Proceedings Article | 19 November 2007
KEYWORDS: Quantum dots, Semiconductors, Electroluminescence, Optoelectronics, Nanostructures, Gallium arsenide, Finite element methods, 3D modeling, Quantum wells, Quantum information
Semiconductor quantum dots have been of major interest in recent years. This has largely been simulated by progress
in quantum dot growth technology, whereby self-organized quantum dots array can be fabricated by MBE and MOCVD
facilities using Stranski Krastanow growth mode. Quantum does material has achieved broad applications in
optoelectronic devices and quantum information fields because of the unique 3D electron confinement. However, a good
understanding about the electronic, excitonic and optoelectronics properties of the quantum materials are very important
in fabrication nanostructure devices based on quantum dots. Based on the 1-band effective-mass theory, a finite element
numerical technique is developed to calculate the electronic structure of truncated conical shaped InAs GaAs vertical
aligned quantum dot molecular, including the wetting layer. Using the axis-symmetry model, the 3D effective-mass
Schrödinger equation with step potential barrier can be reduced to a 2D problem by separating variable technique, which
greatly reduced the calculation cost. Form the calculated results, we found that the coupling effects is obviously when the
separation distance is in the range of the less than 10nm. The wave functions will exhibits large probability in the region
between the quantum dots. In order to consider the effect of the distance between the two layers of quantum dots on the
electronic state coupling, we calculated the results when the distance is 6nm, 11nm, 14nm and 17nm. The ground state,
the second excited and the highest excited state will lower its energy with decreasing the distance between the quantum
dots, but the second excited state will increase its energy. With increasing the distance between the two quantum dots,
the coupling effect will become weaker, and for the ground state, the wave function distribution will tend to localized
only in one of the quantum dot, the energy become something degenerate. The calculated results show that the ground
state and the first excited state are degenerate. With decreasing of the distance, the degenerate states are broken, and the
energy levels are separated. In our simulations, the strain effects are ignored. In the future woks, strain should be taken in
to account as an easy way. The calculated results can help us to examine optoelectronic properties of the semiconductor
nanostructure based on multi sheet of quantum dots with wetting layers.
