Abstract
In epitaxial lateral overgrowth(ELO), steps are found supplied from either misoriented substrate or screw dislocations. An atomically flat and step free ELO layer has been obtained when no screw dislocation exists. In most cases the vertical growth is concducted by the spiral steps. The sources of spiral steps have been found frequently located at corners of the ELO layers, where a high supersaturation is expected.
