Investigating Germanium MOS capacitors and DM-TFETs: A combined experimental computational biosensing study

Abstract

This work demonstrates the experimental and simulation study of the Germanium-based MOS capacitor and dopingless Tunnel FET for biosensing application respectively. Experimental characterization of Au/Ni/Al2O3/Ge MOS capacitors was performed, including device fabrication across varying dimensions, structural validation using scanning transmission electron microscopy (STEM), and elemental analysis via Energy-Dispersive X-ray Spectroscopy (EDS). Capacitance–voltage (C–V) measurements at 1 kHz and 1 MHz reveal frequency-dependent behavior and a notable shift in flatband voltage, confirming the quality and consistency of the MOS stack. The Germanium MOS (Ge-MOS) capacitor has been experimentally fabricated with a process flow involving Ni/Au metallization and Al2O3 layers. In addition, a Ge-MOS capacitor and Ge dopingless TFET has been calibrated using Atlas Silvaco TCAD. This work focuses on the performance of a dielectrically modulated Ge-based MOS capacitor and a dopingless TFET device for a biosensing application. Biomolecule detection occurs through changes in dielectric properties and associated charge densities, which modulate the tunneling barrier width at the source-channel interface. This effect arises from the formation of an electron accumulation region within the undoped Germanium layer. A sensitivity comparison between the Germanium Dopingless Tunnel Field Effect Transistor (Ge-Dl-TFET) and the conventional Dielectrically Modulated Field Effect Transistor (DM-FET) has been carried out, considering parameters such as the dielectric constant (K) and charge density (ρ). Furthermore, calibrated simulation results indicate that the Ge-DL-TFET exhibits a significantly higher relative change in ION (used here as the sensing metric), evaluated at (VGS=VDS=1V), achieving up to a 105 increase for neutral biomolecules and 8 × 104 for charged biomolecules at a charge density of (ρ) = −1 × 1012 cm−2. These results demonstrate that the Ge-Dl-TFET biosensor offers superior biomolecule detection performance compared to the conventional DM-FET biosensor.