Quantitative evaluation of the interface lattice quality of a strain superlattice by strain analysis
Quantitative evaluation of the interface lattice quality of a strain superlattice by strain analysis
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通过应变分析定量评估应变超晶格的界面晶格质量
DOI：
10.1039/c7nr06716j
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发表时间：
2018
期刊：
影响因子：
6.7
通讯作者：
Xie Huimin
中科院分区：
文献类型：
--
作者：
Wen Huihui;Zhang Hongye;Liu Zhanwei;Liu Chao;Liu Shuman;Yang Xinan;Liu Fengqi;Xie Huimin
量子级联激光器中应变超晶格结构的晶格质量直接影响激光器的光电性能和使用寿命。然而，目前纳米尺度上的晶格质量评价方法还不是很成熟，尤其是界面晶格质量的评价。在本研究中，通过子集几何相位分析（S-GPA）结合峰值查找（PF）方法和最优逼近算法（OAA），可以同时准确地确定位于多个界面层中的所有原子，灵敏度约为0.04 Å。在确定界面位置的基础上，通过优化选择多个参考区域，利用改进的S-GPA同时测量了超晶格结构各层的应变分布。基于弹性力学的理论模型，对应变/应力补偿效果进行了定量评价。该方法成功地应用于分子束外延（MBE）生长的In0.6Ga0.4As/In0.44Al0.56As超晶格结构的晶格质量评价。结果表明：界面晶格基本完美，层厚均匀，无缺陷，无应力集中；每个In0.44Al0.56As层和相邻的In0.6Ga0.4As层相互之间提供了有效的应变/应力补偿，减少了形成位错的可能性。在一段时间内，活动区域得到了适当的应变平衡，使其应变几乎为净零。该方法不仅可以在大视场范围内评价超晶格结构的生长质量，而且可以为进一步改进超晶格设计提供定量的实验数据。
The lattice quality of strain superlattice structures in Quantum Cascade Lasers (QCLs) directly influences the photoelectric properties and service life of the lasers. However, the evaluation method for lattice quality on the nanoscale is not very well developed at present, especially for interface lattice quality assessment. In this investigation, all atoms positioned in the multiple interface layers can be simultaneously and accurately determined through Subset Geometric Phase Analysis (S-GPA) combined with a Peak Finding (PF) method and an Optimal Approximation Algorithm (OAA) with a sensitivity of about 0.04 Å. Based on the determined interface location, the strain distribution in all layers of the superlattice structure was simultaneously measured using the improved S-GPA by means of the optimal selection of multiple reference areas. A quantitative evaluation of the strain/stress compensation effect was then carried out based on the theoretical model of elastic mechanics. The proposed method was successfully applied to evaluating the lattice quality of an In0.6Ga0.4As/In0.44Al0.56As superlattice structure grown by Molecular Beam Epitaxy (MBE). The obtained results show that the interface lattices are almost perfect with a uniform thickness of layers, without any defects and stress concentration. Each In0.44Al0.56As layer and adjacent In0.6Ga0.4As layers provided effective strain/stress compensation for each other, reducing the possibility of forming dislocations. In one period, the active region has been properly strain-balanced to give a nearly net zero strain. The proposed method can not only be applied in evaluating the growth quality of the superlattice structure with a large field of view, but also provide quantitative experimental data for further improving the superlattice design.