Emerging device: FINFET, tunnel FET and their applications

Abstract

In order to overcome the limitations of MOSFET, researchers have proposed various alternative techniques like material engineering, gate engineering, work function engineering, structural engineering, spacer engineering, gate oxide engineering and so on. Among these researchers have looked out for an alternative device which can replace the MOSFETs in future. Fin Field-effect Transistor (FinFET) is very promising device and it can replace the traditional MOSFET for low power applications. FinFET can control the channel from all the three side of the gate and provides outstanding performance against SCEs and very high on to off current ratio. FET-based biosensors are gaining interests due to their compact sizes, prevalent manufacturing processes, label-free detection, and established physics-based explanations. The most common geometrical modifications in FETs employed for biomolecule detection are based on gating effect and dielectric modulation. In the former, the gate material of a FET is replaced by a layer of suitable receptors over the gate dielectric material, which upon conjugation of the charged biomolecules reflects a change in the energy bands in the channel, and hence, the currents. In the latter, a portion of the gate dielectric material is etched out to form a nanogap; when biomolecules are immobilized in the nanogap, the dielectric constant of the gap changes, and a change is reflected in the drain current. The gating effect is best suited for charged biomolecules, whereas dielectric modulation aids in sensing both charged and neutral biomolecules. Im et al. proposed a dielectric modulated FET-based biosensor after the ion sensitive FETs proposed in 1970s. Sarkar and Banerjee presented a nanowire TFET in demonstrating the gating effect for positively charged biomolecules. Further, tunneling in photodiodes under zero illumination is involved in developing a portable circuit generating random numbers. The objective of the design is to highlight the importance of tunneling in a simple device such as a photodiode, and show qualitatively how leakage currents arising out of tunneling can be useful for certain purposes.