In situ determination of indium/gallium composition in InxGa1-x nanodroplets on GaAs(1 1 1)A based on the complementarity between XPS and REELS

• In situ precise determination of indium content in In x Ga 1-x nanodroplets. • XPS and REELS complementary use. • Development of a brand new methodology of loss probabilities from REELS spectra. • Elaboration of In x Ga 1-x homogeneous nanodroplets on GaAs(1 1 1)A. This work provides a new tool based on the complementarity between X-ray Photoelectron Spectroscopy (XPS) and Reflection Electron Energy Loss Spectroscopy (REELS). More precisely, this study is focused on the in situ precise determination of indium and gallium composition of self-assembled In x Ga 1-x nanodroplets on GaAs(1 1 1)A substrate during the first stage of III-V quantum dots growth by droplet epitaxy. An XPS intensity model based on In4d and Ga3d core levels enables the estimation of the gallium/indium ratio within the droplets under the assumption of a homogeneous droplet. On the other hand, we develop a brand new decomposition methodology of loss probabilities curves obtained from REELS spectra for droplets deposited on a substrate. The energy of In x Ga 1-x bulk plasmon experimentally obtained and semi-empirically modelled allows to calculate from REELS the indium-gallium composition in the droplet. Comparison between these values obtained by both XPS and REELS provides information about In/Ga mixing to grow binary In x Ga 1-x nanodroplets. Their good agreement shows promising results for the growth of In x Ga 1-x N quantum dots by droplet epitaxy for a very large range of composition.