Using finite-difference time-domain method, the light extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) is investigated. Simulation results show that compared to flat sapphire substrate, the nano-patterned sapphire substrate (NPSS) expands the extraction angles of top surface and sidewalls. As a result, the LEE of transverse-magnetic (TM) polarized light is improved significantly. Roughening on the backside of n-AlGaN surface significantly enhances the LEE of top surface of thin-film flip-chip DUV LEDs. However, the LEE of sidewalls of thin-film flip-chip DUV LEDs is greatly weakened. For bare DUV LED, the LEE of flip-chip LED on NPSS is estimated to be about 15%, which is around 50% higher than that of thin-film flip-chip DUV LED with roughening on the backside of n-AlGaN surface.

中文翻译：

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AlGaN基深紫外发光二极管的光提取效率优化

使用有限差分时域方法，研究了基于 AlGaN 的深紫外发光二极管 (DUV LED) 的光提取效率 (LEE)。仿真结果表明，与平坦的蓝宝石衬底相比，纳米图案蓝宝石衬底 (NPSS) 扩大了顶面和侧壁的提取角。结果，横磁 (TM) 偏振光的 LEE 显着提高。n-AlGaN 表面背面的粗糙化显着提高了薄膜倒装芯片 DUV LED 顶面的 LEE。然而，薄膜倒装芯片DUV LED侧壁的LEE被大大削弱。对于裸露的 DUV LED，NPSS 上倒装芯片 LED 的 LEE 估计约为 15%，比 n-AlGaN 表面背面粗糙的薄膜倒装芯片 DUV LED 的 LEE 高约 50%。