Quantitative investigation of the O2+‐induced topography of GaAs and other III–V semiconductors: An STM study of the ripple formation and suppression of the secondary ion yield change by sample rotation

Abstract

AbstractRoughening procedures including the early stage of the O2+‐induced ripple formation of GaAs were studied quantitatively by scanning tunnelling microscopy (STM). Detailed examinations of the beginning of topography development using fast Fourier transform of the STM images revealed that the ripple formation was not caused by any accidental defects, particles or original irregularity on the substrate, but solely by the conditions of the ion beam. A systematic investigation of the rippled GaAs surface produced under various O2+ bombardment conditions was conducted. The ripple wavelength and the transition depth were almost exactly proportional to EPcos θ, where EP and θ are the energy of the ion beam and the incident angle, respectively. For GaAs, the secondary ion yield transition occurs when the slope of ripples facing the incident O2+ beam reaches a saturation angle of 20–30° from the macroscopic surface plane. Topography change on other III–V semiconductors was also examined for comparison. There was no ripple generation observed for GaP; InP gave a ripple‐like structure without secondary ion yield change. A relatively rough surface resulted on GaSb and InAs at a much shallower depth than for GaAs. Rippling and ion yield changes during depth profiling have been suppressed successfully by sample rotation even in a magnetic sector‐based instrument.