Chemical Synthesis of Metastable Germanium−Carbon Alloys Grown Heteroepitaxially on (100) Si

Abstract

High-quality diamond-structured Ge1-xCx alloys have been grown on (100) Si using ultrahigh-vacuum chemical vapor deposition techniques and novel chemical precursors. Two-dimensional growth of single-crystal heteroepitaxial layers (30−120 nm thick) of germanium−carbon alloys with carbon concentrations up to 7% has been achieved by reactions of GeH4 with germylmethanes, (GeH3)4-xCHx (x = 1−3), at 470 °C. The composition of the materials was established by extensive Rutherford backscattering (RBS) carbon resonance analysis, and the layer crystallinity was characterized by cross-sectional transmission electron microscopy and RBS channeling experiments. RBS ion channeling revealed that the carbon primarily occupied substitutional sites in the diamond-like Ge lattice. Alloys with low carbon content displayed virtually perfect crystallinity whereas materials with high carbon incorporation had structural defects in the form of {111} stacking faults and microtwins. The thin film microstructure of a given alloy com...