Comparative investigation of extended-gate GaAsSb/InGaAs HTFET biosensors for label-free biomolecule detection

The dielectric-modulated heterostructure tunnel FET (HTFET)-based nano-cavity integrated biosensors are emerging as energy-efficient, ultra-sensitive label-free detection platforms. This study investigates and compares three GaAsSb/InGaAs-based biosensor architectures: single cavity dual material double composite gate HTFET (SC-DM-DG HTFET), dual cavity dual material double composite gate HTFET (DC-DM-DG HTFET), and single cavity dual material extended double composite gate HTFET (SC-DM-EDG HTFET). The III–V heterostructure in the SC-DM-EDG HTFET enhances tunnelling probability, gate control, and on-current ( I O N ), thereby providing higher sensitivity than previously reported GaAsSb/InGaAs-based HTFET and FET biosensors. Sensitivity and selectivity parameters for I O N , transconductance ( g m ), and threshold voltage ( V t h ) were evaluated for various neutral and charged biomolecules. Under the standard bias condition ( V DS = 1.5 V, V GS = 1.3 V), the SC-DM-EDG HTFET exhibits the highest I O N of 3.02 × 10 −4 A/ μ m among the three structures; under a separately re-optimized bias ( V DS = 0.9 V, V GS = 1 V), the same structure instead achieves maximum sensitivities of 3.35 × 10 6 ( I O N ) and 3.49 × 10 5 ( g m ) for K = 12, at a correspondingly reduced I O N of 1.91 × 10 −4 A/ μ m. The maximum V t h sensitivity of 0.49 is achieved by this structure under the standard bias condition. In biomolecule differentiation, the SC-DM-DG HTFET demonstrates peak I O N and g m selectivity values of 9.55 and 4.64 for K = 12, respectively, while the peak V t h selectivity value of 0.3 appears in the SC-DM-EDG HTFET also for the same biomolecule. Furthermore, the SC-DM-EDG HTFET achieves superior I O N , g m , and V t h sensitivities for charged biomolecules, confirming its robustness, selectivity, and potential for next-generation, high-performance biosensing applications.