Gate-Tunable Hole and Electron Carrier Transport in Atomically Thin Dual-Channel WSe₂/MoS₂Heterostructure for Ambipolar Field-Effect Transistors

A new method that enables a dual-channel field-effect-transistor (FET) based on a vertically stacked heterostructure of ultrathin n-type MoS₂ and p-type WSe₂ layers for the study of parallel carrier transport was demonstrated. First, a MoS₂ layer was mechanically exfoliated on a SiO₂/Si substrate by the Scotch tape method. The electrodes were patterned by photolithography, followed by e-beam evaporation of Ti/Pt (15/10 nm). An exfoliated WSe₂ layer was transferred onto the device region by the poly(methyl methacrylate) (PMMA)-transfer method, resulting in the formation of a WSe2/MoS2 heterostructure and the contact of WSe₂ with the Pt electrode. To investigate the optical properties of the WSe₂/MoS₂ heterostructure, Raman spectroscopy was employed using a laser with a wavelength of 532 nm. To study the optoelectronic interactions in the heterostructure, photoluminescence (PL) measurements were performed using a laser with a wavelength of 514 nm. Before measurement of the dual-channel WSe₂/MoS₂ FETs, the single-channel FETs of MoS₂ and WSe₂ were separately measured to confirm the doping polarity in each channel material. The transfer characteristics of the single-channel MoS₂ (WSe₂) FET with Ti (Pt) electrodes showed n-type (p-type) unipolar transport. The vertically stacked p- and n-channel heterostructure reduces device fabrication complexities, specifically for ambipolar CMOS invertors. The dual-channel FET demonstrates novel optoelectrical applications of TMDs in stacked 2D materials to achieve highly dense electronics.