Intrinsic p-type Ohmic contacts in monolayer α-CNH: A strategy for overcoming the barriers challenge in 2D FETs

Realizing low-barrier p-type contacts is crucial yet highly challenging for two-dimensional (2D) semiconductor devices. Herein, based on density functional theory, we propose a strategy that leverages the intrinsic properties of the 2D semiconductor to achieve low-barrier p-type Ohmic contacts without introducing additional process complexity. Interfacial interactions and electronic-structure alignment with the electrode material further influence the contact properties. Specifically, we use monolayer α-CNH—a novel 2D semiconductor with a direct bandgap and high carrier mobility—as the channel material. We systematically investigate the electronic properties of metal-CNH contacts. The results show that most three-dimensional (3D) metal-CNH contacts achieve p-type quasi-Ohmic or Ohmic behavior. Such p-type Ohmic contacts, enabled by the inherent material characteristics, effectively suppress the Schottky barrier without introducing an additional tunneling barrier. Moreover, compared to 2D metal-CNH contacts, the 3D metal-CNH contacts exhibit smaller tunneling barriers. Quantum transport simulations further indicate that most of the investigated p-type transistors based on 3D metal-CNH contacts exhibit no lateral Schottky barrier. The strategy for realizing p-type Ohmic contacts demonstrated in our work offers new insights into material selection and contact design for achieving high-performance p-type 2D FETs.