Band-hybridized selenium contact for p-type semiconductors

Abstract

Semimetals can establish a low-resistance contact to semiconductors by suppressing metal-induced gap states. Although semimetals like bismuth have enabled an ultralow contact resistance for n-type two-dimensional semiconductors by mitigating metal-induced gap states, achieving a similar performance for p-type two-dimensional counterparts remains a notable hurdle. Here we introduce an ultrathin selenium interfacial layer with the highest work function among elements, effectively reducing the Schottky barrier height at the interface. Critically, the selenium layer interacts with the gold electrode, inducing band hybridization that transforms the contact interface from a semiconductor to a semimetal. This semimetallic characteristic, with its low density of states near the Fermi level, suppresses the formation of detrimental metal-induced gap states within the semiconductor. Applying this band-hybridized semimetallic contact to p-type WSe2 transistors results in a reduction in contact resistance to 540 Ω μm. Furthermore, the devices achieve a saturated ON-state current density of up to 430 μA μm−1 with an 80-nm channel length. This methodology is highly transferable and can be readily applied to other p-type semiconductors, including black phosphorus and carbon nanotubes, offering a scalable and reliable pathway for establishing low-resistance electrical contacts to nanoscale p-type semiconductor devices.