Design and Performance Analysis of L-shaped Vertical Tunnel-FET for Bio-sensing Application

In VLSI/ULSI circuits, the Tunnel Field Effect Transistor (TFET) has came out as a very good alternative for low power applications. To counter act short-channel effects like DIBL, velocity saturation, quantum confinement, velocity degradation, the TFETs can have a better alternative than compared with conventional MOSFET. TFETs have gated p-i-n profile and band to band tunneling (BTBT) mechanism. To have low power consumption, Tunnel Field Effect Transistor (TFET) relies on decreasing the supply voltage with downscaling. TFETs can be a good alternative for replacing MOSFETs for energy-saving, low power utilization with upgrade sub-threshold swing. The configuration of MOSFET and TFET is resemble with each other with a separate working mechanism. TFET has a gated p-i-n profile, and the conduction of current is taking place by band to band tunneling (BTBT) mechanism, through a barrier in between the energy bands of the source and channel. Although the working principle of the TFET is promising for low power VLSI/ULSI applications, several important issues remain like high $\mathrm{I}_{\mathrm{O}\mathrm{N}}$, low $\mathrm{I}_{\mathrm{OFF}}$ and a low SS over several decades of current. In this work., a gate-on-drain overlapped L-shaped channel TFET is used to sense various biomolecules with dielectric constants between K=1 and 23. Biosensors use L-shaped tunnelling field-effect transistors (LTFETs) because of their low subthreshold swing, low off-state current, and low power requirements. Simulation results indicate that the LTFET structure shows higher on-state current $\left(\mathrm{I}_{\mathrm{ON}} \sim 10^{-7 \mathrm{~A}} / \mu \mathrm{m}\right)$ and higher switching current ratio $(^{\mathrm{I}_{\mathrm{O}\mathrm{N}}}/_{\mathrm{I}_{\mathrm{OFF}}}\sim 10^{-10})$ and a steep subthreshold swing.