Abstract The growth front stacking of bilayer quantum dot (BQD) InAs/GaAs heterostructures was studied by reflection high energy electron diffraction (RHEED). The mean-field theory was employed to describe the quantum dots (QDs) nucleation, which was experimentally monitored during the intensity changes of the (002)-RHEED diffraction spot along the two- to three-dimensional (2D-3D) InAs growth mode transition. The diffusion parameter obtained from fits of the 2D-3D transition curves was associated to the rate of atoms supply from 2D and 3D islands precursors. The variation of the nucleation parameters during the vertical alignment of QDs associated to the coupling of strain fields were related to the changes of the QDs size and the wetting layer thickness. Numerical simulations indicated that these changes reduce the strain in the BQD heterostructures. Damped oscillatory behavior was observed for the InAs/GaAs critical thickness (Hc) as a function of the number of BQD. The bilayer number after which Hc did not vary significantly, coincided with the one without important variation of the diffusion parameters. The number of BQD layers required to reach this quasi-equilibrium condition depends on the growth parameters of the first layer and the spacer layer thickness, as supported by numerical simulations.

中文翻译：

---

双层量子点 InAs/GaAs 异质结构堆叠过程中的成核和扩散过程

摘要 通过反射高能电子衍射(RHEED) 研究了双层量子点(BQD) InAs/GaAs 异质结构的生长前沿堆叠。采用平均场理论来描述量子点 (QDs) 成核，在 (002)-RHEED 衍射斑沿二维至三维 (2D-3D) InAs 生长模式的强度变化过程中对其进行实验监测过渡。从 2D-3D 过渡曲线拟合获得的扩散参数与 2D 和 3D 岛前体的原子供应速率相关。与应变场耦合相关的 QD 垂直排列过程中成核参数的变化与 QD 尺寸和润湿层厚度的变化有关。数值模拟表明，这些变化降低了 BQD 异质结构中的应变。观察到 InAs/GaAs 临界厚度 (Hc) 作为 BQD 数量的函数的阻尼振荡行为。之后 Hc 没有显着变化的双层数与扩散参数没有重要变化的双层数一致。达到这种准平衡条件所需的 BQD 层数取决于第一层的生长参数和间隔层厚度，这得到了数值模拟的支持。