Hybrid simulation of light extraction efficiency in multi-quantum-shell (MQS) NW (nanowire) LED with a current diffusion layer

A multi-quantum-shell (MQS) grown on a GaN nanowire is a promising three-dimensional active region and it is expected to show excellent performance, compared with conventional nitride-based LEDs. However, there are no suitable simulators for calculating optical properties of MQS-LEDs, because of their complex structure. In this study, a hybrid simulation, which is composed of the finite-difference time-domain method, the rigorous coupled wave analysis method, and the ray tracing method, is developed. Applying this useful tool to the calculation of the light extraction efficiency (LEE) of MQS-LEDs, we have found considerable light absorption loss by the large refractive index steps between the active layer, ITO layer and air in the commonly used MQS-LED structure with the ITO electrode. Thus, to eliminate the large refractive index steps, the MQS-LED buried with the n-GaN current diffusion layer, which has a high LEE, was proposed.