Effective electron mobility in Si inversion layers in metal-oxide-semiconductor systems with a high-kappa insulator: The role of remote phonon scattering

The high dielectric constant of insulators currently investigated as altern atives to SiO2 in metal-oxide-semiconductor structures is due to their larg e ionic polarizability. This is usually accompanied by the presence of soft optical phonons. We show that the long-range dipole field associated with the interface excitations resulting from these modes and from their couplin g with surface plasmons, while small in the case of SiO2, for most high-kap pa materials causes a reduction of the effective electron mobility in the i nversion layer of the Si substrate. We study the dispersion of the interfac ial coupled phonon-plasmon modes, their electron-scattering strength, and t heir effect on the electron mobility for Si-gate structures employing films of SiO2, Al2O3, AlN, ZrO2, HfO2, and ZrSiO4 for "SiO2-equivalent" thicknes ses ranging from 5 to 0.5 nm. (C) 2001 American Institute of Physics.