Coalescence of germanium islands on silicon

The growth of Ge islands on Si (Stranski-Krastanov growth mode) is well kno wn (I.N. Stranski, L.v. Krastanov, Akad. Wiss. Wien, Math.-Naturw. Kl. Abtl g. IIb 146 (1937) 797). At larger Ge coverages the islands coalesce and for m a quasi two-dimensional film. We investigated this transition from island growth to quasi two-dimensional films for a rather high Ge deposition rate of 0.25 nm/s. The germanium islands were grown by molecular beam epitaxy. At mean thicknesses of 1.25 and 3.75 nm the surface morphology of Ge deposi tions was observed by atomic force microscopy as a function of deposition t emperature. At temperatures between 500 and 550 degrees C, we confirm the 3 D-island growth as expected from the Stranski-Krastanov growth mode. But be low these temperatures the islands coalesce and form a continuous film (E. Kasper, H. Jorke, J. Vac. Sci. Technol. A 10(4) (1992) 1927). The waviness of the films decrease with decreasing temperatures resulting in smooth laye rs at 300 degrees C growth temperature. (C) 1998 Elsevier Science S.A. All rights reserved.