Device-Quality InGaN Templates With In Content Greater Than 10%: A Potential Solution for Red LED Problems

Abstract Red light-emitting diodes (LEDs) based on InGaN grown on GaN have external quantum efficiency (EQE) limited to a few percent due to several problems, such as low growth temperatures and fairly high compressive strain in the quantum well (QW). Such difficulties can be alleviated if these multiple quantum wells (MQWs) are grown on InGaN templates with In content above 10%. The reduced strain in the active region increases the indium incorporation, which allows for higher growth temperatures for the same emission wavelength. Traditional approaches in growing these high-In-content templates, such as growth at low temperatures or sudden decreases in growth temperature, result in fairly rough surfaces. To improve the surface morphology in these templates, better control of the relaxation rate is necessary. This was carried out by a gradual decrease in the growth temperature throughout the template growth, resulting in device-quality templates. InGaN templates were obtained with In content of 12% and root-mean-square (RMS) surface roughness of 2.2 nm, and a template with In content of 13.4% and RMS surface roughness of 3.4 nm with effective indium content of 12.3%.