Detection of ammonia at low concentrations (0.1-2 ppm) with ZnO nanorod-functionalized AlGaN/GaN high electron mobility transistors

초록

AlGaN/GaN high electron mobility transistors with ZnO nanorod functionalized gates were used for detecting NH3 in the concentration range of 0.1-2 ppm balanced with air at ambient temperatures from 25 to 300 degrees C. A decrease in the high electron mobility transistor drain current was observed for exposure to the NH3-containing ambients, indicating an increase in negative charge at the heterointerface. The detection sensitivity increased monotonically with ammonia concentration at all temperatures, from 0.28% (25 degrees C) and 3.17% (300 degrees C) for 0.1 ppm to 1.32% (25 degrees C) and 13.73% (300 degrees C) for 2 ppm for a drain-source voltage of 1V. The latter condition is attractive for low power consumption. The sensitivity was also a function of applied voltage and was generally higher in the linear region of the current-voltage characteristic of the transistor. The activation energy of the sensitivity was 0.09 eV, and the sensors showed no response to O-2 (100%), CO2 (10%), CO (0.1%), CH4 (4%), and NO2 (0.05%) under the same detection conditions as used for the NH3. The response was less than 1 s, and recovery times were of order similar to 53 s at 25 degrees C. (C) 2017 American Vacuum Society.

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