The dielectrically modulated heterostructure TFET based nanocavity embedded label-free biosensors are emerging as low power, highly sensitive bio-analyte detectors. High sensitivity and fast detection of biomolecules are still a challenge for researchers. In this article, single cavity dual-material extended gate heterostructure (III-V) TFET (SC-DM-EG HTFET) based dielectrically modulated label-free biosensor is proposed; which promises higher sensitivity and better device performances such as, ON current, ION/IOFFratio, subthreshold swing (SS); compared with single cavity dual-material heterostructure TFET (SC-DM HTFET), dual cavity dual-material heterostructure TFET (DC-DM HTFET), as well as, previously proposed FET based biosensors. 2D numerical simulation of the biosensors was performed with SILVACO ATLAS 2D simulation software. III-V heterostructure (InGaAs/Si) and extended gate geometry provide increased tunneling probability, improved gate control, high ION/IOFFratio, and ultra-high sensitivity, compared to IV-IV heterostructure biosensors. The sensitivities of the biosensors are analyzed for both neutral and charged biomolecules, with dielectric constants K=5,7,10,12. Effect of non-ideal issues on sensitivity, such as temperature fluctuation, steric hindrance are also studied for the biosensors mentioned above. Benchmarking is done to provide a quantitative comparison of the proposed biosensor with published literature. A maximum sensitivity of 1.3 × 10 ⁸ , along with the ION/IOFFratio of 2 × 10 ¹² and SS of 25.4 mV/V is noticed in SC-DM-EG HTFET for the dielectric constant of K=12 in a completely filled cavity of neutral biomolecules.