光子晶体反射镜对深紫外发光二极管性能的影响

Effects of photonic crystal reflector on the performance for deep ultraviolet light-emitting diodes

通过三维有限时域差分(3D-FDTD)的光学模拟仿真计算,系统地研究了空气孔型光子晶体反射镜结构中各参数对AlGaN基深紫外发光二极管的光提取效率的影响。研究发现,光子晶体与垂直光线的共振模式主要是由光子晶体的周期决定,而光子晶体的填充率和高度会影响这种共振模式的强度,但是填充率会严重影响横向传播的横向磁(Transverse Magnetic,TM)极性光与光子晶体的散射作用。一个相对更大的填充率更有利于光子晶体对TM极性光的散射;而随着光子晶体中填充铝的深度增加,光子晶体对横向电(Transverse Electric,TE)极性光和TM极性光的散射作用都是先增加后减少,但是当填充深度太深时,金属结构将对TM极性光起到强烈的限制作用,急剧增加金属对TM极性光的吸收,从而使整体光提取效率大幅下降。在优化的条件下,相比没有光子晶体的结构,具有部分填充金属反射镜的光子晶体结构的深紫外发光二极管的TM极性和TE极性光提取效率分别提高了19倍和2倍。

In this work,we utilized three-dimensional finite-difference time-domain(3D-FDTD)to investigate the effect of 2D air-embedded photonic crystal(air PhC)structured reflector on the light extraction efficiency(LEE)for AlGaN-based deep ultraviolet light-emitting diodes(DUV LEDs).We find that the resonance mode for the PhC and vertical light is mainly determined by the period of the PhC.The intensity of the resonance mode is also impacted by the filling factor and height of the PhC.We find that the filling factor can seriously influence the scattering process for transverse magnetic(TM)-polarized light in the PhC structure.A properly large filling factor can contribute more to the scattering process in the PhC structure.As the filled depth of aluminum(Al)in the PhC structure increases,the scattering capability for the transverse electric(TE)-and TM-polarized light firstly increases and then decreases.Nevertheless,when the filling depth is too deep,the metal structure will have a strong confinement on the TM-polarized light and leads to strong metal absorption,which will remarkably reduce the overall LEE.Compared with conventional DUV LEDs,the DUV LEDs with PhC structure that are partially filled with metal reflectors can enhance the LEE for TM-and TE-polarized light by 19 times and 2 times.