A UK consortium had begun work on a £3m Government-funded project to transfer white LED production to cheap silicon wafers.

"The big thing about the project is to reduce the cost," Dr Mike Astles, manager for the project at Qinetiq, told EW. "Most companies doing lighting LEDs are making them on sapphire, routinely on 3in. sapphire. We are planning to take the whole thing up to 6in. silicon which is incredibly cheap."

Working with programme leader Filtronic, which already has a 150mm GaAs wafer fab in the UK, Qinetiq has previously produced GaN amplifiers on silicon for an MoD-funded military project.

"The biggest challenge is trying to put together the two materials which have different lattice constants and different thermal expansion," said Astles. "Our role to control strain. In the amplifier project we used buffer structures to reduce strain and wafer warping to zero."

Although they use similar materials, the blue GaAlN LED die used in white LEDs are less tolerant of imperfect wafers compared with amplifiers. "Light-emitting devices are much more sensitive to defects, and this is where the expertise of Cambridge comes in," said Astles. "The role of Cambridge is to reduce defects."

The third team member, the University of Cambridge, has a world-class GaN and GaAlN LED research group led by Professor Colin Humphries which has a special interest in the defects of light-emitting structures.

Finally, LED packaging specialist Forge Europa completes the consortium.

Initially, Qinetiq and Filtronic will be trying to achieve physically flat 150mm GaN-on-Silicon wafers. "Taking what we know from 4in. up to 6in is going to be a challenge," said Astles.

At the end of the three year project, Qinetiq hopes to be producing 150mm GaN-on-silicon wafers with all the epitaxial layers, suitably defect-low, required for blue LEDs - which Filtronic aims to transfer to its fab.

Does Astles think it can be done? "I am very optimistic as we have a good balanced project team," he said.