First principle calculation for structural properties and bowing parameter in Ga1−xMnxN materials

Using the Full Potential Linear Muffin-Tin orbital (FP-LMTO) method [Savrasov SY, Savrasov DY. Phys. Rev. B 46 (1992) 12181; Savrasov SY, Savrasov DY, Andersen OK. Phys. Rev. Lett. 72 (1994) 372], within the density functional theory [Parr RG, Yang W. Density Functional Theory of Atoms and Molecules. New York: Oxford University Press; 1989. [3]], first-principles calculations have been adopted to investigate the electronic structure and disorder effects in Mn-doped GaN materials in the zincblende (ZB) and wurtzite (W) configurations. The electronic and the structural properties are calculated using the local density approximation (LDA) [Perdew JP, Wang Y. Phys. Rev. B 45(13) (1992) 244. [4]] and generalized gradient approximation GGA [Perdew JP, Wang Y. Phys. Rev. B 33 (1986) 8800. [5]]. Basic properties were determined for the bulk materials (GaN, MnN) as well as for average concentrations (x=0.25, 0.50, 0.75) of the alloys. A trend of band gap bowing parameter calculation is done with respect to Mn concentration and is found to be mainly caused by charge exchange while the volume deformation and structural relaxation contribute to this disorder parameter with smaller magnitude in both considered configurations. This should be expected since there is a weak mismatch between the lattice parameter of the binary compounds and a considerable electro-negativity difference between Mn and (Ga, N) atoms.