First Principles Study For Typical Ⅲ Nitrides Semiconductor Materials

The design and forecast of the structures and properties of materials by computer can be achieved through theoretical calculation and numerical simulation by which waste of time and mistakes in experiments can be avoided.This field is still in the ascendant.Density function theory,as we know,can deal multi-electron system with single-electron system.So binding energy,crystal lattice constants,bulk modules were acquired based on density function theory of semiconductor and metal materials.These results were in a very good agreement with experiments.So theory calculation was an important achievement in electronic theory.The research of energy band starts from developing about qualitative universal disciplinarian to calculating about the complex band structure.There are much arithmetic based on density function theory.Such as LCAO-TB,OPW,PWP,LAPW and LMTO,etc.There have been many applications in electronics,calorifics and optics for typicalⅢnitrides(GaN,InN)semiconductor materials due to their excellent properties.Lots of efforts have been contributed to this field up to date.However,there are still many unresolved problems in this field due to limitation in preparation method and research technique.In this dissertation,the typicalⅢnitrides semiconductor materials(GaN,InN)have been investigated based on plane-wave pseudopotential density functional theory(DFT),which has significative values of theory study and extensive foreground of applications.Main contents of this dissertation included:In the first chapter,the structures and properties ofⅢnitrides semiconductor materials have been introduced.Furthermore,the recent theory study and synthetical method have been summarized.In the second chapter,the basic concept of DFT and the function of CASTEP software have been introduced.In the third chapter,The electronic structures and optical properties of pure and Al & Mg-doped cubic-blende GaN have been studied based on the density functional theory and the generalized gradient approximation(GGA)method.The relationship between the distribution of the electronic states and their structures has been analyzed.The optical function on the doping GaN system have been acquired.The calculation results indicated that the hole concentration of Mg-doped GaN is increased and Mg-doped GaN markedly enhanced the conductivity of the materials;But the carder concentration of Al-doped GaN is not changed and optical bandgap is only broadened.By analyzing Mulliken charge and bond population,the positive charge of Al and Mg are more than any Ga atom,it shows electronegativity of Al and Mg less than Ga atom so they lose electron very easily.The mechanism of luminescence has been explained in terms of analyzing the optical function.It offers theoretical data for the further design and application of optoelectronic materials of GaN.By comparison,there is a good agreement with the existing literatures.The fourth chapter,The structural,electronic and optical properties of zinc blende structure InN have been studied under different high pressures by means of the first-principle calculation with the plane wave pseudo-potential method.In this paper,We have found that the lattice constants decrease with pressure increasing.Comparing the partial density of states under different pressure,we found the conduction band electrons offset to higher energy and the valence band electrons are opposite,so the energy gap is broadened.By analyzing Mulliken charge and bond population,the ionicity of In-N is strong and it is still strong under the pressure.We found the absorption spectrum experienced "blue shift" under pressure.The fifth chapter,The electronic structure and magnetism properties of Cr and Mn-doped cubic-blende InN have been studied based on the density functional theory and the generalized gradient approximation(GGA)method from the first principle.The result shows:pure InN has no magnetism properties but doped-InN has ferromagnetism and magnetic moment is 2.44μ_B,3.24μ_B separately,their magnetism mostly roots in d-d exchange of Mn or Cr and p of N or In because p-d hybridigation;there is a antiferromagnetism coupling between doped-atom and N near it but there is a ferromagnetism coupling between doped-atom and N away it;The total magnetic moment is reduced but doped-InN has still ferromagnetism when doped concentration decreases.The last is about conclusion and expectation of this dissertation.