Electronic band gap of Zn2x(CuIn)1−xX2 solid solution series (X = S, Se, Te)

The Zn2x(CuIn)1−xX2 solid solution series with X = S, Se and Te have been investigated concerning variation of the band gap Eg with the chemical composition, especially, with regard to the two-phase field (miscibility gap) occuring in all three systems. The band gap Eg was determined by diffuse reflection on powder samples of the quaternary alloys. A highly non-linear dependence of Eg on the chemical composition was found, which may be caused by the repulsive interactions of Cu3d and anion 3p states. Moreover, the Eg value of the ternary end member of the solid solution series is even reached in a composition range x ∼ 0.45 (X = S), x ∼ 0.4 (X = Se) and x ∼ 0.3 (X = Te). This is due to a nearly constant band gap within the small single-phase tetragonal region (0 ≤ x < 0.1) and almost no variation within the broad two-phase field.