Comprehensive study of a Pd/Al0.24Ga0.76As-based field-effect-transistor-type hydrogen sensor

An interesting Pd/Al0.24Ga0.76As-based field-effect-transistor-type hydrogen detector is fabricated and studied. The corresponding electronic and hydrogen sensing properties are measured and investigated. Based on the measured results, a hydrogen sensing model is developed. Theoretically, the dipolar layer formed by the hydrogen atoms adsorbed at the Pd–AlGaAs interface can be considered as a two-dimensional layer. Under the 980 ppm H2/air environment, the concentration of hydrogen adsorption sites available at the metal–semiconductor interface, ni, and the effective distance, d, from the Pd–AlGaAs interface to adsorbed hydrogen atoms are 9.5 × 1013 cm−2 and 3 Å, respectively. The simulated curves show excellent agreement with experimental results. In addition, an anomalous decrease phenomenon in transient response is observed which may be caused by the formation of hydroxyl species and water.