On Signal and Noise Characteristics of Lead Sulphide Photoconductive Cell

Abstract

Singnal and noise characteristics of high impedance-type and low impedance-type lead sulphide photoconductive cells are obtained by experiment, and concentration and mobility of majority carriers (holes) are calculated from obtained data.
Low impedance cell shows good signal-to-noise ratio and signal response at low bias voltage (below about 10 volt). Its current noise and non-current noise are both fairly low in comparison with those of high impedance cell.
Generation-recombination noise is predominant in current noise of cells of both types. Low impedance cell has smaller time constant and larger carrier mobility than high impedance cell. This means that PbS film of low impedance cell has a better crystal disposition than that of high impedance cell. Hence, the annealing in the process of preparing low impedance cell is presumed to regularize the crystal disposition of PbS film and improve the cell characteristics if the state of oxidation is adequately maintained.