Dilute Magnetic Semiconductor Gan: Mn (?) Film First Principle Studies

Wide-band-gap GaN semiconductor material has attracted considerable interest recently because of their application for blue light-emitting diodes and lasers. Diluted magnetic semiconductors (DMS) are considered to be potential candidates for present and future technological applications in semiconductor spintronics. People have played close attention to GaN:Mn diluted magnetic semiconductors in recent years because they have higher curie temperature than room temperature. The material was usually made in the form of film in order to be used conveniently.The geometric structures,electronic structures and magnetic properties of Mn-doped GaN (1010) Diluted magnetic semiconductor film are investigated using first-principles calculations. The main works are in the following(1) For the undoped GaN (1010) film, the results of geometric relaxation indicate that, with respect to the ideal truncated surface, the length of the Ga-N bond length 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. This corresponds to a 6.58% contraction with respect to the bond length calculated for the bulk. The buckling angle between the Ga-N surface bond and the surface plane is about 8.56°. The calculations of electronic structure show that two surface bands are formed in the original gap. These results are consistent very well with other references.(2) The defect formation energy is the smallest when Mn is doped in the surface layer of the GaN (1010) film, showing that the site closest to the surface is always favored. The Mn-N bond length is reduced as the Ga-N bond at the surface, but the phenomena of the buckling of Ga-N bond is not observed for Mn-N bond. The electronics structure results reveal a spin polarized impurity band in band structure of Mn-doped GaN (1010) film due to hybridization of Mn3d and N2p orbitals, the Mn impurity bands appear in the gap of spin-up bands, showing that the film material is half metallic and suited for spin injectors.(3) The magnetism of GaN:Mn (1010) film is investigated systematically. The magnetism ground state is antiferromagnetism coupling when the replacement of the nearest neighbor Ga atoms with Mn at sites on the surface layer, while it is ferromagnetism coupling when two Mn atoms are in other configurations. The different magnetic interactions are analyzed by using Stoner model and the change of orbital bonding under different magnetic configurations.