Kim Sun-Kyung, Park Hong-Gyu
Department of Applied Physics, Kyung Hee University, Gyeonggi-do 446-701, South Korea.
Opt Express. 2013 Jun 17;21(12):14566-72. doi: 10.1364/OE.21.014566.
We propose a dielectric Bragg mirror that utilizes coherent coupling with multiple quantum wells (MQWs) to significantly enhance light extraction from GaN light-emitting diode (LED). Full vectorial electromagnetic simulation showed that, under constructive interference conditions, the Bragg mirror consisting of two dielectric (SiO(2)/TiO(2)) stacks and a silver layer led to >30% enhancement in light extraction, as compared to a single silver mirror. Such significant enhancement by a pre-designed Bragg/metal mirror was ascribed to the vertically oriented radiation pattern and reduced plasmonic metal loss. In addition, the gap distance between the MQWs and a Bragg mirror at which the constructive interference takes place could be controlled by modulating the thickness of the first low-refractive-index layer. Moreover, a two-dimensional periodic pattern was incorporated into an upper GaN layer with the designed Bragg mirror and it was shown that a lattice constant of ~800 nm was optimal for light extraction. We believe that tailoring the radiation profile of light emitters by coherent coupling with designed high-reflectivity mirrors will be a promising route to overcome the efficiency limit of current semiconductor LED devices.
我们提出了一种介质布拉格反射镜，它利用与多量子阱（MQW）的相干耦合来显著增强氮化镓发光二极管（LED）的光提取。全矢量电磁模拟表明，在相长干涉条件下，由两个介质（SiO(2)/TiO(2)）堆叠层和一个银层组成的布拉格反射镜与单个银镜相比，光提取增强了30%以上。这种由预先设计的布拉格/金属反射镜带来的显著增强归因于垂直取向的辐射模式和降低的等离子体金属损耗。此外，多量子阱与发生相长干涉的布拉格反射镜之间的间隙距离可以通过调制第一低折射率层的厚度来控制。此外，将二维周期性图案并入具有设计好的布拉格反射镜的上部氮化镓层中，结果表明，约800 nm的晶格常数对于光提取是最佳的。我们相信，通过与设计好的高反射率反射镜进行相干耦合来调整发光体的辐射分布，将是克服当前半导体LED器件效率限制的一条有前途的途径。
