A Symmetric L-Shaped Source Vertical TFET with a GeSi/Si Heterojunction for a High-Sensitivity Label-Free Biosensor

Tunneling field-effect transistor (TFET) biosensors have been widely studied because of their simple operation, low off-state current, and high sensitivity. This paper reports a novel double-symmetric L-shaped source vertical TFET (DLSVH-TFET) with a Ge 0.5 Si 0.5 /Si heterojunction as a label-free dielectric modulated biosensor. The L-shaped source region and pocket region involve vertical tunneling in the proposed TFET, so the on-state current and sensitivity are enhanced. Diagrams of the electric field, surface potential, and energy band are used to explain the working principle of the DLSVH-TFET biosensor. The L-shaped source with Ge 0.5 Si 0.5 /Si heterojunction increases the tunneling rate and tunneling area due to the valence band and conduction band offsets. Moreover, the vertical structure and heterojunction help to eliminate ambipolar conduction and achieve low off-state current. The performance of the proposed biosensor is analyzed by evaluating the drain current, sensitivity, selectivity, and linearity. In addition, the impacts of charged biomolecules and partially filled cavities are investigated. The simulations reveal that the drain current sensitivity is 5.66 × 10 6 for a neutral biomolecule with κ = 12. A linearity fit verification is given, and the results of current sensitivity reveal good linearity of the proposed biosensor with fitness coefficient γ 2 > 0.99.