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Liquid-phase sensors using open-gate AlGaN/GaN high electron mobility transistor structure

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Title: Liquid-phase sensors using open-gate AlGaN/GaN high electron mobility transistor structure
Authors: Kokawa, Takuya Browse this author
Sato, Taketomo Browse this author →KAKEN DB
Hasegawa, Hideki Browse this author
Hashizume, Tamotsu Browse this author
Issue Date: 25-Jul-2006
Publisher: AVS Science & Technology of Materials, Interfaces, and Processing
Journal Title: Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures
Volume: 24
Issue: 4
Start Page: 1972
End Page: 1976
Publisher DOI: 10.1116/1.2214701
Abstract: Liquid-phase sensing characteristics of open-gate AlGaN/GaN high electron mobility transistor (HEMT) structures were investigated in aqueous solutions and polar liquids. In de-ionized water, the open-gate HEMT clearly showed good drain I-V characteristics with current saturation and pinch-off behavior, very similar to I-V characteristics of typical Schottky-gate HEMTs. We observed a fine parallel shift in the transfer curves according to change in the pH value in a solution, indicating the corresponding potential change at the AlGaN surface. The sensitivity for the potential change was 57.5 mV/pH, very close to the theoretical value of 58.9 mV/pH at 24 °C for the Nernstian response to H+ ions. In the low drain bias region, the drain current linearly decreased with the pH value. This also indicated a systematic potential change at the AlGaN surface due to pH change. The present open-gate device showed a fast response to the pH change and a stable operation at fixed pH values. A possible mechanism for the pH response of the AlGaN surface is discussed in terms of equilibrium reactions of hydroxyls at the AlGaN surface with H+ in a solution. It was also found that the device was quite sensitive to changes in the electrostatic boundary conditions of the open-gate area by exposure to polar liquids. The drain current linearly decreased with increasing normalized liquid dipole moment.
Type: article
Appears in Collections:量子集積エレクトロニクス研究センター (Research Center for Integrated Quantum Electronics) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 佐藤 威友

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