Hydrogen-sensitive characteristics of a novel Pd/InP MOS Schottky diode hydrogen sensor

Steady-state and transient hydrogen-sensing characteristics of a novel Pd/I nP metal-oxide-semiconductor (MOS) Schottky diode under atmospheric conditi ons are presented and studied. In presence of oxide layer, the significant increase of barrier height improves the hydrogen sensitivity even at lower operating temperatures. Even at a very low hydrogen concentration environme nt, e.g., 15 ppm H-2 in air, a significant response is obtained. Two effect s, i.e., the removal of Fermi-level pinning caused by the donor level in th e oxide and the reduction of Pd metal work function dominate the hydrogen s ensing mechanism. Furthermore, the reaction kinetics incorporating the wate r formation upon hydrogen adsorption is investigated. The initial heat of a dsorption for the Pd/oxide interface is estimated to be 0.42 eV/hydrogen at om. The coverage dependent heat of adsorption plays an important role in hy drogen response under steady-state conditions. In accordance with the Temki n isotherm behavior, the theoretical prediction of interface coverage agree s well with the experimental results over more than three decades of hydrog en partial pressure.