Assessment of room-temperature phonon-limited mobility in gated silicon nanowires

The technologically important question of whether the reduced density of electron states (DOS) for scattering in one-dimensional (1D) wire transport devices gives an advantage over the planar metal-oxide-semiconductor field-effect-transistor (MOSFET) for electron mobility is assessed by simulations. We self-consistently solve the Schrodinger-Poisson equations to calculate phonon-limited electron mobility in a multisubband cylindrical Si gated wire. We find that the benefit of reduced 1D DOS is offset by an increased phonon scattering rate due to increased electron-phonon wave function overlap and results in a degraded mobility in narrow wires. The applied gate bias voltage and the wire size control the transition from wire geometry to surface field-dominated confinement. The size scale for this 1D to two-dimensional (2D) transition is also found to be surprisingly small: A wire with a 75 A radius has an essentially 2D DOS and has a 2D mobility that is degraded from the planar (100) MOSFET due to the anisotropy of the inversion mobility in different Si crystallographic planes. (C) 2004 American Institute of Physics.