Small-area XPS investigation on ion-induced chemical modifications during depth-profiling of an AlxGa1-xAs/GaAs structure

Depth profiling by argon ion sputtering was carried out on an Al0.3Ga0.7As/GaAs layered structure, using different ion-beam energies (up to 5 keV) and keeping constant the ion current density. When the steady state condition was reached in the ternary layer, in order to investigate the ion-induced chemical modifications, angle resolved small-area x-ray photoelectron spectroscopy (SA-XPS) investigations were carried out on the bottom of the crater resulting from the ion-beam erosion. In order to study the different regions of the damaged layer, attention was focused on the As 3d, Ga 3d and Al 2p signals as well as on the As 2p3/2 and Ga 2p3/2 peaks, which are spread over an energy range about 1000 eV wide and therefore photoemitted from different depths. The results show the different ion-induced effects on the chemical composition of the Al0.3Ga0.7As layer, such as arsenic preferential sputtering, aluminium Gibbsian segregation and further, the formation of elemental species, as a function of the Ar+ energy.