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The in-situ fabrication of rectangular concentration-depth profiles of phosphorus in germanium, with electrically active concentrations approaching 1020 cm-3 is reported. The growth method is atmospheric chemical vapor deposition using germane and phosphine with N2 as carrier gas. Best results have been achieved using a relatively low growth temperature of 350ºC and a low PH3/GeH4 flow ratio, enabling a high concentration of P to be incorporated substitutionally. No P clusters are visible in high-angle annular dark-field STEM images. The results show excellent crystalline quality and acceptable surface uniformity, achieved with growth rates in the range of 5-10 nm / min. There is evidence that further improvements in active concentrations may be achievable by a further reduction in growth temperature and optimization of the gas flow conditions. The process holds promise for future n+junction fabrication in germanium.

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A metal catalyst free direct growth process has been developed for the CVD of carbon nanotubes (CNTs) on carbon implanted SiGe islands or Ge dots on Si substrates. From TEM and Raman measurements, the fabricated CNTs are identified as single-walled CNTs (SWNTs) with diameter ranging from 1.2 to 2.1 nm. Essential parts of the substrate preparation after SiGe or Ge dot growth and carbon ion implantation are a chemical oxidation and preheating at 1000 °C prior to CNT growth. We believe that the lower melting point of Ge and oxidation enhanced surface decomposition assist the formation of carbon clusters.