Electrically doped SiGe-heterojunction TFET based biosensor considering non-ideal hybridization issues: a simulation study

Calibrated simulations are used to study a dielectric modulated, electrically doped, dual metal gate, SiGe heterojunction, double gate TFET biosensor in this work. Use of lower bandgap SiGe at the source side helps in improving the ON current of the biosensor. Electric doping is preferred over physical doping to overcome the random dopant fluctuations and high thermal budget problems. Non-ideal situations having partially and non-uniformly filled cavity regions are analyzed in this work. Partially filled cavity has fill factor less than 100% and is studied by considering 50%, 20%, and 10% fill factors. Different positions of biomolecules inside a partially filled cavity are also studied through extensive simulations and are found to affect the sensitivity largely. Four different non-uniform profiles, decreasing, increasing, convex and concave, are created in the cavity region and their sensitivity values are compared for different dielectric constants (k) and charge densities (Q(Bio)). Among the different non-uniform profiles considered, maximum sensitivity is obtained for decreasing profile and it improves with an increase in dielectric constant and positive charge density while it decreases when negative charge density increases.