Van der Waals Integration of Tungsten Diselenide-Based Radio-Frequency Switches Exceeding GHz.

There is a lack of high-frequency electronics based on 2-dimensional p-type transitional metal dichalcogenides, which originates from channel defects during device fabrication and non-optimized metal-semiconductor-insulator interface. Direct metal deposition inevitably induces n-type dominant carrier transport, and high-k dielectric layers cause an elevated carrier concentration enhancing carrier-carrier scattering. Herein, taking tungsten diselenide (WSe2) as an example, we employ a polyvinyl alcohol (PVA)-assisted transfer of electrodes to realize WSe2 devices with a high carrier mobility and low hole concentration at the same time. This approach circumvents the interfacial defects and lattice distortions caused by atomic bombardment, cluster dynamics, and localized heating of the contact region during direct metal deposition. Compared to polymethyl methacrylate (PMMA) and other transfer media, the water-soluble PVA layer can be removed without organic solvents, leading to high-quality channel and ideal dielectric interface effectively, which suppress Coulomb impurity scattering and carrier-carrier scattering at low hole concentration (~3.5 × 1012 cm-2). This enables a carrier mobility exceeding 140 cm2 V-1 s-1 at room temperature, superior to other heavily doped counterparts. Radio-frequency switches fabricated by transferring a top electrode exhibit a cutoff frequency of 57.5 GHz with a low series resistance of 25 Ω. This realizes the path loss and signal integrity required by 6G communications, rendering WSe2 a highly promising candidate for millimeter-wave applications.