Propriétés structurales, élastiques et optiques de semiconducteurs à grand gap : Les composés B-V, les alliages ZnxCd1-xSe et ZnSe1-xTex, le β-SiC

Abstract

The thesis has been the subject of an experimental and theoretical study on the large band gap with a cubic structure. This work deals with a numerical study only on the B-V compounds and the ZnxCd1-xSe and ZnSe1-xTex alloys for which we employed the virtual crystal approximation provided with the ABINIT program. In the case of β-SiC, we made a comparative study between the numerical results obtained from ab-initio calculation using ABINIT or Wien2k within the Density Functional Theory framework with either Local Density Approximation or Generalized Gradient Approximation for the atomic potentials, and the experimental results obtained in the LPSM laboratory (Paris13, France). The experiments were carried out with the optical spectroscopy methods: Brillouin light scattering, Raman scattering and VIS-IR reflectometry. The physical properties studied are: the second and third order elastic constants, the phonons at the (Γ) point, the permittivity and tensors in the VIS-IR range. The variation of the elastic constants is also numerically studied and the phase transformations are discussed in relation to the mechanical stability criteria