Impact of N on the atomic-scale Sb distribution in quaternary GaAsSbN-capped InAs quantum dots.
Impact of N on the atomic-scale Sb distribution in quaternary GaAsSbN-capped InAs quantum dots.
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DOI：
10.1186/1556-276x-7-653
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发表时间：
2012-11-27
影响因子：
--
通讯作者：
Hierro A
中科院分区：
文献类型：
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作者：
Reyes DF;González D;Ulloa JM;Sales DL;Dominguez L;Mayoral A;Hierro A
最近提出了在InAs/GaAs量子点（QD）上使用GaAsSbN覆盖层用于微光电应用，因为它们能够独立地定制电子和空穴限制势。然而，有一个缺乏知识的结构和成分的变化与过程中的同时锑和氮的掺入。在目前的工作中，我们的特点是使用透射电子显微镜技术的影响，在GaAsSb/InAs/GaAs量子点系统中添加N。首先，远离InAs量子点的区域的应变图显示了N掺入的应变场的巨大减小，但具有更高的不均匀性，这表明在几纳米范围内存在富Sb和贫Sb区域的情况下组分调制增强。另一方面，在两种情况下，量子点和周围的平均应变也是相似的。这可以解释为Sb在量子点上方的积累，补偿了由N掺入引起的拉伸应变以及In-Ga混合抑制。事实上，从像差校正的Z-对比度图像的列分辨率的组成图证实，N的添加增强了锑以上的InAs QD的优先沉积，从而引起的生长前沿的起伏。因此，在GaAsSbN样品的光致发光光谱中的强红移不能仅归因于N相关的导带偏移的减少，而且还归因于Sb对QD能带结构的影响的增强。
The use of GaAsSbN capping layers on InAs/GaAs quantum dots (QDs) has recently been proposed for micro- and optoelectronic applications for their ability to independently tailor electron and hole confinement potentials. However, there is a lack of knowledge about the structural and compositional changes associated with the process of simultaneous Sb and N incorporation. In the present work, we have characterized using transmission electron microscopy techniques the effects of adding N in the GaAsSb/InAs/GaAs QD system. Firstly, strain maps of the regions away from the InAs QDs had revealed a huge reduction of the strain fields with the N incorporation but a higher inhomogeneity, which points to a composition modulation enhancement with the presence of Sb-rich and Sb-poor regions in the range of a few nanometers. On the other hand, the average strain in the QDs and surroundings is also similar in both cases. It could be explained by the accumulation of Sb above the QDs, compensating the tensile strain induced by the N incorporation together with an In-Ga intermixing inhibition. Indeed, compositional maps of column resolution from aberration-corrected Z-contrast images confirmed that the addition of N enhances the preferential deposition of Sb above the InAs QD, giving rise to an undulation of the growth front. As an outcome, the strong redshift in the photoluminescence spectrum of the GaAsSbN sample cannot be attributed only to the N-related reduction of the conduction band offset but also to an enhancement of the effect of Sb on the QD band structure.