A semiconductor structure including: trench-defining layer; an epitaxial layer; and a set of defect-blocking member(s). The trench-defining layer includes a trench surface which defines an elongated interior space called the “trench.” The epitaxial layer is grown epitaxially in the interior space of the trench. Each defect blocking member of the set of defect blocking members: (i) extends from a portion of trench surface into the interior space of the trench; and (ii) is located below a top surface of the epitaxial layer. The defect blocking member(s) are designed to arrest the propagation of generally-longitudinal defects in the epitaxial layer, as it is grown, where the generally-longitudinal defects are defects that propagate at least generally in the elongation direction of the trench.