[en] Thermal desorption of native oxides on GaAs(100), (110) and (111)B surfaces around Au particles are studied in vacuum using in situ microspectroscopy. Two temperature-dependent desorption regimes, common to all surfaces, are identified. The low-temperature desorption regime spatially limited to the vicinity of some Au nanoparticles (NPs) is catalytically enhanced, resulting in oxide pinholes which expand laterally into macro holes many times the size of the catalyzing NPs and with shapes dictated by the underlying crystallography. The high-temperature desorption regime causes homogeneous oxides thinning and, ultimately, complete oxide desorption. The temperature difference between the two regimes is ∼25 °C–60 °C. After oxide desorption and depending on Au size and GaAs surface orientation, Au particles may dissolve the fresh GaAs surface and form mobile AuGa₂/Ga core/shell units, or form stationary AuGa₂ crystallites, or the catalyzing Au particles may run with minimal reaction with the GaAs surface. These results will add to the fundamental understanding of many Au-based nanofabrication processes, particularly the epitaxial growth of vertical and lateral nanowires. (paper)