Semiconductor quantum dots (QDs) in the InAs/AlGaAs system are of great importance due to their promising optoelectronic and nanophotonic applications. However, control over emission wavelength governed by Al content in the matrix is still limited because of an influence of surface Al content on QD size and density. In this paper, we study the growth of In nanostructures by droplet epitaxy on various AlGaAs surfaces. We demonstrate that an increase in the Al content leads to a decrease in the droplet density and an increase in their size, which contradicts the Stranski-Krastanov QD growth. Using a hybrid analytical-Monte Carlo model, we explain this phenomenon by the fact that In adatoms acquire higher mobility on a first indium monolayer which is bound to surface Al atoms. This assumption is confirmed by the fact that a temperature decrease does not lead to a great increase in the critical thickness of droplet formation on the Al-containing surfaces whereas it changes considerably on the GaAs surface. Furthermore, the Al content influence on the formation of In droplets is much less significant than on the growth of InAs QDs by the Stranski-Krastanov mode. This gives an opportunity to use droplet epitaxy to control the matrix bandgap without considerable influence on the QD characteristics.

中文翻译：

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在 AlGaAs 表面液滴外延过程中 In 吸附原子的异常行为

InAs/AlGaAs 系统中的半导体量子点 (QD) 因其有前途的光电和纳米光子应用而非常重要。然而，由于表面 Al 含量对 QD 尺寸和密度的影响，对由基体中 Al 含量控制的发射波长的控制仍然有限。在本文中，我们通过液滴外延在各种 AlGaAs 表面上研究 In 纳米结构的生长。我们证明了 Al 含量的增加导致液滴密度降低和尺寸增加，这与 Stranski-Krastanov QD 增长相矛盾。使用混合分析蒙特卡罗模型，我们通过以下事实来解释这种现象，即 In 吸附原子在与表面铝原子结合的第一铟单层上获得更高的迁移率。温度降低不会导致含铝表面上液滴形成的临界厚度大幅增加，而在 GaAs 表面上发生显着变化，这一事实证实了这一假设。此外，Al 含量对 In 液滴形成的影响远不如 Stranski-Krastanov 模式对 InAs QD 生长的影响。这提供了使用液滴外延来控制基质带隙而不会对 QD 特性产生显着影响的机会。