Bai Jie, Cai Yuefei, Feng Peng, Fletcher Peter, Zhu Chenqi, Tian Ye, Wang Tao
Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, United Kingdom.
ACS Nano. 2020 Jun 23;14(6):6906-6911. doi: 10.1021/acsnano.0c01180. Epub 2020 May 29.
Augmented reality and visual reality (AR and VR) microdisplays require micro light emitting diodes (μLEDs) with an ultrasmall dimension (≤5 μm), high external quantum efficiency (EQE), and narrow spectral line width. Unfortunately, dry etching which is the most crucial step for the fabrication of μLEDs in current approaches introduces severe damages, which seem to become an insurmountable challenge for achieving ultrasmall μLEDs with high EQE. Furthermore, it is well-known that μLEDs which require InGaN layers as an emitting region naturally exhibit significantly broad spectral line width, which becomes increasingly severe toward long wavelengths such as green. In this paper, we have reported a combination of our selective overgrowth approach developed very recently and epitaxial lattice-matched distributed Bragg reflectors (DBRs) embedded in order to address all these fundamental issues. As a result, our μLEDs with a diameter of 3.6 μm and an interpitch of 2 μm exhibit an ultrahigh EQE of 9% at ∼500 nm. More importantly, the spectral line width of our μLEDs has been significantly reduced down to 25 nm, the narrowest value reported so far for III-nitride green μLEDs.
增强现实和虚拟现实（AR和VR）微显示器需要尺寸超小（≤5μm）、具有高外部量子效率（EQE）和窄光谱线宽的微型发光二极管（μLED）。不幸的是，干法蚀刻作为当前制造μLED最关键的步骤会引入严重损伤，这似乎成为实现具有高EQE的超小μLED的一个无法克服的挑战。此外，众所周知，需要InGaN层作为发光区域的μLED自然会表现出显著宽的光谱线宽，对于诸如绿色等长波长来说，这种情况会变得越来越严重。在本文中，我们报告了一种结合最近开发的选择性过生长方法和嵌入的外延晶格匹配分布式布拉格反射器（DBR）的方法，以解决所有这些基本问题。结果，我们直径为3.6μm、间距为2μm的μLED在约500nm处表现出9%的超高EQE。更重要的是，我们的μLED的光谱线宽已显著降低至25nm，这是迄今为止报道的III族氮化物绿色μLED的最窄值。
