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

Abstract

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.