The metallizations of AuGeNi/GaAs(001) and Au/GaAs(001) contacts at 4×10−3Pa and 7×108Pa pressure have been analyzed by using x‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. Our observations show that the high‐pressure ambient inhibits the As sublimation loss and that only interdiffusion takes place without any formation of compounds in those contacts annealed in argon at 7×108Pa. The experimental results are also discussed on the basis of phase diagrams.