TABLE OF CONTENTS In the previous Chapter, we established the basic relations and formalism for the distribution of electrons in the conduction band and holes in the valence band at thermal equilibrium.
Although the equilibrium state for electrons and holes in a semiconductor is the result of interactions between carriers or between carriers and phonons, it does not depend on the way this state is reached. The knowledge of the equilibrium properties is therefore not sufficient and this is all the more true since semiconductor devices usually work under non-equilibrium conditions, In this Chapter, we will thus discuss the dynamics of electrons and holes, including electrical conductivity, Hall effect, diffusion, as well as recombination mechanisms.
Because electrons and holes arc charged particles, they can move in an orderly manner in a semiconductor under the influence of an electric field for example. This motion generates an electrical current, called drift current, which is at the origin of the electrical conductivity phenomenon of certain solids. The magnitude of this current determines whether a solid is a "good" or a "bad" conductor, and is directly related to the density of mobile electrical charge carriers in the solid. In this section, we will try to model the electrical conductivity in solids starting from the Drude model, which is a general model and is valid for any solid which contains mobile charge carriers. This model is based on the kinetic theory of gases which was briefly mentioned...
