Electrical Properties ofn-Type CdTe

Abstract

Transport measurements are reported on high-purity and doped $n$-type single-crystal CdTe with 300°K carrier concentrations ranging from 6×${10}^{14}$ to 2×${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Variations of Hall coefficient ($R_H$) and resistivity ($\rho$) with temperature are investigated. The magnetoresistance ($\frac{\Delta \rho }{\rho }$) and magnetic field dependence of $R_H$ are also examined. The Hall mobility (${\mu }_H$) of high-purity CdTe exhibits a region of intrinsic behavior as it rises rapidly with decreasing temperature from 1050 ${\mathrm{cm}}^2$/V sec at 300°K to values as high as 57 000 ${\mathrm{cm}}^2$/V sec at 30°K. The contributions of acoustic, piezoelectric, and nonpolar optical mode scattering are found negligible. Polar optical mode scattering, however, provides quantitative agreement with the experimental ${\mu }_H$ assuming a k = 0 minimum, $m^{*}=0.11m$ and correcting for the temperature dependence of the static dielectric constant. Corrections to the lattice mobility arising from the nonparabolicity of the conduction band, admixture of $p$ component in the wave function, screening by the carriers, and electron-electron scattering are considered and are shown to be negligible. At low temperatures ${\mu }_H$ is limited by impurity scattering. Carrier concentration, donor depth, and low-temperature mobility data are attributable to a simple singly charged donor impurity. At 300°K $\frac{\Delta \rho }{\rho H^2}<{10}^{-11\mathrm{}}$ ${\mathrm{G}}^{-2\mathrm{}}$. The angular dependence and magnitude of the magnetoresistance is found to be subject to demonstrable but as yet unavoidable electrode effects and hence not useful in providing information about the band structure.