AbstractIn the past years, metal/III‐V compound semiconductor interfaces have been investigated intensively in order to find a suitable metallization scheme meeting the required performance, reproducibility and stability criteria. Equilibrium phase diagrams provide a base for understanding the interfacial reactions, hence solid state equilibria at 600 and 900°C in the Ga‐Ni‐Sb system have been experimentally determined and are presented in this article. In the course of the work the nickel‐rich part of the Ga‐Ni phase diagram has been revised by means of DTA and the diffusion couple technique. This study was undertaken to clarify the true temperature range of stability for the compounds Ga2Ni3 and Ga9Ni13 that is of significant importance for establishing the Ga‐Ni‐Sb phase diagram.