A comparative study of phase stability and film morphology in thin-film M/GaAs systems (M=Co, Rh, Ir, Ni, Pd, and Pt)

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Abstract
To attain reproducible and stable contacts to compound semiconductor devices, it is necessary to achieve thermodynamically stable phases after the reaction of metals with the compound semiconductor. In this study, the final phases produced by the reactions between GaAs and thin metal films of Co, Rh, Ir, Ni, Pd, and Pt have been investigated. They are identified as MGa for M=Co, Rh, Ni, Pd, and Pt, monoarsenides of Co and Ni, diarsenides of Rh, Ir, Pd, and Pt, and Ir3Ga5. These phases, if deposited directly onto GaAs, will produce thermally stable contacts. In addition to the identification of these stable phases, analyses of the products of thin‐film M/GaAs reactions by transmission electron microscopy, x‐ray diffraction, and Rutherford backscattering spectrometry reveal the distribution, grain size, and crystallographic texture of these end phases. Trends in these observations across the six metal/GaAs reactions studied are explained by considering the effects of bond strength and the relative diffusivities of the reacting species. The role of film thickness in determining the final phases and the phase distribution is also considered.