ON THE MECHANISM OF LONG-TERM RELAXATION IN POLYCRYSTALLINE CADMIUM TELLURIDE AND ZINC TELLURIDE FILMS

Photoconductivity and photoconductive relaxation measurements have been carried out on vacuum-evaporated, air-exposed CdTe and ZnTe films in the temperature range 330-130 K to probe into the mechanism of photoconduction in the films. An analysis is made of the long-term photoconductivity as a function of temperature and light intensity in the cases where drift and recombination are governed by the same or different barriers. It is shown that the experimental results can be interpreted in the light of the authors' analysis by assuming a recombination barrier different from the drift barrier, the height of which is not modulated under illumination. It is observed that both the recombination and drift barrier heights vary with the thickness of the film. The average value of the recombination and drift barrier heights are of the order of 0.22 eV and 0.70 eV for ZnTe, 0.04 eV and 0.45 eV for CdTe films respectively.