On a GaAs-based transistor-type hydrogen sensing detector with a Pd/Al_0.24Ga_0.76As metal–semiconductor Schottky gate

Abstract

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 • C. 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 • C). However, at a high temperature region (92 • C), the H 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.

Single-Walled Carbon Nanotubes Modified with Pd Nanoparticles: Unique Building Blocks for High-Performance, Flexible Hydrogen Sensors

“…), where the reaction between Pd and hydrogen (i.e., the formation of palladium hydride) lowers the transport barrier for electrons through the contacts, thus increasing current flow. Sandwiching thin layers of insulators (e.g., oxides) between Pd films and semiconductors forms geometries of field effect transistors where the drain currents vary upon exposure to hydrogen . These commercial (or well-characterized) hydrogen sensors are fabricated with Pd films on rigid substrates (e.g, glass slides, semiconductor wafers, etc.).…”