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_ON), thereby providing higher sensitivity than previously reported GaAsSb/InGaAs-based HTFET and FET biosensors. Sensitivity and selectivity parameters for I_ON, transconductance (g_m), and threshold voltage (V_th) 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_ON of 3.02 × 10^-4 A/μm 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 × 10⁶ (I_ON) and 3.49 × 10⁵ (g_m) for K = 12, at a correspondingly reduced I_ON of 1.91 × 10^-4 A/μm. The maximum V_th 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_ON and g_m selectivity values of 9.55 and 4.64 for K = 12, respectively, while the peak V_th 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_ON, g_m, and V_th sensitivities for charged biomolecules, confirming its robustness, selectivity, and potential for next-generation, high-performance biosensing applications.