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This paper presents an analytical model of AlGaN/GaN MOS-HEMT based pH sensor for the first time to determine pH of different electrolyte solutions. Gouy-chapman stern model has been used to calculate the surface charge density. The results obtained using analytical model have been verified and show good agreement with the simulated results. Cavity length, thickness of AlGaN barrier layer and Al composition have been optimized to improve the sensitivity of the device. It has been observed that the drain current and threshold voltage decreases with increase in pH of the electrolytic solutions. Proposed AlGaN/GaN MOS-HEMT sensor demonstrate a quick response to the pH changes. The maximum drain-on-sensitivity of the device is 132mA/mm-pH. Surface potential and threshold voltage sensitivity of 0.95mV/pH and 950mV/pH respectively have been obtained which is much higher than the Nernstian limit(59.2mV/pH).

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