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 che mical vapor deposition at substrate temperatures ranging from 600 to 900 de greesC. For growth at 600-700 degreesC the films are polycrystalline and th e Ge composition and growth rates are higher (25%) compared to growth on Si under identical conditions. Growth at 800-900 degreesC results in epitaxia lly {0 1 1} oriented films with two sets of grains rotated 90 degrees to ea ch other, consistent with nucleation on the two-fold rotationally symmetric sapphire surface. Growth under identical conditions on recycled sapphire w afers 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 increa se in Al and reduced Ge in the film at the interface. Further studies are n eeded to understand the underlying mechanism. (C) 2001 Elsevier Science B.V . All rights reserved.