Flat, clean, essentially defect‐free GaAs(001) surfaces were produced at 570 °C in an As4overpressure using 1 keV Ar ion bombardment at an impingement angle &fgr; of 15° from the surface plane and a dose of 2.3×1016ions/cm2. Ion bombardment smoothened the surfaces leading to minimum roughness values of ≊0.3 nm and reflection high‐energy electron diffraction (RHEED) patterns that showed streaks with a 2×4 reconstruction. GaAs films grown by molecular beam epitaxy on the sputter cleaned surfaces exhibited strong RHEED oscillations. Cross‐sectional transmission electron microscope images showed that the epitaxial layers and substrates were defect‐free except for 2–3‐nm diam dislocation loops observed 10–20 nm below the substrate surface, separated by ≳100 nm along the interface. ©1995 American Institute of Physics.