Interaction of self-assembled Ge islands and adjacent Si layers grown on unpatterned and patterned Si(001) substrates

For use in electronic devices, self-assembled Ge islands formed on Si(001) must be covered with an additional Si layer. Chemically vapor deposited Si layers initially grow very rapidly over Ge islands because of the catalytic effect of Ge on the reaction of the Si-containing gas. The edges of the Si features covering Ge "pyramids" are rotated by 45 degrees with respect to the edges of the Ge pyramids because of the different mechanisms orienting the Ge islands and the Si features. When multiple layers of islands are formed, the in-plane ordering of the Ge islands depends on the thickness of the Si interlayer separating the island layers. When selective Si is grown on a patterned Si wafer to form the underlying structure for the Ge islands, the position of the islands is influenced by the detailed shape of the Si near the edges, which in turn depends on the thickness of the selectively deposited Si, the pattern size, and the amount of surrounding oxide.