The present disclosure generally relate to methods of processing a substrate in an epitaxy chamber. The method includes applying a passivating agent containing antimony to portions of a silicon substrate exposed through trenches formed in a dielectric layer on the silicon substrate, while applying the passivating agent containing antimony, exposing the silicon substrate to a group IV-containing precursor to form an epitaxial layer having a V-shaped structure having an exposed (111) plane at a bottom of the trenches, and forming a semiconductor layer on the epitaxial layer.