Stoichiometric Engineering of Chalcogenide Semiconductor Alloys for Nanophotonic Applications

A variety of alternative plasmonic and dielectric material platforms—among them nitrides, semiconductors, and conductive oxides—have come to prominence in recent years as means to address the shortcomings of noble metals (including Joule losses, cost, and passive character) in certain nanophotonic and optical‐frequency metamaterial applications. Here, it is shown that chalcogenide semiconductor alloys offer a uniquely broad pallet of optical properties, complementary to those of existing material platforms, which can be controlled by stoichiometric design. Using combinatorial high‐throughput techniques, the extraordinary epsilon‐near‐zero, plasmonic, and low/high‐index characteristics of Bi:Sb:Te alloys are explored. Depending upon composition they can, for example, have plasmonic figures of merit higher than conductive oxides and nitrides across the entire UV–NIR range, and higher than gold below 550 nm; present dielectric figures of merit better than conductive oxides at near‐infrared telecommunications wavelengths; and exhibit record‐breaking refractive indices as low as 0.7 and as high as 11.5. The plasmonic, epsilon‐near‐zero, and low/high‐index characteristics of Bi:Sb:Te alloys are explored. Depending upon composition, they can present plasmonic figures of merit higher than conductive oxides, nitrides, and gold in the UV–Vis range; exhibit dielectric figures of merit better than conductive oxides at telecommunications wavelengths; and achieve record‐breaking refractive indices as low as 0.7 and as high as 11.5.