Electronic Structure of a Hydrogenic Acceptor Impurity in Semiconductor Nano-structures

The electronic structure and binding energy of a hydrogenic acceptor impurity in 2, 1, and 0-dimensional semiconductor nano-structures (i.e. quantum well (QW), quantum well wire (QWW), and quantum dot (QD)) are studied in the framework of effective-mass envelope-function theory. The results show that (1) the energy levels monotonically decrease as the quantum confinement sizes increase; (2) the impurity energy levels decrease more slowly for QWWs and QDs as their sizes increase than for QWs; (3) the changes of the acceptor binding energies are very complex as the quantum confinement size increases; (4) the binding energies monotonically decrease as the acceptor moves away from the nano-structures’ center; (5) as the symmetry decreases, the degeneracy is lifted, and the first binding energy level in the QD splits into two branches. Our calculated results are useful for the application of semiconductor nano-structures in electronic and photoelectric devices

Magnetoexcitons in nanostructures exhibiting cylindrical symmetry

The problem of an exciton in the cylindrical nanostructure exposed to an external static magnetic field is investigated. The theoretical model assumes anisotropic masses which are different inside and outside the nanostructure. The confinement potential has finite value at the boundaries and magnetic field is parallel to the axis of the cylinder. The screened Coulomb interaction between an electron and a hole is assumed. The consistent mathematical procedure is developed to calculate the magnetoexciton eigenfunctions and eigenenergies. Our method applies to the systems exhibiting cylindrical symmetry where, due to confinement effects accompanied by the e-h Coulomb interaction, the separation of relative- and center-of-mass motion is not possible. Numerical calculations have been performed for the quantum disk, the cylinder and the quantum rod. The magnetic field dependent energy spectrum and corresponding wave functions, expressed in terms of known one-particle electron and hole eigenfunctions, are calculated. Additionally, we point out the different role of Coulomb interaction in every case