Structural, electronic and magnetic properties of Mn-doped GaAs(110) surface

First principles total-energy pseudopotential calculations have been performed to investigate STM images of the (110) cross-sectional surface of Mn-doped GaAs. We have considered configurations with Mn in interstitial positions in the uppermost surface layer with Mn surrounded by As (Int(As)) or Ga (Int(Ga)) atoms. The introduction of Mn on the GaAs(110) surface results in a strong local distortion in the underlying crystal lattice, with variations of interatomic distances up to 3% with respect to unrelaxed ones. In both cases, the surface electronic structure is half-metallic (or nearly half metallic) and it strongly depends on the local Mn environment. The nearby Mn atoms show an induced spin-polarization resulting in a ferromagnetic Mn-As and antiferromagnetic Mn-Ga configuration. The simulation of the STM images show very different pattern of the imaged Mn atom, suggesting that they could be easily discerned by STM analysis.