In this work, the scattering mechanism by nano-patterned sapphire substrate (NPSS) for flip-chip AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) has been investigated systematically via three-dimensional finite-difference time-domain (3D FDTD) method. It is found that for the conventional DUV LED with a thick p-GaN layer, the NPSS structure can enhance the light extraction efficiency (LEE) for the transverse magnetic (TM)-polarized light because the TM-polarized light with large incident angles can be scattered into escape cones. However, the LEE for the transverse electric (TE)-polarized light is suppressed by NPSS structure because NPSS structure scatters some TE-polarized light out of the escape cones. Moreover, the highly absorptive p-GaN layer also seriously restricts the scattering efficiency of NPSS structure. Therefore, to reduce the optical absorption, meshed p-GaN structure is strongly proposed to greatly enhance the LEEs for both TM- and TE-polarized light of DUV LEDs grown on NPSS. Compared to the DUV LED with only NPSS structure and that with only meshed p-GaN layer, the LEE for the TE-polarized (TM-polarized) light for DUV LEDs with the combination of NPSS structure and meshed p-GaN structure can be enhanced by 124% (5 times) and 112% (4 times), respectively.

中文翻译：

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纳米图案蓝宝石衬底对AlGaN基深紫外发光二极管发射的TM和TE偏振光的不同散射效果

在这项工作中，通过三维有限差分时域（3D FDTD）系统研究了纳米图案蓝宝石衬底（NPSS）对倒装芯片AlGaN基深紫外发光二极管（DUV LED）的散射机理。 ） 方法。已经发现，对于具有厚p-GaN层的常规DUV LED，由于具有大入射角的TM偏振光可以使横向磁（TM）偏振光的光提取效率（LEE）能够提高，所以NPSS结构可以提高光提取效率（LEE）。散落到逃生锥中。但是，由于NPSS结构将一些TE偏振光从逃逸锥中散射出来，因此NPSS结构抑制了横向电（TE）偏振光的LEEE。而且，高吸收性的p-GaN层也严重限制了NPSS结构的散射效率。所以，为了减少光吸收，强烈建议使用网状p-GaN结构来大大增强在NPSS上生长的DUV LED的TM和TE偏振光的LEEE。与仅具有NPSS结构和仅具有网状p-GaN层的DUV LED相比，可以增强结合了NPSS结构和网状p-GaN结构的DUV LED的TE偏振（TM偏振）光的LEEE。分别减少了124％（5倍）和112％（4倍）。