Dielectrically Modulated Single and Double Gate Tunnel FET Based Biosensors for Enhanced Sensitivity

Abstract

The paper explores the comparative biosensing analysis of single Gate (SG) and double Gate (DG) Extended Source Tunnel FET (ESTFET). The dielectric modulation technique has been incorporated for both the proposed biosensors with increased capture area by introducing nano-cavities near the source and drain region. The biosensing performance parameters like Threshold Voltage Sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta\text{V}_{th}$ </tex-math></inline-formula> ), ON-OFF Current Ratio Sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta\text{I}_{\text{ON}}/\text{I}_{\text{OFF}}$ </tex-math></inline-formula> ), and Drain Current Sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \text{S}_{Id}$ </tex-math></inline-formula> ) are calculated and compared for both the SG-ES and DG-ESTFET based biosensors. Sentaurus TCAD simulator is used for the investigation reported in this paper. The analysis includes neutral, positively and negatively charged biomolecules for various dielectric constants at immobilization layer and biomolecule analogous insulator interface. Further, a comprehensive analysis of partly filled nano-cavity originated from steric hindrance has been conferred to engulf the real time scenario. Different cases of partly filled nano-cavity have been considered to investigate the sensitivity parameters such as convex, concave, increasing and decreasing step profile along with asymmetric probe placement. It is observed that SG-ESTFET based label free biosensor outperform the DG-ESTFET due to the impact of back gate on the drain side nano-cavity. Some important bio-sensing parameters are estimated to have the subsequent values for SG-ESTFET (DG-ESTFET) as 80 mV (74 mV) for threshold voltage sensitivity, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$23\,\,\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15\,\,\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) for ON-OFF current ratio sensitivity and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60\,\,\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$45\,\,\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for drain current sensitivity, respectively. Lastly, different sensitivity parameters of SG-ES and DG-ESTFET are gauged against sensitivities of state of the art biosensors to set out the high sensitivity of our proposed biosensors.