Epitaxial Phases Formation Due to Interaction Between Ni Thin Films and GaAs

Abstract

AbstractSolid state reactions between Ni thin films and (100) GaAs were studied by transmission electron microscopy, X-ray diffraction, Auger electron spectroscopy and Rutherford backscattering. The hexagonal ternary phase Ni2GaAs is formed at the temperature range of 150 to 300°C with the following epitaxial relations to the substrate: (1011)//(001) and [1011]//[100]. The gradual decrease with temperature of the (1011)interplanar spacing of this phase may be related to strain relaxation associated with microtwins formation. At the temperature range of 350 to 550°C precipitation of NiAs in Ni2GaAs matrix and an increase of the twin size are observed. In this range the (1011) interplanar spacing of the ternary phase increases with temperature, possibly due to stoichiometric changes resulting from NiAs precipitation. At 600°C the ternary phase decomposes into NiGa and NiAs with average grain size of about 1 micron in lateral dimension. The cubic phase, NiGa, has simple epitaxial relations with GaAs: (001)//(001) and [010]//[010].Ni atoms are the dominant diffusing species during the ternary phase growth process as was observed in a marker experiment utilizing a very thin Ta Layer interposed between the Ni film and the substrate.