Investigation of carrier mobility degradation effects on MOSFET leakage simulations

Abstract

The term carrier mobility generally alludes to both electron and hole mobility in semiconductors. These parameters characterize how quickly an electron and/or hole moves through a metal or semiconductor when under the influence of an electric field. Most studied mobility models only take into account the influence of temperature and doping concentration which provides less accurate but fast simulation and allows preliminary device description adjustments and analysis. However complete models, like Klaassen, Shirahata or some allowed model combination give results that better fit experimental curves. This work concentrate on such possibilities and shows that, as carriers are accelerated in an electric field, their velocity will begin to saturate when the electric field magnitude becomes significant. Such effects are observed in low, high and inversion mobility models simulated in strain-Silicon devices. These effects are to be accounted for by a reduction of the effective mobility. Furthermore, it is shown that charge carriers in semiconductors are electrons and holes and that, their numbers are controlled by the concentrations of impurity elements, i.e. doping concentration; for that reason doping concentration has great influence on carrier mobility. Carriers are able to flow more quickly in materials with higher mobility; since the speed of an embedded device is limited by the time it takes a carrier to move from one side to the other. Devices composed of materials with higher mobility are able to achieve higher speeds.