TECHNOLOGY I MICRO LEDs MicroLEDs are promising candidates for use in next-generation displays. The red, green and blue microLEDs shown here have dimensions from 20 µm by 20 µm to 100 µm by 100 µm
Enabling high-efficiency microLEDs Sidewall treatments empower microLEDs with size-independent efficiency BY MATTHEW WONG, JAMES SPECK, SHUJI NAKAMURA AND STEVEN DENBAARS FROM THE UNIVERSITY OF CALIFORNIA, SANTA BARBARA THE COMMERCIALIZATION of smartphones and portable electronics has piqued academic and industrial interest in developing better display technologies. It’s a sector that is moving fast, progressing from cathode-ray tubes to liquid crystal displays (LCDs) and more recently organic LEDs (OLEDs), with latter already employed extensively in wearables. However, emerging display applications – namely near-eye displays for virtual-reality, augmented-reality and head-up displays – are demanding even better display performances, such as a superior colour gamut and a greater resolution. Efforts at fulfilling these requirements are driving the rapid development of new display technologies. Among the various candidates for next-generation displays, microLEDs are the most promising, offering a variety of benefits that include a high brightness, 42 ISSUE VIII 2021
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a long operating lifetime, excellent stability and outstanding efficiency characteristics. While there is no official cut-off for the device dimensions of the microLED, with some use the term ‘miniLEDs’ to refer to bigger microLED, it is reasonable to assume that the dimensions of this device are less than 100 μm. The actual value matters a great deal, as it determines the display resolution and the manufacturing cost. To produce a full-colour display, designers tend to employ red, green, and blue colours that match mankind’s visual receptors. So when making a display, designers want to employ microLEDs with these three emission wavelengths. The emitting chips are made from either the InGaN or AlGaInP families of materials. Although InGaN-based LEDs are capable of spanning the entire visible spectrum, red InGaN LEDs are currently limited to the active research stage
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