Detection of ppm‐order hydrogen gas by Pd/AlGaN/GaN high electron mobility transistor‐based sensors

The hydrogen sensing properties of AlGaN/GaN high electron mobility transistors with Pd gate electrodes are demonstrated under various hydrogen concentrations. Remarkable current variation, as high as 1.7 mA at the drain-source voltage of 4 V and gate-source voltage of 0 V, was observed at 140 °C even at 1 part per million (ppm) hydrogen concentration. The logarithmic relation between the detection current variation and the hydrogen concentration was observed. By using the least-square fit to the experimental data, the reliable lower detection value of hydrogen concentration for the present device can be estimated to be about 0.45 ppm, i.e., 450 parts per billion (ppb) as a current variation of 1 mA. In addition, the turn-on and turn-off transient times have been estimated to be approximately 23 and 33 seconds at 160 °C, respectively, in the case of the 100 ppm hydrogen gas. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)