EFFECT OF THICKNESS AND GRANULAR STRUCTURE ON THE ELECTRICAL-CONDUCTIVITY OF THE ACTIVE LAYER IN POLYCRYSTALLINE SILICON TFTS

The variation of the electrical conductivity of the polycrystalline si licon thin film constituting the active layer of p+pp+ accumulation TF Ts is studied as a function of the film thickness. A simple electrosta tic model of the study structure and of its silicon layer, associated with a numerical method of solving 2D-Poisson's equations, allows to s how that the conductivity of the film depends on both carrier trapping at grain boundaries and electrostatic coupling between interfaces, be tween interfaces and grain boundaries parallel to the Si/SiO2 interfac e, when they exist, and between parallel and perpendicular grain bound aries.