Cheaper, brighter LEDs are on the horizon

Cheaper, high-brightness LEDs are promised using a technique being developed by Plessey in Britain following its takeover of University of Cambridge spin-off company CamGaN Ltd.

Gallium nitride (GaN) is at the heart of the new technology and will allow Plessey to exploit synergies with its 6″ processing facility in Plymouth to produce HB LEDs based on CamGaN’s own 6″ GaN-on-silicon technology.

Growing thin HM LEDs on standard, easily available silicon substrate is now possible, leading to a cheaper product. At present, silicon carbide or sapphire substrates are used, which are both expensive and difficult to work.

Plessey believes that the GaN-on-silicon could be about 80% cheaper than LEDs grown on SiC or sapphire because it reduces scrap rates, minimises batch time and allows the use of automated semiconductor processing equipment.

At the same time as these savings, outputs from the LEDs are likely to be more than 250 lumens a watt.

According to the company, the biggest technical challenge preventing the commercialisation of HB LEDs grown on large area silicon substrates has been the large lattice mismatch between GaN and silicon. Overcoming this difficulty is what has produced this latest development.

Plessey’s first samples of a blue LED are characterised by a peak emission at 460 nm. This technology extends to other wavelengths such as cyan and green. Being able to achieve such high brightness at the blue end of the spectrum enables phosphors to be used to produce white light with a balanced spectrum of light emission that is better for the human eye. White outputs of 150 lumens are planned for later this year.