Self-Aligned Hierarchical ZnO Nanorod/NiO Nanosheet Arrays for High Photon Extraction Efficiency of GaN-Based Photonic Emitter
Won-Seok Lee,
Soon-Hwan Kwon,
Hee-Jung Choi,
Kwang-Gyun Im,
Hannah Lee,
Semi Oh,
Kyoung-Kook Kim
Affiliations
Won-Seok Lee
Department of Advanced Convergence Technology, Research Institute of Advanced Convergence Technology, Korea Polytechnic University, Gyeonggi-do 15073, Korea
Soon-Hwan Kwon
Department of Advanced Convergence Technology, Research Institute of Advanced Convergence Technology, Korea Polytechnic University, Gyeonggi-do 15073, Korea
Hee-Jung Choi
Department of Advanced Convergence Technology, Research Institute of Advanced Convergence Technology, Korea Polytechnic University, Gyeonggi-do 15073, Korea
Kwang-Gyun Im
Department of Nano & Semiconductor Engineering, Korea Polytechnic University, Gyeonggi-do 15073, Korea
Hannah Lee
Department of Advanced Convergence Technology, Research Institute of Advanced Convergence Technology, Korea Polytechnic University, Gyeonggi-do 15073, Korea
Semi Oh
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA
Kyoung-Kook Kim
Department of Advanced Convergence Technology, Research Institute of Advanced Convergence Technology, Korea Polytechnic University, Gyeonggi-do 15073, Korea
Advancements in nanotechnology have facilitated the increased use of ZnO nanostructures. In particular, hierarchical and core−shell nanostructures, providing a graded refractive index change, have recently been applied to enhance the photon extraction efficiency of photonic emitters. In this study, we demonstrate self-aligned hierarchical ZnO nanorod (ZNR)/NiO nanosheet arrays on a conventional photonic emitter (C-emitter) with a wavelength of 430 nm. These hierarchical nanostructures were synthesized through a two-step hydrothermal process at low temperature, and their optical output power was approximately 17% higher than that of ZNR arrays on a C-emitter and two times higher than that of a C-emitter. These results are due to the graded index change in refractive index from the GaN layer inside the device toward the outside as well as decreases in the total internal reflection and Fresnel reflection of the photonic emitter.
