Efficient Electrical Control of Thin-Film Black Phosphorus Bandgap

TL;DR

This paper demonstrates a practical method for electrically tuning the bandgap of intrinsic black phosphorus using moderate electric fields, revealing thickness-dependent properties and enabling new device applications.

Contribution

It introduces a direct electrical control technique for black phosphorus bandgap tuning, overcoming previous limitations requiring extremely high electric fields.

Findings

Achieved continuous bandgap tuning from ~300 meV to below 50 meV.

Discovered thickness-dependent bandgap tuning behavior.

Demonstrated effective tuning with moderate electric fields up to 1.1 V/nm.

Abstract

Recently rediscovered black phosphorus is a layered semiconductor with promising electronic and photonic properties. Dynamic control of its bandgap can enable novel device applications and allow for the exploration of new physical phenomena. However, theoretical investigations and photoemission spectroscopy experiments performed on doped black phosphorus through potassium adsorption indicate that in its few-layer form, an exceedingly large electric field in the order of several volts per nanometer is required to effectively tune its bandgap, making the direct electrical control unfeasible. Here we demonstrate the tuning of bandgap in intrinsic black phosphorus using an electric field directly and reveal the unique thickness-dependent bandgap tuning properties, arising from the strong interlayer electronic-state coupling. Furthermore, leveraging a 10-nm-thick black phosphorus in which the field-induced potential difference across the film dominates over the interlayer coupling, we continuously tune its bandgap from ~300 to below 50 milli-electron volts, using a moderate displacement field up to 1.1 volts per nanometer. Such dynamic tuning of bandgap may not only extend the operational wavelength range of tunable black phosphorus photonic devices, but also pave the way for the investigation of electrically tunable topological insulators and topological nodal semimetals.