Dislocation networks in conventional and surfactant-mediated Ge/Si(111) epitaxy

Surface undulations induced by interfacial misfit dislocations in the Ge/Si(l 11) films grown by conventional molecular beam epitaxy and by surfactant-mediated epitaxy with Bi as a surfactant have been analyzed using scanning tunnelling microscopy and elasticity theory. A comparison of the experimentally measured undulation patterns with patterns calculated with elasticity theory leads to identification of the dislocations in both systems as 90 degrees Shockley partial dislocations. Dislocations are primarily arranged into a triangular network in Bi-mediated growth, whereas in conventional epitaxy a strongly disordered honeycomb network prevails. The dislocation density in conventional epitaxy is found to be 30% smaller than in Bi-mediated growth, which is attributed to strong Si-Ge intermixing. (c) 2005 Elsevier B.V. All rights reserved.