Ultraviolet Photodetectors Based on Nanometer-Thick Films of the Narrow Band Gap Semiconductor PbS

Ultraviolet photodetectors (UVPDs) which play important roles in military and civil applications are normally fabricated by using wide band gap semiconductors (WBSs) as building blocks. Unfortunately, the commercialization of UVPDs based on WBSs is often limited by their relatively high fabrication cost owing to the use of very complicated growth instruments. In this work, a sensitive UVPD based on non-WBS lead sulfide (PbS) with a relatively small band gap was proposed. Device analysis revealed that the UVPD made of 48.5 nm PbS nanofilm was highly sensitive to UV illumination at 365 nm. Specifically, the responsivity and specific detectivity under 365 nm illumination were 22.25 A W–1 and 4.97 × 1012 Jones, respectively, which are comparable to or better than most of the conventional WBS-based UVPDs. The PbS nanofilm-based UVPD also exhibits excellent environmental stability. Experimental results and simulations based on technology computer-aided design software confirmed that the abnormal properties of PbS nanofilms are related to the relatively thin thickness and wavelength-dependent absorption coefficients. These results open up an opportunity for narrow band gap semiconductors to realize low-cost-sensitive UVPDs in future optoelectronic devices and systems.