We report on the contact reactions in junctions. The palladium deposition occurs by chemical displacement of Ga and As in acidic palladium baths. When a bath containing glacial acetic acid is used in the activation step, 100 Å of palladium is deposited. Another bath, containing only to enhance the exchange mechanism, results in deposition of 2500 Å palladium. In each case, by neutron activation analysis, gallium and arsenic are detected in the bath. These results allow the formulation of a displacement mechanism according to the reactionin which there is no marked preference for arsenic or gallium. It can be assumed that these acidic baths allow in situ etching of native oxides. The 100 Å Pd film synthesized by the activation bath has been investigated using Auger electron spectroscopy and sputter profiling, grazing incidence x‐ray diffraction, and N2+ ion backscattering. Intermixed layers were obtained directly after palladium deposition. The compounds obtained vary with annealing temperature, forming ternary phases , , and, finally, a single binary phase.