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.

中文翻译：

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自对准分层ZnO纳米棒/ NiO纳米片阵列，用于基于GaN的光子发射极的高光子提取效率。

纳米技术的进步促进了ZnO纳米结构的更多使用。特别是，最近已应用提供渐变折射率变化的分层和核-壳纳米结构来增强光子发射器的光子提取效率。在这项研究中，我们展示了在波长为430 nm的常规光子发射器（C发射器）上的自对准分层ZnO纳米棒（ZNR）/ NiO纳米片阵列。这些分层的纳米结构是在低温下通过两步水热过程合成的，其光输出功率比C发射器上的ZNR阵列高约17％，比C发射器高两倍。