Beam-induced lateral epitaxy (BILE), an epitaxial lateral growth method that does not require oxide masks, was done on prefabricated truncated ridges on a ((1) over bar(1) over bar(1) over bar )B GaAs substrate. We found that ((1) over bar(1) over bar(1) over bar )B facets formed on the top surface of the BILE layer and that the top layer was flatter than that grown on GaAs(001). BILE growth on an off-axis ((1) over bar(1) over bar(1) over bar )B substrate showed that the top surface became flatter with an increase of the off-axis angle. The flatness of the top surface also increased by increasing the growth temperature. These results indicate that the flatness of the top layer depends on the growth mode during BILE and that the suppression of two-dimensional nucleation of rotation twin embryo is important to fabricate a flat top layer using the BILE method. With the optimal growth conditions, we could make a flat surface of the BILE layer on GaAs((1) over bar(1) over bar(1) over bar )B surface. (c) 2005 Elsevier B.V. All rights reserved.