The chemical and morphological behavior of a GaAs surface etched with HCl or H3PO4 solutions was characterized using X-ray photoelectron spectroscopy and atomic force microscopy. With HCl and H3PO4 treatments, Ga-Cl and Ga-PO4 residues were produced, respectively. Elemental As initially formed on bare GaAs increased during the etching of the GaAs substrate in all treatments due to preferential etching of Ga. After removal of the native oxide with HCl treatment, selective-corrosive attack occurred, resulting in a deep hole, on which the flatness of the GaAs surface depends. In particular, the different etch rates between Ga (111) and the other planes with H3PO4 solution led to a severely undulated GaAs surface, which consisted of many hollows and Ga (111) facets. The facets and hollows were revealed to be regularly arrayed and elongated in the [(1) over bar 10] direction.