On a GaAs-based transistor-type hydrogen sensing detector with a Pd/Al_(0.24)Ga_(0.76)As metal-semiconductor Schottky gate

摘要

An interesting transistor-type hydrogen sensing detector based on a GaAs pseudomorphic high electron mobility transistor (PHEMT) with a Pd/Al_(0.24)Ga_(0.76)As metal-semiconductor Schottky gate structure is fabricated and investigated. Steady-state properties and transient responses under different temperatures and hydrogen concentrations are measured and studied. Significant modulations in electrical signals are observed, obviously due to the adsorption of hydrogen atoms at the Pd-semiconductor interface. Also, the studied device exhibits fast response and recovery properties. The corresponding adsorption and desorption time constants (τ_a and τ_b) are 2.5 and 6 s, respectively, under 9970 ppm H_2/air gas at 160℃. Furthermore, based on the Langmuir isotherm and the van't Hoff equation, a hydrogen adsorption heat of —37.02 kJ mole~(-1) is obtained at lower operating temperatures ( ≤ 72℃). However, at a high temperature region ( ≥ 92℃), the ΔH~0 value is increased to -68.62 kJ mole~(-1). The hydrogen adsorption heat at lower and higher temperature regimes is demonstrated and studied. Consequentially, based on the experimental results, the studied device is promising for GaAs integrated circuit (IC) and micro electric and mechanic system (MEMS) applications.