The British Micro LED technology developer Plessey reported that it has successfully developed the world’s first GaN on Silicon-based red LED.

(Image: Plessey)

Whilst InGaN-based blue and green LEDs are commercially available, red LEDs are typically based on AlInGaP material or color converted red. For AR, achieving high efficiency ultra-fine pitch red pixels (< 5 µm) remains elusive due to severe edge effects from AlInGaP material and cavity losses from color conversion processes.

InGaN-based red is attractive as it offers lower manufacturing costs, scalability to larger 200 mm or 300 mm 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.

(Image: Plessey)

Plessey’s InGaN red Micro LEDs have a wavelength of 630 nm at 10 A/cm2, full width at half maximum of 50 nm, hot cold factor over 90% and higher efficiencies over conventional AlInGaP and color 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 – 650 nm using its GaN on Silicon platform.

(Image: Plessey)

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 Micro LEDs in both AR microdisplays and mobile/large display applications.”

Plessey has also developed wafer level bonded monolithic 3,000 ppi GaN on Silicon Micro LED emissive display hybridized to an active-matrix CMOS backplane; as well as native blue and green emission layers on the same wafer. The company said it will continue the development of Micro LED display solutions including the production of full RGB Micro LED displays in 2020.

Plessey will bring its Micro LED developments including active-matrix displays in native blue and green Micro LED, as well as its direct-drive display in HMD, HUD, projection system and more at CES 2020 with Compound Photonics.