[paper] Junctionless pH Sensing BioFET

Nawaz Shafi, Aasif Mohamad Bhat, Jaydeep, Singh Parmar, Chitrakant Sahu, C. Periasamy

Effect of geometry and temperature variations on sensitivity and linearity 

of junctionless pH sensing FET: An experimental study

Superlattices and Microstructures, p. 107186, Mar. 2022,

doi: 10.1016/j.spmi.2022.107186

   
* Malaviya National Institute of Technology Jaipur, India

Abstract: Here-in this work, boron doped poly-silicon based dimensional variants of thin film planar junctionless field effect transistors are fabricated through CMOS compatible process for pH detection. The dimensional variants are classified into two sets as set-1 (channel length, L = 100 μm) and set-2 (channel length, L = 120 μm) with widths of 3 μm, 5 μm, 10 μm, and 20 μm. Sensitivity of the fabricated devices is analyzed using phosphate buffer saline solutions of pH 3.1, 5.2, 7, 9 and 11.2 and is computed in terms of relative shift in threshold voltage (VTh) and maximum drain current (IDS). The reference VTh and IDS are taken at neutral pH 7. Here we have experimentally analyzed the effect on pH sensitivity by varying the device widths and temperatures from 30 °C to 50 °C. It is observed that varying the device width from 3 μm to 20 μm, VTh sensitivity reduces from 19.08% to 9.17% and from 16.03% to 8.5% for set-1 and set-2 devices respectively. Increasing temperature from 30 °C to 50 °C causes reduction of VTh sensitivity from 18.68% to 13.52% for device with W/L = 3μm/100 μm and 16.78%–10.99% for device with W/L = 3μm/120 μm. The reduction in width causes average VTh sensitivity to roll-off by 0.49%/μm and 0.26%/μm for L = 100 μm and L = 120 μm respectively. Also the increase in operating temperature from 30 °C to 50 °C leads VTh sensitivity to roll-off by 0.17%/°C and 0.2%/°C for W/L = 3μm/100 μm and W/L = 3μm/120 μm respectively.

Fig: Junctionless pH sensing BioFET

Acknowledgment: This work was supported by Center of Nano Science and Engineering, Indian Institute of Science, Bangalore under Indian Nanoelectronic Users Program. Authors express gratitude to Materials Research Center MNIT-Jaipur for characterization support.

[paper] Extended gate FET pH Sensor

Shaiful Bakhtiar Hashim, Zurita Zulkifli, Sukreen Hana Herman

Design and Simulation of Electrochemical Equivalent Circuit for Extended gate FET pH Sensor Based on Experimental Value Using LTSPICE XVII

researchsquare.com: November 11th, 2021

DOI:10.21203/rs.3.rs-1031896/v1

  
College of Engineering, UiTM, Selangor (MY)

Abstract: A SPICE model for extended-gate field-effect transistor (EGFET) based pH sensor was developed using standard discrete components. Capacitors and resistors were used to represent the sensing and reference electrodes in the EGFET sensor system and the values of the discrete component were varied to see the output of the transistor. These variations were done to emulate the EGFET sensor output in different pH values. It was found that the experimental transfer and output characteristics of the EGFET were very similar to those from the SPICE simulation. Other than that, the changes of value components in the equivalent circuit did not affect the transfer and output characteristics graph, but the capacitor value produced significant output variation in the simulation. This can be related to the modification on the equivalent circuit was done with additional voltage, VSB (source to bulk) to produce the different VT values at different pH.

Fig: EGFET measurement setup

Acknowledgement: The work is partially supported by KEPU Grant ( 600- RMC/KEPU 5/3 (007/2021)) from Universiti Teknologi MARA