A Compact Model for Undoped
Silicon-Nanowire MOSFETs with Schottky-Barrier Source/Drain
Guojun Zhu, Student Member, IEEE, Xing Zhou, Senior Member,
IEEE, Teck Seng Lee, Lay Kee Ang, Member, IEEE, Guan Huei See, Student
Member, IEEE, Shihuan Lin, Yoke-King Chin, and Kin Leong Pey, Senior Member,
IEEE Trans. Electron Devices,
56, No. 5, pp.
1100-1109, May 2009.
(Manuscript submitted August 6, 2008; revised
January 26, 2009.)
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A comprehensive physics-based compact model for three-terminal undoped
Schottky-barrier (SB) gate-all-around silicon nanowire MOSFETs is formulated
based on a quasi-2-D surface-potential solution and the Miller–Good tunneling
model. The energy-band model has accounted for the screening of the
gate field by the electrons or holes, which has been largely missed in
the literature. Although SB-MOSFETs are essentially ambipolar devices,
we show that the separate modeling of electron and hole currents is simple
yet accurately predicts the final ambipolar current. Thinner oxide
thickness is confirmed to be beneficial to SB-MOSFETs for both ON- and
OFF-state currents. However, smaller nanowire radius (or thinner
body thickness) is found to be only beneficial to SB-MOSFETs with high
SB heights (SBHs) despite the OFF-state current being reduced significantly.
For SB-MOSFETs with low SBHs, the tunneling-current-density enhancement
due to a smaller radius is not able to compensate the reduction in the
contact size, which leads to a degradation of the “ON” current. The
drift current in the channel is shown to be negligible in SB-MOSFETs and
the tunneling/thermionic current through the SB represents the main current-limiting
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