Published online by Cambridge University Press: 27 February 2003
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 Mössbauer spectroscopy experiments, after annealing in vacuum for 1 h at temperatures between 350 and 450 °C. Interdiffusion phenomena mainly result in the formation of five new phases, namely metallic-In, InAs, Fe2As, Fe2Inx As $_{1-x}$ ( $0 \leq x \leq 0.2$
) and Fe3Ga $_{2-x}$
Asx ( $x = 0.2 - 0.3$
), 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 ~40 nm in size after 1 h annealing at 450 °C, while the Fe3Ga $_{2-x}$
Asx phase appears at 400–450 °C 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.