Distribution of Ge in O+ implanted silicon

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We have studied 50 nm Si0.8Ge0.2 buried layers and 800 nm Si0.9Ge0.1 layers, grown by molecular beam epitaxy, which were implanted with 200 keV oxygen O+ ions to a dose of 1.8×1018/cm2. This implantation procedure is similar to that used in the formation of SIMOX (separation by implantation of oxygen), although it was not followed by the usual high temperature anneal. Because the initial implantation profile extends as far as 600 nm below the Si surface, the 50 nm Si0.8Ge0.2 layers were embedded in Si at depths of 600, 500, 400, and 300 nm from the Si surface. The effects of Ge incorporation could then be studied as a function of distance from the surface and position within the implantation profile. Using a scanning transmission electron microscope equipped with energy dispersive x-ray spectroscopy, we examined cross-sectional specimens for the distribution of the Ge in and around the implanted oxide layer. We found that the Ge tended to be excluded from the oxide in all the samples with the 50 nm buried layer. For the case where the oxide was implanted into the midst of an 800 nm layer, the Ge remained in the oxide.