On a Pd/InAlAs metamorphic high electron mobility transistor (MHEMT)-based hydrogen sensor

The hydrogen sensing properties of a Pd/InAlAs metamorphic high electron mobility transistor (MHEMT) are investigated. Experimentally, a threshold voltage shift (ΔVth) of 260 mV is observed upon exposing to a 1% H2/air gas. The drain current sensing response (SR) shows the strong dependence on the gate bias voltage VGS. A maximum SR of 107% is found at the applied voltage of VGS = −0.5 V. In addition, the temperature behavior of SR is predominantly determined by the hydrogen sticking coefficient and the exothermic reaction of hydrogen adsorption. It is also found that rectification ratio R can be changed with different hydrogen concentrations Furthermore, the response rate analyses reveal that the initial response rate is increased with the hydrogen concentration and temperature. The activation energy Ea of 2.88 kJ mol−1 suggests that the studied Pd/InAlAs MHEMT hydrogen sensor has a low barrier for the adsorption of hydrogen.