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pH Sensing Characteristics of Extended-Gate Field-Effect Transistor with Al₂O₃ Layer
Jae Kwon1, Yong Kyoung Yoo2, Jeong Hoon Lee2
1Department of Electronic Engineering, Kwangwoon University, Seoul 01897, Republic of Korea.
Abstract:
A simple and stable pH sensor based on an extended-gate field-effect transistor (EGFET) is demonstrated using electron-beam deposited Al₂O₃ as a pH sensing layer. The threshold voltage of the EGFET is modulated by different pH values of the buffer solution. A control experiment with a bare Au electrode confirms that the stable pH sensing response with linearity and reproducibility originates from the Al2O3 sensing layer. The minimum area of the pH sensing layer is estimated by considering that the different sizes of the sensing layer are easily modeled with different values of external capacitors connected to the readout transistor. The study verifies that the pH detection accuracy is improved by using the reference electrode with a KCl electrolyte.
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