Theoretical Analysis on the Light Extraction Efficiency of GaN-Based Light-Emitting Diodes by Using the Ray Tracing Method
J. Korean Phy. Soc. 2009; 54: 2373~2377
Published online June 15, 2009 © 2009 The Korean Physical Society.

Abstract
The light extraction efficiency of GaN-based light-emitting diodes(LEDs) is theoretically analyzed by using the ray tracing method. Inthis model, each material consisting of a LED is characterized byusing two main parameters, the refractive index and the opticalabsorption coefficient, in order to evaluate the light extractionefficiency. This analytical approach is sequentially applied tovarious enhancement methods, such as a patterned sapphire substrate(PSS), side-surface texturing (SST) and chip shaping, to come upwith the most efficient method. The hemisphere PSS turns out toprovide a higher light extraction efficiency than the cone and thecylinder PSS. The saw-shaped SST and lozenge-type chip-shapingmethod are shown to improve the light extraction efficiency fromthat for a conventional LED. Combinations of two differentenhancement methods are also investigated and some combinations arefound to contribute significantly to the increase in the lightextraction efficiency.
Keywords: Chip shaping, GaN-based LED, Light extraction efficiency, Patterned sapphire substrate, Ray tracing, Surface texturing


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