TABLE OF CONTENTS Field effect is the name given to the experiment in which an electric field is applied to the surface of a semiconductor. In the case of a metal the electric field does not penetrate at all in static conditions, while in the case of an ideal insulator the electric field lines pass through it. A semiconductor is an intermediate and important case, in which there is some penetration of the field into the material under static conditions leading to a modification in the conductance of the sample.
The applied field should vary sufficiently slowly, so that the semiconductor is in thermal equilibrium. In addition, an idealized field effect model considers that the semiconductor doping is uniform and that the properties of the semiconductor are valid from the surface of the semiconductor, i.e., electrons and holes occur only as free carriers and their densities are given by Eqs. (2.1.5) and (2.1.6). In fact, the effect of the surface is to create allowed energy states for the electrons in the proximity of the surface. The term trap is applied to these states to indicate that they are electronic bound states, i.e., electrons occupying these states are not free to move. Interface traps are a fundamental nonideality of a semiconductor surface (interface). For a high quality Si-SiO 2 interface, the interface trap density is so low that its effect can be disregarded and the idealized model presented in this...
