The presence of a 500 Å Ge layer in Au/Ge/Au ohmic contacts to GaAs was found to hinder the agglomeration of Au upon heating. An ohmic contact as uniform as the asdeposited metallization was achieved after heating at 300°C. Heating at 350–500°C resulted in various morphological entities in a Au-rich matrix. The microstructure changed from one with a Au-rich matrix to one with a GaAs-rich matrix and dendritic Au-rich islands at 525±25°C. Heating at 400°C or above resulted in Au-Ga phases with the epitaxial relationships α' (110) ‖ GaAs (100) and Au2Ga (112) ‖ GaAs (100).