Boyong Jia

Valence band structures of InAs/GaAs quantum rings using the Fourier transform method

The valence band structures of strained InAs/GaAs quantum rings are calculated, with the four-band k ? p model, in the framework of effective-mass envelope function theory. When determining the Hamiltonian matrix elements, we develop the Fourier transform method instead of the widely used analytical integral method. Using Fourier transform, we have investigated the energy levels as functions of the geometrical parameters of the rings and compared our results with those obtained by the analytical integral method. The results show that the energy levels in the quantum rings change dramatically with the inner radius, outer radius, average radius, width, height of the ring and the distance between two adjacent rings. Our method can be adopted in low-dimensional structures with arbitrary shape. Our results are consistent with those in the literature and should be helpful for studying and fabricating optoelectronic devices.

THE STRAIN FIELD DISTRIBUTION OF QUANTUM DOT ARRAY WITH CONICAL SHAPE

A systematic investigation is given about the effects of the longitudinal and transverse periodic distributions on the elastic strain field. The results show that the influences of the longitudinal and transverse period on the strain field are just opposite, especially for the path along the center-axis of the quantum dots. In the proper conditions, the influence of periodicity on strain field distribution can be partly eliminated. The results demonstrate that when calculating the effect of the strain field on the electronic structure, one must take the quantum dots periodic distribution into account. It is unsuitable to use the isolated quantum dot model in simulating the strain field and evaluate the influence on electronic structure.

STRAIN DISTRIBUTION AND ELECTRONIC STRUCTURE OF SELF-ORGANIZED InAs/GaAs QUANTUM DOTS

This paper presents a finite element method for calculating the strain distribution, piezoelectric effects and their influences on the electronic structure of self-organized InAs/GaAs quantum dots. The models used for strain calculations are based on the continuum elastic theory, which is capable of treating the quantum dot of arbitrary shapes. A truncated pyramid shaped quantum dot model including the wetting layer is adopted in this work. The electronic energy levels of the InAs/GaAs systems are calculated by solving the three-dimension effective mass Schrodinger equation including the influences on the modification of conduction band edge due to the strain and piezoelectricity. The calculated results indicate that both strain and piezoelectric effects should be considered, especially in treating the electronic structure and optical characteristics for device applications.

Determination on wave function of quantum structures using finite-difference time domain

With the interest in quantum structures, there is a need to have a flexible method that can help us to determine eigenfunctions for these structures. In this article, we present a method that accomplishes this by using the simulation of the Schrödinger equation based on finite-difference time-domain (FDTD). We choose one-and two-dimensional finite square well potential, and one-and two-dimensional harmonic oscillator potential as examples. Giving the initial condition, we determine the eigenfrequencies through a Fourier transform of the time domain data collected at the center point in the problem space. Another simulation implements a discrete Fourier transform at the eigenfrequencies at every point in the problem space, hence, the eigenfunctions can be constructed.