Dielectrically Modulated Source-Engineered Charge-Plasma-Based Schottky-FET as a Label-Free Biosensor

Abstract

In this paper, we propose and simulate a charge-plasma (CP)-based dielectrically modulated (DM) source-engineered Schottky barrier field-effect transistor (SE-SB-FET) as a device for biomolecule sensing. The proposed device employs metal silicide (ErSi1.7) as source/drain regions and Hafnium (workfunction = 3.8 eV) as dual metallic source extensions. The oxide below the source extensions are etched out to create two horizontal L-shaped nanogap cavities for biomolecule detection. The presence of biomolecules is characterized by the change in dielectric constants and the associated charge densities, which, in turn, modulates the Schottky barrier (SB) width at the source-channel (metal/Si) junction, owing to the formation of an electron-CP in an undoped-Si film. A comparative analysis of the SE-SB-FET and the conventional DM-FET in terms of sensitivity has been performed as a function of dielectric constant ( ${K}$ ) and the associated charge density ( $\rho $ ), along with the thickness ( ${T}_{\textsf {C}}$ ) and the length ( ${L}_{\textsf {C}}$ ) of the cavity. Furthermore, calibrated simulations reveal that the relative change in ${I}_{ \mathrm{\scriptscriptstyle ON}}$ (sensing parameter herein calculated at ${V}_{\textsf {GS}}={V}_{\textsf {DS}}={1}$ V) in SE-SB-FET is much better (maximum of ${3}\times $ for neutral; ${2.9} \times $ for charged biomolecules at $\rho =-{1}\times {10}^{{11}}$ cm $^{-{2}}$ ). We further observe a significant improvement in sensitivity at low temperature ( $25\times $ at ${K}={5}$ ; $\rho ={0}$ at 100 K). Thus, SE-SB-FET biosensor provides better sensing capability for biomolecule detection when compared to the conventional DM-FET biosensor.