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Dilute first principles study of magnetic semiconductor tunnel junction GaN:Mn/AlN/GaN:Mn conductance

Author: ChenGuangWei
Tutor: HuangGuiQin
School: Nanjing Normal University
Course: Condensed Matter Physics
Keywords: Diluted magnetic semiconductors (DMS) magnetic tunnel junction GaN conductance first-principle calculation
CLC: TN304
Type: Master's thesis
Year: 2012
Downloads: 56
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Abstract


GaN, which is called the typical representation of the third-generation semiconductor material, is a sort of Ⅲ-Ⅴ Wide-band-gap semiconductor material with excellent performance,and great attention has been paid to the research and application of it. Diluted magnetic semiconductor (DMS) GaN doped with magnical impurity has attracted considerable interest in recent years because of its higher curie temperature than room temperature and ferromagnetism. The material is usually made in the form of magnetic tunnel junction in order to be used conveniently.Based on the first-principles calculation, the geometric structures、electronic structures and conductance of DMS tunnel junction GaN:Mn/AlN/GaN:Mn are studied. Some results are as the following:(1) When Mn is doped in GaN, the bands of spin-up and spin-down are split. The Fermi level cuts only the spin-up band, showing that the material is halfmetallic and is therefore ideal for spin injection.(2) Research on the relationship between the conductance of magnetic tunnel junction GaN:Mn/AlN/GaN:Mn and the thickness of barrier layer reflects that the conductance decreases with the increase of thickness of barrier layer(3) Research on the relationship between the conductance of magnetic tunnel junction GaN:Mn/AlN/GaN:Mn and the doping site of impurity atom Mn. It shows that conductance is larger when the doping Mn atom is closer to the interface. This is due to the contribution of resonant tunnelling as well as coherent tunnelling. Furthermore, the resonant tunnelling efficiency decreases when the thickness of barrier layer increases.(4) Research on the relationship between conductance of magnetic tunnel junction GaN:Mn/AlN/GaN:Mn and the doping density of Mn atom shows that the conductance is decreased with the decrease of the doping density.

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