Pyroelectric properties of the wide-gap CdSe semiconductor in the low-temperature region

In the temperature range $T$ = 4.2–300 K, the spontaneous polarization of nonstoichiometric CdSe samples grown by sublimation at 1423 K and subjected to annealing in selenium vapors is measured. From these data, the temperature dependences of the pyroelectric coefficient in CdSe are calculated. Anomalies are found in the ranges $T <$ 10 K and $T >$ 210 K. A change in the charge state of the defect subsystem of the samples caused by a weak electric field results in strengthening of the anomalies and in the occurrence of a new anomaly at $T$ = 236 K. As a rule, the anomalies at $T<$ 10 K and $T$ = 236 K depend on the polarity of the external action. The action of shunting by the intrinsic conductivity of the sample manifests itself only in the region above 270 K. Investigations of the nonpolar-cut sample leads to somewhat unexpected results: the anomalies are retained, but their values considerably decrease. Within the framework of the crystallophysical approach, attempts are made to explain the anomalies observed below 270 K related both to associates with a dipole moment and to their transformation with the possible participation of an uncontrollable oxygen impurity in macroformations of the cluster type, the orientation of the total dipole moment of which does not coincide with the polar direction of an ideal crystal.