Resistivity and hall coefficient of antimony-doped germanium at low temperatures

Abstract

The Hall coefficient R and resistivityρ of germanium single crystals containing between 5 × 10 14 and 10 18 antimony atoms/cc were reinvestigated at temperatures between 1·3 and 300°K. The low-temperature anomalies—a steep maximum in the log R versus 1/ T curves and a change of slope of the log ρ versus 1/ T curves—are discussed on the basis of impurity conduction. Two different processes of impurity conduction could be distiriguished by adding compensating p-type impurities to n-type germanium and investigating the resulting change of ρ at low temperatures. At small impurity concentrations (small overlap of electron wave functions of neighboring impurities), impurity conduction is possible only if compensating impurities produce empty majority centers. Addition of a small number of compensating impurities to a specimen containing 8·5 × 10 15 antimony atoms cm 3 produced a decrease of the resistivity of impurity conduction because of the increased concentration of empty majority centers. At large impurity concentrations (strong overlap), the localization of the carriers is removed, so that they can migrate through the crystal without the presence of compensators. Addition of compensating impurities to a specimen containing 1·2 × 10 17 antimony atoms/cm 3 caused the resistivity of impurity conduction to increase because of the decrease in carrier concentration and the increase in the number of scattering centers. Qualitative agreement is found between impurity conduction in antimony-doped germanium and that in gallium-doped germanium previously reported. A quantitative comparison was, however, not possible because the degree of compensation could not be determined with sufficient accuracy.