Self-organized pattern formation by the process of reverse epitaxial growth has been investigated on GaAs (001) surfaces during 1 keV Ar+ bombardment at target temperature of 450 degrees C for a wide range of incident angles. Highly ordered ripple formation driven by diffusion instability is evidenced at near normal incidence angles. Concurrent sample rotation shows that the ripple morphology and its orientation do not depend on the incident beam direction; rather they are determined by the symmetry of the crystal face. (C) 2016 Elsevier B.V. All rights reserved.