Abstract: The present invention is a combination of in-situ etching using a grating mask that is formed in semiconductor material only and the subsequent overgrowth of additional semiconductor material to enclose the grating structure prior to exposure to the atmosphere and the contaminants therein. The present invention is based on a two-stage process. First the grating pattern is defined in a semiconductor material, which is the grating mask. This grating mask is created at a position above the material that is to ultimately contain the grating pattern. Upon the completion of the fabrication of the grating mask, the semiconductor structure is moved to a reactor, where in the second stage, the grating pattern defined by the grating mask is transferred into the underlying semiconductor layers by in-situ etching.