Numerical electron mobility model of nanoscale symmetric, asymmetric and independent double-gate MOSFETs

A comprehensive numerical model of electron mobility of nanoscale symmetric, asymmetric DG MOSFETs, and independent Double-Gate (DG) MOSFETs is studied in this paper. Physically derived expressions for electron mobility, including phonon and surface roughness scattering, two most important scattering mechanisms in DG MOSFETs around room temperature, are presented, based on a numerical analytic solution to potential and carrier distribution in DG MOSFETs from accumulation to strong inversion region. A careful description of electron mobility dependence on structure parameters, temperature and effective vertical field is performed and analyzed. Simulation results indicate that for symmetric devices in dependent mode, oxide thickness only slightly affects mobility and increasing temperature monotonically decreases mobility while mobility dependence on silicon film can be complicated, strongly moderated by "volume inversion" and geometric restriction. Study also shows that for asymmetric devices in dependent mode, thicker oxide leads to higher mobility. Symmetric DG MOSFETs biased in independent mode show that mobility is controlled by both electron density induced by one gate and mobility in this set of electrons. The presented model leads to a more clear understanding on DG MOSFETs device physics and provides useful results to modeling development for circuit simulation.