Iron and manganese doped zinc-blende GaN

The electronic structure of Mn and Fe doping impurities in zinc-blende gallium nitride (c-GaN) crystal lattice have been investigated by the LMTO-TB method. The calculations used the 128 site supercells (64 atoms and 64 empty spheres with an impurity at the origin) with Mn and Fe atoms replacing ions in cation and anion sublattices. It is shown that Mn and Fe ions stay magnetic for all types of substitutions in c-GaN crystal lattice. Fe magnetic moment was found to be 3.5 mu (B) and 1.0 mu (B) for cation and anion substitutions, respectively. Similar data for Mn, magnetic moments are 3.3 mu (B), and 1.9 mu (B), The moments are highly localized, though some weak polarization is seen at the closest atoms to the impurity. The total energies for supercells with and without magnetic impurities are used to determine the most probable single substitutional sites for Fe and Mn in c-GaN. The energies of magnetic electrons levels relative to the valence and conduction bands of the host crystal are analyzed by making use of the total and partial densities of states. The results show that combination of optoelectronic and magnetic properties may well be possible for c-GaN iron and Mn doped systems.