深紫外LED芯片金属线网格透明电极与高效出光结构制造的关键技术研究

Deep ultraviolet (DUV) LED is a promising candidate for various applications, including air and water purification, biochemistry detection, disinfection of medical tools and high density storage. It is important to study core manufacturing technology for improving light extraction efficiency of DUV LED chip. This proposal aims to solve core scientific and technological problems of highly efficient DUV LED chip manufacturing. In this proposal, the contact mechanism between metal electrode and p-AlGaN alloys with high Al mole fractions will be investigated in detail. We will develop a metal wire grid transparent conductive electrode (TCE) based on flexible nanoimprint lithography to obtain high transmittance for DUV light wavelength region as well as low sheet resistance. We will employ n-type via hole-based array electrode to improve lateral current sprading performance of DUV LED chip and thus alleviate the current crowding effect around electrode pads. Meanwhile, highly reflective p-type electrode based on the combination of the nanoimprinted metal wire grid and DBR will be designated to minimize the absorption of light by the opaque metal electrodes. The cone-shaped nano-structure grating is formed on sapphire substrate of flip-chip DUV LED by combining dynamic nano-inscribing process and UV nanoimprint lithography in order to enhance light extraction efficiency of DUV LED chip. In all, the research will promote the rapid development and application of DUV LED chip and to provide valuable knowledge for highly efficient DUV LED chip manufacturing.

深紫外LED在空气和水净化、生化监测、医疗工具消毒以及高密度存储等领域具有重大的应用价值，研究高光提取效率深紫外LED芯片制造技术具有重要意义。本项目聚焦高光提取效率深紫外LED芯片制造中的关键问题，研究金属与高Al组分p-AlGaN半导体材料的接触机理，在此基础上构建基于柔性纳米压印技术的高深紫外透光率、低方块电阻金属线网格透明导电电极；采用通孔接触式N型电极实现横向电流均匀扩展，缓解电流聚集现象，并通过金属线网格和DBR相结合的方式形成高反射率P型电极结构，解决金属电极吸光引起的光损耗问题；利用动态纳米刻划加工和紫外固化纳米压印技术在蓝宝石衬底上形成纳米级圆锥形光栅结构，实现对高折射率、多光学界面体系的光子散射操控，提升深紫外LED芯片的光提取效率。该项目的开展将促进深紫外LED芯片的快速发展与应用，并为高光提取效率深紫外LED芯片的制造提供理论指导和技术参考。

深紫外LED在空气和水净化、生化监测、医疗工具消毒以及高密度存储等领域具有重大的应用价值，本项目的开展促进了深紫外LED芯片的快速发展与应用，为高光提取效率深紫外LED芯片的制造提供了理论指导和技术参考。本项目具体研究工作如下：.1）揭示了金属与高Al组分p-AlGaN半导体材料的接触机理，分析了不同金属组合，如Ni/Au、Ni/Pd、Ni/Rh等与高Al组分p-AlGaN材料之间的欧姆接触特性。.2）利用激光直写技术制备了Ni/Au金属线网格透明电极，减轻了金属电极吸光引起的光损耗。分析了Ni/Au金属线网格的周期、占空比、线宽和厚度对其透光率、方块电阻的影响，最终制备了对紫外光透光率高于80%，方块电阻低于30Ω/□的Ni/Au金属线网格透明导电电极。.3）设计与制造了具有高电流扩展均匀性的通孔接触式N型电极结构和高反射率P型电极结构的倒装深紫外LED芯片。揭示了通孔接触式N型电极结构参数与深紫外LED芯片光学、电学和热学性能之间的关系，通过金属线网格和分布式布拉格反射镜相结合形成高反射率P型欧姆接触电极，解决了金属电极吸光引起的光损耗问题。.4）深入分析了圆锥形光栅结构参数（光栅周期、占空比、圆锥形高度和形貌）对深紫外LED芯片光提取效率的影响。通过周期性纳米级圆锥形光栅结构的优化设计，提高了倒装深紫外LED芯片的光提取效率。.5）通过在蓝宝石衬底上形成纳米级圆锥形聚合物光栅结构，使深紫外LED芯片有源区发射的横电（TE）偏振光和横磁（TM）偏振光的光提取效率相比无光栅结构深紫外LED芯片分别提升了20.1%和42%。.6）系统分析了MOCVD原位生长低温GaN成核层、低温AlGaN成核层和溅射AlN成核层对紫外LED芯片发光效率的影响，发现采用溅射AlN成核层不仅可以减小对紫外光的吸收，而且可以显著降低III-V族材料位错密度，使紫外LED芯片的外量子效率效率提升30%。