INSITU DOPING OF SI AND SI1-XGEX IN ULTRAHIGH-VACUUM CHEMICAL VAPOR-DEPOSITION

We report on the growth of germanium-silicon and silicon epitaxial layers by ultrahigh vacuum/chemical vapor deposition. When an in situ clean is used, films grown at 600-degrees-C are defect-free by planar section transmission electron microscopy and no oxygen is detectable by secondary ion mass spectroscopy at the growth interface. In situ doping has been studied using B2H6/H-2 and PH3/H-2 as source gases. Ge0.13Si0.87 films doped with boron up to 5 x 10(19) cm-3 have been grown and sharp doping transitions have been obtained. Phosphorus doping concentrations in silicon are limited by a decrease in growth rate with increasing phosphorus flow rate which is attributed to phosphorus blocking of reaction sites. A model for the decrease in growth rate with PH3/H-2 flow is proposed which provides a good fit to the measurements.