The reactions of diethylzinc (DEZ) on the GaAs(100) surface have been studied using temperature programmed desorption, x‐ray photoelectron spectroscopy (XPS), and high‐resolution electron energy‐loss spectroscopy. DEZ dissociated on the GaAs(100) surface below room temperature forming adsorbed zinc atoms and ethyl groups. The adsorbed zinc metal interacted weakly with the GaAs(100) surface and desorbed near 530 K. The ethyl species formed via DEZ dissociation bond to surface Ga atoms. The resulting surface ethyl‐Ga complexes were stable to approximately 500 K at which point they reacted to form ethylene, hydrogen, and smaller amounts of ethyl radicals and ethane. At high surface ethyl coverages a fraction of the ethyl‐Ga species reacted between 300 and 500 K to form gaseous galliumalkyls. XPS results demonstrate that the decomposition of the adsorbed ethyl groups did not result in carbon deposition onto the surface.