Influence of annealing on the conductivity and photoconductivity of p-type CdTe

On annealing p-type CdTe, considerable change in conductivity takes place. Samples of high resistivity were used for the measurements. Each of a set of samples was annealed at different temperature. After annealing, the temperature dependence of the conductivity and the relaxation curves of the photoconductivity were measured. Analysis of the first set of curves yielded value of energyE _a corresponding to the level occurring in given samples. It was established that this acceptor level is due to V^cd, or V^cd complexes, and is situated at 0.3 eV above the valence band edge. Concentration of these levels is increased by annealing. Furthermore, an energy value ofH=0.79 eV was found, corresponding very probably to the formation energy of a vacancy V^cd.Analysis of the relaxation curves yielded the temperature dependence of _S , _T and the energy distanceE _M of the impurity level that is responsible for photoconductivity. A value of (E _g -E _M )=0.09–0.12 eV was found for all samples studied. This level therefore lies below the conduction band edge and its concentration amounts to 10¹⁴–10¹⁵ cm^–3. The level is probably due to foreign impurities.Two sets of samples were used: both as-grown and Sb-doped. The results for both sets were not much different from each other.Ke Karlovu 3, Praha 2, Czechoslovakia.