Plessey’s pins future on micro-LED displays, and gears up for production
- Release on:2019-04-05
“The business strategy is 100% micro-LED applications: augmented reality, virtual reality, smart watches and large panel outdoor displays,” Plessey president of business development Mike Lee told Electronics Weekly. “Right now, we are in the middle of raising up to $30m. This is an investable space – micro-leds are hot and it’s here in the UK – people are interested.”
Augmented reality glasses in particular, put unique demands on the internal display technology, and Plessey claims to be in a unique position to meet those demands.
The challenge is display intensity: if AR glasses are to be used outdoors, the internal micro-display has to be very bright to compete with ambient light – without excessive bulk, heat or power consumption.
Combining its GaN-on-silicon LED process and chip-making history, the firm can wafer-bond a high-resolution micro-LED display matrix to a CMOS active backplane to create an emissive monolithic display that is far brighter than OLED micro-displays – the other emissive technology vying for a place in AR glasses. The other two possible technologies – DMD (digital micro-mirror) and LCoS (liquid crystal-on-silicon) – are both reflective, adding the bulk of a light source and its optics.
Gearing up for production in under way in Plymouth, according to Lee, with millions of pounds already spent on new equipment. It’s long-awaited third MOCVD reactor – for growing the interface layers and quantum wells needed to build GaN leds on silicon wafers – has been installed .
“Number three is commissioned and going now. It’s robotics based – a full production tool. Reactors one and two are more manual,” he said, adding: “We are pricing MOCVD reactors four and five.”
What happened to the lighting LEDs?
Plessey always argued that its GaN-on-Si process would be cheaper for making lighting-class LEDs compared with the incumbent GaN-on-sapphire process.
And it is, according to Lee, Plessey’s LED die were cheaper to make, but “the problem with power LEDs is that every man and his dog have set up GaN-on-sapphire LED lines and they are quickly becoming commodity”.
Added to this, ‘mid-power’ LEDs are increasingly popular in lighting applications and, according to Lee, 80% of the cost of a mid-power is packaging, so the advantage of a lower-cost die is largely lost.
Native green mico-LEDs
Plessey’s big announcement this week is the development of native green-emitting micro-LEDs – as opposed to the less efficient combination of blue-emitting quantum wells and a blue-to-green quantum dot phosphor.
On the firm’s roadmap is a single micro-display combining native blue and green quantum wells with a phosphor converted red, but before then it is working towards a colour micro-display using three separate die for red, green and blue.
Won’t that be expensive and bulky?
“Right now, it is not the price that is important, but the application. Three panels faster to market than one panel RGB,” said Lee. “The whole market is held back by lack of suitable display. [With incumbent displays] you either have a big battery, or have AR you can’t see out of doors.”
As for size, according to Lee three 1080 displays and the image combining prism will fit inside a cube 4-5mm across.
And a schedule?
“We are testing proof-of-concept and prototypes this year,” said Lee. “Next year, OEMs are taking product to market.”