Defect states in semiconductors: Mn acceptor in GaAs

A non-self-consistent method is presented that enables the calculation of the electronic structure, approximating the local density approximation, of defects in semiconductors over a wide concentration range. For the Mn acceptor in GaAs the method reveals problems in the ab-initio description in the dilute limit, where the Mn acceptor are found to be excessively delocalised. A configuration-interaction scheme is adopted to describe interactions between the defect states and model the acceptor level charging process for varying degrees of acceptor level localisation.