Design and deposition of ZnS antireflection coating for high-performance mid-infrared PbSe photoconductive detectors fabricated by chemical bath deposition

Enhancing the detectivity is still a challenge for uncooled mid-infrared PbSe photoconductive (PC) detectors. Antireflection coating (ARC) provides a convenient solution to this challenge. Herein, antireflection physical modeling was proposed based on microstructural features of PbSe PC detectors. The simulated results show that the surface roughness contributes to the absorption enhancement of PbSe detectors, which reflects the advantage of the chemical bath deposition (CBD) manufacturing technology. Meanwhile, being the optimal ARC choice, ZnS ARC with thickness from 300 to 420 nm could induce more than 20 % absorption improvements in coarse CBD-PbSe films, which is confirmed by a signal enhancement from CBD-PbSe PC detectors covered with ZnS ARC. Combing with a noise reduction, the peak detectivity (D*) is almost doubled from 0.8 × 1010 to 1.5 × 1010 cm‧Hz1/2‧W−1 after depositing a desired ZnS ARC. Furthermore, ZnS ARC significantly eliminates the performance degradation of detectors triggered by moisture in the air. The low-cost ZnS ARC with good repeatability, which combines the characteristics of antireflection and passivation, provides an available solution to promote the industrialization of PbSe PC detectors.