High-Performance Black Phosphorus MOSFETs Using Crystal Orientation Control and Contact Engineering

We report high performance, orientation-controlled, and locally back-gated black phosphorus (BP) n-MOSFETs and p-MOSFETs with titanium and permalloy contacts, respectively. Devices with channel length ranging from 0.3 to $0.7~\mu \text{m}$ are analyzed. Armchair-oriented BP p-MOSFETs (n-MOSFETs) display 3.5 times (1.5 times) higher maximum current compared with zigzag devices. Saturated transconductance values up to 4.8 times (1.6 times) higher for BP p-MOSFETs (n-MOSFETs) oriented along the armchair direction compared with the zigzag direction are observed. Using this orientation control and contact engineering, n-MOSFETs with transconductance of $110~\mu \text{S}/\mu \text{m}$ and p-MOSFETs with contact resistance as low as 0.31 $\text{k}\Omega \cdot \mu \text{m}$ are demonstrated.