Impurity conduction in indium-doped germanium

Abstract Studies were made of electrical conductivity at low temperatures in germanium crystals grown with indium and antimony EE majority and minority impurities respectively. The indium densities were kept small enough (〈2 × 1016 cm−3) to ensure that impurity conduction was controlled by the degree of compensation, which was carefully determined from Hall and resistive behaviour in the extrinsic temperature range. The impurity conduction results illustrate trapping of electrons on preferred acceptor sites at the lowest temperatures, in accordance with the model recently postdated by Mott (1956) and elaborated by Price (1957, 1958). The trapping energy ∊t is some 10−3 ev. The mobility of electrons involved in the impurity conduction process appears to be essentially temperature independent-a result at variance with the predictions of Conwell (1956). However the increase of mobility with impurity density does generally follow the lines of Conwell's model.