Native red InGaN LEDs on silicon for microLED displays

11-12-2019 | Plessey | Lighting Technologies

Plessey has successfully developed what is claimed to be a world’s first GaN on Silicon-based Red LED.

While InGaN-based Blue and Green LEDs are commercially available, Red LEDs are generally based on AlInGaP material, or colour converted Red. For AR, delivering high-efficiency ultra-fine pitch Red pixels (<5µm) remains elusive because of severe edge effects from AlInGaP material and cavity losses of the colour conversion processes.

InGaN-based Red is attractive as it provides lower manufacturing costs, scalability to larger 200mm or 300mm wafers and better hot/cold factor over incumbent AlInGaP-based Red. Nonetheless, producing red spectral emission with InGaN material is challenging because of the high indium content causing significant strain in the active region, consequently decreasing crystal quality and creating many defects. The company has overcome these difficulties by utilising a proprietary strain engineered active region to produce an efficient InGaN Red LED.

The company's InGaN Red microLEDs provide a wavelength of 630nm at 10A/cm2, full width at half maximum of 50nm, hot/cold factor over 90% and higher efficiencies above conventional AlInGaP and colour converted Red at ultra-fine pixel pitches. With this result, the company now can manufacture native Blue, Green and Red InGaN material or tune wavelengths from 400-650nm using its GaN on Silicon platform.

Dr Wei Sin Tan, director of Epitaxy and Advanced Product Development, at Plessey, said: “This is an exciting result as it creates a path towards low-cost manufacturing of ultra-fine pitch and efficient Red InGaN pixels, which will accelerate the adoption of microLEDs in both AR microdisplays and mobile/large display applications. Our innovative solutions have once again proven Plessey’s position as the world leader in microLED technology.”

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