基于SiC衬底的GaN基功率LED光电热耦合与光子调控的研究

The GaN-based blue light-emitting diodes (LED）plays an important role in solid-state lighting. Blue LED with a coating of a yellow phosphor material can be used as a white light source. High power LED is expected to be the right replacement of conventional light sources and the ideal choice for green lighting. However, due to several possible loss mechanisms and the phenomenon of total internal reflection, the light extraction efficiency of LEDs is still low because of the most light emitted from active layer is trapped inside the LED chips. Furthermore, LED's internal quantum efficiency peaks at low driving currents and drops significantly at higher currents. This phenomenon is called "efficiency droop". Both of these phenomena result in the thermal effect and reduce the LED performance. By studying the internal relations and interactive coupling mechanism of the electrical,thermal and optical processes in LED chip, the purpose of this project is to investigate the droop mechanism and of LED under high current injection. This project focuses on the coupling mechanism between the light extraction efficiency and several PhCs structures,including weak etched PhCs,deep etched PhCs,and embedded PhCs. In this research, the coupled-mode theory and time-domain electromagnetic simulation will be employed to study the mechanism that the PhC and amorphous PhC control the light radiation. The ultimate goal of this project is to design the optimal structure of GaN-based LED on the SiC substrates and fabricate high efficiency power GaN-based LED on the same substrates experimentally. This project will provide an important theoretical basis and technical support for the new optoelectronic devices.

基于InGaN/GaN 的功率LED在固体发光器件中扮演着重要的角色，目前限制GaN基功率LED在照明领域应用的一个重要因素是界面反射导致光提取效率较低,而且在大电流注入下出现效率下降（Droop）的现象，从而导致LED迅速发热并影响其性能。本课题通过研究功率LED的电学、热学和光学过程之间的内在联系和相互耦合机制，揭示在大电流注入下功率LED效率降低与其光电热物理过程的联系和规律；研究深刻蚀、浅刻蚀以及嵌入式光子晶体结构与LED有源区的耦合机理，运用复耦合模理论和时域电磁方法分析周期、准周期光子晶体对LED中光子调控的规律；给出基于SiC衬底的大功率GaN基LED最佳结构设计方法，并制备高效率SiC衬底功率LED，实现高效的电光转换。该项目的实施，不仅可以拓宽传统LED的设计原理和开发思路，也可为新型电光转换器件的发展提供重要的理论依据和技术支持。

在本课题中，我们通过研究功率LED的电学、热学和光学过程之间的内在联系和相互耦合机制，揭示了功率LED发光效率与其光电热物理过程的联系和规律；通过理论分析结合时域电磁方法计算的方法探索了提高LED发光效率的新途径, 研究了深刻蚀、浅刻蚀以及嵌入式光子晶体结构与LED有源区的耦合机理，分析了准晶态光子晶体和复合结构光子晶体对LED中光子调控的规律；搭建了LED光电热测试系统和LED可靠性测试系统平台，提出了一种基于遗传算法的BP神经网络的LED寿命预测模型，并对部分理论计算结果进行了验证。该项目的完成，不仅可以拓宽传统LED的设计原理和开发思路，也可为新型电光转换器件的发展提供重要的理论依据和技术支持。