Transport Properties and Device Prospects of Ultrathin Black Phosphorus on Hexagonal Boron Nitride

Abstract

Black phosphorus (BP) has re-emerged as a promising layered material with significant potential for future nanoelectronic applications. Several recent studies have demonstrated an improvement in the transport properties of BP channels when insulated from SiO2 substrates using hexagonal boron nitride (hBN) (or when fully encapsulated). This improvement is typically characterized using extractions of mobility based on the empirical relationship between conductivity and carrier density. However, this does not provide insight into the transport mechanisms, nor it allows accounting for differences in intrinsic (e.g., bandgap and effective mass) and extrinsic (e.g., trap density/distribution and Schottky barrier heights) properties in the analysis. Here, we present a modeling approach for Schottky-barrier MOSFETs with low-dimensional channel materials based on the Landauer theory. To analyze transport improvement in hBN-insulated BP channels we fabricate and measure BP Schottky-barrier-MOSFETs with and without the hBN insulating layer. Our analysis demonstrates ~80% improvement in low-field effective channel mobility and an (energy averaged) scattering mean free path that is >5 times larger for BP devices with an underlying hBN layer compared to devices with BP directly on SiO2.