Two-Dimensional Magnetotransport in a Black Phosphorus Naked Quantum Well

TL;DR

This study demonstrates the creation of two-dimensional hole gases in black phosphorus quantum wells, revealing independent 2-D electronic and atomic structures, with high mobility and quantum oscillations observed at high magnetic fields.

Contribution

We fabricated black phosphorus quantum wells with controlled thickness, suppressed oxidation, and observed 2-D hole gases via magnetotransport, showing 2-D electronic behavior independent of atomic layer thickness.

Findings

Observed Shubnikov-de Haas oscillations up to 35 T

Achieved field effect mobilities up to 600 cm$^2$/Vs

Demonstrated 2-D electronic structure in multilayer black phosphorus

Abstract

Black phosphorus (bP) is the second known elemental allotrope with a layered crystal structure that can be mechanically exfoliated down to atomic layer thickness. We have fabricated bP naked quantum wells in a back-gated field effect transistor geometry with bP thicknesses ranging from $6\pm1$ nm to $47\pm1$ nm. Using an encapsulating polymer superstrate, we have suppressed bP oxidation and have observed field effect mobilities up to 600 cm$^2$/Vs and on/off current ratios exceeding $10^5$. Importantly, Shubnikov-de Haas (SdH) oscillations observed in magnetotransport measurements up to 35 T reveal the presence of a 2-D hole gas with Schr\"odinger fermion character in an accumulation layer at the bP/oxide interface. Our work demonstrates that 2-D electronic structure and 2-D atomic structure are independent. 2-D carrier confinement can be achieved in layered semiconducting materials without necessarily approaching atomic layer thickness, advantageous for materials that become increasingly reactive in the few-layer limit such as bP.