Structural properties of heteroepitaxial germanium-carbon alloys grown on Si (100)

Heteroepitaxial films of Ge1-xCx (x < 7%) alloys have been grown on Si (100 ) substrates using ultrahigh-vacuum chemical vapour deposition reactions in volving GeH4 and several different germylmethane precursors (GeH3)(4-x)CHx (x = 1-3), at temperatures in the range 470-540<degrees>C. The layer compos ition and crystallinity were assessed using Rutherford back-scattering spec troscopy, including C-resonance analysis, and the film microstructure was c haracterized using cross-sectional transmission electron microscopy. Irresp ective of the particular germylmethane precursor used for deposition, alloy s with low C concentrations had high crystallinity with low defect density, whereas those with high C content had an increased density of structural d efects. Greater C incorporation generally led to films with flatter and smo other surfaces, implying that the addition of C had compensated strain due to lattice mismatch and promoted two-dimensional growth.