Vertical cubic GaN LEDs on 150mm 3C-SiC substrates

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Our research is based on gallium nitride and its alloys, an amazing family of materials which can emit light over a wide range of colours - from the infra-red (IR) to the ultra-violet (UV). Already these materials are widely used in light emitting devices that are part of our everyday lives, perhaps most commonly in blue light emitting diodes (LEDs) and laser diodes (LDs). The LDs are at the heart of the blu-ray HD-DVD player, whilst the blue LEDs are combined with phosphors that emit other colours of light to produce white light. Such white LEDs are now very common in bicycle lights, torches and backlighting for displays on portable electronic devices from mobile phones to tablet computers.However, the efficiency of green LEDs is much lower than that of blue LEDs: this is called the green-gap problem. If we could make green LEDs more efficient we could produce low-cost high quality white light by mixing red, green and blue LEDs, eliminating the need for phosphors. This would make LED lighting even more efficient than it is now and also improve the quality of the light. A key reason green LEDs are less efficient than blue is because there is a much stronger internal electric field inside the green LEDs. However, if we can grow the gallium nitride in a different form, cubic, from the standard form, hexagonal, we can eliminate this internal electric field across the LED, which should greatly increase its efficiency. We have found an exciting new way to do this, by growing the gallium nitride LEDs on a special form of a material called silicon carbide, developed by a small company called Anvil Semiconductors. Together Cambridge, Anvil and Plessey have just completed an innovate UK funded project that has demonstrated many of the key steps to deliver high efficiency, low cost GaN based green LEDs based on cubic GaN, i.e. the growth and processing of cubic-GaN on 150mm diameter SiC on Si substrates. This offers a route to the large scale, low cost manufacture of green LEDs along side Plessey's existing (hexagonal) GaN on Si technology for blue LEDs. This new project will enable the cubic GaN technology to be taken to the next level, allowing the production of the 150mm SiC/Si substrates to be scaled up (Anvil), the quality of the cubic-GaN to be further improved (Cambridge), the cubic-GaN growth process to be transferred to industrial growth machines and a commercial device process to be developed (Plessey). This will bring efficient, low cost green LEDs one step closer, advancing the replacement of incandescent lights and CFLs with solid state lighting. It would also reduce electricity usage, save carbon emissions and generate new manufacturing jobs in UK industry.