IMPROVED GROWTH-MORPHOLOGY OF SI-GE-C HETEROSTRUCTURES THROUGH THE USE OF SB SURFACTANT-ASSISTED MOLECULAR-BEAM EPITAXY

Carbon incorporation in Si and SiGe heteroepitaxial structures offers exciting opportunities in the design of novel, Si-based electronics. R ecent results suggest that in order to realize the potential of this m aterial system, methods for achieving high carbon concentrations (in e xcess of 5 at.%) without sacrificing crystalline quality must be devel oped. We have investigated the use of Sb as a surfactant to assist in the incorporation of carbon during growth of Si and SiGe epitaxial lay ers by molecular beam epitaxy. For samples in which Sb is not used, re flection high-energy electron diffraction (RHEED) shows that the wafer surfaces roughen soon after the carbon is introduced. As growth proce eds, the layers eventually twin and become defective, especially for t hicker layers and higher carbon concentrations (> 2%). Roughening occu rs at even lower carbon concentrations for the case of SiGeC growth as we have grown Si1-x-yGexCy/Si1-yCy' heterostructures with y' > y, and observe RHEED patterns are streaked during the Si1-y'Cy' deposition b ut spotted during the Si1-x-yGexCy deposition. The presence of less th an or equal to 1 monolayer of Sb on the surface of the substrate prior to epitaxy is shown in this work to substantially reduce roughening o f the growth front, resulting in a dramatic reduction in defect densit y with minimal Sb incorporation (<10(17) cm(-3)). Transmission electro n microscopy and secondary ion mass spectrometry data relating to the quality of the layers and the amount of Sb incorporation will be discu ssed.