Effect of point defects on the electronic density of states of ScN studied by first-principles calculations and implications for thermoelectric properties

We have investigated the effect of defects and impurities on the electronic density of states of scandium nitride using first-principles calculations with the generalized gradient approximation and hybrid functionals for the exchange correlation energy. Our results show that Sc and N vacancies can introduce asymmetric peaks in the density of states close to the Fermi level. We also find that the N vacancy states are sensitive to total electron concentration of the system due to their possibility for spin polarization. Substitutional point defects shift the Fermi level in the electronic band according to their valence but do not introduce sharp features. The energetics and electronic structure of defect pairs are also studied. By using hybrid functional calculations, a correct description of the band gap of scandium nitride is obtained. Our results envisage ways for improving the thermoelectric figure of merit of ScN by electronic structure engineering through stoichiometry tuning and doping.