Ge:GaAs heterostructures were investigated by photoemission from core levels excited with soft x rays. Epitaxial and amorphous films were grown by condensing Ge on surfaces cleaved from n- GaAs held at 300 and 20 °C, respectively. On the GaAs side of the heterostructure, the Fermi level is pinned (0.75±0.1) eV above the valence band edge, regardless of whether the Ge overgrowth was crystalline or amorphous. This may be caused by chemisorption-induced defects. The valence band discontinuity depends on the structure of the Ge film and amounts to 0.42 with epitaxial and to 0.65 eV with amorphous overgrowths. Half a monolayer of As (most probably bound as GeAs) and ∠0.03 monolayer of Ga were found to be segregated at the crystalline film surfaces.