Compound semiconductors grown on porous alumina substrate as a novel hydrogen permeation membrane

Abstract

A highly p-type-doped InGaAs film was grown on a porous alumina substrate by metalorganic chemical vapor deposition (MOCVD). This structure was proposed as a novel hydrogen selective permeation membrane. In the p-type film, hydrogen atoms are converted to protons by giving their electrons to the dopant atoms. The protons easily diffuse in the film at elevated temperatures and are desorbed as hydrogen molecules from the surface of the film. When the hydrogen gas is supplied to both side of the film and there is difference in pressure, only hydrogen can penetrate into the film and move to the lower-pressure side. Preliminary experimental results are shown in this paper. Large amount of hydrogen was found in both the epitaxial InGaAs film (grown on InP) and the poly-crystal InGaAs films (grown on sapphire and porous alumina). Hydrogen was desorbed when the film was annealed in nitrogen gas. Hydrogen was absorbed into the film again by annealing in hydrogen gas. Scanning electron microscope (SEM) pictures suggest that a dense poly-crystal film without pin-holes was grown on the porous alumina substrate.