Analysis on light extraction property of AlGaN-based flip-chip ultraviolet light-emitting diodes by the use of self-assembled SiO2 microsphere array
Analysis on light extraction property of AlGaN-based flip-chip ultraviolet light-emitting diodes by the use of self-assembled SiO2 microsphere array
复制标题
自组装SiO2微球阵列AlGaN基倒装紫外发光二极管的光提取性能分析
DOI：
10.1117/12.2510488
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Zhang, Jing
中科院分区：
文献类型：
--
作者：
Liu, Cheng;Melanson, Bryan;Ooi, Yu Kee;Hartensveld, Matthew;Zhang, Jing
由于AlN（蓝宝石）/空气界面处的折射率对比度较大，对于高效深紫外（UV）发光二极管（led）来说，光提取效率（η提取）仍然是一个很大的挑战。各种表面图案化的方法，如微球设计和图案化蓝宝石衬底已提出，以解决低η萃取问题。然而，这些先前提出的方法都涉及到额外的复杂的制造步骤，并且这些器件的偏振相关分析尚未在实验中进行研究。在这项工作中，我们研究了在280 nm倒装UV led上使用700 nm sio2微球阵列来提高萃取效率的可行性。采用角度和偏振相关的电致发光测量方法，比较了280 nm led带和不带sio2微球阵列的情况。与无sio2微球阵列相比，微球阵列的UV LED在相对于c轴的小角度处的横向电（TE）偏振光强增强，而在相对于c轴的大角度处的强度减弱，例如，在θ = 0°处的强度增强高达7.4%。而横磁偏振光在小角度下强度基本保持不变，在大角度下强度下降。三维有限差分时域模拟的截面近场电场分布证实了sio2微球阵列的使用导致光子在蓝宝石/ sio2微球界面处散射，从而增强了小角度te光子的提取。模拟结果表明，在不降低总输出功率的情况下，sio2sphere UV LED的光辐射模式被重塑为小角度偏好模式，与测量结果有很大的一致性。
Light extraction efficiency (ηextraction) remains as a big challenge for high-efficiency deep-ultraviolet (UV) lightemitting diodes (LEDs) due to the large refractive index contrast at the AlN(sapphire)/air interface. Various surface patterning approaches such as microdome design and patterned sapphire substrates have been proposed to address the low ηextractionissue. Nevertheless, these previously proposed methods all involved additional complicated fabrication steps and the polarization-dependent analysis for these devices has not been investigated experimentally. In this work, we investigate the feasibility of using 700-nm SiO2microsphere array on 280 nm flip-chip UV LEDs to improve the ηextraction. Angle- and polarization-dependent electroluminescence measurements have been performed to compare the 280 nm LEDs with and without the SiO2microsphere array. The UV LED with microsphere array showed enhancement for transverse-electric (TE)-polarized light intensities at small angles while decreased intensities at large angles with respect to c-axis, as compared to the device without SiO2microspheres For instance, up to 7.4% enhancement is observed at θ = 0°. However, for transverse-magnetic (TM)-polarized light, the intensities largely remain the same at small angles while decrease at large angles. Cross-sectional near-field electric field distribution from three-dimensional finite-difference time-domain simulation has confirmed that the use of SiO2microspheres array resulted in scattering of photons at the sapphire/SiO2microspheres interface, which eventually leads to enhanced TE-photons extraction at small-angles. From simulation, the light radiation patterns from the UV LED with SiO2spheres are reshaped to a small-angle-favored pattern without reducing the total output power, showing great consistency with the measurement results.
影响因子：
2.4
作者：
Ooi, Yu Kee;Zhang, Jing
通讯作者：
Zhang, Jing
影响因子：
2.3
作者：
Takano, Takayoshi;Mino, Takuya;Hirayama, Hideki
通讯作者：
Hirayama, Hideki