Electrically active state of cobalt impurity in lead telluride

The resistivity, the Hall coefficient, the thermo-emf, the magnetic susceptibility, and the optical transmission of cobalt-doped lead telluride in the temperature range 4.2-300 K were investigated. It is shown that in PbTe the Co impurity is electrically active and gives n-type conductivity. The Hall coefficient was calculated as a function of the temperature. The experimental results show that an energy level of Co is present in the band gap of PbTe(Co) at a distance Delta E = (60+/-10) meV from the bottom of the conduction band. It is concluded that introducing Co does not change the dispersion relation for electrons in the conduction band. (C) 1996 American Institute of Physics.