Theoretical Analysis on the Light Extraction Efficiency of GaN-Based Light-Emitting Diodes by Using the Ray Tracing Method

Abstract

The light extraction efficiency of GaN-based light-emitting diodes(LEDs) is theoretically analyzed by using the ray tracing method. In this model, each material consisting of a LED is characterized by using two main parameters, the refractive index and the optical absorption coefficient, in order to evaluate the light extraction efficiency. This analytical approach is sequentially applied to various enhancement methods, such as a patterned sapphire substrate(PSS), side-surface texturing (SST) and chip shaping, to come up with the most efficient method. The hemisphere PSS turns out to provide a higher light extraction efficiency than the cone and the cylinder PSS. The saw-shaped SST and lozenge-type chip-shaping method are shown to improve the light extraction efficiency from that for a conventional LED. Combinations of two different enhancement methods are also investigated and some combinations are found to contribute significantly to the increase in the light extraction efficiency.