Indirect enhancement of PbS photoconductivity by ferroelectric field effect in a $PbS/PbTiO3/Si$ heterostructure

A lead sulphide/lead titanate/silicon $(PbS/PbTiO3/Si)$ heterostructure was manufactured by successive deposition of $PbTiO3$ and PbS thin film on a single crystalline, $p$-type, Si substrate. Chemical methods were used for deposition. A three electrode configuration was used to control the photoconductivity of PbS thin film by field effect, through the ferroelectric $PbTiO3$ thin film. The spectral distribution of the photoconductive signal shows two maxima, situated at 1.1 and 2.45 μm. It was found that the photoconductive signal at 1 μm varies of about eight times when the voltage applied on the Si substrate is varied between $−1$ and $+1 V.$ At 2 μm the photoconductive signal is almost independent of the applied voltage on the Si substrate. The observed results are explained considering a ferroelectric field effect by which the photogenerated carriers in Si influence the photoconductive signal in the PbS thin film.