| Exciton and impurity properties of semiconductor nanowires and related systems have been investigated theoretically. Valuable information about specific characteristics is obtained by determining the excitonic properties in these low-dimensional systems. Since nanowires exist in a wide variety of materials and sizes, most calculations in this thesis are kept as general as possible, allowing a very large "window" of applicability of the results.;The excitonic properties were first treated in the most simple case, i.e. without any dielectric mismatch effects. The effective interaction potential and the exciton binding energy was calculated for different states of the electron and hole and we were able to present 'exact' numerical results. In order to reduce the computational burden for future calculations, these results were used to be fitted to three analytical approximate expressions. I also investigated the influence of a magnetic field and calculated the binding energy as a function of the magnetic field, where it was found that the ground state binding energy is mostly affected by a variation of the magnetic field.;Next, the dielectric mismatch was taken into account. The interaction potential becomes significantly more complicated and has been studied in detail in this chapter. Again, an appropriate analytical formula for the effective potential was proposed, which now accounts for the effect of dielectric mismatch. Also the binding energy as function of the wire radius was calculated for different values of the dielectric mismatch and fitted to an analytical expression.;Also positively and negatively charged excitons in wires with different dielectric constants. Due to previous work on excitons, reconstructing the 2D effective potential for trions is an easy and very simple task, allowing an immediately start with calculations of trion binding energies and wave functions.;Finally, energy levels of an impurity near a metallic interface were investigated. The energy levels of a donor as a function of its position was calculated and compared to the bulk values to demonstrate the effect of the metallic interface. In view of potential quantum computing applications, the effect of an electric field moving the electron away from the donor site to the interface was studied. |
