Variation of Persistent Internal Polarization with the Intensity of Illumination in CdS Single Crystals

Electret studies have been done in single crystals of CdS by simultaneous application of electric field and illumination. The variation of total charge stored in the sample with intensity of illumination $I$ is studied. Two limiting values, $I_{\mathrm{lm}}$ and $I_{\mathrm{hm}}$ in this curve at which the variation changes its sign, have been predicted which are very important from the application point of view. The depolarization studies have resulted in two electron trapping levels in CdS samples, one at 0.69 eV and the other at 0.07 eV. A theory is developed to explain the depolarization current.