a small number of places in the world to have gallium nitride growth equipment, alongside advanced electron microscopy and a range of other equipment for characterising and measuring the physical properties of this material. At the heart of the centre is a wafer growth centre for producing Gallium nitride-based materials and devices.

The promise is not only that gallium nitride LEDs will cut lighting bills, but LEDs based on this technology are dimmable and will only need changing once every 60 years.