Schottky-Barrier-Free vdW Contact in a 2D Penta-NiN2/Biphenylene Network Heterostructure

Schottky-barrier-free van der Waals (vdW) metal–semiconductor heterostructures hold great potential to overcome contact resistance problems in electronic devices with superior device functionality. However, a longstanding challenge in designing such heterostructures is finding materials with perfectly matched electronic energy levels and band alignments at the heterojunction interface. To address this challenge, we propose a novel vdW heterostructure composed of two-dimensional pentagonal nickel diazenide (penta-NiN2) [ACS Nano 15, 13539–13546 (2021)] and biphenylene network (BPN) [Science 372, 852–856 (2021)] monolayers, serving as a semiconducting channel and a metal electrode material at the heterojunction interface, respectively. Based on first-principles calculations, we find that the vertically stacked penta-NiN2 and BPN can form a commensurate heterostructure with a negligible lattice mismatch of 0.15%, and their intrinsic electronic features are well preserved, forming a vdW contact. More interestingly, we show that such stacking results in a Schottky-barrier-free p-type contact at the vertical interface, suggesting resistance-free hole transport across the heterojunction. Unlike conventional pentagon-based vdW stacks, the electronic energy bands of the heterostructure and semiconducting channel are well aligned at the lateral interface of the heterojunction. These results show that penta-NiN2/BPN could be a promising candidate for developing low-resistance and high-speed field-effect transistors and optoelectronic devices.