Mobility of Charge Carriers in Semiconducting Layer Structures

The electrical resistivities and the Hall constants of the compound semiconductors GaSe, Mo${\mathrm{S}}_2$, Mo${\mathrm{Se}}_2$, and W${\mathrm{Se}}_2$, which crystallize in layer structures, have been measured at temperatures ranging from 100 to 700°K. The Hall mobilities derived from these measurements are all of the order of 100 ${\mathrm{cm}}^2$/V sec at room temperature, and they exhibit a temperature dependence of the form $\mu \propto {\left(\frac{T}{T_0}\right)}^{-n}$, where $n=2.1\mathrm{}$ for GaSe, $n=2.6\mathrm{}$ for Mo${\mathrm{S}}_2$, and $n=2.4\mathrm{}$ for Mo${\mathrm{Se}}_2$ and W${\mathrm{Se}}_2$. A short-range interaction is discussed which couples the charge carriers in highly anisotropic layer structures to the nonpolar optical lattice modes. The relatively low room-temperature mobilities as well as the high values of the exponents $n$ are explained in terms of the proposed interaction.