Universality of electron mobility in Ge MOSFETs investigated by Monte Carlo simulation

The behavior of electron mobility in Ge MOSFETs when plotted versus the effective electric field is investigated by Monte Carlo method. Similar to the Si MOSFETs, the electron mobility in Ge MOSFETs also has the universal behavior and the Ge electron mobility is about 50% larger than that in Si under low effective electric field. But under high effective field (5×10⁵V/cm), the electron mobility in Ge MOSFETs is only 10% higher than that in Si MOSFETs. The effects of Coulomb scattering, substrate bias and surface roughness scattering on electron mobility have been discussed in details. The coulomb scattering is actually the factor responsible for the deviation of mobility curves from universal behavior. The electron mobility in high effective electric field is very sensitive to the surface roughness scattering.