title: High-Performance p-Type Black Phosphorus Transistor with Scandium Contact.
abstract: A record high current density of 580 μA/μm is achieved for long-channel, few-layer black phosphorus transistors with scandium contacts after 400 K vacuum annealing. The annealing effectively improves the on-state current and Ion/Ioff ratio by 1 order of magnitude and the subthreshold swing by ∼2.5×, whereas Al2O3 capping significantly degrades transistor performances, resulting in 5× lower on-state current and 3× lower Ion/Ioff ratio. The influences of moisture on black phosphorus metal contacts are elucidated by analyzing the hysteresis of 3-20 nm thick black phosphorus transistors with scandium and gold contacts under different conditions: as-fabricated, after vacuum annealing, and after Al2O3 capping. The optimal black phosphorus film thickness for transistors with scandium contacts is found to be ∼10 nm. Moreover, p-type performance is shown in all transistors with scandium contacts, suggesting that the Fermi level is pinned closer to the valence band regardless of the flake thickness.
authors.affiliation: Department of Electrical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.affiliation: IBM T. J. Watson Research Center , Yorktown Heights, New York 10598, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Engel
authors.affiliation: IBM T. J. Watson Research Center , Yorktown Heights, New York 10598, United States.
authors.forename: Damon B
authors.initials: DB
authors.lastname: Farmer
authors.affiliation: IBM T. J. Watson Research Center , Yorktown Heights, New York 10598, United States.
authors.forename: Shu-Jen
authors.initials: SJ
authors.lastname: Han
authors.affiliation: Department of Electrical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: H-S Philip
authors.initials: HS
authors.lastname: Wong
keywords: black phosphorus; metal contact; moisture; scandium; transistor; vacuum anneal