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

• Published in: IEEE transactions on electron devices Vol. 66; no. 4; pp. 1905 - 1910
• Main Authors: Hafiz, Syed Adeebul, Iltesha, Ehteshamuddin, M., Loan, Sajad A.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Biomolecules; Biosensors; Cavity resonators; Charge density; Charge-plasma (CP); Detection; dielectrically modulated (DM); Field effect transistors; Holes; Logic gates; Metal silicides; Molecular biophysics; nanogap; Permittivity; Schottky barrier (SB); Semiconductor devices; Sensitivity; Silicides; Silicon; Silicon films; source-engineered-SB-field-effect-transistor (SE-SB-FET)
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2019.2896695

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 (ErSi 1.7 ) 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 (<inline-formula> <tex-math notation="LaTeX">{K} </tex-math></inline-formula>) and the associated charge density (<inline-formula> <tex-math notation="LaTeX">\rho </tex-math></inline-formula>), along with the thickness (<inline-formula> <tex-math notation="LaTeX">{T}_{\textsf {C}} </tex-math></inline-formula>) and the length (<inline-formula> <tex-math notation="LaTeX">{L}_{\textsf {C}} </tex-math></inline-formula>) of the cavity. Furthermore, calibrated simulations reveal that the relative change in <inline-formula> <tex-math notation="LaTeX">{I}_{ \mathrm{\scriptscriptstyle ON}} </tex-math></inline-formula> (sensing parameter herein calculated at <inline-formula> <tex-math notation="LaTeX">{V}_{\textsf {GS}}={V}_{\textsf {DS}}={1} </tex-math></inline-formula> V) in SE-SB-FET is much better (maximum of <inline-formula> <tex-math notation="LaTeX">{3}\times </tex-math></inline-formula> for neutral; <inline-formula> <tex-math notation="LaTeX">{2.9} \times </tex-math></inline-formula> for charged biomolecules at <inline-formula> <tex-math notation="LaTeX">\rho =-{1}\times {10}^{{11}} </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">^{-{2}} </tex-math></inline-formula>). We further observe a significant improvement in sensitivity at low temperature (<inline-formula> <tex-math notation="LaTeX">25\times </tex-math></inline-formula> at <inline-formula> <tex-math notation="LaTeX">{K}={5} </tex-math></inline-formula>; <inline-formula> <tex-math notation="LaTeX">\rho ={0} </tex-math></inline-formula> at 100 K). Thus, SE-SB-FET biosensor provides better sensing capability for biomolecule detection when compared to the conventional DM-FET biosensor.