Defects and their reduction in Ge selective epitaxy and coalescence layer on Si with semicylindrical voids on SiO<formula> <tex>$_{2}$</tex> </formula> masks

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Formation of semicylindrical voids on SiO2 masks in Ge layers selectively grown on Si has positive impacts for reduction of threading dislocation density (TDD). Semicylindrical voids are formed through selective epitaxial growth (SEG) and coalescence of SEG Ge layers. A cross-sectional transmission electron microscope (TEM) observation reveals that a threading dislocation (TD) is terminated at a semicylindrical void, resulting in the reduction of TDD. The semicylindrical voids also contribute to the suppression of two-dimensional defects generated at the coalesced interfaces between the SEG Ge layers, which were widely observed in previous reports. Plan-view TEM observations reveal that there are TDs inclined to be parallel to the semicylindrical voids, and plan-view TEM observations show a large (4 μm × 4 μm) TD-free area in the Ge layer with the semicylindrical voids.