Origin of Charge Density atLaAlO3onSrTiO3Heterointerfaces: Possibility of Intrinsic Doping

Abstract

As discovered by Ohtomo and Hwang, a large sheet charge density with high mobility exists at the interface between ${\mathrm{SrTiO}}_3$ and ${\mathrm{LaAlO}}_3$. Based on transport, spectroscopic, and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies introduced by the pulsed laser deposition process used by all researchers to date to make these samples is the source of the large carrier densities. Annealing experiments show a limiting carrier density. We also present a model that explains the high mobility based on carrier redistribution due to an increased dielectric constant.