Thermal Conductivity of II-VI Compounds and Phonon Scattering byFe2+Impurities

Abstract

The thermal conductivities $\kappa$ of over twenty different single crystals of synthetic ZnO, ZnS, ZnSe, ZnTe, CdTe, and of natural, cubic ZnS have been measured from temperatures of 3 to 300 K. The results for the undoped crystals above 30 K can be scaled using the parameter $\overline{M}\delta {\Theta }^3$, where $\overline{M}$, $\delta$, and $\Theta$ are the average mass, interatomic spacing, and Debye temperature, respectively. A comparison of these results with those in the literature for BeO, CdS, CdSe, HgSe, HgTe, Si, Ge, GaAs, and InSb show that the same scaling parameter applies for most of them. The compounds HgSe and HgTe exhibit anomalously low $\kappa$ values. Crystals doped with ${\mathrm{Fe}}^{2+}$ show a resonant-type one-phonon scattering from the five low-lying energy levels of this $3d^6$ ion. Group theory shows that the strongest scattering occurs for phonons of energy $2\Delta$, where $\Delta$ is the interlevel spacing of the ${\mathrm{Fe}}^{2+}$ ion.