Observation of Local Tilted Regions in Strain-Related SiGe/Si Buffer Layers Using X-Ray Microdiffraction

The microstructure of strain-relaxed Si_1-xGe_x/Si films that relaxed by different dislocation nucleation mechanisms has been investigated using x-ray microdiffraction with a directed beam footprint of 1 µm x 5 µm. Intensity variations in the x-ray microtopographs of samples having stepgraded intermediate layer, which relaxed by dislocation multiplication, are due to the presence of local titled regions which are larger in area than the diffracted x-ray beam. In contrast, microtopographs of uniform composition layers, which relaxed by surface roughening and subsequent random dislocation nucleation, show little intensity contrast as the local tilted regions in these samples are much smaller than the diffracted x-ray beam. The difference in microstructure arises from the different distributions of 60° misfit dislocations in these two types of samples.