XPS modeling of GaN/GaAs nanostructure grown by the Droplet Epitaxy technique

The contribution of XPS spectroscopy and its associated modeling to the study of metallic and semiconductor nanostructure design is highlighted in this work. We first give a brief description of the growth kinetics of pure and binary materials on hydrophilic substrates showing the real shape of the nanodroplets to be a spherical cap. This morphology is implemented in the XPS signal modeling of pure and binary nanodroplets. Then, the theoretical calculations will be compared to the XPS intensities in situ carried out on the Ga/GaAs(111)A and GaN/ GaAs(111)A nanostructures. This comparison allows the shape of Ga and GaN nanodroplets to be determined, giving their radius, height and coverage. Finally, XPS results are compared to AFM and SEM studies to confirm the XPS modeling. Moreover, the influence of using inelastic mean free paths or effective attenuation lengths in the XPS signal modeling is discussed.