Electronic structure and exchange coupling of Mn impurities in III-V semiconductors

Dilute magnetic semiconductors are without doubt among the most interesting classes of magnetic materials. However, the nature of their electronic structure and magnetic exchange is far from understood, and important discrepancies exist between widely used phenomenological models and first-principles electronic-structure descriptions. Here we apply the ab initio self-interaction-corrected local-spin-density method to study the electronic structure of Mn-doped III-V semiconductors. For (GaMn)As, our results with the (d(5)+h) configuration agree with the Zener model description and predict p-d exchange that is in good agreement with experiment. The ground state in (GaMn)N and (GaMn)P is the d(4) configuration with no intrinsic carriers. If, however, holes are introduced extrinsically, carrier-mediated exchange is possible, but the p-d exchange is predicted to be lower in p-type GaN, as compared with GaP and GaAs. Nevertheless, because of the smaller lattice constant, the estimated Curie temperature is higher than in (GaMn) As, at comparable doping levels.