Thermodynamic and electronic study of Ga-1 _ xMnxN films. A theoretical study

Abstract

Periodic slab calculations based on density functional theory were performed at the B3LYP level to gain insight into the surfaces of wurtzite GaN nanostructures. The (10 (1) over bar0) and (11 (2) over bar0) GaN surfaces are the most thermodynamically stable surfaces, the energy of the former being slightly smaller than that of the latter. The thermodynamic stability associated with the equilibrium shape of nanowires was determined using the calculated values.Doping with Mn further decreases the surface energy of (10 (1) over bar0) and (11 (2) over bar0). The minimum surface energy of Ga-1 _ xMnxN (0.04 <= x <= 0.17) is found at x similar to 0.08, for (10 (1) over bar0) and (11 (2) over bar0) slab models. Substitution of Ga with Mn in different positions relative to the surface shows that the total energy increases as the Mn atoms move from the surface layer to the interior sites of the slabs. Mn doping is also responsible for decreases in the band gap energy: the minimum calculated band gap in the Ga-1_xMnxN (slab was found at x similar to 0.17, whereas the (11 (2) over bar0) surface presented the corresponding minimum at x similar to 0.04. The magnetic associated with Mn were observed to increase as the ion positions moved closer to the serfaces. (C) 2011 Elsevier B.V. All rights reserved.