Field-effect-assisted photoconductivity in PbS films deposited on silicon dioxide

Lead sulfide ~PbS! thin films were deposited from a chemical bath onto SiO2 /Si ~n-type! substrates. Pseudo-metal–oxide–semiconductor devices were obtained by evaporating source and drain gold electrodes on a PbS surface and aluminum gate electrode on a Si substrate. Field-effect-assisted photoconductivity in the PbS layer was investigated at room temperature, in the 800– 2700-nm-wavelength domain for different values and polarities of the drain and gate voltages. The best results were obtained for a positive gate, when both semiconductors are in depletion. An enhancement of about 25% of the photoconductive signal is obtained compared with the case when the gate electrode is absent or is not used. A simple model is proposed that explains the behavior of the dark current and photoconductive signal in PbS film with changing the gate voltage. © 2002 American Institute of Physics. @DOI: 10.1063/1.1468277#