Barettin Daniele, De Angelis Roberta, Prosposito Paolo, Auf der Maur Matthias, Casalboni Mauro, Pecchia Alessandro
Department of Electronic Engineering, University of Rome 'Tor Vergata', Via del Politecnico 1, I-00133 Rome, Italy.
Nanotechnology. 2014 May 16;25(19):195201. doi: 10.1088/0957-4484/25/19/195201. Epub 2014 Apr 24.
We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In₀.₄₈Ga₀.₅₂ buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, [Formula: see text] bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband [Formula: see text] approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further verifications, which have clarified some aspects of the experimental results and helped us to develop a suitable model for the spectrum, by assuming a not equiprobable weight from each dot, a model which is extremely consistent with the experimental data.
我们报告了在In₀.₄₈Ga₀.₅₂缓冲层上的闪锌矿InP表面量子点（QD）的数值模拟。我们的模型严格基于实验结构，因为我们直接通过原子力显微镜结果推断出三维量子点。针对这种实际结构给出了连续介质机电、[公式：见正文]能带结构和光学计算结果，同时还给出了与推断出的量子点具有相同半径和高度的透镜形量子点的基准计算结果。通过比较两种不同结构得到的结果，展示了有趣的异同点，得出结论：使用更实际的结构可以在量子点建模方面带来显著改进。事实上，推断出的量子点的电子p类能级的显著分裂似乎证明，即使在多带[公式：见正文]方法中，实际的实验结构也能重现正确的对称性和通常由原子计算给出的正确分裂。此外，空穴的能级和对称性强烈依赖于量子点的形状。特别是，据我们所知，它们的波函数对称性似乎与之前用闪锌矿理想结构（如透镜或截顶金字塔）模拟得到的任何结果都不相似。振子强度的大小也强烈依赖于量子点的形状，推断出的量子点的强度较低，特别是对于电子和空穴基态之间的跃迁，这是由于波函数重叠的显著减少。我们还将在含有约60个量子点的均匀样品上测量的实验光致发光光谱与从单量子点计算得出的数值系综平均值进行了比较。数值光谱的更宽能量范围促使我们进行进一步验证，这些验证澄清了实验结果的一些方面，并帮助我们通过假设每个量子点的权重不等概率来开发一个适用于该光谱的模型，该模型与实验数据极其一致。
