Nickel-phosphide contact for effective Schottky barrier modulation in black phosphorus p-channel transistors

We demonstrate a new contact technology for realizing a near band edge contact Schottky barrier height (ΦB) in black phosphorus (BP) p-channel transistors. This is achieved via the use of high work function nickel (Ni) and thermal anneal to produce a novel nickel-phosphide (Ni2P) alloy which enables a record low hole ΦB of ∼12 meV. The formation of reactive Ni2P/BP contact was found to further improve the transmission probability as compared to the Ni/BP contact. Moreover, the penetration of Ni2P in the source and drain regions could additionally reduce the parasitic series resistance, leading to drive current improvement.