Vapor-Phase Deposited High-Performance Uncooled PbS Short-Wave Infrared Photodetectors and Their Sensitization Dynamics

Infrared photodetectors based on polycrystalline PbS are very attractive in light of their low cost, high performance, and high-temperature operation. However, the photoactive layers are often based on chemical bath deposition that limits their mass production. Meanwhile, the photosensitization dynamics are yet not fully understood. Here, high-performance PbS photodetectors based on sputtering deposition and a study of the sensitization dynamics in a two-step sensitization process based on oxidation and iodination are reported. The oxidation inhibits the subsequent iodination, which changes the iodination from diffusion control to surface reaction control and by extension favors the complete iodination of the whole PbS films in an optimized sensitization process. The iodination improved carrier lifetime by a combination of defection passivation, doping tuning, and the formation of a charge separation structure. The resultant PbS photodetectors show a specific detectivity approximate to 7.7 x 1010 Jones at a cutoff wavelength of 2.7 mu m, on par with conventional uncooled PbS photodetectors. The application of PbS photodetectors in infrared imaging is finally successfully demonstrated. The development of vapor-phase deposition and the deepened understanding of sensitization mechanism favor the application of high-performance lead chalcogenide infrared photodetectors.