Vertical gate cavity bulk-planar junctionless FET-based biosensor for label-free detection of biomolecules

Abstract

In this paper, we propose a vertical gate bulk-planar junctionless field-effect transistor (VGC-BPJLFET)-based biosensor for the label-free detection of neutral and charged target biomolecules. The vertical gate structure exhibits better performance due to high gate controlability in the channel region, which improves the drain current of the device. The enhancement in drain current significantly increases the sensing capability of the biosensor. To sense the neutral (APTES, biotin, streptavidin, protein, etc) and charged (deoxyribonucleic acid (DNA)) target biomolecules, the VGC-BPJLFET biosensor includes a vertical nanogap cavity in between the gate electrodes of the device in which HfO2 behaves as the functionalization layer. However, for the detection of both neutral and charged biomolecules, the two electric parameters (dielectric constant (K) and the charge density (ρ)) are considered in the etched nanogap cavity. Furthermore, to see the potentiality of the VGC-BPJLFET biosensor, the proposed biosensor has been compared to the lateral gate cavity BPJLFET biosensor in terms of drain current, sensitivity, linearity and signal-to-noise ratio characteristics. From the comparison, it has been observed that the proposed device has a higher sensitivity of ∼104 and ∼103 with the conjugation of neutral (APTES (K = 3.57)) and charged (DNA (ρ = −1 × 1011 cm−2)) biomolecules, respectively. The VGC-BPJLFET biosensor also carries the better sensing capability to sense the target biomolecules with the presence of unwanted (air) biomolecules in the etched nanogap cavity.