Investigation of Light Extraction of InGaN LEDs With Surface-Textured Indium Tin Oxide by Holographic and Natural Lithography

Blue InGaN LEDs with periodically surface-textured indium tin oxide by holographic lithography were compared with those textured randomly by natural lithography where polystyrene spheres (PSs) with required diameter were employed as a mask for dry-etching process. It was found that the employed texturing processes not only exhibit unchanged I-V characteristics but also improve light output power. The turn-on threshold voltages of all the textured InGaN LEDs are similar to that of a conventional LED chip. An LED textured with a regular pattern with 600 nm pitch exhibits a maximum power enhancement of 65.2% at an injection current of 350 mA as compared with that of an original one. In addition, the LEDs with this 600 nm array pattern present much better light extraction than that textured with equal dimensioned PSs, which is indicative of the superior diffraction-dominated light extraction behavior.