为了提高发光二极管（LED）的光提取效率, 并比较不同光栅形状对LED光提取效率的影响, 采用严格耦合波法优化了与矩形、等腰三角形、等腰梯形光栅分别集成的倒装LED, 使它们出光面透射率达到最优, 随后使用有限时域差分法模拟计算它们的光提取效率。经过模拟计算和理论分析可得3种不同结构LED最优光栅参量（光栅占空比f、光栅周期p、光栅厚度h）和过渡层厚度d分别是: f=0.35,p=150nm,h=80nm,d=190nm;f=0.45,p=175nm,h=80nm,d=190nm; f=0.7,p=150nm,h=80nm,d=190nm。结果表明, 3种最优的LED结构在波长0.4μm～0.5μm范围内, 矩形光栅倒装LED和等腰三角形光栅倒装LED出光面透射率相同, 等腰梯形光栅倒装LED出光面透射率最低;由于光透射率最低, 导致等腰梯形光栅倒装LED光提取效率较低, 最高仅为58.07%, 但是由于等腰三角形光栅倒装LED特殊的光栅形状加上高的光透射率, 其光提取效率可以达到77.75%。此研究可以为制备高光提取效率LED提供理论方法指导。

In order to improve the light extraction efficiency of light-emitting diodes (LED),the influences of different grating shapes on the light extraction efficiency of LED were compared.The flip chip LEDs, which was integrated with rectangle, isosceles triangle and isosceles trapezoidal grating, were optimized by rigorous coupled wave method to make the transmittance of the light-exiting surface best. Finite-difference time-domain method was used to simulate the efficiency of light extraction. After simulation calculation and theoretical analysis, the optimal grating parameters (grating duty ratio f, grating period p, grating thickness h) and transition layer thickness d of the LEDs with 3 different structures can be obtained: f=0.35,p=150nm, h=80nm, d=190nm; f=0.45,p=175nm,h=80nm,d=190nm; f=0.7,p=150nm,h=80nm, d=190nm. The results show that, in the wavelength of 0.4μm to 0.5μm,the flip-chip LED of the rectangular grating and the flip-chip LED of the isosceles triangle grating have the same transmittance.The flip-chip LED of The isosceles trapezoidal grating has the lowest transmittance. Because of the lowest transmittance, the light extraction efficiency of the flip-chip LED of the isosceles trapezoidal grating is lower and the highest is only 58.07%. The optical extraction efficiency of the flip-chip LED of the isosceles triangle grating with special grating shape can reach 77.75%.The study can provide theoretical guidance for manufacturing high light extraction efficiency LED in the future.