Exciton Complexes in Self-Assembled In(Ga)As/GaAs Quantum Dots
Exciton Complexes in Self-Assembled In(Ga)As/GaAs Quantum Dots
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自组装 In(Ga)As/GaAs 量子点中的激子配合物
DOI：
10.1007/978-3-540-39180-7_3
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
M. Bayer
中科院分区：
文献类型：
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作者：
M. Bayer
在这篇文章中，我们将介绍我们最近的光谱研究的结果，单一的In（Ga）As/GaAs自组装量子点。我们利用光致发光激发光谱研究了量子点中激子的吸收光谱，并将其与受限单粒子壳层结构的关系进行了研究。我们发现量子点结构的对称性对吸收有很大的影响：量子点结构的对称性越低，吸收就越复杂。对于点的高对称性，我们证明了一个非平凡的相互作用的电子-空穴复合物的量子配置的混合导致不同的吸收光谱，这是由有限的电子壳层的数量控制。我们还将讨论激子-声子相互作用对光谱的影响。最重要的是，对于temperaturesthe宽度的发射线似乎是有限的激子的辐射寿命。然而，已经在中等温度下耦合到声子有相当大的影响。特别是，在室温下的线宽是几个meV的顺序，使术语“人工原子”不再是合理的。然后我们将转向量子点中激子的精细结构效应。我们将证明，精细结构是一个非常敏感的工具，以获得洞察量子点的对称性。有意的对称性破缺可以由具有不同于量子点对称轴的取向的磁场引起。这使得暗激子的详细研究。此外，我们展示了如何带电激子可以区分从中性激子看精细结构。最后，我们将讨论可以从量子点组装的最简单的功能单元，即“双原子”量子点分子。我们将展示一个隧道诱导分裂的能级，它可以是高达30毫电子伏的势垒宽度低于5纳米。在激子精细结构上寻找这些系统，给出了两个量子点电子态相干耦合的唯一证明。
In this contribution we will present the results of our recent spectroscopic studies of single In(Ga)As/GaAs self-assembled quantum dots. We will develop the relation between the excitonic states in quantum dots and the confined single particle shell structure, for which we have studied the absorption spectrum of excitons by photoluminenscence excitation spectroscopy. We find that the absorption varies strongly with the symmetry of the dot structures: It becomes increasingly complicated the more the symmetry of the quantum dot is reduced. For dots of high symmetry we demonstrate that a non-trivial mixing of quantum configurations of the interacting electron--hole complex leads to distinct absorption spectra which are controlled by the number of confined electronic shells. We will also discuss the impact of exciton--phonon interaction on the optical spectra. Most importantly, for temperaturesthe width of the emission lines seems to be limited by the radiative lifetime of the excitons only. However, already at moderate temperatures the coupling to phonons has a considerable influence. In particular, at room temperature the linewidth is on the order of several meV, so that the term ‘artificial atom’ is no longer justified. Then we will turn to fine structure effects of excitons confined in quantum dots. We will demonstrate that the fine structure is a very sensitive tool to obtain insight into the symmetry of the quantum dots. An intentional symmetry breaking can be induced by a magnetic field with an orientation different from the quantum dot symmetry axis. This allows for a detailed study of dark excitons. Further, we show how charged excitons can be distinguished from neutral excitons by looking at the fine structure. Finally, we will discuss the simplest functional unit that can be assembled from quantum dots, the ‘two-atomic’ quantum dot molecule. We will demonstrate a tunneling induced splitting of the energy levels which can be as large as 30 meV for barrier widths below 5 nm. Looking for these systems at the exciton fine structure gives a unique proof of the coherent coupling of the electronic states of the two quantum dots.