The consequences of high injected carrier densities on carrier localization and efficiency droop in InGaN/GaN quantum well structures
The consequences of high injected carrier densities on carrier localization and efficiency droop in InGaN/GaN quantum well structures
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DOI：
10.1063/1.3703062
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发表时间：
2012-04-15
影响因子：
3.2
通讯作者：
Humphreys, C. J.
中科院分区：
文献类型：
--
作者：
Hammersley, S.;Watson-Parris, D.;Humphreys, C. J.
InGaN/GaN量子阱发光二极管效率下降的根本原因引起了人们极大的兴趣，提出了几种物理机制来解释这一现象。在本文中，我们报告的观察减少本地化诱导的S形温度依赖性的峰值光致发光能量随着激发功率密度的增加。这种S形依赖性是载波定位的关键指纹。在S形深度减小的激发功率密度范围内，我们还观察到每单位激发功率的积分光致发光强度减小，即，效率下降。因此，效率下降的开始发生在与载流子离域的开始相同的载流子密度处。我们将这些实验结果与理论模型的预测的载流子本地化的影响，由于在InGaN/GaN量子威尔斯的光学性质上的随机分布的In原子的浓度的局部变化。在此基础上的理论与实验的比较，我们属性的S形温度依赖性的饱和可用的局域态的减少。我们建议，这种饱和的本地化状态是一个促成因素的效率下降，从而非本地化的载流子重组非辐射。(C)2012年美国物理学会。[http：//dx.doi.org/10.1063/1.3703062]
There is a great deal of interest in the underlying causes of efficiency droop in InGaN/GaN quantum well light emitting diodes, with several physical mechanisms being put forward to explain the phenomenon. In this paper we report on the observation of a reduction in the localization induced S-shape temperature dependence of the peak photoluminescence energy with increasing excitation power density. This S-shape dependence is a key fingerprint of carrier localization. Over the range of excitation power density where the depth of the S shape is reduced, we also observe a reduction in the integrated photoluminescence intensity per unit excitation power, i.e., efficiency droop. Hence, the onset of efficiency droop occurs at the same carrier density as the onset of carrier delocalization. We correlate these experimental results with the predictions of a theoretical model of the effects of carrier localization due to local variations in the concentration of the randomly distributed In atoms on the optical properties of InGaN/GaN quantum wells. On the basis of this comparison of theory with experiment we attribute the reduction in the S-shape temperature dependence to the saturation of the available localized states. We propose that this saturation of the localized states is a contributory factor to efficiency droop whereby nonlocalized carriers recombine non-radiatively. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3703062]