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Tunnel FET is a type of field effect device in which current transport phenomena occur due to quantum tunneling between source and channel. The band-to-band (B2B) tunneling current (IDS) of TFET devices is governed by following Equation 2.1 [15–26]. The tunneling probability T(E) is given by WKB (Wentzel-Kramers- Brillouin) approximation.

(2.1)

Here in Equation 2.1, m* is the effective mass of charge particle, Eg is band gap, ΔΦ is the energy range for B2B Tunneling window over which tunneling can take place. And collectively tox, tsi, εox, εsi known as device design parameters called the oxide and silicon films thickness and dielectric constants, respectively. The remaining constant such as “ћ” is called reduced Planck’s constant, “|q|” known as electronic charge. The tunneling window (ΔΦ) in the tunneling probability can be also expressed: . As shown, Equation 2.1 has a unique property, which provides full facilities for a process engineer to optimize device characteristics, which is useful for circuit design purpose for optimization of an advanced low-power circuit and system such as IoTs.