Design and Performance of a Dielectrically Modulated Electron–Hole Bilayer Tunneling FET Biosensor: Effects of Nanogap Cavity on Sensitivity and Voltage Requirements

This study investigates a biosensor utilizing a dielectrically modulated electronhole bilayer tunneling field-effect transistor (DMEHBTFET) for high-sensitivity applications through numerical device simulation. The research examines three configurations to assess the influence of nanogap cavity placement on biosensor performance concerning bias supply voltage: standard DM-EHBTFET, overlapped DM-EHBTFET, and nonoverlapped DM-EHBTFET. In the standard configuration, the nanogap cavities span both gates. The overlapped design positions them within the overlapping regions of both gates, whereas the nonoverlapped configuration locates the cavities in the nonoverlapping areas of both gates. Simulation results reveal that the standard and overlapped biosensors require minimum bias voltages of $V_{\text {DD}} = 5.5$ V and $V_{\text {DD}} = 4.5$ V, respectively, for detection, while the nonoverlapped biosensor necessitates only 1 V. The nanogap cavity design in the nonoverlapped DMEHBTFET isolates specific regions of both gates, with a length of LOV, from the channel by a 2-nm HfO2 insulator, thereby enhancing electrostatic coupling. This nonoverlapped device consumes 82% less bias voltage than the standard version, rendering it suitable for low-voltage applications. The drain current sensitivity of the nonoverlapped biosensor for a biomolecule with ${K} = 12$ was 431 and 1208 times greater than that of the overlapped and standard biosensors, respectively. For K = 12, the nonoverlapped biosensor exhibits a drain current sensitivity of 3e9, anon/off current ratio sensitivity of 2.3e9, a cutoff frequency sensitivity of 2.8e8, and a transconductance sensitivity of 5.45e8. The performance of the nonoverlapped biosensor is evaluated in terms of steric hindrance, and it surpasses recent DM-TFET biosensors, establishing it as a promising candidate for high-sensitivity applications.