Electron Mobility and Scattering Processes in AgBr at Low Temperatures

Abstract

The Hall effect for electrons released by light in high-purity crystals of AgBr has been studied experimentally in the temperature range 4\ifmmode^\circ\else\textdegree\fi{} to 120\ifmmode^\circ\else\textdegree\fi{}K. The observed mobilities exceed 20 000 ${\mathrm{cm}}^{2}$/volt-sec at very low temperatures. The general features of the dependence of low-field Hall mobilility on temperature can be understood by comparison with standard theory. A nearly exponential dependence of mobility on $\frac{1}{T}$ is observed from 40\ifmmode^\circ\else\textdegree\fi{} to 120\ifmmode^\circ\else\textdegree\fi{}K, as predicted for scattering by optical vibrations of the lattice. The slope of the ($log\ensuremath{\mu}$) versus $\frac{1}{T}$ data agrees quite well with the Debye $\ensuremath{\Theta}$ for the longitudinal optical mode as deduced from reststrahlen data. Below 40\ifmmode^\circ\else\textdegree\fi{}K the observed mobilities can be explained in terms of a combination of the effects of optical, acoustical and charged impurity scattering. The last process appears to dominate below 15\ifmmode^\circ\else\textdegree\fi{}K. High-field effects are observed which can be explained by classical transport theory assuming a conduction band of standard from as well as isotropic scattering.