Hydrogen sensing properties of a Pd/AlGaN-based Schottky diode are improved by the deposition of SiO2 at the metal/semiconductor (MS) interface. The wide Schottky barrier height variation of the MOS diode could be attributed to the large electric field across the SiO2 layer. This leads to the presence of more hydrogen dipoles caused by the polarization effect. The sensing response of the MOS diode at room temperature (1.3 × 105) is comparable to that of the MS one at 150 °C (2.04 × 105). Thus, the MOS-type sensing device shows the benefit of low-temperature operation. Kinetic analyses confirm that the short response times of the MOS diode are attributed to high reaction rate at the Pd/SiO2 interface.
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