  We report the fabrication of low-leakage rectifying Pt and Au Schottky diodes
and Au-gated metal-semiconductor field effect transistors (MESFETs) on n-type
SrTiO3 thin films grown by hybrid molecular beam epitaxy. In agreement with
previous studies, we find that compared to Pt, Au provides a higher Schottky
barrier height with SrTiO3. As a result of the large dielectric constant of
SrTiO3 and the large Schottky barrier height of Au, the Au-gated MESFETs are
able to modulate ~1.6 x 1014 cm-2 electron density, the highest modulation yet
achieved using metal gates in any material system. These MESFETs modulate
current densities up to ~68 mA/mm, ~20x times larger than the best demonstrated
SrTiO3 MESFETs. We also discuss the roles of the interfacial layer, and the
field-dependent dielectric constant of SrTiO3 in increasing the pinch off
voltage of the MESFET.
