Electrical and Optical Properties of Epitaxial Films of PbS, PbSe, PbTe, and SnTe

Single-crystal films of PbS, PbTe, PbSe, and SnTe have been grown on heated alkali-halide substrates. The temperature dependence of the mobility, Hall coefficient, and resistivity between 77°K and 300°K and the dependence of the magnetoresistance upon sample orientation and magnetic field strength at 77°K have been studied. Analysis of the refractive indices, measured interferometrically in the 2.0- to 15.0-μ region, has yielded optical dielectric constants and the direct energy gaps as functions of temperature. These studies indicate that the single-crystal films have electrical and optical properties comparable to those found in bulk material. Discussions of film formation and strain phenomena are presented and compared with the experimental results. Some of the limitations of these materials are discussed with particular emphasis on the role of structure of the films on the electrical properties.