Improvement in External Quantum Efficiency of InGaN-Based LEDs by Micro-Textured Surface with Different Geometric Patterns

This investigation elucidates the traditional p-side-up InGaN/GaN multiple-quantum well (MQW) light-emitting diodes (LEDs) with different geometric patterns of microtextured indium-tin-oxide (ITO) surface using standard photolithography and wet chemical etching technique. The LEDs fabricated with the surface-textured ITO, concave and convex patterns, have the same forward voltage as the reference LED with planar-ITO, but provide higher light output power, increased by 7.9% and 16.3%, at 20 mA current injection, respectively. In addition, the external quantum efficiency (EQE) of LEDs were also enhanced from 18% (planar) to 19.4% and 21% (concave and convex patterned). The larger light output power and higher external quantum efficiency could be attributed to the microtextured ITO surface. With the textured ITO surface, especially the convex pattern, with light scattering effect at the ITO/air interface, photons could escape from the device more easily, thus increasing the light output power and external quantum efficiency of GaN-based LEDs at the same time. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.055202jes] All rights reserved.