Etude des niveaux energetiques des defauts dans la bande interdite du selenium amorph (a-Se)

Abstract

The present work consists on the elaboration and the characterization of pure and As doped a-Se thin films in order to study the electronic and optical properties of a-Se. The first part of this thesis will treat the case of the influence of addition of As on the electronic properties of a-Se. the transient photoconductivity measurements show that As doping of a-Se eliminated the shallow defects linked to the dihedral angle in a-Se chains and introduces important changes in the density of defects in the band gap. This changes increase the relative importance of the deep defect levels in As doping a-Se and thus explain the widely reported hole lifetime shorting with As addition. The second part concerns the optic characterization of a-Se thin films. This method has allowed us to confirm the presence of photoinduced effect in a-Se, the transmission specters realized by UV-Visible spectrophotometer of these films show that the gap of samples illuminated with blue and white natural light shifts to lower energies while their refractive index increases at room temperature. This effect is accompanied by a remarkable crystallization phenomenon