Are microLEDs the next big (small) thing?

By Philip Ling   |   March 31, 2022   |   Provided By Avnet Silica

The potential of microLEDs goes far beyond smaller indicators and flashing lights.

Light-emitting diode technology is versatile, but microLEDs have really changed the way we look at it. As the name suggests, microLEDs are tiny versions of the regular LEDs engineers use in embedded systems.

Size may be key to their identity, but their potential goes far beyond making smaller indicators and flashing lights. The main application areas for microLEDs are displays of various shapes and sizes, from the very small to the very big.

Avnet spoke with Ron Mertens, CEO and Founder of Micro-LED-Info, a website dedicated to microLED technology, to find out more.

Is a microLED essentially still just a P-N junction diode made to emit photons, like a regular LED, but just a lot smaller?

Mertens: Yes, basically this is correct. The microLED die itself is a tiny LED chip. There’s no real standard, but we consider LEDs smaller than 100 um in size (length, we assume square chips) to be microLEDs. Note that there are also mini-LEDs, used mainly in LCD display backlighting, which are 200 um in size and smaller (i.e. 100 to 200 um).

Just how small are we talking about here?

Mertens: Anything below 100 um is considered to be a microLED. The actual chip size will depend on the application, display type and performance – and in microdisplays we are seeing chip sizes of 5 um or even smaller.

You used the term “microdisplay” in reference to microLEDs. What exactly does that mean?

Mertens: A microdisplay is defined as a very small display used for near-eye applications (i.e. not direct view). These displays are usually under 1-inch in size, with high performance (in terms of resolution, brightness, refresh rates). Microdisplays are produced today using several technologies (LCDs, OLEDs and more) and microdisplays can also be powered by microLEDs.

Do you think microLED microdisplays will displace existing technology or create its own application area?

Mertens: The main advantages of microLEDs are increased brightness and higher power efficiency compared to OLED or LCD-based displays. In microdisplays these parameters are very important, especially for outdoor applications. This could help create a potential market for microLED microdisplays. We do not yet see new application areas for microLED microdisplays, but it is too early to tell.

When do you think microLED microdisplays will go mainstream?

Mertens: It will likely take quite a bit of time. We already see some simple monochrome devices on the market, but the path toward high-performance full-color and cost-effective microLED microdisplays is not clear yet.

What substrate materials are best for making microLED microdisplays?

Mertens: They are produced directly on a silicon substrate and a silicon backplane.

Given that they are so small, is there anything special or challenging about the manufacturing process?

Mertens: The small size of microLED chips creates many challenges. For example, as chip size drops, so does the efficiency of the LEDs, because of side-wall defects and other issues (this is true for most microLED chips, but not all). Another issue is the need to transfer the chips from the LED epiwafer to the final display substrate – what we refer to as a transfer process. Considering that most microLED microdisplays could comprise tens of millions of individual LED chips, doing this quickly and reliably is a huge challenge.

Transfer process

Developing an efficient transfer process for microLED chips is crucial to the technology’s success (Source: Micro-LED-Info)

Is this like MEMS technology? Will we see microprocessors, memory and communication interfaces being integrated on the same chip as micro-LEDs?

Mertens: I am not an expert on MEMS or wafer integration technology, but generally speaking the display industry is evolving, and such systems could perhaps indeed be developed.

Conclusion

MicroLED is an exciting display technology, one that has attracted billions of R&D dollars in recent years, from display makers and application makers, led by Apple and others. The technology is not ready for mass adoption yet, as the industry has to solve many of the challenges, including mass transfer, efficiency, costs and more. For microdisplays, however, the technology is relatively mature, and the market potential exists. We could soon see more such displays in production and hopefully the beginning of mass adoption by 2025 and onward. To read more about microLED technology, visit www.microled-info.com

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Philip Ling

Philip Ling is a senior technology writer with Avnet. He holds a post-graduate diploma in Advanced M...

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