Galvanomagnetic Effects in Cadmium Sulfide

Abstract

The Hall and magnetoresistance effects were measured at 297, 196, and 77°K in single crystals of $n$-type CdS having a room-temperature resistivity of 4 Ω-cm. The results of the measurements were consistent with a simple single-valley model of the energy surfaces in the conduction band and can be summarized in terms of two Hall mobilities ${\mu }_{H1\mathrm{}}$ and ${\mu }_{H3\mathrm{}}$ and a magnetoresistance parameter $\xi =\frac{\Delta \rho }{\left({\rho }_0{\mu }_{H1\mathrm{}}{\mu }_{\mathrm{Hi}}{B}^2\right)}$, where $\frac{\Delta \rho }{{\rho }_0}$ is the relative change in resistivity in a transverse magnetic field $B$, and $i$ may be 1 or 3, depending on the directions of current and magnetic field with respect to the $c$ axis. The measured Hall mobilities ${\mu }_{H1\mathrm{}}$ were 390, 840, and 5600 ${\mathrm{cm}}^2$/V-sec, and the values of $\xi$ were 0.077, 0.074, and 0.045 at the three respective temperatures. A two-terminal method of measuring the ratio $\frac{{\mu }_{H1\mathrm{}}}{{\mu }_{H3\mathrm{}}}$ was devised, which yielded the values 1.014, 1.05, and 1.32 at the three temperatures. The magnitude of the mobility at the two upper temperatures is explained quite well on the basis of combined optical mode and piezoelectric scattering by assuming an effective mass $m^{*}=0.19\mathrm{}{m}_e$, while at the lowest temperature impurity scattering also contributes. The temperature-dependent anisotropy is larger than predicted for piezoelectric scattering, possibly due to some form of anisotropic defect scattering.