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

The dielectric and structural properties of $LaAlO3$ make it an attractive epitaxial gate oxide for nanometer-scale field effect transistors. However, the growth of epitaxial $LaAlO3$ directly on Si has not been possible to date. In order to achieve $LaAlO3$ epitaxy, we use a $SrTiO3$ template layer whose thickness minimizes elastic strain and atomic-level buckling at the interface. We find that $LaAlO3$ 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 $LaAlO3/SrTiO3/Si$ structure show no evidence of an amorphous $SiO2$ layer. Capacitance-voltage measurements on thin films of epitaxial $LaAlO3/SrTiO3/Si$ with $LaAlO3$ thicknesses between 13 and 110 nm show a dielectric constant for the $LaAlO3$ 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 $∼8×1010cm−2eV−1$⁠.