Modelling Charged Defects in Non-Cubic Semiconductors for Radiation Effects Studies in Next Generation Materials
This final report summarizes the results of the Laboratory Directed Research and Devel- opment (LDRD) Project Number 212587 entitled "Modeling Charged Defects in Non-Cubic Semiconductors for Radiation Effects Studies in Next Generation Electronic Materials" . The goal of this project was to extend a predictive capability for modeling defect level energies using first principle density functional theory methods (e.g., for radiation effects assessments) to semiconductors with non-cubic crystal structures. Computational methods that proved accurate for predicting defect levels in standard cubic semiconductors, were found to have shortcomings when applied to the lowered symmetry structures prevalent in next generation electronic materials such as SiC, GaN, and Ga203, stemming from an error in the treatment of the electrostatic boundary conditions. I describe methods to generalized the local moment countercharge (LMCC) scheme to position a charge in bulk supercell calculations of charged defects, circumventing the problem of measuring a dipole in a periodically replicated bulk calculation.