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

TL;DR

This study demonstrates ambipolar transport and an insulator-to-metal transition in black phosphorus using ionic-liquid gating, revealing potential for advanced electronic devices with tunable conductivity.

Contribution

It reports the first observation of an electric-field-induced insulator-to-metal transition in black phosphorus via ionic-liquid gating, highlighting its potential for functional electronic applications.

Findings

Ambipolar behavior with ON-OFF ratio of 5,000.

Band gap of 0.35 eV determined from transfer curve.

Achieved ultra-high carrier density of 10^14 cm^-2.

Abstract

We report ambipolar transport properties in black phosphorus using an electric-double-layer transistor (EDLT) configuration. The transfer curve clearly exhibits ambipolar transistor behavior with an ON-OFF ratio of 5*10^3. The band gap was determined as = 0.35 eV from the transfer curve, and Hall-effect measurements revealed that the hole mobility was ~ 190 cm^2/Vs at 170 K, which is one order of magnitude larger than the electron mobility. By inducing an ultra-high carrier density of ~ 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. Our 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.