Enhancement of light extraction efficiency in the GaN-based light-emitting diodes by selective growth of ZnO nanorods

We demonstrate high light extraction efficiency of GaN-based light-emitting diodes (LEDs) using the selective growth of ZnO nanorods (NRs). The chemical wet-etched hexagonal patterns of ZnO transparent conductive film were used to achieve the selective growth of ZnO NRs, which could be grown at the non-etched hexagonal pattern regions due to the wet-etching effect. The optical transmittance of GaN-based LEDs was decreased by forming additional different types of ZnO transparent conductive films, such as the hexagonal ZnO patterns and the ZnO NRs selectively grown on hexagonal ZnO patterns. However, the light output power of GaN-based LEDs increased on decreasing the optical transmittance by employing a hexagonal ZnO transparent conductive film and selectively grown ZnO NRs. Based on these results, we suggest that the combined structure of the surface hexagonal patterns and the selectively grown ZnO NRs decreases the optical transmittance, but is more effective in improving the light extraction efficiency in the GaN-based LEDs.