An insight into the design of a graded channel gate-all-around (GAA) MOSFET for biosensing applications

This paper presents a novel biosensor, the graded channel gate-all-around (GC-GAA) silicon nanowire-FET biosensor, which utilizes dielectric modulation through a cavity carved from the drain side for label-free biomolecule detection. The biomolecules that become fixed in the cavity region alter the device's electrical properties, such as impedance, resistance, capacitance, and charge field effect, resulting in changes in the biosensing device's threshold voltage, drain current, and sub-threshold slope. The cavity length varies between 10 and 14 nm, and different dielectric constants are used. The study investigates the effect of various biomolecules on the device's performance, including drain current (for dielectric constant = 1 and3.57), sub-threshold slope, threshold voltage, switching ratio, energy band, transconductance, and electric field. The obtained drain currents for device-1 are 2.96 µA and 2.75 µA with threshold voltage of 0.78 V and 0.76 V for S_D/D_S graded channel respectively for copper as gate metal. Similarly the drain currents for device-2 are 0.97 µA and 1.13 µA with threshold voltage of 0.73 V and 0.68 V for S_D/D_S graded channel respectively. However, for device-3 the drain currents are 0.91 µA and 1.08 µA with threshold voltage of 0.73 V and 0.67 V. The results indicate that higher dielectric constants result in higher drain current levels and increased device sensitivity. The GC-GAA-NWFET biosensor demonstrated high sensitivity (~ 138 mV) and low leakage current, making it a promising candidate for biosensing applications.