Electrostatic carrier doping of GdTiO 3 /SrTiO 3 interfaces

Heterostructures and superlattices consisting of a prototype Mott insulator, GdTiO 3 , and the band insulator SrTiO 3 are grown by molecular beam epitaxy and show intrinsic electronic reconstruction, approximately ½ electron per surface unit cell at each GdTiO 3 /SrTiO 3 interface. The sheet carrier densities in all structures containing more than one unit cell of SrTiO 3 are independent of layer thicknesses and growth sequences, indicating that the mobile carriers are in a high concentration, two-dimensional electron gas bound to the interface. These carrier densities closely meet the electrostatic requirements for compensating the fixed charge at these polar interfaces. Based on the experimental results, insights into interfacial band alignments, charge distribution, and the influence of different electrostatic boundary conditions are obtained.