p-Type Nanowire Schottky Barrier MOSFETs: Comparative Study of Ge- and Si-Channel Devices

摘要

We investigate the performance of Ge and Si channel p-type nanowire Schottky barrier metal–oxide–semiconductor field-effect transistors (SB-pMOSFETs) based on rigorous quantum mechanical calculations. The multiband $kcdot p$ method and the nonequilibrium Green's function are used. We find that Ge SB-pMOSFETs show superior performance in terms of ON-state current $(I_{{rm ON}})$, subthreshold swing, and the equivalent oxide thickness scaling. In particular, $I_{{rm ON}}$ of Ge SB-pMOSFETs is estimated to become about 2.5 times larger than that of Si SB-pMOSFET if the possibility of achieving low Schottky barrier height (SBH) in Ge-channel devices is taken into account. As the channel width is scaled down to a few nanometers, however, the differences in device performance become smaller. This is explained by the increase of the tunneling effective mass due to the heavy–light hole coupling effect and the effectively increased SBH due to the size quantization effect.