Liquid-phase sensors using open-gate AlGaN/GaN high electron mobility transistor structure
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.
Journal
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- Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures
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Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 24 (4), 1972-1976, 2006-07-25
AVS Science & Technology of Materials, Interfaces, and Processing
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Details 詳細情報について
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- CRID
- 1050282813955864832
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- NII Article ID
- 120000956602
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- HANDLE
- 2115/14592
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- ISSN
- 0734211X
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- Text Lang
- en
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- Article Type
- journal article
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- Data Source
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- IRDB
- CiNii Articles