High-Performance WSe₂ Top-Gate Devices with Strong Spacer Doping

Abstract

Because of the lack of contact and spacer doping techniques for two-dimensional (2D) transistors, most high-performance 2D devices have been produced with nontypical structures that contain electrical gating in the contact regions. In the present study, we used chloroauric acid (HAuCl4) as a strong p-dopant for WSe2 monolayers used in transistors. The HAuCl4-doped devices exhibited a record-low contact resistance of 0.7 kΩ·μm under a doping concentration of 1.76 × 1013 cm–2. In addition, an extrinsic carrier diffusion phenomenon was discovered in the HAuCl4–WSe2 system. With a suitably designed spacer length for doping, a normally off, high-performance underlap top-gate device can be produced without the application of additional gating in the contact and spacer regions.

High-Photosensitivity WSe2 Phototransistor with Electrically Self-Isolated C8-BTBT as a Light Absorption Layer

“…Recently, two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS 2 , MoSe 2 , WS 2 , and WSe 2 , have attracted tremendous attention as next-generation semiconductors due to their fascinating electrical and optical properties. − The electrical properties of 2D TMD-based field effect transistors can be effectively and nondestructively tuned by coating various organic molecules on their surface due to surface charge-transfer doping or formation of heterostructures. − However, many previous reports found that this may result in an increase of both ON and OFF current, severely limiting the signal-to-noise ratio (SNR) when applied to photosensing applications (i.e., phototransistors). − An example of such an increase in OFF current after coating organic molecules on a 2D TMD-based transistor is shown in Figure S1. Therefore, the effective application of organic coatings on TMD-based phototransistors dictates that it is necessary to limit potential OFF current increases and act as a light absorption layer to improve the photosensitivity (i.e., SNR) of TMD-based phototransistors.…”

Lateral homojunctions of WSe2 through contact surface engineering with SF6 plasma etching

“…However, the ion-implantation, a processing widely used in silicon technology for precise doping, is of little use in doping ultrathin 2D semiconductors of layered transition metal dichalcogenides (TMDs), which has triggered noticeable research efforts towards alternative mechanisms. So far, various approaches such as chemical doping, 13 plasma doping, 14 metal contact doping [15][16][17] and spacer doping [18][19][20] have been explored to achieve different doping for lateral/vertical p-n homojunctions based on mechanically exfoliated WSe 2 or CVD-grown species.…”

Antimony–Platinum Modulated Contact Enabling Majority Carrier Polarity Selection on a Monolayer Tungsten Diselenide Channel

“…In general, TMDs are composed of transition metal atoms, such as tungsten (W) or molybdenum (Mo), that are sandwiched between two layers of chalcogen atoms, such as sulfur (S), selenium (Se), or tellurium (Te), by strong intralayer covalent bonding. Tungsten diselenide (WSe 2 ) has gained significant attention because of the direct band gap of ∼1.65–1.75 eV , and high electron and hole mobilities, − making it promising for complementary metal oxide semiconductor (CMOS) applications. − However, the position of the Fermi-level pinning (FLP), arising from the metal-induced gap states (MIGS) and interface traps, has been identified to be close to midgap at the metal–WSe 2 interface. , This FLP issue in metal contacts causes high Schottky barriers (0.5–0.6 eV) for both electron and hole transport in WSe 2 transistors . Among common metals studied in the literature, − palladium (Pd) contact was explored as a proper p-contact on WSe 2 because of its high work function, good oxidative stability, and better adhesion to 2D materials.…”