Observations on Transport in Contacts to 2D Semiconductors Using Diverse Contact Structures

Most semiconducting nanomaterials would be perfect for use in nanoscale transistors if only the transport between metal contacts and the atomic-scale crystal could be mastered. Over the years, we (speaking both personally for my lab and collectively for the field) have cleaned, damaged, preserved, gapped, removed, and doped the 2D semiconductor beneath the source/drain top contacts – so, where does that leave us? While I won’t pretend to have a definitive answer to this question, I will offer a few observations based on work from my group. We have explored the impact of intentional damage to MoS₂ and WS₂ immediately prior to contact metal deposition, finding a benefit for few-layer films with a few seconds of ion beam exposure [1]. With further ion beam bombardment, we explored clean edge contacts to various 2D semiconductors that showed superb and consistent scalability, but at a notable cost to contact resistance [2] – a tradeoff that would have to be carefully managed. Finally, we discovered an intriguing asymmetry in the scaling of top contacts to MoS₂ that suggests greater scalability of the drain-side [3] – perhaps an asymmetry worth embracing for future 2D transistor technologies. There is so much more to understand and improve in the metal-2D contact interface; these observations will hopefully provide some insights for moving forward.<br/> <br/>[1] 2D Mater. 6:034005 (2019)<br/>[2] Nano Lett. 19:5077 (2019); IEEE Electron Device Lett. 42:1563 (2021)<br/>[3] Adv. Mater. 35:2210916 (2023)