Design and performance investigation of a germanium-based TFET biosensor with N⁺ SiGe pocket for biomolecule sensing applications

Abstract This paper presents and simulates a germanium (Ge)-based Tunnel Field-Effect Transistor (TFET) biosensor consists of N⁺ SiGe pocket and a dual high-k dielectric materials (HfO 2 /TiO 2 ) for label-free biomolecule detection. The low bandgap of Ge (0.66 eV) enables efficient Band-To-Band Tunnelling (BTBT) at a low drain voltage, while the high-k TiO 2 dielectric enhances electrostatic coupling within the nanoscale sensing cavity (35 nm × 5 nm). The N⁺ SiGe pocket introduced at the drain-channel junction suppresses ambipolar conduction and significantly reduces Drain-Induced Barrier Lowering (DIBL), thereby improving electrostatic control. The device is simulated using Silvaco ATLAS TCAD and achieves an ON-state current (I on ) of 1.15 × 10 − 6 A, an OFF-state current (I off ) of 1.24 × 10⁻¹⁷ A, an I on /I off ratio of 9.25 × 10¹⁰ and a subthreshold swing of 36.96 mV/dec at V DS = 0.3 V. The combined effect of dielectric modulation and pocket engineering results in simulated sensitivity of 1.23 × 10¹² for neutral biomolecules, 1.82 × 10¹² for negatively charged biomolecules and 1.14 × 10¹² for positively charged biomolecules. The analysis of cavity geometry, dielectric properties, cavity filling factor and temperature dependence further evaluates the operating characteristics and robustness of proposed biosensor. The proposed device exhibits high simulated sensitivity at low operating voltage, indicating its potential for future low-power biosensing applications.