Sputter cleaning and smoothening of GaAs(001) using glancing-angle ion bombardment

Flat, clean, essentially defect-free GaAs(001) surfaces were produced at 570°C in an As₄ overpressure using 1 keV Ar ion bombardment at an impingement angle φ of 15°from the surface plane and a dose of 2.3×10¹⁶ ions/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.