Tungsten diselenide (WSe2) has emerged as a promising ambipolar semiconductor material
for field-effect transistors (FETs) due to its unique electronic properties, including a sizeable band
gap, high carrier mobility, and remarkable on–off ratio. However, engineering the contacts to WSe2
remains an issue, and high contact barriers prevent the utilization of the full performance in electronic
applications. Furthermore, it could be possible to tune the contacts to WSe2 for effective electron or
hole injection and consequently pin the threshold voltage to either conduction or valence band. This
would be the way to achieve complementary metal–oxide–semiconductor devices without doping
of the channel material.This study investigates the behaviour of two-dimensional WSe2 field-effect
transistors with multi-layer palladium diselenide (PdSe2) as a contact material. We demonstrate that
PdSe2 contacts favour hole injection while preserving the ambipolar nature of the channel material.
This consequently yields high-performance p-type WSe2 devices with PdSe2 van der Waals contacts.
Further, we explore the tunability of the contact interface by selective laser alteration of the WSe2
under the contacts, enabling pinning of the threshold voltage to the valence band of WSe2, yielding
pure p-type operation of the devices.