A MODEL FOR HETEROGENEOUS GROWTH OF SI1-XGEX FILMS FROM HYDRIDES

Growth rates for Si(1-x)Ge(x) films (0 less-than-or-equal-to x less-than-or-equal-to 0.19) have been measured between 610-750-degrees-C using low pressure H-2/SiH4/GeH4 mixtures and at different temperatures these rates show different dependencies on composition x. A model attributes this complex behavior to competition between an increasing rate for desorption of surface hydrogen and a decreasing sticking probability for the reactive hydrides as x increases. The latter effect is explicitly reported for the first time. GeH4 is found to be approximately 4.7 times more reactive than SiH4, and relative surface hydrogen coverages on Si and Si0.87Ge0.13 films measured by secondary ion mass spectroscopy are compared with the model.