Polarization screening and induced carrier density at the interface of LaAlO3 overlayer on SrTiO3 (001)

We investigate the role of lattice polarization in determination of induced carrier density at the n-type interface of LaAlO3 overlayer on SrTiO3 (001) by carrying out density-functional-theory calculations. When no oxygen vacancy or defect is present, the magnitude of polarization screening in the LaAlO3 layers is found to be correlated with the carrier charge induced at the interface. For the interfaces with less than seven LaAlO3 layers, the density of induced carrier is smaller than 0.1 electrons per unit-cell and the electrostatic screening can be covered by the interface state consisting of Ti d(xy) state. When the overlayer becomes thicker, the extended bound state in the SrTiO3 side contributes to the charge screening. (C) 2010 American Institute of Physics. [doi:10.1063/1.3455877]