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Dilute magnetic semiconductor GaN: Mn (?) Film First Principle Studies

Author: WangJiXia
Tutor: HuangGuiQin
School: Nanjing Normal University
Course: Condensed Matter Physics
Keywords: Diluted magnetic semiconductors Film GaN First-principles calculations
CLC: O484
Type: Master's thesis
Year: 2011
Downloads: 15
Quote: 0
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Abstract


GaN is an excellent performance of Ⅲ - Ⅴ wide bandgap semiconductor material , known as a typical representative of the third generation of semiconductor materials , and high-profile research and application . Doped GaN-based system, the formation of magnetic impurities in dilute magnetic semiconductor (DMS) , much attention in recent years due to its Curie temperature above room temperature . For ease of application , the material is often made ??into a film form . In this thesis, using first-principles calculation of diluted magnetic semiconductor GaN: Mn (1010) film geometry , electronic structure and magnetic properties . Specific research work has three aspects: (1) for the undoped GaN (1010) film, after relaxation atom position and the ideal position of atoms comparison shows the surface of Ga atoms to the body movement, and Ga atomic bonding the surface layer of N atoms moving to in vitro , leading to surface Ga-N dimer bond length contraction and reverse . And in vivo compared to the 6.58% bond lengths , torsion angle of 8.56 ° . Electronic Structure of the body with respect to significant changes in features two distinct surface belt is in the forbidden band . GaN (1010) film structural relaxation and electronic structure calculations are consistent with the existing literature results . (2) For the Mn - doped GaN (1010) film , Mn atoms doped in the surface layer when the defect formation can be minimized , that the GaN (1010) Mn atoms in the film more easily doped in the surface layer . After relaxation , is similar to the Mn-N bond length in the surface layer with a Ga- N bond length must shrink, but no significant torsional Mn-N bond . The electronic structure calculations show that doping of Mn atoms of makes Mn3d N2p orbital hybridization , a spin-polarized impurity band , only spin-up band across the Fermi surface , the doped film showed a semi - metallic , suitable for spin injection . (3) For thin film magnetic GaN: Mn (1010) , the results of our calculations is when two magnetic Mn atoms in the film surface instead of Ga atoms of the two nearest neighbor magnetic ground state of the anti - ferromagnetic coupling , whereas when two magnetic ground state magnetic Mn atoms in the film surface, alternative second nearest neighbor two Ga atoms or replacement under the surface layer of Ga atoms similar to the body for the ferromagnetic coupling . In this paper, the the Stoner model explains the emergence of antiferromagnetic coupling between the surface of the nearest neighbor Mn atoms . In addition, according to the electronic structure calculated from the atomic orbital bonding angle analysis of the formation mechanism of the different magnetic interactions .

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics
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