Embedded technologies developer, Plessey, confirms that it has developed the world’s first red-LED based on the commercially-available material InGaN.
Thus far only blue and green LEDs were made from InGaN. Same-material red was not possible to achieve because the high indium content induced significant strain in the active region, reducing crystal quality and creating defects. Red LEDs were typically based on AlInGaP or came from colour conversion processes. This clashed with applications such as augmented reality (AR) and microdisplays where high-efficiency ultra-fine pitch red pixels (< 5µm) are needed. At such fine pixel pitches, the AlInGaP material shows adverse effects and cavity losses from colour conversion.
Now Plessey claims it has successfully overcome these challenges by using a proprietary strain engineered active region to create an efficient InGaN red-LED. InGaN-based red is attractive as it offers lower manufacturing costs, it scales to larger wafers (200-300mm) and has a better hot/cold factor.
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 than conventional AlInGaP or colour-converted red. With this result, Plessey can now manufacture native blue, green and red InGaN material, or tune wavelengths from 400-650nm using its GaN-on-silicon technology.
“This is an exciting result since it creates a path towards low-cost manufacturing of ultra-fine pitch and efficient red InGaN pixels. This will accelerate the adoption of microLEDs in both AR microdisplays and mobile/large display applications,” said Dr Wei Sin Tan, Director of Epitaxy and Advanced Product Development at Plessey.