AFM morphological characterization and Raman study of germanium grown on (111)GaAs

► We epitaxially grow Ge layers on (100), (111)Ga and (111)As surfaces of GaAs substrates. ► We evidence the role of arsenic as both dopant and surfactant. ► Substrates oriented in different direction can induce different growth modes. ► With Raman scattering we evidence that Ge phonon band position is shifted with respect to bulk Ge.