Jin Yuanhao, Yang Fenglei, Li Qunqing, Zhu Zhendong, Zhu Jun, Fan Shoushan
Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China.
Opt Express. 2012 Jul 2;20(14):15818-25. doi: 10.1364/OE.20.015818.
Significant enhancement in the light output from GaN-based green light-emitting diodes (LEDs) was achieved with a hemicylindrical grating structure on the top layer of the diodes. The grating structure was first optimized by the finite-difference time-domain (FDTD) method, which showed that the profile of the grating structure was critical for light extraction efficiency. It was found that the transmission efficiency of the 530 nm light emitted from the inside of the GaN LED increased for incidence angles between 23.58° and 60°. Such a structure was fabricated by electron-beam lithography and an etching method. The light output power from the LED was increased approximately 4.7 times compared with that from a conventional LED. The structure optimization is the key to the great increase in transmission efficiency. Furthermore, the light emitted from the edge of the LED units could be collected and extracted by the grating structures in adjacent LED units, thus enhancing the performance of the whole LED chip.
通过在基于氮化镓的绿色发光二极管（LED）顶层采用半圆柱形光栅结构，实现了光输出的显著增强。首先通过时域有限差分（FDTD）方法对光栅结构进行了优化，结果表明光栅结构的轮廓对光提取效率至关重要。研究发现，从氮化镓发光二极管内部发射的530nm光在入射角为23.58°至60°之间时传输效率会提高。这种结构是通过电子束光刻和蚀刻方法制造的。与传统发光二极管相比，该发光二极管的光输出功率提高了约4.7倍。结构优化是传输效率大幅提高的关键。此外，从发光二极管单元边缘发射的光可以被相邻发光二极管单元中的光栅结构收集和提取，从而提高整个发光二极管芯片的性能。
