Thermal and Electronic Transport Properties ofp-Type ZnSb

Galvanomagnetic, thermoelectric, and thermal-conductivity measurements were made on single-crystal specimens of $p$-type ZnSb, which has the orthorhombic symmetry $D_{2h}$. A horizontal zone-recrystallization process with an antimony-rich molten zone was used to produce the single crystals. Copper doping was used to control the hole concentration. Methods are described for making electrical and thermal contacts to this material. The experimental measurements included electrical resistivity and Hall effect (77.3° to 325°K) and extensive magnetoresistance measurements at 77.3°K. Measurements of thermoelectric power and thermal conductivity were made along the principal axes of oriented single-crystal cubes at 0°C. Considerable anisotropy was measured in the electrical conductivity. It was found that ${\sigma }_c=1.5\mathrm{}$ ${\sigma }_a=2.5\mathrm{}$ ${\sigma }_b$, approximately. The Hall effect and the thermoelectric power $\alpha$ were found to be isotropic. A slight (12%) anisotropy was measured in the thermal conductivity $\kappa$. For thermoelectric applications, the highest figure of merit, $Z=\frac{{\alpha }^2\sigma }{\kappa }$, is obtained with thermal and electrical currents directed along the $c$-axis of the crystal. At 0°C, the maximum $Z$ was found to be 0.74×${10}^{-3\mathrm{}}$ ${\left(\mathrm{°}\mathrm{K}\right)}^{-1\mathrm{}}$. The experimentally observed results of the galvanomagnetic measurements are shown to be in agreement with a model for the electrical conduction processes which assumes that the valence band is composed of a single valley which is parabolic in k and has general ellipsoids for surfaces of constant energy. This model also assumes a relaxation time which is either a scalar function of energy or a diagonal tensor with a factorable energy dependence.