Growth and characterisation of Cd 1− xMg xSe mixed crystals

Abstract

Cd 1− x Mg x Se mixed crystals for 0 < × < 0.55 have been grown by the high-pressure Bridgman method under an argon overpressure. The dependence of the energy gap, the luminescence and the electrical properties on the Mg concentration has been investigated. Luminescence and transmission spectra show that the band-gap energy is considerably larger than that of “pure” CdSe and for Cd 0.45Mg 0.55Se we measured about 2.82 eV at T = 40 K. As grown Cd 1− x Mg x Se solid solutions with x < 0.4 exhibit n-type conductivity and low electrical resistivity (ϱ < 1 Ω cm at room temperature). The maximum of electron concentration 1.3 × 10 18 cm −3 was obtained for Cd 0.85Mg 0.15Se. An attempt to explain the dependence of free-carrier concentration on composition by a model of Fermi-level pinning is presented.