Performance Improvement of a ZnGa₂O₄ Extended-Gate Field-Effect Transistor pH Sensor

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Sensing

Background:

• Metal oxide semiconductor field-effect transistors (MOSFETs) are crucial for sensing applications.
• Extended-gate field-effect transistors (EGFETs) offer a versatile platform for chemical and biological sensing.
• Developing stable and sensitive pH sensing materials is essential for various applications.

Purpose of the Study:

• To fabricate and characterize ZnGa2O4 sensing films for EGFET-based pH detection.
• To investigate the effect of oxygen ratio during sputtering on film properties and sensing performance.
• To evaluate the impact of annealing on the performance of ZnGa2O4 EGFET pH sensors.

Main Methods:

• ZnGa2O4 sensing films were prepared using RF magnetron sputtering.
• Films were integrated with a commercial MOSFET to form an EGFET.
• Oxygen flow rate was varied to control film stoichiometry.
• Annealing at 700 °C was performed to optimize film structure.
• Sensitivity and linearity were measured in the pH range of 2-12.

Main Results:

• The ZnGa2O4 EGFET exhibited high sensitivity and linearity in both constant current and constant voltage modes.
• Optimal deposition conditions (6% oxygen ratio) yielded a sensitivity of 23.14 mV/pH and 33.49 μA/pH.
• Linearity values reached 92.1% and 96.15% under optimal conditions.
• Annealing significantly improved the sensing performance of the ZnGa2O4 EGFET pH sensor.

Conclusions:

• ZnGa2O4 is a promising material for developing high-performance EGFET pH sensors.
• Optimizing sputtering parameters and employing annealing are critical for enhancing sensor sensitivity and stability.
• The developed ZnGa2O4 EGFET sensor offers a viable solution for accurate pH monitoring.