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We developed a semi-analytical quasi-ballistic transport model for the nanowire metal-oxide-semiconductor field-effect transistors, dealing with finite lengths of source, channel, and drain. For the modeling, we used a combination of one-flux scattering matrices and analytical solutions of Boltzmann transport equations. The developed model was in quantitatively good agreement with numerical results, and well represented intermediate-scaled devices. In addition, we illustrated that the finite source seriously affect the distribution function of the carriers injected from the source, and the finite drain does for the backscattering into the channel from the drain. Finally, our model and results would help to understand physical aspects regarding quasi-ballistic transport in nanoscale devices. [ABSTRACT FROM AUTHOR]

We investigated the phonon-limited electron mobility in rectangular silicon nanowire metal-oxide-semiconductor field-effect transistors (Si NW MOSFETs) using the Kubo-Greenwood formula. Although cross-sectional electrostatics has been actively investigated, the cross-sectional distribution of the spatially resolved mobility has not been studied yet. In this paper, we discuss the corner effects based on spatially resolved mobility analysis. Taking into account the subband composition for local electrons, we could study the cross-sectional spatially resolved carrier transport. A strongly confined Si NW MOSFET showed that mobility hardly fluctuated in the cross-sectional distribution with strong volume inversion. On the other hand, a less-confined Si NW MOSFET showed that the corner mobility was lower than the side mobility; therefore, our result could imply that the corner effects were not positive for improvement in mobility. [ABSTRACT FROM AUTHOR]

A study on size-dependent subband structures of silicon nanowires (SiNWs) aligned along [100] direction, ranging from 0.77 to 2.69 nm in width, is performed by the first-principles calculation. Combined with a compact model adopting Landauer’s formula, on-currents of ballistic SiNW field effect transistors (FETs) are estimated and assessment of size-dependent performance is conducted. Size-dependent injection velocity strongly depends on Fermi level measured from the conduction band edge when carriers are degenerate. It is also supposed that the Fermi level has a peak value at a certain wire width. Despite variation in the size-dependent Fermi level and injection velocity, large SiNW FETs show large on-currents owing to their larger gate capacitances resulting from longer periphery. The on-current in the case of a multichannel SiNW FET reveals that size-dependent subband structures of nanowires have a serious effect on performance. As the results, although the normalized on-current decreases with decrease in wire width in the assessed multichannel FETs because both the saturation velocities and the normalized capacitances decrease, there can be a maximum in the normalized on-current in a larger wire owing to the maximized Fermi level and injection velocity. [ABSTRACT FROM AUTHOR]