Analysis of Channel-Length Dependent Transport under Constant Electric Field Conditions with MOCVD-Grown Single-crystalline Monolayer MoS₂ FETs

The electrical characteristics of two-dimensional (2D) material field-effect transistors (FETs) have often been studied using exfoliated flakes or powder-CVD single crystals. However, these approaches typically exhibit large device-to-device variations, hindering reproducibility and systematic evaluation. To achieve a reliable and quantitative assessment of 2D material FETs, statistical analyses using high-quality, wafer-scale uniform films are essential. In this study, we realized a highly uniform single-crystalline monolayer MoS₂ film on a sapphire substrate via a self-aligned and self-limiting epitaxial growth mechanism. The correlations among channel length, drain current, and field-effect mobility under constant electric field conditions were elucidated by using 4-probe and transfer length method(TLM)-type FETs. 4-probe measurements revealed an intrinsic carrier mobility of ~ 50 cm²/Vs, confirming the high crystallinity of the film. By removing contact resistance effects through 4-probe or TLM analyses, the intrinsic electric field (Ed) across the channel was accurately estimated. Comparison of device performance under constant E_d conditions revealed that the drain current increased with decreasing channel length in the long-channel regime (L_ch = 50 μm - 3.5 μm), while it decreased in the short-channel regime (L_ch = 2 μm - 80 nm). The underlying mechanisms for the performance transition will be discussed in terms of the strain and defects induced by contact metals.