High-transconductance molybdenum disulfide top-gate transistors using epitaxial interface engineering

Abstract

High transconductance is a key performance metric in field-effect transistors, directly influencing voltage gain, switching speed and bandwidth. In two-dimensional field-effect transistors, achieving a high transconductance requires a low equivalent oxide thickness, scaled channel length and preserved carrier mobility—three factors that are difficult to optimize simultaneously. Reduced equivalent oxide thickness (less than 1 nm) can be achieved with high-κ-dielectric integration, but such scaling often introduces dielectric-related scattering that degrades mobility and limits transconductance. Here we show that an epitaxial interface engineering approach can be used to create monolayer molybdenum disulfide top-gate field-effect transistors with a high transconductance of 0.45 mS µm−1 at an equivalent oxide thickness of around 1 nm. We grow an epitaxial aluminium film directly on molybdenum disulfide in an ultrahigh vacuum, which is followed by in situ low-pressure oxidation to form an epitaxially derived aluminium oxide interfacial layer. This layer supports uniform integration of hafnium oxide and suppresses dielectric-induced scattering, leading to strong gate control without notable mobility degradation. Monolayer molybdenum disulfide top-gate field-effect transistors with a transconductance of 0.45 mS µm−1 at an equivalent oxide thickness of around 1 nm can be created with the help of an epitaxially derived aluminium oxide interfacial layer.