AlGaN/GaN HEMT based sensor and system for polar liquid detection

Abstract In this paper, a GaN-high electron mobility transistor (HEMT) based sensor is designed, fabricated and characterized for polar liquid sensing. The fabricated HEMT sensor chip is packaged by using low temperature co-fired ceramic (LTCC) technique. The sensor shows a typical drain current of 21.2 mA at 3.3 V. The fabricated sensor shows a percentage change of 1.78%, 2.18% and 6.3% in drain current for mercury chloride, copper chloride and sodium chloride respectively with respect to the drain current of pure water. The readout circuit shows a change of 0.15, 0.20 and 0.34 mA in drain current for acetone, water and methanol respectively and ensures the detection of different polar liquids. Due to the novel inter-digital structure, the sensor shows a sensitivity of 5.98 mA/mm/Debye at a drain voltage of 3.3 V. Sensing mainly depends on the dipole moment because the change in the dipole moment of the liquid causes a change in surface potential at the gate sensing area. This paper gives a theoretical and practical perspective on polar liquid detection using both, the sensor and system.