The Alloying of Gold and Gold Alloy Ohmic Contact Metallizations with Gallium Arsenide

Abstract

The alloying of gallium arsenide with thin films of pure gold and the gold 12% germanium‐silver‐gold ohmic contact metallization used for a FET, has been investigated using optical and scanning electron microscopy. The heating rate and maximum temperature attained during heat‐treatment was found to govern the morphology of the pure gold films, and to a lesser extent the ohmic contact metallizations. The alloying cycle commences with decomposition of the underlying and diffusion of gallium into the metal at about 260°C. Melting commences above about 480°C with pure gold and 360°C with the contact metallization. The final gallium content of the metal increases as the temperature is increased and the solidification temperature of both a pure gold and multicomponent contact heated to 525°C is . The interface is very irregular consisting of approximately rectangular depressions, often over 1 μm deep, filled with metal.