Semiconducting character of LaN: magnitude of the band gap, and origin of the electrical conductivity

Lanthanum nitride (LaN) has attracted research interest due to its promise in enabling efficient and cost-effective synthesis of ammonia from N₂ gas. Despite exciting progress in the field, the electronic character of LaN (metallic, semi-metallic, or semiconducting) has not been conclusively determined. We investigate the electronic and defect properties of LaN with hybrid DFT calculations. In contrast to previous claims that LaN is semi-metallic, our calculations show that LaN is a direct-gap semiconductor with a band gap of 0.75 eV. Nitrogen vacancies and substitutional oxygen atoms are two unintentional shallow donors with low formation energies that can explain the origin of the observed electrical conductivity. Our calculations clarify the semiconducting nature of LaN and reveal candidate point defects that can explain its measured electrical conductivity.