Enhanced Performance of WS₂ Field‐Effect Transistor through Mono and Bilayer h‐BN Tunneling Contacts

Abstract

Transition metal dichalcogenides (TMDs) are of great interest owing to their unique properties. However, TMD materials face two major challenges that limit their practical applications: contact resistance and surface contamination. Herein, a strategy to overcome these problems by inserting a monolayer of hexagonal boron nitride (h‐BN) at the chromium (Cr) and tungsten disulfide (WS2) interface is introduced. Electrical behaviors of direct metal–semiconductor (MS) and metal–insulator–semiconductor (MIS) contacts with mono‐ and bilayer h‐BN in a four‐layer WS2 field‐effect transistor (FET) are evaluated under vacuum from 77 to 300 K. The performance of the MIS contacts differs based on the metal work function when using Cr and indium (In). The contact resistance is significantly reduced by approximately ten times with MIS contacts compared with that for MS contacts. An electron mobility up to ≈115 cm2 V‐1 s‐1 at 300 K is achieved with the insertion of monolayer h‐BN, which is approximately ten times higher than that with MS contacts. The mobility and contact resistance enhancement are attributed to Schottky barrier reduction when h‐BN is introduced between Cr and WS2. The dependence of the tunneling mechanisms on the h‐BN thickness is investigated by extracting the tunneling barrier parameters.

Self‐Forming p–n Junction Diode Realized with WSe2 Surface and Edge Dual Contacts

“…The output curves measured with the In surface contacts exhibited quasi-ohmic behavior that is typically observed with In surface contacts (Figure S3a, Supporting Information). In contrast, an unconventional conduction behavior was observed with the edge-contacted device (3)(4), as illustrated in Figure 2b. This configuration exhibited p-type polarity even though a low work function metal such as In was used, which reveals the influence of Fermi-level pinning of the edge-contacted WSe 2 .…”

“…Owing to the growing need to address scaling problems in electronics, transition metal dichalcogenides (TMDs) have been considered as next‐generation semiconductor materials with appropriate bandgap, inherent mobility, and optically ultralow thickness. [ 1–6 ] Despite the popularity of conventional Si‐based, complementary metal‐oxide‐semiconductor (CMOS) circuits, ultrathin TMD layers are promising channel replacements because they facilitate structural flexibility and miniaturization for the development of next‐generation transparent electronics. [ 7,8 ] Among the TMDs, tungsten diselenide (WSe 2 ), whose monolayer consists of one layer of W atoms sandwiched between two layers of Se atoms, exhibits excellent properties and outstanding potential for use in applications such as valley‐based electronics, [ 9,10 ] spin‐electronics, [ 11,12 ] and optoelectronics.…”

“…Owing to the growing need to address scaling problems in electronics, transition metal dichalcogenides (TMDs) have been considered as next-generation semiconductor materials with appropriate bandgap, inherent mobility, and optically ultralow thickness. [1][2][3][4][5][6] Despite the popularity of conventional Si-based, complementary metal-oxide-semiconductor (CMOS) which can affect the electrical properties of such diodes. [19,22] This method reduces the number of required fabrication steps, minimizing contamination during the processing.…”

MoTe2-Based Schottky Barrier Photodiode Enabled by Contact Engineering

“…At higher bias voltages, the probability of tunneling is increased as the barrier is reshaped from a trapezoid to a triangle, where the Fowler–Nordheim tunneling (FNT) is dominant, which can be described by the following equation − I = A q 3 m 0 V 2 2 m * normal⌀ normalB 8 π h normal⌀ normalB d 2 m * exp ( − 8 π d 2 m * ⌀ B 3 / 2 3 hqV ) …”

“…Our device shows Schottky contact at the barrier interface, and charge transfer across the barrier is dominant due to the tunneling behavior. At low bias voltages, direct tunneling (DT) is dominated, which can be approximated by the following equation − I = A q 2 V 2 m * normal⌀ normalB h 2 d exp ( − 4 π d 2 m * ⌀ B h ) …”