Integration of Ohmic contacts into van der Waals (vdW) heterostructures is critical for realizing electronic and optoelectronic functionalities. However, to date no scalable methodology for gaining electrical access to buried monolayer two-dimensional (2D) semiconductors exists. Here we report viable edge contact formation to hexagonal boron nitride (hBN) encapsulated monolayer MoS$_2$ for the first time. By combining reactive ion etching, $it in$-$it situ$ Ar$^+$ sputtering and annealing, we achieve a relatively low edge contact resistance (46 $pm$ 10 k$unicode[STIXGeneral,Times]{x3A9}cdotunicode[STIXGeneral,Times]{x3BC}$m), high mobility (up to ~30cm$^2$/Vs) and high on-current density (>50 $unicode[STIXGeneral,Times]{x3BC}$A$/unicode[STIXGeneral,Times]{x3BC}$m at $it V_{rm DS}$ = 3V), comparable to top contacts. Furthermore, the atomically smooth hBN environment also preserves the intrinsic MoS$_2$ channel quality during fabrication, leading to a steep subthreshold swing (116 mV/dec) with a negligible hysteresis. Edge contacts exhibit a higher electron transmission probability than top contacts, as revealed by our quantum transport simulations, and can be arbitrarily narrow, which opens the door to further shrinkage of 2D device footprint.
Published in: "arXiv Material Science".