Hydrogen sensitive negative switching behavior in metal-oxide-semiconductor devices

Hydrogen sensitive switching device with a Pd-thin SiO2-(n)Si-(p+)Si structure which has thyristor-like S-shape property and of which threshold voltage was sensitive to hydrogen concentration was studied by using an impedance measurement for the first time. The switching device was considered to be a series connection of MIS junction and p+n junction. Four equivalent circuit parameters of two parallel connections of a capacitance and a resistance corresponding to two junctions were estimated under several bias and hydrogen conditions. Dependence of the parameters on bias voltage and on ambient hydrogen concentration is shown. The properties of these parameters reveal the behavior of MIS and p+n junction and their mutual interaction. A hydrogen sensitive switching mechanism is discussed. The impedance method is available to clarify the operation mechanism of the switching device.