Ab initio study of In adsorption on AlxGa1–xAs substrates at the first stages of droplet epitaxy

In this work we study the adsorption of In on Al_xGa_1–xAs substrates at the first stage of droplet epitaxy with goal of explaining the anomalous behavior observed in previous experiments where an increase in the content of chemically  active Al in Al_xGa_1–xAs substrates led to an increase in the surface mobility of In adatoms affecting the final distribution of InAs quantum dots. DFT simulations showed that when In adatoms directly interact with As-terminated substrates, there is no deviation from normal behavior, but when In binds with a fully formed In wetting layer, the results are in agreement with those observed in our experiments – increasing Al content led to a decrease in adsorption  energy, which means that surface mobility of adatoms has increased. We assume that this specific effect of droplet epitaxy is caused by lack of a stabilizing As layer, allowing the formation of In dimer rows and direct  interaction of adatoms with them.