Field-effect modulation of the transport properties of nondoped SrTiO ₃

We have fabricated SrTi O3 (100) single crystal field-effect transistors with amorphous and epitaxial CaHf O3 gate insulator layers. The devices with amorphous insulator layers showed nearly temperature independent behavior. The transistors with epitaxial interfaces exhibited a large improvement over the amorphous devices. The field-effect mobility was found to increase at low temperature, reaching 35 cm2 V s at 50 K. This result shows that the carriers accumulated by the field effect on the SrTi O3 side of the gate interface behaved as would be expected for electron-doped SrTi O3. An insulator-metal transition, induced by field-effect doping, was observed in epitaxial SrTi O3 -based transistors.