Amorphous Copper Gallium Oxide Extended Gate Field-Effect Transistor pH Sensor

The structural characteristics and the sensitivity of copper gallium oxide (CGO) extended gate field-effect transistor (EGFET) pH sensors were investigated in this study. An amorphous CGO thin film was synthesized by co-sputtering Cu and Ga2O3 targets, ensuring uniform composition throughout the film. The voltage sensitivity was found to be 51 mV/pH with an excellent linearity of approximately 99.59%, and the current sensitivity was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$80~\mu $ </tex-math></inline-formula>A<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {1/2}}$ </tex-math></inline-formula>/pH with a linearity of around 99.1%. The sensor demonstrated good linearity and stability across a pH range from 2 to 10. The net hysteresis value of the sensor was approximately 0.003 V. These results indicate that CGO-based EGFETs are promising candidates for reliable and high-performance pH sensing.