Density and spatial distribution of charge carriers in the intrinsic n -type LaAlO3 -SrTiO3 interface

Abstract

In order to establish the density and spatial distribution of charge carriers intrinsic to the n -type LaAlO3 -SrTiO3 heterointerface, we carry out first-principles calculations on the (LaAlO3) n (SrTiO3) 15 slab model with n=2-10. As the thickness of the LaAlO3 layer increases, the charge transfer from LaAlO3 to SrTiO3 converges to half an electron per two-dimensional unit cell. It is found that the electrons in the conduction band of SrTiO3 consist of various types of interface-bound states. The mobile electrons evaluated by excluding those states tightly bound to the interface within 2 nm or having large effective masses are in good agreement with the experimental carrier densities for all LaAlO3 thicknesses, suggesting that the loosely bound states play a major role in the transport property. A large calculation including up to (LaAlO3) 5 (SrTiO3) 30 shows that about 70% of electrons are confined within 3 nm from the interface, which is in good comparison with the experiments. It is found that the transferred electrons decay exponentially at short distances from the interface, but there is a crossover to an algebraically decaying region at ∼4nm. © 2009 The American Physical Society.