Topographical structure of MBE grown cubic InxGa1-xN films studied with a MeV ion microprobe and by AFM

Cubic InxGa1-xN films (x = 0.02), grown on (001) GaAs substrates by plasma- assisted MBE, have been studied by 2 MeV He+ channeling, with both RES and PIXE detection, using a scanning nuclear microprobe to achieve lateral reso lution of a few microns. A laterally constant surface segregation of indium with decay lengths of the order of 50 nm was observed by RES in all sample s. Lateral indium L X-ray yield fluctuations on a scale of 10 mu m were obs erved by micro-PIXE, but not by micro-RES, in one sample. They could be att ributed to thickness variations of the epitaxial cubic InxGa1-xN layer aris ing from Ga droplet formation during epitaxial growth, taking into account the different analysis depths of RES and X-ray production. Direct surface i maging with Atomic Force Microscopy confirmed a strongly modulated surface topography. (C) 2000 Elsevier Science B.V. All rights reserved.