Effective Capacitance and Drive Current for Tunnel FET (TFET) CV/I Estimation

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Through mixed-mode device and circuit simulation, this paper provides an estimate of the effective output capacitance <formula formulatype="inline"><tex Notation="TeX">$(C_{\rm EFF})$</tex></formula> and drive current <formula formulatype="inline"><tex Notation="TeX">$(I_{\rm EFF})$</tex></formula> for delay (<formula formulatype="inline"><tex Notation="TeX">$ \tau_{f} = \hbox{0.69} R_{\rm sw}C_{\rm EFF}$</tex></formula>, where <formula formulatype="inline"><tex Notation="TeX">$R_{\rm sw} = V_{\rm DD}/\hbox{2}\ I_{\rm EFF}$</tex></formula>) estimation of unloaded tunnel field-effect transistor (TFET) inverters. It is shown that unlike MOSFET inverters, where <formula formulatype="inline"><tex Notation="TeX">$C_{\rm EFF}$</tex> </formula> is approximately equal to the gate capacitance <formula formulatype="inline"><tex Notation="TeX">$(C_{\rm gg})$</tex> </formula>, in TFET inverters, the output capacitance can be as high as 2.6 times the gate capacitance. A three-point model is proposed to extract the effective drive current from the real-time switching current trajectory in a TFET inverter. </para>