AlGaN/GaN HEMT based liquid sensors

Mehandru, R.; Luo, B.; Kang, B. S.; Kim, Jihyun; Ren, F.; Pearton, S. J.; Pan, C.-C.; Chen, G.-T.; Chyi, J. I.

doi:10.1016/s0038-1101(03)00318-6

Cited by 75 publications

(28 citation statements)

References 20 publications

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“…The possibility of pH sensing using undoped AlGaN/GaN HEMT has been reported previously by Mehandru et al [7]. The fabricated two-terminal device shows significant decreases upon exposure of the gate area to solvents (water, acetone and HCl) [7]. Recently, we have also reported the sensing responses of both bulk n-GaN and undoped AlGaN/GaN based two-terminal devices in aqueous solution with various pH levels and also in polar liquids [8].…”

Section: Introductionmentioning

confidence: 94%

Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure

Abidin

Hashim

Sharifabad

et al. 2011

Sensors

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The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V) characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications.

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Section: Introductionmentioning

confidence: 94%

Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure

Abidin

Hashim

Sharifabad

et al. 2011

Sensors

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“…The pH response of GaN surfaces using ISFET structures was recently reported by Steinhoff et al 8 However, no work on the pH response to AlGaN surfaces was done, and mechanism of pH response is not understood yet. Although Stutzmann et al 9 and Mehandru et al 10 reported preliminary results on the response of open-gate AlGaN / GaN HEMTs to polar liquids, the sensing properties of such devices have not systematically been investigated so far.…”

Section: Introductionmentioning

confidence: 99%

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

Kokawa

Sato

Hasegawa

et al. 2006

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Liquid-phase sensing characteristics of open-gate AlGaN / GaN high electron mobility transistor ͑HEMT͒ 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.

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“…The gate area of the HEMT can be used to modulate the drain current in the FET mode or for use as the electrode for the Schottky diode. A variety of gas, chemical and health-related sensors based on HEMT technology have been demonstrated with proper surface functionalization on the gate area of the HEMTs, including the detection of hydrogen, mercury ion, prostate specifi c antigen (PSA), DNA and glucose (Lothian et al, 1992;Luther et al, 1999;Johnson et al, 2000;Schalwig et al, 2002b;Eickhoff et al, 2003;Kim et al, 2003a;Mehandru et al, 2004;Pearton et al, 2004;Shen et al, 2004;Kang et al, 2004aKang et al, , 2004bKouche et al, 2005;Kryliouk et al, 2005;Tien et al, 2005aTien et al, , 2005bWang et al, 2005aWang et al, , 2005bWang et al, , 2005cKang et al, 2005bKang et al, , 2005cKang et al, 2006;Wang et al, 2006;Gangwani et al, 2007;Jun et al, 2007;Pearton et al, 2007;Kang et al, 2007aKang et al, , 2007bKang et al, , 2007cWang et al, , 2007cChen et al, 2008;Johnson et al, 2009;Yu et al, 2008;Wright et al, 2009).…”

confidence: 99%