Modelling of Quantum Dots with the Finite Element Method

TL;DR

This paper demonstrates the use of the finite element method to model various quantum dot geometries, providing detailed energy and wavefunction calculations that align well with analytical solutions and experimental data.

Contribution

The authors applied FEM to compute energy levels and wavefunctions for diverse quantum dot shapes, including complex geometries, and incorporated diffusion effects in potential modeling.

Findings

FEM accurately predicts energy levels with low deviation from analytical solutions.

Size quantization effects depend on quantum dot shape.

Diffusion effects influence potential depth and band alignment.

Abstract

Considering the increasing number of experimental results in the manufacturing process of quantum dots with different geometries, and the fact that most numerical methods that can be used to investigate quantum dots with non-trivial geometries require large computational capacities the finite element method becomes an incredibly attractive tool for modeling semiconductor QDs. In the current article, the authors have used the FEM to obtain the first twenty-six probability densities and energy values for the following GaAs structures: rectangular, spherical, cylindrical, ellipsoidal, spheroidal, and conical QDs, quantum rings, nanotadpoles, and nanostars. The results of the numerical calculations were compared with the exact analytical solutions and a good deviation was obtained. The ground states energies dependence on the element size was obtained to find the optimal parameter for the investigated structures. The abovementioned calculation results were used to obtain valuable insight into the effects of the size quantization s dependence on the shape of the QDs. Additionally, the wavefunctions and energies of spherical CdSe/CdS quantum dots were obtained while taking into account the diffusion effects on the potential depth with the use of a piecewise Woods-Saxon potential. The diffusion of the effective mass and the dielectric permittivity is obtained with the use of a normal Woods-Saxon potential. A structure with a quasi-type-II band alignment was obtained at the core size of 2.2nm. This result is consistent with the experimental data.