Gate-Normal Negative Capacitance Tunnel Field-Effect Transistor (TFET) With Channel Doping Engineering

Abstract

In this work, a negative capacitance tunnel FET (NCTFET) with the tunneling current in the normal direction to the gate is proposed with channel doping engineering and its electrical characteristics are investigated using TCAD simulations with calibrated model parameters. The new NCTFET has a p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -doping (for n-type operations) in the channel overlap region, which plays a role to suppress the corner (source edge) band-to-band tunneling (BTBT) that degrades the on/off transition. By optimizing the doping concentration of the channel overlap region (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CH,OV</sub> ), the on-current gets ~3.5 times enhanced and the averaged subthreshold swing (SS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AVE</sub> ) becomes reduced from 82.5 mV/dec to 43.9 mV/dec. Furthermore, the effects of epi-channel thickness (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CH</sub> ) and source overlap length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S,OV</sub> ) variations are analyzed by simulating 2D contour BTBT generation rates and electron densities. With the optimized device parameters (4 nm T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CH</sub> and 35 nm L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S,OV</sub> ), the on-current is additionally ~1.6 times improved without the SS and the ambipolar current degradations.