Observation of tunable bandgap and anisotropic Dirac semimetal state in black phosphorus

TL;DR

This study demonstrates that potassium doping in black phosphorus enables a wide tunable bandgap and induces an anisotropic Dirac semimetal state, offering potential for advanced electronic and optoelectronic applications.

Contribution

We show that surface doping with potassium induces a giant Stark effect, enabling control over the bandgap and the realization of a tunable Dirac semimetal state in black phosphorus.

Findings

Dopant-induced bandgap tuning via the Stark effect.

Observation of a transition from semiconductor to Dirac semimetal.

Anisotropic Dirac dispersion in black phosphorus.

Abstract

Black phosphorus consists of stacked layers of phosphorene, a two-dimensional semiconductor with promising device characteristics. We report the realization of a widely tunable bandgap in few-layer black phosphorus doped with potassium using an in-situ surface doping technique. Through band-structure measurements and calculations, we demonstrate that a vertical electric field from dopants modulates the bandgap owing to the giant Stark effect and tunes the material from a moderate-gap semiconductor to a band-inverted semimetal. At the critical field of this band inversion, the material becomes a Dirac semimetal with anisotropic dispersion, linear in armchair and quadratic in zigzag directions. The tunable band structure of black phosphorus may allow great flexibility in design and optimization of electronic and optoelectronic devices.