This paper investigates the mechanisms that limit the efficiency and the reliability of InGaN-based LEDs, by presenting an analysis carried out on devices having two quantum wells that emit at different wavelengths (405 nm and 495 nm). A color-coded test structure was designed in order to easily quantify the optical characteristics of both quantum wells, and to describe in detail the stress dynamics as a function of In-content and of the position of the quantum wells.

The attention was focused on: (i) electrical degradation induced by constant current stress at high temperature, that was found to be related to a diffusion process; (ii) degradation of the optical parameters, which was dominantly ascribed to an increase in SRH recombination and to a decreased carrier injection efficiency; (iii) effect of indium content and carrier distribution on the efficiency and reliability of the devices. The results strongly suggest that the internal quantum efficiency is limited by a low injection efficiency and by the quantum confinement Stark effect. In addition, the results on optical degradation highlight the presence of different mechanisms that contribute to the degradation: the role of Shockley-Read-Hall recombination, carrier escape and Auger processes are discussed.

本文通过对具有两个发射不同波长（405 nm 和 495 nm）的量子阱的器件进行分析，研究了限制 InGaN 基 LED 效率和可靠性的机制。设计了一种颜色编码的测试结构，以便轻松量化两个量子阱的光学特性，并详细描述作为 In 含量和量子阱位置的函数的应力动力学。

注意力集中在：(i) 高温下恒流应力引起的电退化，发现与扩散过程有关；(ii) 光学参数的退化，这主要归因于 SRH 复合的增加和载流子注入效率的降低；(iii) 铟含量和载流子分布对器件效率和可靠性的影响。结果强烈表明内部量子效率受到低注入效率和量子限制斯塔克效应的限制。此外，光学退化的结果突出了导致退化的不同机制的存在：讨论了肖克利-雷德-霍尔复合、载流子逃逸和俄歇过程的作用。