On the behaviour of residual conductivity in CdSe

We report some measurements on residual conductivity in CdSe. In such a sample the electron-phonon interaction plays a dominant role. Our measurements confirm the results obtained in a previous work on a CdS sample. However in the present experiment, more refined measurements performed at liquid-nitrogen temperature allow a better insight into the intimate connection existing among residual conductivity and electron-phonon interaction. A theoretical calculation previously made is now discussed and improved, in order to explain the experimental data. It is shown that as the conductivity decreases, the residual current shows an anomalous lowering, so that a maximum appears in the apparent resistivity of the sample. Such a maximum is also related to a maximum of the acoustic-absorption coefficient that takes place in the same condition.