Ga-rich GaAs (0 0 1) surfaces are successfully observed by scanning tunneling microscopy (STM) during high-temperature annealing in molecular beam epitaxy. With a substrate temperature of 550degreesC, reflection high-energy diffraction patterns and reflectance anisotropy spectra confirm a (4 x 2) Ga-stabilized surface. STM images clearly show alteration of the surface reconstructions while scanning. It is postulated that detaching and attaching of Ga adatoms may be the cause of this surface dynamics. For these conditions it is determined that zeta(4 x 4), zeta2(4 x 4) and zeta(4 x 6) reconstructions co-exist on the surface. The zeta2(4 x 4) reconstruction contains a Ga tetramer cluster. (C) 2002 Elsevier Science B.V. All rights reserved.