Chalcogen-Assisted Enhanced Atomic Orbital Interaction at TMD-Metal Interface and Sulfur Passivation for Overall Performance Boost of 2-D TMD FETs

Metal-semiconductor interface is a bottleneck for the efficient transport of charge carriers through transition metal dichalcogenide (TMD)-based FETs. Injection of charge carriers across such interfaces is mostly limited by the Schottky barrier at the contacts that must be reduced to achieve highly efficient contacts for carrier injection into the channel. Here, we introduce a universal approach involving dry chemistry to enhance atomic orbital interaction among various TMDs (MoS2, WS2, MoSe2, and WSe2) and metal contacts. Quantum chemistry among TMDs, chalcogens, and metals has been explored using detailed atomistic (DFT and NEGF) simulations, which is then verified using Raman, PL, and XPS investigations. Atomistic investigations revealed lower contact resistance due to the enhanced orbital interaction and unique physics of charge sharing between constituent atoms in TMDs with the introduced chalcogen atoms that are subsequently validated through experiments. In addition to contact engineering, which resulted in contact resistance (extracted via the Y-function method as low as 119 and in MoS2 and WS2, respectively), a novel approach to cure/passivate the dangling bonds present at the 2-D TMD channel surface has been demonstrated. While the contact engineering improved the ON-state performance of the 2-D TMD FETs by orders of magnitude, chalcogen-based channel passivation was found to improve gate control significantly. This resulted in an overall performance boost. The engineered TMD FETs were shown to have performance on par with the best reported until now.