Improvement in light extraction efficiency of high brightness InGaN-based light emitting diodes

Abstract

Light extraction efficiency is important to the brightness of LEDs. In this study, various texturing and roughing schemes were formed on the surface or interface of InGaN-based LED structure grown on sapphire substrate to investigate their effects. Throughout the research, temperature-dependent PL measurement was used to calculate the internal quantum efficiency so as to derive the light extraction efficiency. The light extraction efficiency is around 60 to 65% while the epitaxy and substrate are flat. On the other hand, the light extraction efficiency reaches an optimal value of around 85% while the p-GaN surface is textured and the substrate is patterned. However, for LED having only one-side surface texturing structure optimized on either p- or n-side, the light extraction efficiency can be already as high as 75 to 80%. Methods for further enhancement, such as use of ZnO nanorod on chip surface, were also discussed.