Realization of Highly Efficient InGaN Green Light-Emitting Diodes with Laser-Annealed Multiple-Quantum Well Structures: Formation of Quantum Dot Structures

Abstract

High-efficiency InGaN-based green light-emitting diodes (LEDs) with high brightness are required for future highresolution displays and lighting products. Conventional green LEDs based on InGaN multiple quantum wells (MQWs) greatly suffer from the low efficiency owing to the poor material quality and quantum-confined Stark effect. InGaN quantum dots (QDs) were used as the active region to address these issues because of their stronger localization and enhanced radiative recombination characteristics. In this research, InGaN QDs were formed in the InGaN/GaN MQWs via laser annealing and their application in obtaining highly efficient long wavelength green LEDs was demonstrated. Compared with that of the as-grown MQWs, the PL peak of the laser-annealed MQWs showed an intensity enhanced by 14.3% and a red-shift of 5 nm. The internal quantum efficiency (IQE) of the laser-annealed MQWs was enhanced by 12.3%. The scanning transmission electron microscopy results showed the formation of QD structures, which could account for the enhancement in the IQE. Because of the formation of QDs in the laser-annealed MQWs, the green LED with the laser-annealed MQWs showed a 6 nm red-shift in peak wavelength and a 14.3% increase in light output power. The droop efficiency at 350 mA was reduced from 35.1% in the LED with the as-grown MQWs to 12.8% in that with the laser-annealed MQWs. This study provided a promising way to obtain longer wavelength green LEDs with enhanced performance.