Structural and electronic properties of cubic rocksalt AlxSc1−xN random alloys from ab initio calculations

We report the results of our calculations of the lattice parameters and fundamental band gaps in the rocksalt structured quasibinary random alloy aluminum scandium nitride (${\mathrm{Al}}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}\mathrm{N}$) in the range of $0\ensuremath{\le}x\ensuremath{\le}1$. ${\mathrm{Al}}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}\mathrm{N}$ is a random alloy with very promising properties for the introduction of novel functionalities in (opto)electronic devices. The lattice parameters for the cubic rocksalt ${\mathrm{Al}}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}\mathrm{N}$ deviate positively from Vegard's law with a small bowing. The fundamental band gap shows a more complex behavior and contrary to previous reports, the fundamental band gap in rocksalt ${\mathrm{Al}}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}\mathrm{N}$ is indirect. Furthermore, rocksalt ${\mathrm{Al}}_{x}{\mathrm{Sc}}_{1\ensuremath{-}x}\mathrm{N}$ allows band-gap engineering in the range from $1.4$ to $7.1\phantom{\rule{4pt}{0ex}}\mathrm{eV}$.