Indium oxide/n-GaAs junctions have been prepared by deposition of indium oxide layers onto n-type GaAs by means of reactive evaporation of In in the presence of oxygen. The electrical and structural properties and the chemical composition of the resulting junctions have been investigated as a function of the oxygen pressure and substrate temperature during deposition. The analytical tools employed were Auger electron spectroscopy, x-ray diffraction, capacitance-voltage measurements, and current-voltage measurements in the dark at room temperature and elevated temperatures. The results show that the substrate temperature during deposition dominated the interface composition, especially the degree of In oxidation. The oxygen pressure mainly affected the oxide stoichiometry and the In oxidation state in the bulk of the oxide. The resulting changes in the oxide and interface properties had direct implications on the barrier height and the ideality factor of the junctions. The best diodes yielded barrier heights of 0.85 eV and ideality factors of 1.04. The role of the deposition parameters in determining the diodes characteristics is discussed.