| This thesis covers research based on ab initio calculations (Hartree-Fock combined with Configuration Interaction) on two materials systems: SiO2 defects in a tetrahedral network and ZnO defects in a wurtzite crystal.;Owing to its importance in the semiconductor industry, SiO2 has been studied extensively. Of particular interest here is the oxygen "vacated-site" defect, which has been studied by the Lucovsky group from XAS data. We start with a SiO2 cluster constructed with optimized bond lengths, bond angles, and medium-range order. The same geometrical basis is then applied to the oxygen vacated-site defect structure. General properties of its ground and excited states within the band gap are revealed.;Wurtsite ZnO is a candidate material for light emission. Dr. Reynolds working in the Aspnes group has developed a series of processing steps leading to significant p-type behavior, and has investigated the effect of the different steps using Raman scattering. Here, the intermediate and final stages of this progression are investigated theoretically. We explore the relationship between various defect sites and p-type conductivity. The ZnO defects are studied with a structural model that uses the experimentally determined parameters. Defect sites related to N doping and single Zn/O vacancies are created and compared. H atoms are also introduced to mimic conditions that occur in metal-organic chemical vapor deposition (MOCVD) with associated Raman frequencies calculated. |
