Atomic and electronic structure of Mn-doped GaN (1 1̄ 00) film from first-principles calculations

In this paper, a first principles calculation is used to investigate the atomic and electronic properties of Mn-doped GaN (11̅00) film. The ultrasoft pseudo-potential and general gradient approximation for the exchange and correlation energy functional are used with a cutoff of 30 Ry for the expansion of the electronic wave function in plane waves. In the calculational supercell, a Ga atom is substituted by a Mn atom, which corresponds to a Mn-doping concentration of 6.25%. To determine the energetically most favorable doping site, substitution on the Ga site in different layer of the film is considered. Starting from an ideal surface, the relaxation is performed by minimizing the total energy with respect to the atomic positions in the slab. Simulations show that, with respect to the ideal truncated surface, the length of the Ga-N bond at the surface is reduced and a bond buckling is observed with an inward displacement of the Ga atom with respect to the N atom.