Electronic structures of electron-doped ${\mathrm{SrTiO}}_{3-\delta }$ and ${\mathrm{Sr}}_{1-x}{\mathrm{La}}_x{\mathrm{TiO}}_3$ have been investigated within the ab initio band-structure approach using a supercell containing eight basic units. A small amount of electron doping is found to drive ${\mathrm{SrTiO}}_3$ metallic, with the Fermi level moving into the conduction band in both the systems. Clustering of oxygen vacancies in the case of ${\mathrm{SrTiO}}_{3-\delta }$ gives rise to distinct non-rigid-band-like evolution of the electronic structure, trapping doped charge carriers in midgap states; similar effects are not observed for ${\mathrm{Sr}}_{1-x}{\mathrm{La}}_x{\mathrm{TiO}}_3$, explaining the difference in the Hall measurements of these two closely related compounds.

• Received 13 June 1997

DOI:https://doi.org/10.1103/PhysRevB.57.2153