Double carrier transport in electron doped region in black phosphorus FET

TL;DR

This study reports the observation of double carrier transport in highly electron-doped black phosphorus FETs, revealing complex conduction behavior linked to second subband occupation with high mobility.

Contribution

It demonstrates the existence of double carrier transport in black phosphorus FETs and links it to second subband occupation, advancing understanding of its electronic properties.

Findings

Hall mobility reaches 5400 cm2/Vs at 4.2 K in electron doped region

Anomalous shoulder in conductivity indicates second carrier emergence

Positive magnetoresistance and additional oscillations suggest second subband involvement

Abstract

The double carrier transport has been observed in thin film black phosphorus (BP) field effect transistor (FET) devices in highly electron doped region. BP thin films with typical thickness of 15 nm were encapsulated by hexagonal boron nitride (h-BN) thin films to avoid degradation by air exposure. Their Hall mobility has reached 5300 cm2/Vs and 5400 cm2/Vs at 4.2 K in the hole and electron doped regions, respectively. The gate voltage dependence of conductivity exhibits an anomalous shoulder structure in electron doped region. In addition, at gate voltages above the shoulder, the magnetoresistance changes to positive, and there appears an additional slow Shubnikov-de Haas oscillation. These results strongly suggest the appearance of the second carriers, which originate from the second subband with localized band edge.