自组装单层胶体晶体衍生微纳米结构提高氮化镓基LED出光效率的研究

The key for solid-state lighting is to improve the light output power of GaN based light-emitting diodes (LEDs). The light output power of the LED is limited by low internal quantum efficiency and light extraction efficiency. Improving the light output power of GaN based LEDs by using micro/nanostructures has been a focus in this area. In this project, we try to explore the mechanism that how the micro/nanostructures can enhance the light output power of GaN based LEDs. Based on this understanding, it is proposed to prepare nano-patterned sapphire substrate (N-PSS) for nitride epitaxial and LED device fabrication. Furthermore, ordered metal nanoparticle arrays can be implemented into the LED device by using nanosphere lithography. In the end, the light output power of GaN based LEDs is expected to improve greatly by a combined effect of the nano-patterned sapphire substrate and the surface plasmon caused by the ordered metal nanoparticle arrays. Thus, a new avenue to improve the light output power of GaN based LEDs by using micro/nanostructures derived from self-assembled monolayer colloidal crystals is envisioned, which will promote their real application in solid-state lighting.

发展半导体固态照明的关键是提高GaN基LED芯片的发光效率。LED芯片的发光效率主要取决于内量子效率和光提取效率。利用微纳米结构提高GaN 基LED发光效率成为近年来研究的重点。本项目在深入理解微纳米结构对GaN基LED芯片发光效率影响机制的基础上，以自组装聚苯乙烯胶体晶体单层为基础，制备纳米级图形化蓝宝石衬底，进行氮化物外延生长和LED芯片制作，并通过纳米球刻蚀技术在LED芯片中植入有序金属纳米颗粒阵列。最终，通过纳米级图形化蓝宝石衬底和有序金属纳米颗粒阵列的表面等离子体激元特性的协同作用，实现GaN基LED发光效率最大限度的提升。由此，有望开辟一条基于胶体化学自组装微纳米结构的提高GaN基LED发光效率的新途径，进一步推动GaN基LED在照明领域的实际应用。

发展半导体固态照明的关键是提高GaN基LED芯片的发光效率。LED芯片的发光效率主要取决于内量子效率和光提取效率。利用微纳米结构提高GaN 基LED发光效率成为近年来研究的重点。本项目在深入理解微纳米结构对GaN基LED芯片发光效率影响机制的基础上，以自组装聚苯乙烯胶体晶体单层为基础，制备了一系列衍生微纳米结构并用于提高GaN基LED 的出光效率。首先解决了高质量、大面积胶体晶体单层的制备问题，在此基础上发展出了经济简单的全湿化学法制备纳米图形化蓝宝石衬底的技术，在纳米图形化蓝宝石衬底上外延生长了GaN基LED芯片，器件光输出功率相对于平片提高了56%。结合胶体化学自组装技术与胶体晶体薄膜转移技术，制备了高质量（2+1）维光子晶体超晶格，通过对超晶格的禁带位置进行精密调控使其与GaN基LED的发光波长相匹配，并把其应用于GaN基LED作为背反射镜，LED的出光效率提高了近97%，电致发光强度提高了近130%。此外，还探索了胶体晶体单层衍生微纳米结构在一些其他光电器件如太阳能电池、氧化锌场效应器件等方面的应用。胶体微纳米球化学自组装作为一种有序微纳米结构的制备方法，成本低，效率高，易于大面积实施，普适性强，由此有望开辟一条提高GaN基LED器件以及其他光电器件性能的新途径。