STUDY OF LATERAL POLYSILICON PN DIODES C-V CHARACTERISTICS - MODELINGAND EXPERIMENTS

In this work, we propose a monodimensional numerical modeling of later al polysilicon PN diode C-V characteristics by taking into account the localization of the traps at the grain boundaries. The C-V characteri stic simulation shows that for high doping concentration, the curve be havior is similar to the case of monocrystalline junction. However, fo r low doping concentration, these characteristics present a succession of down stairs shape. This is due to the intergranular trap states pi nning of the Fermi level and consequently, to the electrostatic potent ial shielding at the grain boundaries. In the simulation, we consider the following parameters: doping concentration, intergranular traps st ates density and their energetic position, number of the grain boundar ies and crystallite size. The obtained results show that the electrost atic potential shielding is stronger for large crystallites, for high intergranular trap densities and for deepest traps. The simulated C-V characteristics have been fitted to the experimental measurements. For a doping concentration equal to 6 x 10(16) and 7 x 10(17) cm(-3), the corresponding values of the trap density are 10(12) and 2 x 10(12) cm (-2), respectively. (C) 1998 Published by Elsevier Science Ltd. All ri ghts reserved.