DFT Study On The Structure And Physical Properties Of Ⅲ-Ⅴ Compound Semiconductor

The development of science and technology contribute to the wide applications of various materials in production and peoples livelihood.At the same time,the progress of designing and synthesizing novel materials is never stopped.Thanks to the semiconductor technology and the computer technology,many software and programs based on density functional theory have been developed for simulating and modeling materials,which make it possible to predict the physical properties of materials through crystal structure.The rise of those materials software greatly improve the efficiency of developing potential materials.Predicting novel semiconductor materials have received extensive attention from researchers,semiconductors with excellent characteristics are constantly being proposed under such a background.In this thesis,seven novel Ⅲ-Ⅴ semiconductors in the P3₁21 phase and the Pmn2₁ phase are proposed（P3₁21-AlN,P3₁21-GaN,P3₁21-AlP,P3₁21-GaP,Pmn2₁-AlN,Pmn2₁-GaN,and Pmn2₁-InN）,their structural,mechanical,electronic and optical properties,as well as stability and elastic anisotropy are investigated in detail by density functional theory,the calculated characteristics indicated they all have potential to become high-performance materials in optoelectronic materials.This thesis provides theoretical supplements for subsequent related research or laboratory synthesis.The Cambridge Sequential Total Energy Package（CASTEP）codes are used for structural optimization calculations.All subsequent calculations are based on the optimized structure.The generalized gradient approximation（GGA）of the Perdew-Burke-Ernzerhof（PBE）scheme is used for the calculation of mechanical stability and dynamic stability,and the results showed that all the proposed crystal structures were stable.To prove the reliability of the theoretical calculations,the lattice constants and elastic constants of the allotropes in sphalerite and wurtzite structures are calculated.The results the calculated values are very close to the experimental data,which proves that the lattice constants and elastic constants in this thesis are credible.For the materials in the P3₁21 phase（P3₁21-AlN,P3₁21-GaN,P3₁21-AlP,and P3₁21-GaP）:the calculated bulk modulus,shear modulus and Poissons ratio indicate that they are all brittle materials.P3₁21-AlN and P3₁21-GaN possess high hardness values,their Vickers hardness is 18.7 GPa and 18.1 GPa,respectively.The calculation results of elastic anisotropy show that these four materials all have obvious elastic anisotropy,P3₁21-AlN has the largest elastic anisotropy,and P3₁21-GaP has the smallest elastic anisotropy.The hybrid functional（HSE06）is applied for calculating electronic band structure.The band structures show that they all have obvious bandgaps,indicating that they are semiconductor materials.P3₁21-AlN,P3₁21-GaN,and P3₁21-GaP are direct bandgap semiconductor materials,with bandgaps of 4.51 eV,2.36 eV and 1.84 eV,respectively.P3₁21-AlP is an indirect bandgap semiconductor with a bandgap of 2.01 eV.In addition,the photoelectron absorption of P3₁21-AlP is the largest among the four mentioned structures,which means P3₁21-AlP possess good potential for being optoelectronic devices.And the calculated results indicated that P3₁21-AlN,P3₁21-GaN and P3₁21-GaP are suitable for LED materials,the corresponding light region for the bandgap is ultraviolet region,green region and red region,respectively.For the materials in the Pmn2₁ phase（Pmn2₁-AlN,Pmn2₁-GaN,and Pmn2₁-InN）:Pmn2₁-AlN and Pmn2₁-GaN exhibit brittle,but Pmn2₁-InN exhibits ductile.The Pmn2₁-InN exhibits the largest elastic anisotropy,Pmn2₁-AlN exhibits the smallest elastic anisotropy.The calculated Vickers hardness shows that Pmn2₁-AlN and Pmn2₁-GaN possess high Vickers hardness of 16.3 GPa and 12.8 GPa,respectively.The electronic band structures were calculated by the hybrid functional（HSE06）.The AlN/GaN/InN in Pmn2₁ phase are all direct bandgap semiconductors,and their bandgaps are 5.17 eV,2.77 eV and 0.47 eV,respectively.Pmn2₁-GaN,Pmn2₁-AlN,and Pmn2₁-InN present great application potentials in blue LED material,ultraviolet LED material,and infrared LED material.