Defect levels in doped silicon using Koopmans spectral functionals

Substitutional defects in insulating crystalline materials lead to the formation of impurity levels within the forbidden gap that play an essential role in determining the properties of electronic devices. The need for large supercells has often limited the simulation of these systems to standard density-functional theory calculations precluding access to spectral properties. In this work we address this class of problems using Koopmans-compliant functionals, that are a novel orbital-density-dependent approach that describes accurately charged excitations and the electron addition/removal processes. Given the success in the description of the band structure of semiconductors and insulators -- with results comparable to state-of-the-art many-body perturbation theory methods -- here we use Koopmans functionals to predict the energy levels of defects in doped silicon.