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

The high dielectric constant of insulators currently investigated as alternatives to ${\mathrm{SiO}}_{\mathrm{2}}$ in metal–oxide–semiconductor structures is due to their large 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 coupling with surface plasmons, while small in the case of ${\mathrm{SiO}}_{\mathrm{2}},$ for most high-κ materials causes a reduction of the effective electron mobility in the inversion layer of the Si substrate. We study the dispersion of the interfacial coupled phonon-plasmon modes, their electron-scattering strength, and their effect on the electron mobility for Si-gate structures employing films of ${\mathrm{SiO}}_{\mathrm{2}},$ ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}},$ AlN, ${\mathrm{ZrO}}_{\mathrm{2}},$ ${\mathrm{HfO}}_{\mathrm{2}},$ and ${\mathrm{ZrSiO}}_{\mathrm{4}}$ for “${\mathrm{SiO}}_{\mathrm{2}}$ -equivalent” thicknesses ranging from 5 to 0.5 nm.