Performance Improvement of a ZnGa<sub>2</sub>O<sub>4</sub> Extended-Gate Field-Effect Transistor pH Sensor
Chia‐Hung Chen, Shu-Bai Liu, Sheng-Po Chang
Abstract
High Resolution Image Download MS PowerPoint Slide ZnGa 2 O 4 sensing films were prepared using an RF magnetron sputtering system and connected to a commercial metal oxide semiconductor field-effect transistor (MOSFET) as the extended-gate field-effect transistor (EGFET) to detect pH values. Experimental parameters were adjusted by varying the oxygen flow rate in the process chamber to produce ZnGa 2 O 4 sensing films with different oxygen ratios. These films were then treated in a furnace tube at an annealing temperature of 700 °C. The sensitivity and linearity of the constant current mode and the constant voltage mode were measured and analyzed in the pH range of 2–12. Under the deposition conditions with an oxygen ratio of 6%, the sensitivity reached 23.14 mV/pH and 33.49 μA/pH, with corresponding linearity values of 92.1 and 96.15%, respectively. Finally, the sensing performance of the ZnGa 2 O 4 EGFET pH sensor with and without annealing processes was analyzed and compared.