Double-Gate Thin-Base MOS Transistor: The Correct Theory
C-T Sah and B.B. Jie
University of Florida, US
MOS transistor, double gate
The theoretical analyses made by recent authors on the double-gate thin-base MOS transistor are incorrect, including the pure-base analyses reviewed by Ortiz-Conde, Garcia-Sanchez, Juin J. Liou (TED54, 131, Jan.2007). A simple device physics error was made from neglecting in the Yuan Taur model (EDL21, 245, May 2000) which everyone followed beyond its limit, and a simple electrostatics was overlooked resulting in unphysical divergence. Consequences based on the very simple correct model are described, including three surface-potential-controlled bipolar channels, reduction of unipolar channel current, significant subthreshold current, mobile-carrier space-charge-limitation, longitudinal electric field gradient, channel contact types, and many others well known in the ancient (~1950) theories of current transport in insulators and low conductivity materials and devices. The original intent of reaching the ultimate small-dimension limit by using pure base to eliminate the statistical thermodyamic fluctuation of the local impurity atom number fluctuation in the impure base, is not tenable, due to the fundamental Debye Length, which lowers the on current and increase the off current, seriously increases the wishful low standby power and lowers on/off current ratio. Two-dimensional effects such as the longitudinal electric field gradient, is especially serious when channel length is comparable to or less than the Debye length. Characteristics from cominations of applied voltage to the four (or five) terminals are discussed.
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Nanotech 2007 Conference Program Abstract