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 layers 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 distortions 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 \emph{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.