Hydrogen-sensitive silicon tunnel MIS switching diodes

Palladium thin SiO2-n-p⁺silicon switching diodes have been fabricated in which the turn-on voltage changes in proportion to the hydrogen concentration in the ambient gas. In the typical diode operated at 100°C, the switching voltage decreases from 5.1 to 3.6 V for 10 ppm hydrogen in air within 2 min and the off-state disappears for 100 ppm within 30 s. Hydrogen sensitivity is ascribed to the increase of a current gain in two transistor model of the device due to the change in palladium work-function.