The use of self-organization of nanostructures during growth of materials h
aving a high lattice mismatch e.g. Ge on Si offers new possibilities for de
vice applications. The Ge layers were grown on Si(001) substrates by low pr
essure chemical vapour deposition. Island size statistics derived from the
atomic force micrographs show a trimodal size distribution at high average
Gr layer thicknesses, whereas at low Ge layer thicknesses only a narrow mon
omodal island size distribution exists. Transmission electron micrographs r
eveal the type of relaxation of the Ge islands and the shape of islands aft
er being capped by a Si overlayer. A correspondence beta cen the broadening
of the spectral emission and the island morphology can be concluded from p
hotoluminescence measurements. Multiple stacked island layers exhibit a sig
nificant increase of integral intensity in comparison with a single layer o
f islands, grown under equal conditions. A clear vertical correlation betwe
en island positions in different lavers and a continuous enlargement of isl
and size in upper layers is found on transmission electron micrographs of s
tacked island layers. (C) 1998 Elsevier Science S.A. All rights reserved.