On the Radiation Profiles and Light Extraction of Vertical LEDs With Hybrid Nanopattern and Truncated Microdome Surface Textures
On the Radiation Profiles and Light Extraction of Vertical LEDs With Hybrid Nanopattern and Truncated Microdome Surface Textures
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DOI：
10.1109/jqe.2012.2223199
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发表时间：
2013
影响因子：
2.5
通讯作者：
Yu-Ting Wang;Y. Chou;Liang-Yi Chen;Yu-Feng Yin;Yen-Chen Lin;Jian-jang Huang
中科院分区：
文献类型：
--
作者：
Yu-Ting Wang;Y. Chou;Liang-Yi Chen;Yu-Feng Yin;Yen-Chen Lin;Jian-jang Huang
n 面朝上的垂直发光二极管 (LED) 的优点是可以雕刻厚 n-GaN 层的表面，以改善光提取并调整辐射轮廓。在本文中，采用两步表面图案化，重点是了解纳米图案和截断微圆顶的角光衍射。通过实验和理论研究了具有混合表面纹理的 LED 的光输出增强。结果表明，当光与截头微圆顶相互作用时，光会通过光栅效应和弯曲侧壁发生衍射，从而在远离法向表面 64° 处产生最大增强。另一方面，从随机分散的纳米图案中发现了几乎全向的增强。对于混合结构，由于半导体层中的导模被纳米图案或微米圆顶衍射，因此混合结构的光提取的百分比增加近似于两种类型的表面纹理的线性叠加。结果提出了一个有趣的指导方针，可以提高 LED 光输出并通过多步表面图案调整角辐射。
The n-side-up vertical light emitting diodes (LEDs) have the advantage of carving the surface of the thick n-GaN layer to improve light extraction and to adjust radiation profiles. In this paper, a two-step surface patterning is employed with the focus on understanding angular light diffractions from both nanopatterns and truncated microdomes. Light output enhancement of the LEDs with hybrid surface texturing is investigated experimentally and theoretically. The results suggest that light is diffracted through the grating effect and curved sidewalls when interacting with truncated microdomes, resulting in a maximum enhancement 64° away from the normal surface. On the other hand, nearly omni-directional enhancement was found from the randomly scattered nanopatterns. As for the hybrid structure, since guided modes in the semiconductor layers are diffracted by either nanopatterns or microdomes, the percentage increase of light extraction from the hybrid structure is approximately the linear superposition of both types of surface textures. The results suggest an interesting guideline to improve LED light output and to adjust angular radiation with the mutlistep surface patterning.