作为当前最高效的环保型照明器件，LED在人们生活和工作中的应用场合越来越广。然而LED在大电流下较显著的内量子效率损失（即Droop效应）严重制约着LED向大功率方向发展。因此，有必要找到造成Droop效应的根本原因。目前已有的研究仅能够证明影响Droop效应的物理过程主要包括俄歇复合和载流子泄漏，但在计算或实验分析中引入了过多的假设并且缺乏有效的对比，因而难以明确大电流下造成Droop效应的根本原因。 俄歇复合和载流子泄漏对载流子寿命有着不同的影响——俄歇复合会减小相应注入水平下的载流子寿命，而载流子泄漏只影响注入到有源区的载流子浓度，而不会直接影响载流子寿命。因此，针对载流子寿命随注入电流的变化规律进行研究有助于更准确地认识Droop效应的机理。本论文从LED载流子寿命的评测方法入手来分析LED中的载流子复合规律并探究 Droop效应的主要原因，取得的主要结果如下。 首先，本论文依据差分载流子寿命理论，设计了差分载流子寿命的测试系统。通过消除系统内会影响测试结果的寄生效应，最终优化得到的测试系统其测试结果稳定、可靠。 在获得了不同注入水平下的载流子寿命和LED效率后，论文分别对从俄歇复合和载流子泄漏两方面对载流子复合过程进行了拟合和对比。结果发现，如果假设俄歇复合是引起Droop 效应的唯一原因，那么内量子效率和载流子寿命随电流变化的关系很难同时满足；如果忽略俄歇复合，考虑载流子退局域化过程和载流子泄漏，则可以很好地同时拟合内量子效率和载流子寿命随电流变化的曲线。据此结果推断，大电流下LED的Droop效应主要是由载流子泄漏引起的。 最后，针对载流子泄漏，对比分析了不同量子阱数LED的发光特性。发现当量子阱数目较少时，有源区对载流子的捕获能力不足，导致较多的载流子直接从有源区“飞跃”而泄漏；而当量子阱数目较多时，有源区对载流子的捕获能力增强，但随注入电流增加载流子输运的不对称性加剧，Droop效应更加显著。

Acting as the most environmentally friendly high power lighting device, the application areas of light-emitting-diodes are more and more wide in peoples’ work and daily life. However, the large efficiency loss in high injection currents, well known as droop, limits the development of LED to high power applications. Current research can just effectively demonstrate the origin of efficiency droop is between Auger recombination and carrier leakage. But since too many assumptions are brought in as well as the lack of effective comparisons between them, it can’t obtain the basic law. Auger recombination and carrier leakage have different influence on carrier lifetime. The increase of Auger recombination may decrease the value of carrier lifetime, while carrier leakage just change the actual carrier density in active area that has no effect on carrier lifetime. Thus, the analysis on the relationship between carrier lifetime and injection currents does well in the more accurate recognition for efficiency droop. In this article, the work begin with the measurement of carrier lifetime and then analyze the recombination characteristics. The main results obtained are as follows. Firstly, based on the theory of differential carrier lifetime, we design a system to measure the carrier lifetime at different current levels. By eliminating the parasitic effects that may influence the accuracy of carrier lifetime in the system, the reliable measurement result can be obtained. Having got carrier lifetimes at different injection currents, we separately fitting the internal quantum efficiency and carrier lifetime to compare the influence degree of Auger recombination and carrier leakage. According to the fitting results, singly consider Auger recombination can’t fit the two origins simultaneously. But when ignoring Auger recombination and considering the influence of carrier delocalization at the initial stage of Droop, carrier leakage can fit the data effectively. As a result, it can be inferred that carrier leakage is the main cause for efficiency droop at high injection levels. Finally, we analyze the relationship between the characteristics of luminescence and the number of quantum wells. It is found that if the number is not enough, more carriers may fly over the multi-quantum-wells because the capture ability of active area is low. When the number is large enough at a certain stage, the number of captured carriers in active area is increased, leading to more output light. However, the increased length for carriers to move also promotes the asymmetry for electrons and holes that decrease the quantum efficiency more rapidly at high injection level that worsen the droop.