Modification of the growth mode of Ge on Si by buried Ge islands

Photoluminescence experiments on double Ge layers were performed to give deep insights on the growth mode of Ge on Si in the presence of buried 4.5 monolayers of Ge islands. The critical coverage of the island formation and the wetting layer thickness were confirmed to be reduced in the second Ge layer. In addition, a drastic increase of the island density as well as a shape transition were observed by atomic force microscopy. These modifications of the growth mode are explained in terms of the surface strain induced by the buried Ge islands and the reduction of the nucleation barrier due to the alloying. (C) 2000 American Institute of Physics. [S0003-6951(00)03725-6].