Enhancement of light extraction efficiency for GaN-based light emitting diodes using Zro(2) high-aspect-ratio pattern as scattering layer

Abstract

We developed the direct patterning process of the ZrO2 high-aspect-ratio (HAR) pattern for light-extraction efficiency of GaN-based blue light-emitting diodes (LEDs). ZrO2 HAR pattern, which has relatively high refractive index and acts as scattering layer, was formed on GaN-based blue LEDs using ultraviolet-nanoimprint lithography (UV-NIL) with mixture of ZrO2 nanoparticle and monomer. The photons generated from the multi quantum well layer can escape the ITO (Indium Tin Oxide) layer more easily due to gradual refractive index and optical path that increased via waveguide mode. The ZrO2 patterned LED with high pattern density showed the high brightness in same input current. The patterned LED with pitch of 1 mu m showed the 25.7% higher light output power than a un-patterned LED at a driving current of 20 mA.