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In low-temperature epitaxial Si deposition methods such as molecular beam epitaxy (MBE), pre-epitaxial substrate preparation usually incorporates a high temperature (≳800 °C) step. Elimination of this step is essential to wider applicability of these epitaxial methods. We show that Si(100) wafers exposed to HF vapors in a laboratory ambience are bulk terminated and that such termination is stable in air for several tens of minutes, and in vacuum for several hours. It is possible to obtain good epitaxy, as determined by surface diffraction and transistor characteristics, provided epitaxy is commenced on these bulk-terminated surfaces. We also give evidence that under certain conditions, bulk-terminated surfaces are maintained in low-temperature epitaxy using the method of ultrahigh vacuum chemical vapor deposition.

The thermal stability of SiGe films deposited by ultrahigh-vacuum chemical vapor deposition was studied. Various Ge compositional profiles, including boxes, trapezoids, and triangles were examined. Planar-view transmission electron microscopy was performed following growth and after furnace annealing at 950 °C for 30 min to determine the presence and density of misfit dislocations. All profiles showed very similar stability behavior when expressed in terms of the total thickness of the film, heff, and the effective strain present in the layer, εeff. Following the anneal, misfit dislocations were observed when heff exceeded the critical thickness, as defined by Matthews and Blakeslee [J. Cryst. Growth 27, 118 (1974)], by a factor of ∼2.

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