Chemical routes to Ge/Si(100) structures for low temperature Si-based semiconductor applications

The authors describe very low temperature (350–420 °C) growth of atomically smooth Ge films (0.2–0.4 nm roughness) directly on Si(100) via gas-source molecular beam epitaxy. A carefully tuned admixture of (GeH₃)₂CH₂, possessing unique pseudosurfactant properties, and conventional Ge₂H₆ provides unprecedented control of film microstructure, morphology, and composition. Formation of edge dislocations at the interface ensures growth of virtually relaxed monocrystalline Ge films (∼40–1000 nm thick) with a threading dislocation density less than 10⁵ cm^-2 as determined by etch pit measurements. Secondary ion mass spectroscopy showed no measurable carbon incorporation indicating that C desorbs as CH₄, consistent with calculated chemisorption energies.