Light Extraction Simulation of Surface-Textured Light-Emitting Diodes by Finite-Difference Time-Domain Method and Ray-Tracing Method

The light extraction efficiency (η l ) of surface-textured light-emitting diodes (LEDs) is calculated using a simulation based on the combination of the finite-difference time-domain (FDTD) method and the ray-tracing method. Considering the transmittance and light-scattering effects, which depend on the size of the surface-textured structure (STS), we investigated the dependence of η l on the size of the STS including the period and aspect ratio. As a result, a clear dependence on the size of the STS has been shown. Furthermore, by optimizing the size of the STS, we found η l to be about 4 times larger than that of the surface flat structure (SFS). In addition, we demonstrated that the absorption coefficient of the GaN layer (α GaN ) affected η l of the STS more strongly than that of the SFS. We suggest that both wide light-scattering and a high GaN crystalline quality are important points for improving η l when texturing the top surface of LEDs.