Design and Performance Analysis of Tunnel Field Effect Transistor With Buried Strained Si1−x Ge x Source Structure Based Biosensor for Sensitivity Enhancement

Abstract

In this paper, a dielectrically modulated symmetrical double gate, having dual gate material, Tunnel Field-Effect transistor with Buried strained Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> source structure, has been investigated as a biosensor. This structure is proposed for the very first time to electrically detect the biological molecules at very low power consumption. In the proposed biosensor structure, the top thin Si channel of TFET is overlapped with the Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> source. This increases the tunneling area, due to which ON current of the biosensor also increases. To detect the biomolecules a nanogap cavity has been created over 1nm gate oxide. Also to decrease the short channel effects, dual-gate material with different metal work functions is used on both the symmetrical double gates. By varying the small bandgap material (Ge) mole fraction in the SiGe and after inserting different biological molecules (of the different dielectric) in a cavity, the variation in transfer characteristic, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> current ratio, SS along with their sensitivity is studied. Also, to signify the presence of biomolecules in the cavity, the g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ratio as a sensing metric is studied under the sub-threshold region. Along with the fully filled biomolecules cavity, the partially filled cavity and the effect of a steric hindrance have also investigated in this paper with various non-uniform step patterns of biomolecules in the cavity. Because, in a more practical situation, the steric hindrance effect doesn't allow the cavity to be entirely filled. Also, this paper addresses the optimization of drain current sensitivity, by different cavity length with different source overlapping cavity.