Performance investigation of Z-shaped gate dielectric modulated electrically doped junctionless TFET based biosensor for biomedical application

Abstract

This paper presents a novel Z-shaped gate dielectric-modulated electrically doped junctionless tunnel field-effect transistor (ZG-DM-ED-JL-TFET), designed for label-free biomolecule detection in biosensing applications. To enhance detection sensitivity, the device incorporates deliberately misaligned nanogap cavities within both the source and channel region. The electrically doped configuration is established by applying polarity gate voltages of PG-1 = +1.2 V and PG-2 = -1.2 V, which induce the requisite $n^{+}$ drain and $p^{+}$ source regions without the need for conventional doping techniques thereby reducing fabrication complexity and mitigating random dopant fluctuation (RDF) issues prevalent in conventional TFETs. For biosensing functionality, selective oxide etching is employed to form nanogap cavities adjacent to the source and gate dielectric interfaces, enabling dielectric modulation through biomolecular interaction. The device performance is comprehensively evaluated using Silvaco ATLAS simulations, with key parameters including carrier concentration profiles, energy band diagrams, electric field distribution, band-to-band tunneling (BTBT) rate, transfer characteristics ($I_{DS}$ - $V_{GS}$), drain current ($I_{DS}$) sensitivity, switching ratio ($I_{ON}/I_{OFF}$), and subthreshold swing (SS) sensitivity. In-depth analysis further explores the impact of cavity geometry, steric hindrance, fill factor variation, and temperature-dependent responses. The sensor’s effectiveness is assessed using both neutral biomolecules such as uriease ($k=1.64$), streptavidin ($k=2.1$), APTES ($k=3.57$), ferrocytochrome c ($k=4.7$), bacteriophage T7 ($k=6.3$), keratin ($k=8$), and gelatin ($k=12$) and charged biomolecules with surface charge densities of $\pm 10^{11}$ cm⁻², $\pm 5\times 10^{11}$ cm⁻², and $\pm 10^{12}$ cm⁻². Simulation results validate the ZG-DM-ED-JL-TFET’s high sensitivity, low-power operation, and promising potential for next-generation biomedical diagnostic platforms.