Non-ballistic Modeling Transport of Phonon Scattering in Carbon Nanotube and Silicon Nanowire Field-Effect Transistors

Abstract

The effects of acoustic and optical phonon scattering on the electrical transport characteristic of carbon nanotube (CNT) and silicon nanowire (Si NW) field-effect transistors (FETs) are examined using the top of the barrier model. The phonon scattering effects are incorporated into the device model via the transmission coefficients into the ballistic Landeur Buttiker formalism. It is revealed that the effective mean free path (MFP) denoted by Leff is dominated by the acoustic phonon MFP at low energy. Nevertheless, Leff is limited by the optical phonon MFP at higher temperatures. At a low VG, the current reduction is due to the electron-acoustic phonon interaction and at a high VG, the current is limited by the optical phonon. The ballisticity of the device in which the ratio of scattering current to the ballistic current for various channel lengths, L, at different gate bias are also studied. It is shown that the transistor with a shorter channel length operates as a ballistic device as the length approaches the phonon MFP. In addition, the drain-induced barrier lowering (DIBL), sub threshold swing (SS) and on-off ratio of the devices are computed. Finally, the voltage transfer characteristic (VTC) is also explored to observe the functionality of the models as potential logic gates.