The effect of adsorption on the electrical properties of structures based on oxidized porous silicon

Abstract

The effect of adsorption of hydrogen-sulfide and acetone polar molecules on current-voltage characteristics and time dependences of the current was studied for the 〈Pd-por-Si(O)-p+-Si-Al〉 structures based on oxidized porous silicon. Structures of two types were obtained—those with a Schottky barrier and those with space-charge-limited currents. The presence of a positive space charge was found near the palladium electrode; this charge defined the current-voltage characteristics in the region of V<0.2 V and varied appreciably depending on the gas used. The parameters of the layer of oxidized porous Si and the range of operating voltages corresponding to the most marked effect of a gas were determined. A maximum current variation up to 103 times under the action of hydrogen sulfide with a concentration of ∼10 ppm was obtained for the structures with the Schottky barrier with a reverse voltage close to that of reversible breakdown. The results obtained are explained by the charge exchange of traps, which is corroborated by a Fermi level shift and a Schottky barrier lowering caused by the adsorption of polar molecules.