  We discuss unreported transitions of oxidized GaAs surfaces between
(super)hydrophilic and hydrophobic states when stored in ambient conditions.
Contact angles higher than 90deg and high adhesive force were observed for
several air-aged epitaxial samples grown under different conditions as well as
on epi-ready wafers. Regardless of the morphologies of the surface,
superhydrophilicity of oxygen-plasma treated samples was observed, an effect
disappearing with storage time. Reproducible hydrophobicity was likewise
observed, as expected, after standard HCl surface etching. The relation between
surface oxides and hydrophobic/hydrophilic behavior is discussed.
