Thermodynamic Analysis of Vapor Phase Growth of Fe:ZnSe Single Crystals

Fe:ZnSe single crystals are promising materials for mid-infrared (4–5 μm) lasers. Here we present thermodynamic analysis of the vapor phase growth of Fe:ZnSe single crystals by a modified free growth method. Doping with Fe atoms was performed during the growth process. The single crystals were grown from sublimates of the binary compounds ZnSe and FeSe placed in separate source compartments. Vapors of the starting materials were directed to a single-crystal seed in the growth zone through calibrated orifices. Calculations were performed for physical transport in a helium atmosphere. We took into account three main steps of the growth process: vaporization of the starting materials in the source compartments, transport of the vapor to the growth zone, and crystal growth on the seed. The rate of the growth process was assumed to be limited by mass transport from the source to the growth zone, controlled by the geometric dimensions and mutual arrangement of the elements of the growth ampule. The experimental data on the dopant concentration are compared to the calculation results. The proposed growth technique is shown to ensure preparation of single crystals up to 8 cm³ in volume, with a Fe concentration of up to 5 × 10¹⁸ cm^–3.