The influence of surface reconstructions on the surface morphology duringin situlayer-by-layer etching of GaAs(001) has been studied based on the observation of reflection high-energy electron-diffraction measurements. For the etching,AsBr3is used as a reactive source etchant under solid source molecular beam epitaxy conditions, focusing on a high temperature region in which the etching rate is limited by a supply rate ofAsBr3resulting in a constant value. Despite the fact that the etching starts on a layer-by-layer basis, an initially smooth surface turns considerably rougher depending on the stoichiometry associated with the surface reconstruction. The best morphology after a removal of 250 nm is obtained in the Ga-rich (3×1) reconstruction region close to the phase transition boundary to the As-rich (2×4). This is also verified by the measurement of scanning electron microscopy and atomic force microscopy. ©1997 American Institute of Physics.