MicroLED displays are screens built from tiny versions of the same sort of gallium nitride chips you find in LED lights. They promise double or triple the power efficiency of today’s OLED and LCD screens and brightness that is orders of magnitude better. So, it’s no surprise that both a crowd of startups and at least one gargantuan gadget-maker are all racing toward making the first commercial screens.
Most startups have chosen to develop so-called monolithic displays, which build the display as a single chip or two chips bonded together. It’s potentially a shorter route to success, but it’s likely going to be useful only for very small screens such as those needed for augmented reality gear.Apple, with its deeper pockets and early start, is going for a technological high-dive with a higher degree of difficulty. Its formulation could be used for smart watches and ultimately even larger formats. One startup thinks it can match or maybe beat Apple to the ultimate prize: a microLED smartphone screen.
Such a smartphone would last at least two days without a recharge if today’s usage patterns hold up, says Reza Chaji, CEO of Waterloo, Ont.-based startup VueReal. But at UHD resolution, smartphones are the most demanding application for microLEDs, he says. Success with a smartphone, though, would be a “New York, New York” kind of moment. If you make a microLED smartphone work, you can make a larger screen of any size with the same or even less difficulty. And that’s why all of VueReal’s efforts are focused on the smartphone, says Chaji.
Unlike in monolithic displays, the pixels in the screens VueReal and Apple are chasing are made up of individual LED chips. And that leads to three big manufacturing problems. First, LEDs are fantastically efficient at the size used in lighting, but shrinking them down to micrometer-scale saps their efficiency. LEDs have border areas that leak current that could otherwise go to making light. As the chips get smaller, the ratio of border to light-emitter gets closer to 1:1 and efficiency sinks like a pair of lead swim trunks.
Second, displays are unforgiving of errors. A yield of 99 percent might sound good, but it’s belly-flop-on-national-TV bad in displays. For UHD resolution, it would mean as many as 250,000 dead pixels, which is something you’d definitely notice.
And finally, there’s the question of how you get 20 million individual LEDs into their respective spots on a screen in something less than several weeks’ time.According to Chaji, VueReal has solved all three problems. But it’s the last that’s perhaps most crucial and the one that offers the most contrast to what observers assume Apple is doing. Though Apple won’t talk about its microLED display manufacturing technology, those who have examined the company’s patents believe it is working on a sort of rapid “pick-and-place” mass transfer technology, where LEDs are delivered from a batch and individually put in place on a substrate.
Chaji won’t reveal how VueReal’s technology, called solid printing, works, but says “it enables us to do a lot of parallel transfer into a display, and it could populate a TV in less than 10 minutes.” He says it is more like photocopying or document printing than a pick-and-place. Those using pick-and-place “might be ahead of us because they started sooner, but in the long term I think our solution will surpass pick and place,” says Chaji.The company plans to be ready for full production in 2021, when it will be able to supply technology, equipment, and materials to partners.