Abstract: The subject invention involves a method of preparing defect-free semiconductor material layers by growing a semiconductor material buffer layer on a substrate, masking with a dielectric film, and etching to open spaced seed windows. Another layer of a III-V or II-VI material is then grown in the longitudinal direction from the seed window, followed by lateral growth of the same material to form an epitaxial film and a structure which provides a defect free surface for further epitaxial layers.