Investigation of a Metal–Insulator–Semiconductor Pt/Mixed Al[sub 2]O[sub 3] and Ga[sub 2]O[sub 3] Insulator/AlGaN Hydrogen Sensor

Pt/mixed and reactive insulator/AlGaN metal−insulator−semiconductor (MIS)-type hydrogen sensors were fabricated using a photoelectrochemical oxidation method to directly oxidize AlGaN employed for increasing the sensor response to hydrogen gas. When hydrogen gas was sensed, the MIS hydrogen sensors exhibited a larger reduction of the barrier height and series resistances than that of the Pt/AlGaN metal–semiconductor (MS)-type hydrogen sensors. As a result, the MIS hydrogen sensors could detect the hydrogen concentration lower than 100 ppm /air while the MS hydrogen sensors could not detect such low hydrogen concentration. This provides a promising potential candidate of using a mixed and insulator for AlGaN-based hydrogen gas sensors.