Article

Biomedical Microdevices

, Volume 12, Issue 5, pp 849-854

Fluidic measurement of electric field sensitivity of Ti-GaAs Schottky junction gated field effect biosensors

  • Woo-Jin ChangAffiliated withDepartment of Electrical and Computer Engineering, Department of Bioengineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign
  • , Ho-Jun SukAffiliated withDepartment of Electrical and Computer Engineering, Department of Bioengineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign
  • , A. K. M. NewazAffiliated withDepartment of Physics and Center for Materials Innovation, Washington University in St. LouisDepartment of Physics and Astronomy, Vanderbilt University
  • , Kirk D. WallaceAffiliated withDepartment of Physics and Center for Materials Innovation, Washington University in St. Louis
  • , Samuel A. WicklineAffiliated withDepartment of Physics and Center for Materials Innovation, Washington University in St. Louis
  • , Stuart A. SolinAffiliated withDepartment of Physics and Center for Materials Innovation, Washington University in St. LouisBlackett Laboratory, Imperial College London Email author 
  • , Rashid BashirAffiliated withDepartment of Electrical and Computer Engineering, Department of Bioengineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign Email author 

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Abstract

We report the electric field and pH sensitivity of fluid gated metal-semiconductor hybrid (MSH) Schottky structures consisting of a Titanium layer on n-type GaAs. Compared to standard field-effect sensors, the MSH Schottky structures are 21 times more sensitive to electric field of −46.6 V/cm and show about six times larger resistance change as pH of the solution is decreased from 8.17 to 5.54. The potential change at the fluidic gate and passivation layer interface by bias voltages and pH are mirrored by the metal shunt, resulting in larger depletion widths under the Schottky junction and resistance change as compared to sensors with no Schottky junction. 2D numerical simulation results are in good agreement with the measured data and suggest thinner mesa with lower doping density can further increase device sensitivity.

Keywords

Field effect biosensor Schottky junction Fluidic measurement Electric field sensing