A Computational Investigation of Electron Energy States for Vertically Coupled Semiconductor Quantum Dots
Yiming Li and Hsiao-Mei Lu
National Nano Device Laboratories and National Chiao Tung University, TW
Keywords: Electron Energy States, artificial molecules, Vertically Coupled Semiconductor Quantum Dots
We study the induced property of ground and excited state energies of electrons confined in 3D nanostructures that the In_xGa_1-xAs QDs are embedded into GaAs matrix and have a vertically coupled topology. The disk- (DI) and conical-shaped (CO) QDs separated by an interdistance are investigated. Our 3D model includes an effective one electronic band Hamiltonian, the energy- and position-dependent electron effective mass approximation, finite hard wall confinement potential, and Ben Daniel-Duke boundary conditions. Based on a nonlinear iterative method we simulate the same size coupled QDs. For both shapes when the two dots are totally separated, the QD1 is constructed with no any bounded states (x=0.8) and the QD2 is formed to be have only two bounded states (x=0). When these two QDs are within a finite distance, we have found the induced energy states are heavily dependent on the QDs shapes and interdistance. Both of the ground and excited states are decreased when the interdistance is decreased. Due to the stronger wave functions interaction, the DI-shaped coupled QDs have larger ground state variation than that of CO-shaped QDs. For the excited states, we have similar but weaker interaction for both shapes. Our study enhances the physical interests and applications.
NSTI Nanotech 2003 Conference Technical Program Abstract