Optical properties of InSb films deposited on sapphire substrates by rf sputtering

Abstract

We have deposited InSb films by rf sputtering on sapphire substrates of various surface orientations [(0001), (112̄0), (011̄2), and (011̄0)]. The epitaxial InSb(111) films are grown only on (0001) sapphire substrates at substrate temperatures 280–320 °C, while the films deposited on (112̄0), (011̄2), and (011̄0) sapphires show that they have polycrystalline structures even when they were deposited at high substrate temperatures. Optical properties of these films are investigated by using spectroscopic ellipsometry. A linear regression analysis and a Bruggeman effective-medium approximation reveal that the epitaxial film has a few void networks in the film. Polycrystalline InSb films, on the other hand, contain a large number of void networks deep in the film medium. Both epitaxial and polycrystalline films have rough-surface overlayers of a few tens of Å.