| Aluminum nitride(Al N) crystal is a representative of the third generation of semiconductor materials, making them ideal for the development of new optoelectronic devices. Because the large size, high-quality Al N bulk crystals are very difficult to be prepared, the investigations about the Al N crystal properties(especially about the effects induced by doping) have been blocked, hindering the development of new Al N-based devices. This paper contains two main works:(a) the growth of Al N crystals are experimentally studied, and the corresponding characterizations are also delivered;(b) considering the experimental parameters, the properties of doped Al N crystals are theoretically investigated. This paper mainly focuses on the influence of doping, and the full potential linearized augmented plane wave method based on the density functional theory is used for the first-principles calculations of Group I, II, IV and the transition metals doped wurtzite Al N crystals. The crystal structure, electronic density of states, band structure, magnetic and optical properties which affect the nature of the doped crystals are discussed. These studies are benificial supplementions for the theoretical research of doped Al N. This paper also concentrates on the analysis of various changes in properties of doped Al N crystal through different methods and elements, trying to explore the rules and mechanisms behind the phenomenons. The p-type conductivity, magnetism and optical anisotropy of the doped Al N crystals with Group I elements are highlights of this study.This paper is divided into six chapters described as follows: first chapter introduces the research background of Al N as well as an overview of the major content in this thesis; the second chapter explains the relevant theoretical background of the first principles calculations in detail; in the third chapter, the experimental preparation and characterization of wurtzite Al N crystals have been demonstrated, and the electronic density of states of intrinsic, vacancy and oxygen defect Al N crystals have been theoretically analyzed; in the fourth chapter, at first, we have studied the p-type, dilute magnetism and optical properties of Group IA elements(Li, Na, K) doped Al N crystals while the Li, Na, K doping of another Group III-V compound(Al P crystals) has also been calculated for comparison, then, the formation mechanism of magnetism as well as change of optical anisotropy induced by doping has been described, in addition, the magnetism induced through Group IB non-magnetic elements(Ag, Cu) doping has also been investigated; chapter five has studied various properties of C-Si codoped Al N crystals, furthermore, the comparative analysis of electronic structures in the other Group IV elements codoped Al N crystals has been exhibited, in the meantime, the electronic density of states of the doped Al N with Group II(Mg, Zn, Ca, Sr, Ba) has been discussed, in addition, the variation trend of the spin-polarized electronic density of states in different transition metal elements(Sc, Ti, V, Cr, Mn, Fe, Co, Ni) doped Al N has been described to compare with the Group I elements doped Al N; in chapter six, the conclusion of this paper has been revealed, and the follow-up work is prospected. The main results of this paper are as follows:(1) The physical vapor transport method has been used to prepare the bulk Al N single crystal with a maximum size of 2.2 cm by spontaneous nucleation, laying favorable foundations for the development of new Al N-based optoelectronic devices.(2) The Group IA alkali metals(Li, Na, K) and F codoped wurtzite Al N crystals has been proposed. Combined with other doping configurations of O, the crystal structure, electronic structure, band structure, ferromagnetic and optical properties of doped Al N have been analyzed by the first principles calculations.It is found that the Li-O codoped Al N has very low formation energies no matter in Al-rich or N-rich growth circumstances, and the weakening of localization of the impurity levels above the top of the valence band is very favorable for the p-type doping of Al N. The diluted magnetism has been induced in all the other doped situations except Li-F and Na-F. The O and F atoms still retain their instrinsic non-magnetic states after the incorporation. It is interesting to note that the spin polarization energy of Li-F codoped Al N is zero, indicating that this method can be used to adjust the band gap of Al N crystals without changing the intrinsic non-magnetic state. In addition, the codoping has significantly improved the optical anisotropies of Al N crystals which is beneficial for the applying of Al N crystals in light emitting areas.(3) The ferromagnetic properties of Group IA elements(Li, Na, K) doped Al P systems has been investigated with the discussion of charge transfer mechanism.By first principles calculations, it is found that in 3.125% doping concentration, the net magnetic moment of Li doped Al P is almost zero, and Na, K doped Al Ps do not have stable magnetism at room temperature either. However, with the reducement of the doping concentration, the localization of impurity levels is strengthened which is beneficial for the reduction of spin polarization energy, so it is possible for the Li-doped Al P to obtain stable ferromagnetic ground state.(4) The p-type and magnetic properties of Ag-doped Al N is studied by the first principles calculations with the Cu doped Al N investigated for comparison.The study has found that the Ag doping has realized the p-type characteristic in Al N with direct bandgap as well as small crystal deformation. The asymmetry of spin polarized electronic density of states in Ag-doped Al N comes from the Ag(Cu)-d state and N-2p state hybridization. The ferromagnetism is influenced by the doping concentration. In the 6.25% doping concentration, Ag-doped Al N achieves stable ferromagnetic ground state; when the impurity concentration increases to be 12.5%, the ferromagnetic ground state disappears.
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