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 (Δ V th) of 260 mV is observed upon exposing to a 1% H 2/air gas. The drain current sensing response ( S R) shows the strong dependence on the gate bias voltage V GS. A maximum S R of 107% is found at the applied voltage of V GS = −0.5 V. In addition, the temperature behavior of S R 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 E a of 2.88 kJ mol −1 suggests that the studied Pd/InAlAs MHEMT hydrogen sensor has a low barrier for the adsorption of hydrogen.