利用FDTD方法研究具有表面微纳结构氮化镓基倒装薄膜LED芯片的光萃取效率。通过优化表面结构并研究了器件的光萃取效率随p-GaN层厚的变化。研究发现, 具有表面光子晶体和六棱锥结构的器件的光萃取效率最大值比无表面微结构器件分别提高了56%和97%。尽管两种表面结构都能有效提高器件的光萃取效率, 然而采用光子晶体的方案对p-GaN厚度和腔长要求极为苛刻。采用六棱锥结构则不仅可以获得更高的光萃取效率, 并且还将大大降低实验上材料外延生长及器件制备的难度。

Light extraction efficiency (LEE) of flip-chip thin-film LEDs (FC-TFLEDs) with different surface textures were performed by using finite difference time domain method. The surface textures and different thicknesses of p-GaN layer were optimized for high LEE FC-TFLEDs. It is found that the maximum LEE of FC-TFLEDs with photonic crystals and hexagonal cones is 1.56 and 1.97 times to that of FC-TFLEDs with flat surface, respectively. Both types of the surface textures can improve the LEE of FC-TFLEDs, however, it is much difficult to obtain high LEE FC-TFLEDs by employing photonic crystals. The simulated results show that the LEE of FC-TFLEDs is effectively improved by the use of the hexagonal cones, in addition, it can greatly reduce the difficulty in LED material growth and device fabrication.