Research on Lead Chalcogenide Polycrystalline Photodetectors

Uncooled PbS and PbSe polycrystalline photoconductive detectors are widely used in NIR and MWIR range applications for their low cost and superior performance. Lead salt polycrystalline thin films are usually obtained by chemical bath deposition, physical vapor deposition, chemical vapor deposition, molecular beam epitaxy and atomic layer deposition. Chemical bath deposition is widely used because of its low cost and high crystal quality.

Regardless of deposition techniques, as-grown lead salt polycrystalline thin films must be thermally treated in certain atmosphere to be sensitive to infrared radiation. It is an important direction of uncooled MWIR photodetectors to optimize depositon and annealing technology to obtain more uniform and sensitive films.

The lead salt films with uniform morphology and controllable thickness were obtained by using a self-made chemical bath depositon device. In order to improve the sensitivity of lead salt film to infrared radiation, the film was thermally treated with a certain atmosphere in a tube furnace. 

Figure（1）Schematic diagram of chemical bath deposition.   Figure（2）a.The as-grown film. b. oxidized film. c. oxidized and iodinated film.

The D* of PbS films prepared by CBD can reach 2×10¹⁰ Jones at room temperature, and the responsivity and EQE are both higher than that of commercial detector PbS010010TO5. 

Figure（3）Comparison of responsivity and EQE between PbS films prepared by CBD and commercial detector PbS010010TO5.