An X-ray diffraction and Mossbauer study of interdiffusion phenomena at the interface between Fe and In0.5Ga0.5As(001)

Polycrystalline iron thin films on ion-etched monocrystalline In0.5Ga0.5As/InP (001) substrates were prepared using ion-beam sputtering deposition. The interface reaction was characterised by X-ray diffraction and conversion electron Mossbauer spectroscopy experiments, after annealing in vacuum for 1 h at temperatures between 350 and 450 degreesC. Interdiffusion phenomena mainly result in the formation of five new phases, namely metallic-In, InAs, Fe2As, Fe2InxAs1-x (0 less than or equal to x less than or equal to 0.2) and Fe3Ga2-xAsx (x = 0.2 - 0.3), in agreement with the predictions of the phase diagrams. InAs results from the decomposition of the semiconductor substrate and remains (001)-textured. The iron-arsenide grains grow into the substrate below the Fe/In0.5Ga0.5As interface. The In precipitates reach similar to40 nm in size after 1 h annealing at 450 degreesC, while the Fe3Ga2-xAsx. phase appears at 400-450 degreesC with an either textured or disordered structure. Finally, the overall activation energy for the thermal reaction is calculated to be 1.5 eV in the latter temperature range.