Improved Electrical Uniformity and Performance via Low-Cost Hybrid Wet Transfer Method for van der Waals Source/Drain Contact Formation in MoS₂ Field-Effect Transistors

Abstract

A hybrid wet transfer method for the fabrication of MoS2 field-effect transistor (FET) array is demonstrated by using polymethyl methacrylate (PMMA) support and hydrofluoric (HF) assistance, which significantly reduces the fabrication complexity and cost. The MoS2FET array is fabricated with amorphous HfO2 as a gate dielectric, undoped CVD monolayer MoS2 as a conduction channel, and Ag as source/drain (S/D) electrodes. Transmission electron microscopy, Raman spectroscopy, and photoluminescence spectrum confirm the integrity of the monolayer MoS2 film and the well-fit, damage-free interface between MoS2 and Ag or HfO2, demonstrating the feasibility of this transfer method. The FET exhibits an impressive on-off current ratio of up to $3.1 \times 10^{{8}}$ at a drain voltage ( ${V}_{\text {DS}}$ ) of 1 V and a substantial on-current up to $271 \; \mu $ A $\mu $ m $^{-{1}}$ at ${V}_{\text {DS}} = 3$ V and gate voltage = 5 V. The electrical measurements of 200 transistors show a low threshold voltage of 0.72 V with a standard deviation of 0.17 V and a high field-effect mobility of 69.9 cm $^{{2}}\cdot \text {V}^{-{1}}\cdot \text {s}^{-{1}}$ with a standard deviation of 9.8 cm $^{{2}}\cdot \text {V}^{-{1}}\cdot \text {s}^{-{1}}$ . Furthermore, the devices exhibit a low contact resistance of 1.49 k $\Omega \cdot \mu $ m with a standard deviation of 0.33 k $\Omega $ , indicating good electrical uniformity and exceptional performance for the Ag S/D electrodes.