Phonon-Limited Electron Mobility Behavior and Inherent Mobility Reduction Mechanism of Ultrathin Silicon-on-Insulator Layer with (111) Surface and Ultrathin Germanium-on-Insulator Layer with (001) Surface

Abstract

One-dimensional self-consistent calculations and relaxation time approximations are used to study the phonon-limited electron mobility behavior of the inversion layer at room temperature for ultrathin body Si(111) and Ge(001) layers in single-gate (SG) and double-gate (DG) silicon-on-insulator (SOI) and germanium-on-insulator (GOI) metal–oxide–semiconductor (MOS) field-effect transistors (FETs). Assuming a 5-nm-thick SOI layer, it is shown that intravalley phonon scattering (acoustic-phonon scattering) in the DG SOI MOSFET inversion layer is strongly suppressed within a range of medium and high effective field (Eeff) values; DG SOI MOSFETs have higher phonon-limited electron mobility than SG SOI MOSFETs. Many simulations strongly indicate that, for medium Eeff values, the suppression of acoustic-phonon scattering in a 5-nm-thick DG SOI MOSFET primarily stems from the reduction of the form factor (F00) value. Although similar phenomena are observed in approximately 7-nm-thick GOI layers with a Ge(001) surface, it is shown that there is little merit in using the Ge(001) surface for DG GOI MOSFETs.