Inverse Tapered AlGaN Micropillar and Nanowire LEDs for Improved Light Extraction Efficiency at 270 nm
Inverse Tapered AlGaN Micropillar and Nanowire LEDs for Improved Light Extraction Efficiency at 270 nm
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DOI：
10.1109/jphot.2022.3221353
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发表时间：
2022-12
影响因子：
2.4
通讯作者：
Bryan Melanson;M. Seitz;Jing Zhang
中科院分区：
文献类型：
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作者：
Bryan Melanson;M. Seitz;Jing Zhang
深紫外（DUV）发光二极管（led）在广泛的应用中显示出巨大的潜力，但由于其异常差的光提取效率（ηEXT），与可见led相比，其外部量子效率（EQEs）较差。微柱和纳米线阵列是提高DUV led光强的一种成功方法。我们之前的工作已经报道了在加热羟基基化学中湿蚀刻过程中AlGaN微柱中“反锥度”剖面的发展。本文根据实验结果，采用时域有限差分模拟方法，研究了逆变径对270 nm AlGaN微结构和纳米结构的ηEXT的影响。结果表明，在直径为1 μm、高度为1 μm的微观结构中，tem极化发射的ηEXT可以从~ 45%增加到95%以上，te极化发射的ηEXT可以从~ 35%增加到85%以上，反向锥角为5°。纳米结构的结果也表明，通过调整反锥角可以显著改善ηEXT。这些发现，以及我们展示的反锥形高铝含量AlGaN微纳米结构，可以使基于高宽高比结构和高ηEXT阵列的高EQE DUV led的开发成为可能。
Deep-ultraviolet (DUV) light emitting diodes (LEDs) show great potential in a wide range of applications, but suffer from poor external quantum efficiencies (EQEs) when compared to visible LEDs, due to their exceptionally poor light extraction efficiency (ηEXT). One successful method of improving the ηEXT of DUV LEDs is the use of micropillar and nanowire arrays. Our previous works have reported the development of an “inverse taper” profile in AlGaN micropillars during wet etching in heated hydroxyl-based chemistries. Here, we study the effects of inverse tapering on the ηEXT of AlGaN microstructures and nanostructures at 270 nm using finite-difference time-domain simulations, in accordance with our experimental results. Results show that ηEXT can be increased from ∼45% to more than 95% for TM-polarized emission in microstructures with diameters of 1 μm and heights >1 μm, and from ∼35% to more than 85% for TE-polarized emission by an inverse taper angle of 5 °. Results for nanostructures also indicate significant ηEXT improvements through tuning of the inverse taper angle. These findings, along with our demonstration of inverse tapered high Al-content AlGaN micro and nanostructures, could enable the development of record-high EQE DUV LEDs based on arrays of high aspect ratio structures with high ηEXT.