Etude théorique et pratique de la cathodoluminescence en vue de la détermination de l’influence des défauts dans les semiconducteurs II-VI

Abstract

The objective of this thesis is the theoretical and experimental study of the cathodoluminescence intensity (ICL) to determine the influence of different physical parameters: material parameters, parameters of the incident electron beam and the temperature. A theoretical model that allows the calculation of the cathodoluminescence signal, as a function of incident electron beam parameters, adapted to cadmium telluride bulk material p-type has been established. Through this model we were able to evaluate the role and contribution of each of these parameters. The modeling is based on solving the equations of continuity of both types of charge carriers to both the surface and volume of the material. To do this a method of self-consistent calculation in order to determine the concentration of the charge carriers in excess and the width of the depletion region at the material surface has been used. The numerical simulation results permitted us to determine the effect of the most important parameters that govern the behavior of cathodoluminescence. The dependence of the cathodoluminescence intensity with the local thermal effect induced by the electron beam has also been studied. Furthermore, the simulation allowed us to analyze deeply the role of defects on properties of the barrier height at the semiconductor surface. Using experimental measurements of the cathodoluminescence intensity at room temperature on a list of samples of p-type CdTe and Cd0.96Zn0.04Te, we have been able to clarify, through a comparative study, the effects of various experimental conditions such as: the hydrogenation, the annealing, the plastic deformation, the side effects and addition of zinc. Our simulation work has been validated by various experimental measurements. These later show a great agreement with the results obtained by simulation.