The electrostatic doping technique has a remarkable ability to reduce random dopant fluctuations (RDFs), fabrication complexity and high thermal budget requirement in the fabrication process of nano-scale devices. In this paper, for the first time it has been propose and simulated a junction-free electrostatically doped tunnel field-effect transistor (JF-ED-TFET) based biosensor for label-free biosensing applications. The dielectric modulation concept has been used to sense biomolecules using a nano-cavity incorporated within the gate oxide layer near to the source end. The sensing response of the JF-ED-TFET biosensor has been analyzed in terms of the electric field, energy band and transfer characteristic and sensitivity in terms of ON-current, ION/IOFF ratio and subthreshold swing. The sensitivity of the biosensor has been investigated based on practical challenges such as different filling factors and step-profiles generated from the steric hindrance. The effect of temperate and nano-cavity dimension variations on device performance has been also analyzed. In this work, various types of biomolecules such as Streptavidin (k = 2.1), Ferro-cytochrome c (k = 4.7), keratin (k = 8) and Gelatin (k = 12) has been considered for the performance investigation.