Electron-Doped Semiconducting Rocksalt Al _<i>x</i> Sc _{1– <i>x</i>} N: An Emerging Transparent Conducting Nitride

Transparent conductors are a unique class of materials that simultaneously exhibit optical transparency and high electrical conductivity, a rare combination critical for many optoelectronic applications. Traditionally, most transparent conductors are oxides or two-dimensional materials, where a wide band gap ensures transparency, while doping-induced free carrier concentrations lead to electrical transport. Here, we present an emerging class of transparent conductors based on III-nitrides, exemplified by electron-doped rocksalt aluminum scandium nitride (r-Al0.56Sc0.44N), which exhibits very high optical transparency of ∼98.8% at 550 nm and room temperature electrical conductivity of 19.1 S.cm–1. Molecular beam epitaxy deposited, single-crystalline r-Al0.56Sc0.44N exhibits a direct optical band gap of 3.3 eV, facilitating high visible-range solar transparency of ∼85.5% and a small visible spectrum haze ratio of ∼11.6%. Further, high electron concentration arising from oxygen-doping makes r-Al0.56Sc0.44N moderately conductive. Our work establishes electron-doped r-Al0.56Sc0.44N as a promising transparent conducting nitride for solar cells, light-emitting-diodes, liquid-crystal-displays, touchscreens, transparent-heaters, UV-photodetectors, and power electronics applications.