The mechanism of GaAs beam-induced lateral epitaxy (BILE) on (001) GaAs substrate by molecular beam epitaxy (MBE) was investigated by systematically varying the crystal orientation of ridges on the surface. In the growth sequence of BILE, a certain number of facets were first formed on the growth front in connection with the crystal orientation of the ridges. These facets competed with each other as they grew. As a result, the formation of the dominant facet determined the main shape. The crystal orientation of the ridge largely affected the formation of facets and their development. The cross-sectional images of the grown layers observed by a scanning electron microscope (SEM) indicates that the facets formed in the following order from first to last: (111)A facets, (110) facets, (111)B facets, and (001) facets. During the growth, facet formation was largely controlled by the intersurface diffusion of adatoms, although shadowing effects also influenced the grown shapes. (c) 2004 Elsevier B.V. All rights reserved.