Epitaxy of Si_1-xge_x by ultrahigh-vacuum chemical vapor deposition using Si₂H₆ and GeH₄

Disilane and germane were used to grow Si_1-xGe_x epilayers at 550°C by ultrahigh-vacuum chemical vapor depo-sition (UHVCVD). The solid composition x and growth rate of Si_1-xGe_x were evaluated from double-crystal X-ray rocking curves and show very strong dependence on the total source gas flow rate ([GeH₄] +[Si₂H₆]) and the gas ratio ([GeH₄]/[GeH₄]+[Si₂H₆]). The solid composition increases with increase of the gas ratio and also with in-creasing the total source flux by keeping gas ratio constant. The growth rate increases with the solid composition at lower values and then becomes saturated in the higher composition range (x>0.22). The results can be ex-plained by the relationships of the source fluxes, relative incorporation efficiency at activated surface sites and hydrogen desorption under different growth conditions.