First-principles calculations of native defects in tetrahedrally-coordinated isovalent semiconductors

Abstract

This thesis describes the development, the application and the analysis of the accuracy of state-of-the-art ab initio calculations in the description of intrinsic point defects in technologically important tetrahedrally coordinated isovalent semiconductors.

The calculations presented in this thesis are based on the density-functional theory. The effective single-particle equations derived from the density-functional theory in the Kohn-Sham scheme are solved numerically using the plane-wave basis representation of the valence electrons and the pseudopotential description of the core electrons.

The use of the plane-wave basis enforces periodic boundary conditions. The calculation of the properties of isolated defects within periodic boundary conditions is customarily referred to as the supercell approximation. The supercell method is analyzed in detail in the thesis, with a special emphasis on the calculation of charged point defects.

The developments in the numerical methods presented in this thesis include the implementation of a non-local screened-exchange operator for the improved description of the exchange and correlation energy and a non-uniform charge-compensation scheme for charged point defects in a massively-parallel plane-wave pseudopotential software package.

The included papers present the most accurate numerical electronic structure calculations to date for vacancies in silicon and silicon-germanium, and for interstitials in silicon carbide.