<p>The biosensing performance of a GaAs delta-pocket-doped heterojunction vertical TFET (V-TFET) is explored in this study. The study mainly evaluates the device response for different biomolecules characterized by distinct dielectric constants, including streptavidin, biotin, bacteriophage-T7, and gelatin. The proposed device structure incorporates a nanocavity close to the source region, which acts as the sensing site where biomolecules are immobilized. The impact of these biomolecules on the device behavior is investigated by analyzing variations in the drain current–gate to source voltage (I_D–V_GS) characteristics. A delta-doped layer is incorporated between the source and channel regions to reduce the OFF-state leakage current while enhancing the ON-state drive current. The incorporation of different biomolecules leads to noticeable variations in key electrical characteristics such as drain current, electric field distribution, threshold voltage (V_th), surface potential, and transconductance sensitivity. The sensing capability of the biosensor is further assessed using both neutral and charged biomolecules. The device exhibits a subthreshold swing of 19.603&#xa0;mV/dec, while the maximum ON-current reaches 6.34 × 10^–5 A/ µm in the presence of gelatin with a dielectric constant (κ) of 12. Moreover, the calculated transconductance sensitivity and drain current sensitivity are 1.78 × 10⁶ and 1.2 × 10⁷, respectively. A comparison with previously reported biosensors demonstrates that the proposed structure offers improved sensitivity and sensing performance.</p>