The surface morphology of GaP liquid‐phase epitaxial layers has been studied for a wide range of growth conditions in order to determine the origin of the commonly observed corrugated or lamellar surface structure. A double slider apparatus was used for decanting the melts to preserve the high‐temperature morphologies and to permit controlled growth or meltback over selected areas of the substrate. The effect of melt supercooling was examined by varying the cooling rate and melt thickness. These results when combined with observations of the selected area meltback and regrowth experiments demonstrate that the lamellar morphology does not result from the action of capillarity forces on the last liquid to freeze or from interface instabilities associated with constitutional supercooling, as previously suggested. It is shown that the morphology is determined by the substrate orientation and is principally a manifestation of the microscopically layered nature of the liquid‐solid interface.