Interface roughening of Ge $\delta$ layers on Si(111)

Ge δ layers, grown by molecular-beam epitaxy (MBE), surfactant-mediated epitaxy, and solid-phase epitaxy were characterized in situ by high-resolution low-energy electron diffraction and post growth by x-ray standing waves. Initial growth of Ge on Si is found to proceed in a double-bilayer fashion. Subsequent Si deposition leads to a bilayer growth mode. MBE Si deposition is accompanied by Si-Ge site exchanges leading to increased interfacial roughening, which can be partially reduced by solid-phase epitaxy and use of surfactants