COMPARISON AND ANALYSIS OF PD-GAAS AND PT-GAAS SCHOTTKY DIODES FOR HYDROGEN DETECTION

Hydrogen-sensing behaviors of Pd- and Pt-GaAs Schottky diodes, fabricated on the same GaAs substrate, have been systematically compared and analyzed as a function of hydrogen partial pressure and temperature by I-V and DELTAI-t methods under steady-state and transient conditions. The effects of hydrogen adsorption on the device parameters such as the barrier height and the ideality factor are investigated. The significant differences in their hydrogen sensing characteristics have been examined in terms of sensitivity limit, linearity of response, response rate, and response time. Adsorption activation energy of hydrogen and the heat of adsorption per hydrogen molecule on the surface of Pd and Pt are investigated and compared in both devices in a low-temperature range (27-100-degrees-C). For the temperature range investigated, Pd-GaAs shows better performance for H-2 detection than Pt-GaAs under the same testing conditions. The physical and chemical mechanisms responsible for hydrogen detection are discussed. Analysis of the steady-state reaction kinetics using I-V method confirmed that the atomistic hydrogen adsorption process is responsible for the barrier height change in the diodes.