Ferromagnetism in Mg-doped AlN from ab initio study

Ab initio calculations based on spin density functional theory were carried out to investigate Mg-doped AlN as a possible dilute magnetic semiconductor. It was found that both Al vacancy and substitutional Mg impurity in AlN lead to spin-polarized ground states. However, sufficient Al vacancy concentration may be difficult to achieve under thermal equilibrium because of the high formation energy of Al vacancy. On the other hand, formation energy of Mg defect is fairly low and the authors' calculations predict a ferromagnetic coupling among MgN4 tetrahedra. Based on the analysis on Cu-doped ZnO [L. H. Ye , Phys. Rev. B 73, 033203 (2006)], room temperature ferromagnetism can be expected in AlN doped with 7% of Mg which can be incorporated at a growth temperature of 2000 K under N-rich condition. (c) 2006 American Institute of Physics.