Phase equilibria in the In-Co-As system at 475°C

D. Swenson, Sutopo, Y. A. Chang

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Phase equilibria in the In-Co-As system are established at 475°C, using X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA). The phases indium, CoAs(α), CoAs2(α) and CoAs3 are shown to be in thermodynamic equilibrium with InAs. A ternary phase of unknown crystal structure, with a narrow range of homogeneity centered about the composition Co0.48In0.37As0.15, is found to exist in this system. A quaternary, 600°C In-Ga-Co-As phase diagram sample is also analyzed in the present study, and shows that cobalt-rich CoGa is in thermodynamic equilibrium with In0.63Ga0.37As. These results, in conjunction with previous investigations of the Ga-Co-As system, suggest that CoAs(α) would be suitable as a thermodynamically stable contact material to InxGa1-xAs for any value of x. However, there may be some practical problems associated with the fabrication of CoAs(α) using conventional deposition methods. It is further suggested that both stoichiometric and cobalt-rich CoGa should be studied as potentially stable contact materials to InxG1-xAs, and in particular to In0.53Ga0.47As, which is among the most technologically important compositions of the InxGa1-xAs semiconductor alloy.

Original languageEnglish
Pages (from-to)215-221
Number of pages7
JournalMaterials Chemistry and Physics
Issue number3
Publication statusPublished - 1 Jan 1996


  • Cobalt
  • Indium arsenide
  • Indium gallium arsenide
  • Metal/semiconductor contacts
  • Phase diagrams


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