First-principles study of defect energetics and magnetic properties of Cr, Ru and Rh doped AlN

Abstract Spintronics offers more efficient data storage and quantum computing. Dilute magnetic semiconductors (DMS) are viewed as a sustainable means of achieving practical spintronics. Incorporating transition metal ions into a semiconductor lattice and creating ferromagnetic material is an important aspect of DMS research. This work explores the magnetic properties of Cr, Ru, and Rh doped w-AlN through spin-polarized density functional theory calculations of the electronic structure using supercell models. Formation energies of the point defects computed as a function of Fermi level predict that Cr 4+ , Ru 4+ and Rh 3+ are the most probable charge states for dopant Cr, Ru and Rh atoms, respectively, substituted for Al in w-AlN. Cr-doped AlN with Cr in Cr 4+ charge state is found to be stable in the ferromagnetic state rather than in the antiferromagnetic state for all the concentrations of Cr considered (1.85 to 16.67% of Al). Whereas Ru and Rh doped AlN with Ru and Rh in Ru 4+ and Rh 3+ charge states are unstable in the ferromagnetic state. The electronic density of states (DOS) of Cr-doped AlN in the ferromagnetic state shows that the system remains an insulator, with Fermi level placed directly above the valence band maximum (VBM) for Cr less than 5.56%. With Cr between 7.40 and 12.96%, the system exhibits a half-metal state with Fermi level located on the Cr 3d spin-up peaks occurring on the shoulder of VBM. The DOS transforms to normal metal state at 16.67% Cr with the Fermi level placed on both the spin-up and spin-down Cr 3d DOS. The half metal feature is absent in the DOS of energy-favored antiferromagnetic models of Ru and Rh doped systems. With changes in dopant concentration, the Fermi level falls nonsequentially between the DOS peaks or on the spin-up and spin-down DOS peaks originating from gap states of 4d electrons.