Metallurgical study of Ni/(Ga,Al) As contacts. III. Transmission electron microscopy characterization of ternary superstructured phases in the reacted layers

Solid-state interactions of Ni thin films on (111) GaAs and (111) AlAs were investigated using transmission electron microscopy. We show that the experimental determination of the Ni-Ga-As and Ni-Al-As ternary phase diagrams, and the accurate determination of the atomic composition and crystalline structure of the various ternary solid solutions are absolutely required to understand the x-ray and electron diffraction patterns, and thus identify the compounds in the reacted layers and explain the different steps of the reactions. For this purpose, we report the results obtained on three typical samples, where hexagonal superstructured ternary phases have been observed.