First Principles Study For Typical Semiconductor Materials

Density function theory, as we know, can deal multi-electron system with single-electron system. Binding energy,lattic constants ,bulk modules were presented based on density function theory of semiconductor and metal materials. These results were in a very good agreement with experiments. Theory calculation was an important achievement in electronic theory. A lots of experiments data were obtained and the large,quick computers were also developed in recent years. The calculations by simulating are becoming more and more powerful, and the theory resulted the research of energy band from develop qualitative universal disciplinarian to the complex band structure of typical materials. There are much arithmetic based on density function theory. Such as LCAO-TB,OPW,PWP,LAPW and LMTO, etc. The PWP was used in this thesis. In this thesis, the main research works can be divided into three parts: 1 The plane-wave pseudopotential method within the local-density approximation and generalized gradient approximation was used to investigate the effect of hydrostatic pressure on the structures of BN,BP and BAs. For each compound, two phases were considered: Zincblend(ZB) and Rocksalt(RS). We optimized their structures and obtained the equilibrium lattic constants and bulk modulus. The total energies as functions of volume indicated the transition pressures and transition volumes. These results were in well consist with experimental values and some theoretical works, the discrepancy between our results and some theoretical works come from the computed method. From the bond property of these compounds, we interpreted the reason why BN was more harder than BP and BAs was. We also obtained the relation of band gaps versus pressure for ZB structure. It was found that the indirect band gap of BN increased with decreasing volume, but inversely for BP and BAs. 2,Electronic structure and total energy of BN, AlN and GaN (with wurtzite structure) have been computed by means of plane wave pseudo-potential method (PWP) with GGA and LDA. We obtained the lattice constants and elastic moduli by using GGA and LDA. We found that the lattice constants were in good agreement with experiments, Elastic moduli which deduced by using LDA was closer to experiments than that of using GGA one. Every compound's band gap and absorption coefficient under pressure were obtained and compared with experiments. 3,Electronic structure of ZnS: V supercell was computed by means of plane wave pseudo-potential method(PWP) with generalized gradient approximation(GGA). The optical property was studied and the calculation results were in consist with the values calculated by the theory of crystal field and with the experiment results. Through doping impurity, we found that the energy level has a shift about -2.5ev. The Mulliken charge of V was 0.28, which was smaller than Zn. The covalence of bond S-V was strongest than that of other bonds, since the bond length was the shortest.