Defect levels are a problem for standard implementations of density-functional theory and the error also influences the energetics. We demonstrate that the HSE06 functional, which describes the electronic structure of all group-IV semiconductors well (including Ge), gives highly accurate charge transition levels, too, if the defect wave function is host related—independent of localization. The degree of fulfilling the generalized Koopmans’ theorem shows the reliability of the results and the highest-occupied eigenvalue always seems to give the correct vertical ionization energy.

• Received 24 March 2010

DOI:https://doi.org/10.1103/PhysRevB.81.153203