Defects at surfaces and interfaces — A scattering theoretical approach

A theory for isolated defects at surfaces and interfaces of semiinfinite solids is presented and applied to vacancies at or near surfaces. Vacancy-induced changes in the surface electronic structure of a simple cubic s-band model are discussed in detail and are found to converge very slowly to corresponding bulk vacancy results when the defect is moved into the solid. Results for Ga and As vacancies at GaAs surfaces are discussed in connection with recent experimental data.