Dislocation networks in conventional and surfactant-mediated Ge/Si(1 1 1) epitaxy

Surface undulations induced by interfacial misfit dislocations in the Ge/Si(1 1 1) 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° 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.