(Invited) High Efficiency Green-Yellow Emission from InGaN/GaN Quantum Well Structures Grown on Overgrown Semi-Polar (11-22) GaN on Regularly Arrayed Micro-Rod Templates
The Sheffield team has developed an overgrowth approach for 2" (11-22) semi-polar GaN with significantly enhanced crystal quality on nanorod templates fabricated by self-organised nickel nano-mask approach. Very recently, a new overgrowth approach based on optical lithography mask pattern technique has been developed, where regularly arrayed micro rod templates can be cost-effectively fabricated and the size of the micro rods can be well controlled. The new approach has led to further improvement in both crystalline quality and surface morphology. This has been confirmed by high resolution transmission microscopy (TEM) studies, demonstrating further significant reduction in both dislocation density and basal stacking fault density.
InGaN/GaN multiple quantum well structures with high In compositions have been grown on such semi-polar GaN templates, and we have achieved strong emission at long wavelengths, even down to ~600 nm. For the green-yellow emission at 555 nm, we have obtained an internal quantum efficiency (IQE) of up to 14%, and 7-10% for the pure yellow emission at ~570 nm. Con-focal photoluminescence (PL), micro-PL, time-resolved PL (TRPL), and micro-TRPL have been performed