**4. Simulation strategy for a DM TFET as a label-free biosensor**

The most convenient way to analyze a biosensor is on a computational platform where the physics-based models applied to the architecture assist in analyzing its performance. There are a number of industrial simulators and most of them come equipped with provisions for defining a geometry and feeding it through iterations of selective models available in their libraries.

The embedded nanogap in a DM TFET is designed by substituting that region in the gate dielectric with a dielectric material (oxide) whose dielectric constant can be altered as per requirement [38]. For charged biomolecules, the charges are considered at the oxide-semiconductor interface. By varying the dielectric constant and the charge, the immobilization of biomolecules may be mimicked appropriately.

The models for TFETs must be chosen with care. Since TFETs usually have high source doping concentration to achieve large band bending at equilibrium, therefore, Fermi-Dirac statistics is necessary [50]. Bandgap narrowing is important for heavily doped geometries [50]. Nonlocal band-to-band tunneling models are essential to create a suitable simulation environment for the device whose principle of operation is interband tunneling [50]. Field dependent mobility models may be used [50].
