Auger electron spectroscopy has been used to monitor the adsorption of CCl4 on an As-rich GaAs(100) surface at 300 K. Intensities of the Ga (55 eV), As (34 eV), C (270 eV) and Cl (181 eV) transitions have been used to estimate surface number densities at saturation and relative C:Cl stoichiometry of the surface species. Number densities of (4.3 +/- 0.2) x 10(14) and (2.0 +/- 0.2) x 10(14) cm-2 are obtained for carbon and chlorine respectively, suggesting that coverage saturates near one theoretical monolayer and that the C:Cl stoichiometry is approximately 2:1. These data are discussed in terms of a reactive adsorption mechanism.Auger electron spectroscopy has been used to monitor the adsorption of CCl4 on an As-rich GaAs(100) surface at 300 K. Intensities of the Ga (55 eV), As (34 eV), C (270 eV) and Cl (181 eV) transitions have been used to estimate surface number densities at saturation and relative C:Cl stoichiometry of the surface species. Number densities of (4.3 +/- 0.2) x 10(14) and (2.0 +/- 0.2) x 10(14) cm-2 are obtained for carbon and chlorine respectively, suggesting that coverage saturates near one theoretical monolayer and that the C:Cl stoichiometry is approximately 2:1. These data are discussed in terms of a reactive adsorption mechanism.