Epitaxial growth and characterization of Ge_1-xC_x alloys on Si(100)

The initial stages (<20 monolayers) of molecular beam epitaxial growth of Ge_1-xC_x on Si(100) has been studied using both in situ surface analytical techniques and ex situ electron microscopy. The Ge _1-xC_x films studied had nominal C concentrations of 0.2<x<0.8. In situ reflection high-energy electron diffraction indicates crystalline, layer-by-layer growth for room temperature deposition of lower C concentrations (x<0.4) films and amorphous growth for higher C concentrations. Subsequent high-temperature anneals between 350 and 600°C caused the Ge and C to phase separate, with the Ge forming defective islands while the C precipitates out of the diamond lattice. Mechanisms leading to the C concentration-dependent island morphologies are suggested.