Au-Gated SrTiO3 Field-Effect Transistors with Large Electron Concentration and Current Modulation

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.