The origin of the electrical inactivity of iron and tin impurity atoms in crystalline and vitreous alloys A III B IV (A = Ga, In; B = Te, S)

Tin and iron impurity atoms in the structure of crystalline and vitreous alloys Ga_1?y Te_y (y = 0.6, 0.8) and In_1?y Te_y (y=0.6) are shown to be stabilized in their normal valence states. It is demonstrated that the electrical inactivity of tin and iron impurity ions is caused by the compensating effect of Ga⁺ and In⁺ ions, which are responsible for the fixed position of the Fermi level at the midpoint of the band gap. Tin impurity ions in the structure of the β-In₂S₃ crystal are analogs of two-electron centers (with a negative Hubbard energy) proposed for chalcogenide glasses. Within this model, Sn²⁺ ions are ionized acceptors and Sn⁴⁺ ions are ionized donors.