Post-Treatment of Monolayer MoS₂ Field-Effect Transistors with H₂O Vapor: Alleviation of Remote Channel Doping

Atomic layer deposition (ALD) of high-k dielectric films on MoS 2 channels can lead to inadvertent remote electron doping of channels owing to nonequilibrium ALD conditions, such as the low temperatures and short purge times required for pinhole-free coating, as well as the weak physical adsorption of ALD precursors on MoS 2 . In this study, we propose the application of a simple and effective H 2 O vapor post-treatment (H 2 O PT) at 100 °C immediately after complete integration of bottom- and top-gate monolayer MoS 2 field-effect transistors (FETs), to address the inadvertent channel doping effect. When H 2 O PT was applied to bottom-gate monolayer MoS 2 FETs with an ALD-Al 2 O 3 passivation layer, the mitigation of channel doping was confirmed through electrical and optical measurements. Chemical analyses indicated that H 2 O PT alleviated the remote doping effect by reducing the number of C/H impurities and possible oxygen defects near the ALD-Al 2 O 3 /MoS 2 interface. These impurities and defects were associated with the incomplete reaction of the ALD precursor due to the nonequilibrium ALD used for the complete coating of Al 2 O 3 on MoS 2 . Applying H 2 O PT to top-gate monolayer MoS 2 FET arrays significantly narrowed the distributions of the threshold voltage and subthreshold swing. Moreover, it reduced the gate dielectric leakage current induced by the dielectric damage incurred during physical vapor deposition of the gate electrode. Finally, the time-dependent stability of top-gate monolayer MoS 2 FETs subjected to H 2 O PT was confirmed for at least two months in air.