Electrical properties and interfacial structure of epitaxial LaAlO3 on Si (001)

The dielectric and structural properties of LaAlO(3) make it an attractive epitaxial gate oxide for nanometer-scale field effect transistors. However, the growth of epitaxial LaAlO(3) directly on Si has not been possible to date. In order to achieve LaAlO(3) epitaxy, we use a SrTiO(3) template layer whose thickness minimizes elastic strain and atomic-level buckling at the interface. We find that LaAlO(3) grown on this template layer is crystalline and initially strained, but relaxes to its bulk lattice constant within 7 unit cells. Cross-sectional transmission electron microscopy and inelastic electron tunneling spectroscopy studies of the LaAlO(3)/SrTiO(3)/Si structure show no evidence of an amorphous SiO(2) layer. Capacitance-voltage measurements on thin films of epitaxial LaAlO(3)/SrTiO(3)/Si with LaAlO(3) thicknesses between 13 and 110 nm show a dielectric constant for the LaAlO(3) layer of 24, the same value as for the bulk. After a post-deposition low temperature anneal, these oxide heterostructures show no Fermi level pinning and an interface state density of similar to 8 x 10(10) cm(-2) eV(-1). (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3148243]