The solid-state part of the Ga-As-S-O quaternary equilibrium phase diagram has been established from thermodynamic calculations. It is shown that GaS forms a chemically stable interface with GaAs, while As2S3 tends to react with GaAs and the reaction results in elemental As segregation at the GaAs/native sulfide interface. A recently developed chemical vapor deposition of GaS provides, hence, an ideal chemical passivation of GaAs.

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The solid phase part of the Hg-Zn-TeO equilibrium phase diagram has been estimated from thermodynamic calculations. It was found that, contrary to other A2B6 tellurides, ZnTe possesses a preferable oxidation of metal, leaving elemental tellurium at the native oxide-ZnTe interface. It is shown that, as a result, the electrical properties and thermal stability of the native oxide-Hg,-,Zn,Te interface are superior to those of the native oxide-Hgi-,Cd,Te interface. Hence, in terms of the interface properties, Hg,_,Zn,Te seems to be a better material for infrared device applications. It is also demonstrated that for a semiconductor compound the equilibrium phase diagram qualitatively determines the electrical properties of the native oxide-semiconductor interface.

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