Light Extraction Efficiency Analysis of Flip-Chip Ultraviolet Light-Emitting Diodes With Patterned Sapphire Substrate
Light Extraction Efficiency Analysis of Flip-Chip Ultraviolet Light-Emitting Diodes With Patterned Sapphire Substrate
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DOI：
10.1109/jphot.2018.2847226
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发表时间：
2018-08-01
影响因子：
2.4
通讯作者：
Zhang, Jing
中科院分区：
文献类型：
--
作者：
Ooi, Yu Kee;Zhang, Jing
基于3-D时域有限差分模拟方法，研究了蓝宝石衬底上微圆顶图案化AlGaN基倒装紫外（UV）发光二极管（LED）在230 nm和280 nm波长下的偏振相关光提取效率（eta（提取））。分析了三种类型的图案化蓝宝石衬底（PSS）：底侧PSS、顶侧PSS和双面PSS。我们的研究结果表明，蓝宝石衬底上的微圆顶形图案化是主要有利于增强横向磁（TM）偏振输出。具体地，对于具有底侧PSS的230 nm和280 nm UV LED，可以分别获得高达近似4.5倍和近似2.2倍的TM偏振eta（提取）增强，并且对于具有顶侧PSS的230 nm和280 nm UV LED，可以分别获得近似6.3倍和近似1.8倍的TM偏振eta（提取）增强。通过采用双侧PSS，对于230 nm和280 nm UV LED，可以分别实现TM偏振eta（提取）的高达近似11.2倍和近似26倍的增强。相比之下，微圆顶形PSS充当横向电偏振光子的反射器，这导致230 nm和280 nm倒装芯片UV LED的光提取受到严重限制。因此，预计这项研究将作为指导设计高效率的中，深紫外LED的PSS。
This study investigates polarization-dependent light extraction efficiency (eta(extraction)) of AIGaN-based flip-chip ultraviolet (UV) light-emitting diodes (LEDs) emitting at 230 nm and 280 nm with microdome-shaped patterning on sapphire substrate based on 3-D finite-difference time-domain simulations. Three types of patterned sapphire substrates (PSS) have been analyzed: bottom-side PSS, top-side PSS, and double-sided PSS. Our results show that microdome-shaped patterning on sapphire substrate is predominantly beneficial in enhancing transverse-magnetic (TM)-polarized output. Specifically, TM-polarized eta(extraction) enhancement of up to similar to 4.5 times and similar to 2.2 times can be obtained for 230 nm and 280 nm UV LEDs with bottom-side PSS, respectively, and similar to 6.3 times and similar to 1.8 times for 230 nm and 280 nm UV LEDs with top-side PSS, respectively. By employing double-sided PSS, up to similar to 11.2 times and similar to 26 times enhancement in TM-polarized eta(extraction) can be achieved for 230 nm and 280 nm UV LEDs, respectively. In contrast, the microdome-shaped PSS act as a reflector for transverse-electric-polarized photons which leads to severe limitation in light extraction for both 230 nm and 280 nm flip-chip UV LEDs. Thus, it is expected that this study will serve as a guidance in designing PSS for high-efficiency mid- and deep-UV LEDs.