Enhancement of hole mobility due to confinement in small diameter [110] silicon nanowires

We present results on a detailed computation of electron and hole low-field mobility for [110] axially oriented free standing SiNWs with diameters up to 3.1 nm and at various temperatures, where the principal charge scattering mechanism is through acoustic phonons, and both confined and bulk phonons are considered. The band structure for these SiNWs is determined by using a sp³d⁵s* TB scheme and the confined acoustic phonon dispersion for each SiNW is obtained by solving the elastic continuum wave equation. Bulk phonon dispersion is considered to be linear and a Debye cut-off energy is used to define the domain of bulk phonon wavevectors. Electron and hole - acoustic phonon scattering rates are calculated from the first order perturbation theory and deformation potential scattering, where TB electron and hole wavefunctions are incorporated. Finally, low-field mobility values are determined through momentum relaxation time approximation, and confirmed for electron-confined phonon interaction through ensemble Monte Carlo simulations.