Fluorine is known to strongly influence the dopant diffusion and electrical activation in Si. Similar effects might be exploited in Ge for optimizing its application in microelectronics. The role of F on the electrical activation of As in Ge after thermal treatments is elucidated. We have found that F, enriching the Ge matrix with vacancies strongly affects the electrical response of As-doped junctions. We also demonstrated that the F-interstitials clusters, formed next to the end-of-range region, have an acceptor-like behavior. These phenomena are characterized by chemical and electrical profiling analyses and by positron annihilation lifetime spectrometry.