Co/GaAs interfacial reactions

Abstract

The reactions of metals with GaAs are substantially more complex than comparable metal-silicon systems. In this paper, phase formation in the Co-GaAs system is examined in detail and contrasted with other metal-GaAs and metal-silicon systems. Both elemental and microstructural characterization techniques are used, and the limitations of each are discussed. Cobalt begins to react with GaAs at 375 °C and initially forms a ternary phase of approximate composition, Co2GaAs. Subsequent reactions or higher-temperature annealing results in the formation of binary phases CoGa and CoAs. The observed phase formation is controlled by the species with the largest diffusion coefficient, and this species is determined by the temperature. At sufficiently high annealing temperatures, arsenic is lost from the surface, and an epitaxial CoGa phase is formed on the GaAs.