**7. A circular gate TFET as a DM biosensor**

This section presents a geometry of TFET, a Circular Gate TFET (CG) as a dielectric-modulated biosensor, and discusses some of the results. The CG TFET has a non-uniform gate in the form of a semi-circle. This gate engineering introduces flexibility into the architecture of the device, and aids in optimization of chief electrical parameters, primarily the ambipolar current and ratio of on and off currents [53]. One of the techniques of reducing ambipolar current in a TFET apart from asymmetric source-drain doping is the introduction of gate-drain underlap [3, 45, 53]. In case of Circular Gate TFET, the gate being circular in shape, the gate dielectric thickness is dependent on the radius of the circle. A gate-drain underlap in the architecture shall decrease the thickness of the gate dielectric, which shall, in turn, increase the influence of the gate on the channel. Therefore, reduced ambipolar current can be achieved with appropriate ratio of on and off current simultaneously.

A circular gate TFET as a DM biosensor is depicted in **Figure 2a**. The total length of the Silicon body TFET is 100 nm, where the source and drain are 30 nm each. An embedded nanogap is incorporated into the geometry to immobilize the biomolecules. The embedded nanogap is usually etched out of a dielectric formed by a native oxide. We have considered a native oxide of 1 nm in the nanogap, which is assumed to remain after the gap is etched out.
