First-principles Study On Doped Aluminium Nitride

In recent years,with the continuous development of electronic information technology,electronic products have gradually developed towards miniaturization,portability and multi-function.In order to meet the development needs of high-power and large-scale integrated circuits,the requirements for packaging substrate materials in electronic components（especially the heat dissipation capacity）are getting higher and higher.As a new type of ceramic material with excellent comprehensive properties,AlN has good mechanical properties,dielectric properties,thermodynamic properties,low production cost,non-toxic and pollution-free,has gradually become a new generation of ideal ceramic packaging substrate materials after Al₂O₃ceramics,so how to obtain AlN ceramics with good comprehensive properties has become the main direction of current research.Limited by experimental equipment and testing methods,it is difficult to analyze the influence of atomic structure on material properties through experimental research at present,and the lack of in-depth understanding of theoretical research on doped AlN restricts its further development.With the continuous development of computational materials science,first-principles calculation methods can be used to conduct theoretical research on the structure and properties of doped AlN,and analyze the influence of different element doping on the structure and properties of AlN from the atomic point of view,which has a good theoretical guiding value for the further understanding and improvement of the structure and properties of AlN ceramic materials.Therefore,this paper uses the first-principles calculation method based on density functional theory to calculate the crystal structure（lattice constant,crystal cell volume）,electronic structure（band structure,density of states）,mechanical properties（elastic constants,body modulus,shear modulus,young’s modulus,hardness）,thermodynamic properties（Debye temperature,melting point）and lattice thermal conductivity of AlN which doped with 14 kinds of atoms（C、O、Be、Mg、Ca、Zn、Cd、Hg、Sc、Y、Ce、Si、Ni、Tl）and co-doped with 3 kinds of atoms（Si、Y、Tl）with C atoms and different content of O atoms respectively.The effects of doping elements and doping methods on the structure,mechanical properties,thermodynamic properties and lattice thermal conductivity of AlN are further analyzed,which provides a theoretical basis for the experimental study in the future.the main findings are as follows:1.The calculated lattice constants of AlN are a=b=3.125（?）,c=5.009（?）,band gap is 4.105e V,bulk modulus is 190GPa,shear modulus is 100.2GPa,Young’s modulus is255.7GPa,hardness is 14.98GPa,Deye temperature is 843.47K,melting point is 2005.9K and lattice thermal conductivity is 42.576W/m·K.It shows that AlN is a direct wide band gap semiconductor,its structure is stable,the material is tough,it has good mechanical and thermodynamic properties,and there is little difference from the experimental results and Related calculation results,indicating that the model and parameters used in the calculation are reasonable and credible.2.In the doped AlN,C、Mg、Cd、Hg、Sc、Y、Tl、Ca、Ce atoms increase the lattice constant and cell volume of AlN from small to large,while Ni、Si、Zn、Be、O atoms decrease the lattice constant and cell volume of AlN from small to large.O、Ce、Si doping AlN forms n-type doping,C、Be、Mg、Ca、Zn、Cd、Hg、Sc、Y、Ni、Tl doping AlN forms p-type doping,and the band gap value decreases after doping.The structure of doped AlN has mechanical stability,and the material shows toughness.After doping,the shear modulus,Young’s modulus,hardness,Debye temperature,melting point and lattice thermal conductivity all decrease,but only the bulk modulus of C and Y doped AlN increases,which are 195.4GPa and 191.9GPa respectively.Among them,the shear modulus,Young’s modulus and hardness of Tl doped AlN are the highest,which are 91.2GPa,234.2GPa and 13.09GPa,respectively.The Debye temperature of Si-doped AlN is the highest,which is 795.20K.The lattice thermal conductivity of Tl、Si doped with AlN is higher,which are 31.760W/m·K,31.714W/m·K,respectively.While the shear modulus,Young’s modulus,hardness,Debye temperature,melting point,and lattice thermal conductivity of Ce-doped AlN are the smallest,which are 44.0GPa,121.9GPa,3.35GPa,528.19K,1712.0K,and 5.073W/m·K,respectively.On the whole,Ce-doped AlN will significantly reduce the mechanical properties,thermodynamic properties and lattice thermal conductivity of AlN,while C、Y、Si and Tl doped AlN has better overall performance.3.In co-doped AlN,Si、Y、Tl and C co-doped AlN form high efficient p-type doping,while in Si,Y,Tl and O co-doped AlN,with the increase of O content,too many electron carriers are introduced,showing metal state characteristics and no obvious band gap.The structure of Si-O co-doped AlN is unstable,and the rest of the co-doped AlN structures are all stable.Tl-O3 co-doped AlN showed slight brittleness,while the rest of the co-doped AlN showed toughness.The bulk modulus of Si-O4 co-doped AlN is 232.9GPa,which is larger than that of AlN.The hardness of Tl-O and Tl-O2 co-doped AlN is greater than that of AlN,which are 19.87GPa and 15.25GPa,respectively.The shear modulus、Young’s modulus、Debye temperature、melting point and lattice thermal conductivity of co-doped AlN are all lower than that of AlN.The shear modulus and Young’s modulus of Si-O4co-doped AlN are the smallest,which are 56.3GPa and 156.4GPa,respectively.The Debye temperature of Tl-O4 co-doped AlN is the smallest,which is 600.41K.The melting point of Tl-O3 co-doped AlN is the smallest,which is 1536.6K.The lattice thermal conductivity of Si-O4 co-doped AlN is the smallest,which is 7.607W/m·K.The Deye temperature、melting point and lattice thermal conductivity of Si-C co-doped AlN are higher than those of Si、C doped AlN,reaching 840.30K、1998.9K and 41.607W/m·K,respectively.In Si、Y、Tl and O co-doped AlN,with the increase of O content,the lattice thermal conductivity of co-doped AlN decreases.