XPS analysis of (100) GaAs surfaces after applying a variety of technology-etchants

XPS measurements were undertaken on differently treated (100)-GaAs surfaces using $\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and 3d core level peaks of As and Ga and the 1s level peak of 0. The $\text{2p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ level peaks are more sensitive to the direct surface composition while the 3d peaks reflect the more bulk-like composition. It was found that 0 is bonded to surface As atoms in NaOH + H₂O₃ etched samples, while in HCl etched samples 0 is probably bonded to defects produced by the formation of GaO bonds. Depth profiles obtained by sputtering show a depletion of both Ga and As in the surface region. The depletion of Ga, however, is much more obvious in the HCl treated samples compared to NaOH + H₂O₂ treated samples. In interpretation of depth profiles obtained by sputtering one has to be aware of sputtering artifacts demonstrated also in this paper.