The growth of SiGe on sapphire using rapid thermal chemical vapor deposition

We have grown SiGe on (1 (1) over bar 0 2) sapphire using rapid thermal chemical vapor deposition at substrate temperatures ranging from 600 to 900 degreesC. For growth at 600-700 degreesC the films are polycrystalline and the Ge composition and growth rates are higher (25%) compared to growth on Si under identical conditions. Growth at 800-900 degreesC results in epitaxially {0 1 1} oriented films with two sets of grains rotated 90 degrees to each other, consistent with nucleation on the two-fold rotationally symmetric sapphire surface. Growth under identical conditions on recycled sapphire wafers that had experienced an integrated circuit process (ion implantation, plasma etching, metal depositions, etc.) results in single crystalline {0 0 1} oriented films. This change in nucleation is correlated with an increase in Al and reduced Ge in the film at the interface. Further studies are needed to understand the underlying mechanism. (C) 2001 Elsevier Science B.V. All rights reserved.