TY - CHAP AB - We present a quantitative parameter-free method for calculating defect states and charge-transition levels of point defects in semiconductors. It combines the strength of density-functional theory for ground-state total energies with quasiparticle corrections to the excitation spectrum obtained from many-body perturbation theory. The latter is implemented within the G0W0 approximation, in which the electronic self-energy is constructed non-self-consistently from the Green’s function of the underlying Kohn–Sham system. The method is general and applicable to arbitrary bulk or surface defects. As an example we consider anion vacancies at the (110) surfaces of III–V semiconductors. Relative to the Kohn–Sham eigenvalues in the local-density approximation, the quasiparticle corrections open the fundamental band gap and raise the position of defect states inside the gap. As a consequence, the charge-transition levels are also pushed to higher energies, leading to close agreement with the available experimental data. AU - Schindlmayr, Arno AU - Scheffler, Matthias ED - Drabold, David A. ED - Estreicher, Stefan K. ID - 18593 SN - 0303-4216 T2 - Theory of Defects in Semiconductors TI - Quasiparticle calculations for point defects at semiconductor surfaces VL - 104 ER -