Performance Assessment of Charge Plasma Based Full Gate, Short Gate and Asymmetrical VTFET Biosensor

This paper investigates a full gate charge plasma based heterojunction vertical tunnel field effect transistor (FG-CP-VTFET) as a dielectrically modulated biosensor. The FG-CP-VTFET biosensor is also compared with a short gate charge plasma heterojunction vertical TFET (SG-CP-VTFET) and an asymmetrical charge plasma heterojunction vertical TFET (AS-CP-VTFET) biosensor with similar dimensions. We explore the fundamental physics of these designs and compare their capabilities to detect neutral and charged molecules by evaluating the effect of charge density on the dielectric constant of biomolecules. It is determined that short-gate, full-gate, and asymmetrical heterojunction TFETs incorporating GaSb as the n-type TFET source material are potential candidates for supply voltages less than 1.2 V. The short gate device has the advantage of having a reduced miller capacitance due to its short gate structure and a higher drive current due to the narrow bandgap source material. Moreover, the right and left gate alignment of the asymmetrical gate structures significantly affects the device sensitivity. Hence, the simulation is carried out to analyze gate misalignment impacts on biosensor surface potential, and drain current sensitivity. Additionally, different figures of merits (FOMs) for the device are computed using the dielectric constant range of 1-12, including sensitivity, linearity, and assessment of noise characteristics. The Silvaco TCAD, which is widely available, has been utilized to simulate the proposed CP-VTFET biosensors. A detailed comparison of the values of the FOMs revealed that the FG-CP-VTFET is a potential device in terms of linearity and sensitivity.