The thermal stability of SiGe films deposited by 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.