AlGaN/GaN Schottky diode hydrogen sensor performance at high temperatures with different catalytic metals

Schottky diodes on AlGaN/GaN heterostructures with Pt, IrPt, and PdAg catalytic metals are fabricated and characterized from 200 °C to 800 °C for H2 sensing. Over this large range of temperature, the forward current of all the diodes increases with exposure to H2 gas, which is attributed to Schottky barrier height reduction caused by the atomic hydrogen absorption on the metal-oxide interface. The results indicate that AlGaN/GaN heterostructure Schottky diodes are capable of high-temperature H2 sensor operation up to 800 °C. As temperature increases, the hydrogen detection sensitivity of Pt and IrPt diodes improves due to the more effective H2 dissociation. However, the sensitivity of PdAg diodes degrades with the increase of temperature due to thermal instability of PdAg. At a range of temperature from 200 °C to 300 °C, PdAg diodes exhibit significant higher sensitivity compared with Pt and IrPt diodes. IrPt and Pt diodes show higher sensitivity at temperatures above 400 °C.