Optoelectronics

Native Red InGaN LEDs on silicon microLED displays

9th December 2019
Lanna Cooper

Plessey, an embedded technologies developer at the forefront of microLED technology for the Augmented Reality (AR) and display markets, has successfully developed a world’s first GaN on Silicon-based Red LED. Whilst InGaN-based Blue and Green LEDs are commercially available, Red LEDs are typically based on AlInGaP material or colour converted Red.

For AR, achieving high efficiency ultra-fine pitch Red pixels (less than 5µm) remains elusive due to severe edge effects from AlInGaP material and cavity losses from colour conversion processes.

InGaN-based Red is attractive as it offers lower manufacturing costs, scalability to larger 200mm or 300mm wafers and better hot/cold factor over incumbent AlInGaP-based Red.

However, achieving red spectral emission with InGaN material is challenging due to the high indium content inducing significant strain in the active region, subsequently reducing crystal quality and creating numerous defects. Plessey has successfully overcome these challenges by using a proprietary strain engineered active region to create an efficient InGaN Red LED.

Plessey’s InGaN Red microLEDs have a wavelength of 630nm at 10A/cm2, full width at half maximum of 50nm, hot cold factor over 90% and higher efficiencies over conventional AlInGaP and colour converted Red at ultra-fine pixel pitches. With this result, Plessey now has the capability to 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.”

Other recent ground-breaking milestones from Plessey includes the world’s first wafer level bonded monolithic 3,000ppi GaN on Silicon microLED emissive display hybridised to an active-matrix CMOS backplane; as well as native Blue and Green emission layers on the same wafer. Plessey are continuing to rapidly develop microLED display solutions with their roadmap including the production of full RGB microLED displays in 2020.

Plessey will be exhibiting at CES 2020 on #21861, South Hall 1, LVCC. Joining forces with Compound Photonics, a pioneer in compact high resolution microdisplay technologies, to develop the world’s smallest 1080p microLED based near-eye display solution for AR/MR applications.

Demonstrated at CES will be the game-changing active-matrix displays in both native Blue and Green; as well as the brand new direct-drive display with the first generation development kit. The technology will be showcased within a HMD, HUD, projection system and more.

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