Low temperature metallic state induced by electrostatic carrier doping of SrTiO${}_3$

Transport properties of SrTiO${}_3$-channel field-effect transistors with parylene organic gate insulator have been investigated. By applying gate voltage, the sheet resistance falls below $R_{\mathrm{\square }}$ $\sim$ 10 k$\mathrm{\Omega }$ at low temperatures, with carrier mobility exceeding 1000 cm${}^2$/Vs. The temperature dependence of the sheet resistance taken under constant gate voltage exhibits metallic behavior ($dR$/$dT$ $>$ 0). Our results demonstrate an insulator to metal transition in SrTiO${}_3$ driven by electrostatic carrier density control.