Impurity and phonon-limited electron mobilities in 〈110〉-oriented silicon nanowires

We discuss impurity- and phonon-limited electron mobilities in (110)-oriented silicon nanowires. We show that (1) boron acceptors behave as tunnel barriers for the electrons, while phosphorous donors behave as quantum wells giving rise to Fano resonances in the transmission; (2) As a consequence, the room-temperature mobility is typically much larger in P-doped than in B-doped nanowires; (3) In particular, the mobility can be strongly hindered by acceptors in Si nanowires embedded in SiO₂; (4) On the opposite, the impurity-limited mobility can increase with decreasing nanowire diameter in gate-all-around nanowires with high-K oxides, due to both the efficient screening of the impurity potential and band structure effects; and (5) the electron-phonon coupling is enhanced in small nanowires and is the dominant scattering mechanism at room temperature for impurity concentrations up to a few 10¹⁸ cm^-3.