Ambipolar Insulator-to-Metal Transition in Black Phosphorus by Ionic-Liquid Gating

We report ambipolar transport properties in black phosphorus using an electric-double-layer transistor configuration.. The transfer curve clearly exhibits ambipolar transistor behavior with an ON OFF ratio of similar to 5 x 10(3). The band gap was determined as congruent to 0.35 eV from the transfer curve, and,Hall-effect measurements revealed-that the hole mobility was,similar to 190 cm(2)/(Vs) at 170K, Which is 1 order of Magnitude larger than the electron mobility. By inducing an ultrahigh carrier density of similar to 10(14) cm(-2), an electric-field-induced transition from the-insulating state to the Metallic state was realized, due to both electron and hole doping. Out results suggest that black phosphorus will be a good candidate for the fabrication of functional devices, such as lateral p-n junctions and tunnel diodes, due to the intrinsic narrow band gap.