Fundamental Study of InP-Based Open-Gate Field-Effect Transistors for Application to Liquid-Phase Chemical Sensors

摘要

We prove with this paper that InP-based open-gate field-effect transistors (FETs) work well as liquid-phase chemical sensors. The open-gate FET clearly exhibited current saturation and a pinch-off behavior in the electrolyte, resulting in a rapid response to the gate bias applied via the electrolyte. A series of sensing measurements showed that the surface potential of the InP linearly changed with the pH values of the electrolytes in a pH range from 3.0 to 12.0. The pH sensitivity of the open-gate FETs depended on the ion species contained in the electrolyte. A Si_3N_4 layer was useful as an ion selective membrane for the InP open-gate FETs to improve the selectivity of H~+ ions.