Observation of local tilted regions in strain-relaxed SiGe/Si buffer layers using x-ray microdiffraction

The microstructure of strain-relaxed Si1-xGex/Si films that relaxed by diff erent dislocation nucleation mechanisms has been investigated using x-ray m icrodiffraction with a diffracted beam footprint of 1 mu m X 5 mu m. Intens ity variations in the x-ray microtopographs of samples having step-graded i ntermediate layers, which relaxed by dislocation multiplication, are due to the presence of local tilted regions which are larger in area than the dif fracted x-ray beam. In contrast, microtopographs of uniform composition lay ers, which relaxed by surface roughening and subsequent random dislocation nucleation, show little intensity contrast as the local tilted regions in t hese samples are much smaller than the diffracted x-ray beam. The differenc e in microstructure arises from the different distributions of 60 degrees m isfit dislocations in these two types of samples. (C) 1999 American Institu te of Physics. [S0003-6951(99)03105-8].