Microstructural evolution of Co₂GaAs thin film on GaAs substrate

Interfacial reactions and epitaxial growth of the microstructure between cobalt thin film and (100)-oriented GaAs substrate have been studied, using X-ray diffraction, transmission electron microscopy and EDS analysis. Cobalt thin films were deposited by e-beam evaporation, and were subsequently annealed at 400 °C. The reaction layer evolved due to the annealing was identified as the ternary phase, Co₂GaAs, that was grown epitaxially on the substrate. The new orientation relationship between Co₂GaAs and GaAs substrate was found as 〈110〉Co₂GaAs ∥ 〈100〉GaAs and {001}Co₂GaAs ∥ {011}GaAs. These results can be well explained upon matching the unit cells of Co₂GaAs and GaAs. Upon the annealing at 600°C, the Co₂GaAs phase is usually decomposed to stable binary phases, CoGa and CoAs.