LOW-TEMPERATURE CONDUCTIVITY AND WEAK-LOCALIZATION EFFECT IN BARELY METALLIC GAAS

Low-temperature measurements of the conductivity, the Hall effect and the magnetoresistance have been performed on an n-GaAs sample of impurity concentration close to its critical value for the metal-insulator transition. The magnetoconductivity is analysed in the context of the weal-localization theory, and the inelastic scattering time tau(epsilon) is deduced from the same model in two different ways for each temperature. It is found that tau(epsilon) varies as T-1 in the whole temperature range. This behaviour is compared with the theoretical predictions, Discrepancies are found between the weak-localization theory and the experimental data for magnetic fields larger than 0.4 T.