Transport in the metallic regime of Mn-doped III-V semiconductors

The standard model of Mn doping in GaAs is subjected to a coherent potential approximation (CPA) treatment. Transport coefficients are evaluated within the linear response Kubo formalism. Both normal and anomalous contributions to the Hall effect are examined. We use a simple model density of states to describe the undoped valence band. The CPA band structure evolves into a spin split band caused by the p-d exchange scattering with Mn dopants. This gives rise to a strong magnetoresistance, which decreases sharply with temperature. The temperature (T) dependence of the resistance is due to spin-disorder scattering (increasing with T), CPA band-structure renormalization, and charged impurity scattering (decreasing with T). The calculated transport coefficients are discussed in relation to the experiment, with a view of assessing the overall trends and deciding whether the model describes the right physics. This does indeed appear to be the case, bearing in mind that the hopping limit needs to be treated separately, as it cannot be described within the band CPA.