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 relaxation in multilayers of Ge islands grown on Si(100) is investigated by transmission electron microscopy and atomic force microscopy. We find that the dislocations are generated inside the islands and propagate into the silicon spacers remaining confined within the columnar regions above the islands themselves. Thus the dislocations drive the vertical ordering of the stacked relaxed islands in a way similar to the strain induced self-ordering mechanism in the strained islands.