Temperature dependence of photoconductivity and noise in CdS-based devices

Experimental results concerning photoconductance and noise vs light intensity and wavelength for different values of the temperature in a CdS-based photoconducting device are presented and compared with the prediction of a theory based on a barrier-type photoconduction model developed in a previous paper. Temperature is varied from 300 to 225 K, a range where photoresponsivity, noise, and a few parameters entering the theory present a change of about one order of magnitude. At lower temperatures the occurrence of persistent photoconductivity prevents a suitable check of the model. Relative variations of the responsivity and of the noise with temperature are accounted for by the theory without the introduction of free parameters, while absolute values of these quantities are also correctly reproduced in the whole explored range of light intensity and wavelength, assuming a suitable value for the light quantum efficiency. Other parameters entering the theory were either measured on the device or taken from literature. The analysis of the results also shows that the noise component related to the barrier height spontaneous fluctuations is strongly influenced by temperature changes, while the noise components related to the electron-transport process within the conduction band of CdS are practically unaffected by temperature in the range of variation of this quantity given in this paper.