Efficient emission of InGaN-based light-emitting diodes:toward orange and red

Indium gallium nitride(InGaN)-based light-emitting diodes(LEDs)are considered a promising candidate for red-green-blue(RGB)micro displays.Currently,the blue and green LEDs are efficient,while the red ones are inefficient for such applications.This paper reports our work of creating efficient InGaN-based orange and red LEDs on silicon(111)substrates at low current density.Based on the structure of InGaN yellow LEDs,by simply reducing the growth temperature of all the yellow quantum wells(QWs),we obtained 599 nm orange LEDs with peak wall-plug efficiency(WPE)of 18.1%at 2 A/cm^2.An optimized QW structure was proposed that changed two of the nine yellow QWs to orange ones.Compared with the sample containing nine orange QWs,the sample with two orange QWs and seven yellow QWs showed similar emission spectra but a much higher peak WPE up to 24.0%at 0.8 A/cm^2 with a wavelength of 608 nm.The improvement of peak WPE can be attributed to the improved QW quality and the reduced active recombination volume.Subsequently,a series of efficient InGaN-based orange and red LEDs was demonstrated.With further development,the InGaN-based red LEDs are believed to be attainable and can be used in micro LED displays.

Efficient InGaN-based yellow-light-emitting diodes

Realization of efficient yellow-light-emitting diodes(LEDs) has always been a challenge in solid-state lighting.Great effort has been made, but only slight advancements have occurred in the past few decades. After comprehensive work on InGaN-based yellow LEDs on Si substrate, we successfully made a breakthrough and pushed the wall-plug efficiency of 565-nm-yellow LEDs to 24.3% at 20 A∕cm^2 and 33.7% at 3 A∕cm^2. The success of yellow LEDs can be credited to the improved material quality and reduced compressive strain of InGaN quantum wells by a prestrained layer and substrate, as well as enhanced hole injection by a 3 D pn junction with V-pits.