Electronic structure, magnetic ordering, and optical properties of GaN and GaAs doped with Mn

The electronic structure and the properties of superdoped GaN(As):Mn (a concentration of Mn from 1.56% to 12.5%) are studied by using the tight-binding linear-muffin-tin-orbital method. Calculations show that the ferromagnetic state is lower in energy than the paramagnetic and antiferromagnetic states for both materials GaN:Mn and GaAs:Mn with all Mn concentrations. At the Fermi energy electronic states are 100% spin polarized, excluding GaAs:Mn with 12.5% of Mn. The most important difference between two materials concerns the energy position and localization of the Mn spin-majority states. In GaN these impurity states lie inside the fundamental gap and are well localized. In GaAs they are positioned near the top of the valence band and are strongly hybridized with it. This difference is clearly seen in the calculated magnetic, optical and, especially, kinetic properties of these materials, which are significantly different. Our investigation of codoping in GaN:Mn (substitution of O for N or Zn for Ga) shows that the atoms of O and Zn change the occupation of Mn bands and strongly affect both magnetic moments and conductivity.