Enhanced Light Extraction Mechanism of GaN-Based Light-Emitting Diodes Using Top Surface and Side-Wall Nanorod Arrays

Using a self-catalyst vapor-liquid-solid mechanism, random indium-tin-oxide (ITO) nanorod arrays were deposited on the top surface and side-wall of GaN-based light-emitting diodes (LEDs) by electron-beam deposition. When the side-wall nanorod arrays and the top surface ITO nanorod arrays were deposited at an oblique-angle of 45°, roughened surface morphology and matched refractive index of 1.6 between air and the p-GaN layer could be obtained. Comparing the conventional LEDs without ITO nanorod arrays, a 34% light output power increase was attributed to the roughened top and side-wall surface morphology and the matched refractive index caused by the ITO nanorod arrays. Not only were the side-wall nanorod arrays used to increase light output power, but the light output divergence angle could be widened by using side-wall nanorod arrays.