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

Chia-Hsun Chen; Shu-Bai Liu; Sheng-Po Chang

doi:10.1021/acsomega.3c09965

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

ACS Omega. 2024 Mar 20;9(13):15304-15310. doi: 10.1021/acsomega.3c09965. eCollection 2024 Apr 2.

Authors

Chia-Hsun Chen¹, Shu-Bai Liu², Sheng-Po Chang³

Affiliations

¹ Institute of Electro-Optical and Material Science, National Formosa University, Yunlin 632301, Taiwan.
² Department of Electronic Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City 80778, Taiwan.
³ Department of Microelectronics Engineering, National Kaohsiung University of Science and Technology, Kaohsiung City 88157, Taiwan.

Abstract

ZnGa₂O₄ 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 ZnGa₂O₄ 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 ZnGa₂O₄ EGFET pH sensor with and without annealing processes was analyzed and compared.