CHARACTERISTICS OF B-DOPED SI1-XGEX GROWTH-RATES BY CHEMICAL-VAPOR-DEPOSITION USING SI2H6, GEH4, AND B2H6 GASES

Low temperature heteroepitaxy of highly B-doped Si1-xGex on Si by low pressure CVD has been investigated from the viewpoint of growth rate. The growth temperature was 550-730-degrees-C, and the concentration of B was 10(18)-10(21) cm-3. For the undoped and B-doped Si0.75Ge0.25, t he growth rate was limited by the supply of Si2H6 and GeH4 to the surf ace at temperatures above 630-degrees-C and by the desorption of hydro gen from the surface at temperatures below 630-degrees-C. The activati on energy of the growth rate was 2.0 eV for undoped alloy below 630-de grees-C. A reduced activation energy was found for in situ B-doping. T he growth rates of alloy (the surface reaction rates of Si2H6 and GeH4 ) increase with increases in the surface density of B deposited by the decomposition of B2H6 on the surface. The deposition rate of B is det ermined only by the quantity of B2H6 supplied to the surface and does not depend on the composition of the alloy surface layer or the growth temperature.