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SiH4 and GeH4 deposition of Si1−xGex layers by a rapid thermal process very low pressure chemical vapor deposition method has been studied in this paper. The Ge incorporation rate increases to a maximum value and then decreases as temperature increases. The growth rate of the SiGe alloy reaches its maximum value and then decreases as Ge composition increases. Ge incorporation also enhances the Si deposition rate in the Si1−xGex alloy. These results have been explained by increasing the hydrogen desorption rate at low temperatures and low value of x (the germanium concentration) and decreasing the adsorption probability of reactive hydrides at high temperature and high value of x.

X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectrometry (LEISS) have been employed to study the kinetics of etching by atomic hydrogen of Ge overlayers on Si(100). The coverage of Ge as deduced by both XPS and LEISS decreases dramatically after exposure to atomic hydrogen, and the decrease is exponential with exposure time. The etch rate of Ge derived from these experiments is found to be a linear function of the flux of atomic hydrogen at sufficiently low temperatures (<180 °C). The rate of etching also depends upon the substrate temperature and a maximum in the etch rate is observed at about 180 °C. A kinetic model is proposed to describe the experimental data quantitatively. The model successfully describes the variation in the rate of etching as functions of the flux of atomic hydrogen and substrate temperature. In particular, the peak observed in the etch rate as a function of substrate temperature is interpreted as due to a similar variation in the coverage of an important reaction intermediate, namely a GeH2(a) surface species.

Low-energy ion scattering spectrometry (LEISS) and x-ray photoelectron spectroscopy (XPS) have been employed to quantify in situ the near-surface composition of strained Si1−xGex epitaxial thin films grown on Si(100) substrates using GeH4 and Si2H6 as sources. The use of LEISS reveals the Ge concentration in essentially the first monolayer, whereas XPS is sensitive to several monolayers. We find that the extent of Ge surface segregation implied by each technique follows the trend: LEISS-Ge%≫XPS-Ge%≫bulk-Ge%. A two-site model (involving surface and bulk states) cannot account for both the XPS and LEISS results, rather a model invoking Ge enrichment in the subsurface layers is required to explain the data.

Recent experimental results concerning Ge segregation in Si1−xGex epitaxial thin films deposited on Si(100) substrates using Si2H6 and GeH4 cannot be accounted for by a simple two-site model involving surface and bulk states. This is due to Ge enrichment in the subsurface layers. Here, we demonstrate that a simple model based on the regular solution theory, which invokes both nearest, and next-nearest neighbor interactions, can explain the Ge enrichment in the subsurface. A computer simulation using the Monte Carlo method verifies the assumptions made in the model, and both methods show excellent agreement with the experimental data.