Understanding omni-directional reflectors and nominating more dielectric materials for deep ultraviolet light-emitting diodes with inclined sidewalls
Understanding omni-directional reflectors and nominating more dielectric materials for deep ultraviolet light-emitting diodes with inclined sidewalls
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DOI：
10.1063/5.0019650
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发表时间：
2020-09
影响因子：
3.2
通讯作者：
Yuxin Zheng;J. Zhang;Le Chang;Chunshuang Chu;Kangkai Tian;Quan Zheng;Qing Li;Yonghui Zhang
中科院分区：
文献类型：
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作者：
Yuxin Zheng;J. Zhang;Le Chang;Chunshuang Chu;Kangkai Tian;Quan Zheng;Qing Li;Yonghui Zhang
在这项工作中，通过三维有限差分时域方法系统地研究了倒装芯片algan基深紫外发光二极管（DUV led）倾斜侧壁全向反射器（ODR）的独特性能和巨大优势。研究发现，虽然Ag的反射率远低于Al，但在一定入射角范围内，Ag基ODR的斜侧壁DUV LED的光提取效率并不总是低于Al基ODR。这是因为ODR在倾斜侧壁上的全内反射（TIR）对提取光起着重要的作用。我们还发现，如果发生表面等离子激元（SPPs）共振吸收，TIR的反射率会被强烈抑制。为了避免SPP共振吸收，本工作提出了斜侧壁ODR的设计策略：如果斜侧壁DUV LED的ODR结构采用薄介电层，则应选择高折射率材料作为介电层；如果ODR结构采用较厚的介电层，则应选择低折射率材料作为介电层。
In this work, unique properties and tremendous advantages for an omni-directional reflector (ODR) on an inclined sidewall for flip-chip AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) are systematically investigated via a three-dimensional finite-difference time-domain method. It is found that although the reflectivity of Ag is far lower than that of Al, the light extraction efficiency for the inclined sidewall DUV LED with the Ag-based ODR is not always lower than that with Al-based one within certain incident angles. The reason is that the total internal reflection (TIR) of the ODR on the inclined sidewall plays an important role in extracting light. We also find that the reflectivity for TIR can be strongly suppressed if surface plasmon polaritons (SPPs) resonance absorption occurs. To avoid SPP resonance absorption, our studies in this work propose the design strategy for ODR on the inclined sidewall as follows: if the ODR structure of the DUV LED with an inclined sidewall adopts thin dielectric layers, the high-index material should be selected as the dielectric layer; if a thick dielectric layer is adopted for the ODR structure, the low-index material should be selected as the dielectric layer.