The First-principles Of AlN Based Diluted Magnetic Semiconductors

The information carrier of traditional electronic components such as diodeand audion, has been electronic charge, but the electronic spin has never beenconsidered. In recent years, studies on the semiconductor spintronics indicatethat the diluted magnetic semiconductors(DMSs) can be used to manage andstore information by means of electronic charge and spin, and havingextensive application in magnetics, optics and electrics. The ideal DMSs shouldexhibit ferromagnetism at room temperature. However, up to now, DMSs havegot little practical applications because of the poor reproducibility of theirpreparation. The theoretical calculation is thus necessary for the production andanalysis of DMSs.With the development of science and technology, the capability ofcomputers becomes more and more advanced, which makes it possible to designnew functional materials by computer simulations. In this paper, our purposewas to predict new AlN-based DMSs, which exhibit ferromagnetism at roomtemperature, by computer simulations, and direct sample preparationtheoretically.Using the first-principles method based on the density functional theory (DFT), we first investigated the geometrical and electronic structure and foundthey were in excellent agreement with experimental data, which providedwell-defined preferences for latter calculation. Then supercell was employed tobuild the vacancy model for AlN. The results showed that Al vacancy in AlNlead to spin-polarized ground states and half-metallic ferromagnetism. Themagnetic moment in the supercell is 1.0μm, mainly contributed to the unpaired2p electrons of the N atoms around the vacancy site. While pure AlN and Nvacancy in AlN did not have spin-polarized ground states and half-metallicferromagnetism. The formation energy of Al vacancy is lower than that of Nvacancy, and the introduction of vacancy into AlN does not induce significantchange in optical properties.Supercell was employed to build the model of Al₁₅MN₁₆(M=Mg,Cu,Zn,Pd). The computational results showed that all the four structures lead tospin-polarized ground states and half-metallic ferromagnetism, but themagnitude and origin of magnetic moment were different. The magneticmoments for Al₁₅MgN₁₆ and Al₁₅ZnN₁₆ are 1.0μB, mainly contributed to theunpaired 2p electrons of the N atoms around Mg or Zn atoms. While themagnetic moments for Al₁₅CuN₁₆ and Al₁₅PdN₁₆ are 2.0μB, mainly contributed tothe hybridization between p electrons of the N atoms and d electrons of Cu or Pdatom. The doping of Mg, Cu, Zn and Pd in AlN don't induce significant changein optical properties; The calculation of formation energy showed an order ofAl₁₅MgN₁₆＜Al₁₅CuN₁₆＜Al₁₅ZnN₁₆＜Al₁₅PdN₁₆. The ferromagnet is stable in Al₁₅MN₁₆(M=Mg,Cu,Zn,Pd). The Curie temperature from the Heisenbergmodel within the mean-field approximation showed an order of Al₁₅CuN₁₆＞Al₁₅PdN₁₆＞Al₁₅MgN₁₆＞Al₁₅ZnN₁₆, and the values higher than 350K. These resultssuggested that Al₁₅MN₁₆(M=Mg,Cu,Zn,Pd)may exhibit ferromagnetism atroom temperature and present a new promising DMSs.