Low-angle incidence microchannel epitaxy (LAIMCE) is a technique to obtain a lateral overgrowth using molecular beam epitaxy. In order to produce a wide and flat lateral overgrowth of GaAs, the effect of the crystallographic orientation of microchannel on GaAs LIMCE was investigated. The cross-sectional shape of GaAs LAIMCE was Studied by scanning electron microscope and found to largely change by the choice of microchannel orientation. For example, the layer grown from a microchannel with the orientation of -10 degrees off from [0 1 0] showed a trapezoidal shape, while the layer grown from a microchannel with that of +10 degrees off from [0 1 0] had an inverted-triangular shape with a sharp peak on the growth front. The layer grown from that of +20 degrees off from [0 (1) over bar 1] had a vertical side. Detailed observation of the layers revealed that several kinds of facets, such as (1 0 1), (1 (1) over bar 2)B, (1 1 (n) over bar), (3 1 0), formed on the side and shaped the layers. As adatoms on the surface diffuse from these facets to the top of the layers, the lateral growth would be suppressed. Therefore, it is important to control the growth condition not to form facets on the side, at least to suppress the formation of the facets with strong nature of inter-surface diffusion of adatoms form side to top. (C) 2008 Elsevier B.V. All rights reserved.