Experimental Study of the Detection Limit in Dual-Gate Biosensors Using Ultrathin Silicon Transistors

Ting Wu, Abdullah Alharbi, Kai Dyi You, Kim Kisslinger, Eric A. Stach, Davood Shahrjerdi

Research output: Contribution to journalArticlepeer-review

Abstract

Dual-gate field-effect biosensors (bioFETs) with asymmetric gate capacitances were shown to surpass the Nernst limit of 59 mV/pH. However, previous studies have conflicting findings on the effect of the capacitive amplification scheme on the sensor detection limit, which is inversely proportional to the signal-to-noise ratio (SNR). Here, we present a systematic experimental investigation of the SNR using ultrathin silicon transistors. Our sensors operate at low voltage and feature asymmetric front and back oxide capacitances with asymmetry factors of 1.4 and 2.3. We demonstrate that in the dual-gate configuration, the response of our bioFETs to the pH change increases proportional to the asymmetry factor and indeed exceeds the Nernst limit. Further, our results reveal that the noise amplitude also increases in proportion to the asymmetry factor. We establish that the commensurate increase of the noise amplitude originates from the intrinsic low-frequency characteristic of the sensor noise, dominated by number fluctuation. These findings suggest that this capacitive signal amplification scheme does not improve the intrinsic detection limit of the dual-gate biosensors.

Original languageEnglish (US)
Pages (from-to)7142-7147
Number of pages6
JournalACS nano
Volume11
Issue number7
DOIs
StatePublished - Jul 25 2017

Keywords

  • bioFETs
  • biosensor
  • detection limit
  • silicon-on-insulator
  • super-Nernstian
  • ultrathin silicon

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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