Influence of dislocations on vertical ordering of Ge islands in Si Ge multilayers grown by low pressure chemical vapour deposition

The presence of misfit and threading dislocations formed by strain relaxati on in multilayers of Ge islands grown on Si(100) is investigated by transmi ssion electron microscopy and atomic force microscopy. We find that the dis locations are generated inside the islands and propagate into the silicon s pacers remaining confined within the columnar regions above the islands the mselves. Thus the dislocations drive the vertical ordering of the stacked r elaxed islands in a way similar to the strain induced self-ordering mechani sm in the strained islands.