Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

Abstract

In-plane heterostructures of transition metal dichalcogenides (TMDCs) have attracted much attention for high-performance electronic and optoelectronic devices. To date, mainly monolayer-based in-plane heterostructures have been prepared by chemical vapor deposition (CVD), and their optical and electrical properties have been investigated. However, the low dielectric properties of monolayers prevent the generation of high concentrations of thermally excited carriers from doped impurities. To solve this issue, multilayer TMDCs are a promising component for various electronic devices due to the availability of degenerate semiconductors. Here, we report the fabrication and transport properties of multilayer TMDC-based in-plane heterostructures. The multilayer in-plane heterostructures are formed through CVD growth of multilayer MoS2 from the edges of mechanically exfoliated multilayer flakes of WSe2 or Nb x Mo1–x S2. In addition to the in-plane heterostructures, we also confirmed the vertical growth of MoS2 on the exfoliated flakes. For the WSe2/MoS2 sample, an abrupt composition change is confirmed by cross-sectional high-angle annular dark-field scanning transmission electron microscopy. Electrical transport measurements reveal that a tunneling current flows at the Nb x Mo1–x S2/MoS2 in-plane heterointerface, and the band alignment is changed from a staggered gap to a broken gap by electrostatic electron doping of MoS2. The formation of a staggered gap band alignment of Nb x Mo1–x S2/MoS2 is also supported by first-principles calculations.

Single-Gate MoS2 Tunnel FET with a Thickness-Modulated Homojunction

“…In terms of gate controllability, density functional theory calculation 41 advocates the supremacy of out-of-plane heterostructures over their in-plane counterparts because the dangling bond (DB) states remain even after the perfectly bonded heterointerface is formed in in-plane heterostructures. Experimentally, the negative differential resistance (NDR) trend for the in-plane n-MoS 2 /p + -MoS 2 heterostructure grown using chemical vapor deposition method is just recently reported, 42 indicating that the effect of DB states may not be significant since NDR trends evidently indicate the smooth gate controllability between type II and type III band alignments. On the other hand, the advantage of out-of-plane vdW heterostructures is that any of 2D materials can be arbitrarily stacked with weak vdW force without considering the lattice mismatch.…”

Two-Dimensional Semiconductors and Transistors for Future Integrated Circuits

“…In 2022, TSMC and its cooperators developed a wafer-scale semiautomated dry transfer process for monolayer WS 2 utilizing the weakly coupled interface between semimetal Bi and 2D materials . Meanwhile, an in situ growth strategy based on chemical reactions has also been developed to prepare vertical vdWHs, − as well as in-plane heterostructures that are difficult to realize though mechanically lateral stitching. − In 2014, Ajayan’s group prepared vertical WS 2 /MoS 2 vdWHs using a one-step CVD growth strategy, as shown in Figure d. Meanwhile, by controlling the growth temperature, they also obtained in-plane WS 2 /MoS 2 heterostructures.…”

Anti‐Ambipolar Heterojunctions: Materials, Devices, and Circuits

“…Besides, these analyses also suggest that creating a highly ordered junction is essential for optimizing AATs performance in the future. [ 44 ] Overall, the carrier transport mechanisms or paths of anti‐ambipolar heterojunctions vary depending on the materials used, as reported in the literature. In most cases, 2D materials rely mainly on band‐to‐band vertical tunneling, while organic semiconductors most rely on drift‐diffusion transport or short‐through current in the lateral direction.…”