First-Principles Study of Gate-Tunable Reversible Rectifying Behavior in 2D WGe₂N₄–TaSi₂N₄ Heterojunction Diodes: Implications for Logic Devices

Since the diode is one of the common electronic components in modern semiconductor electronics, realizing diodes with superior and controllable rectifying behaviors based on two-dimensional materials is important for next-generation electronics. Herein, gate-tunable in-plane (IP) and out-of-plane (OP) heterojunction diodes composed of the semiconductive WGe2N4 and metallic TaSi2N4 are reported based on first-principles calculations. The interfacial properties and rectifying characteristics of the IP and OP heterojunction diodes are systematically investigated. The results demonstrate that the Schottky barrier in the IP diode is much larger than that in the OP diode, resulting in a smaller current of the IP diode. The IP diode exhibits a much higher rectification ratio of 107 than the OP diode of 104 under the zero gate voltage. Noticeably, the rectifying behaviors of both diodes can be effectively modulated by the gate voltages. The positive gate voltages increase the current of IP and OP Schottky diodes and improve the rectification ratio to 109 and 105, respectively. Moreover, the negative gate voltage makes the rectifying direction of the OP Schottky diode reverse with a rectification ratio larger than 106. Our results provide a reference for designing superior two-dimensional diodes with controllable rectifying behaviors and pave the way for the design of logic devices in the future

Prediction of Semiconducting 2D Nanofilms of Janus WSi₂P₂As₂ for Applications in Sub‑5 nm Field-Effect Transistors

Searching for eligible two-dimensional (2D) semiconductors to fabricate high-performance (HP) short-channel field-effect transistors (FETs) at the nanoscale is essential toward the continuous miniaturization of devices. Herein, we predict the 2D Janus WSi2P2As2 semiconductor and propose it as a qualified channel material for sub-5 nm FETs by using first-principles calculations. The results demonstrate that the monolayer Janus WSi2P2As2 is a 2D semiconducting nanofilm with a band gap of 0.83 eV, a hole mobility of 490 cm2 V–1 s–1 in the armchair direction, and an out-of-plane polarization. Benefiting from these outstanding intrinsic characteristics, the performance of the 5 and 3 nm gate-length WSi2P2As2 FETs can fulfill the International Technology Roadmap for Semiconductors for HP standards after employing optimizing strategies, including underlap structure, dielectric project, and cold source. Our results promote the development of new 2D nanomaterials and device architectures for designing HP short-channel FETs

High-Performance Single-Molecule Switch Designed by Changing Parity of Electronic Wave Functions via Intramolecular Proton Transfer

Molecular switches, as one of the functional molecular components, play a vital role in nanoscale logic circuits. Here, the effect of intramolecular proton transfer on the current of single-molecule devices consisting of a keto or enol molecule sandwiched between two magnetic zigzag graphene nanoribbon (zGNR) electrodes is theoretically investigated. The keto and enol tautomers interconvert into each other by intramolecular proton transfer. The results show that the current of the keto molecular device is hardly observed, whereas that of the enol molecular device is significantly enhanced, demonstrating a highly efficient switching effect with the ON/OFF ratio up to 3.4 × 10². Moreover, spin currents of the device with an enol isomer display giant bipolar rectification, with the largest rectification ratio of 1.4 × 10⁵ when the two zGNR electrodes are antiparallely spin-polarized. The underlying mechanism is attributed to the parity matching principle of electronic wave functions in the core molecule and zGNR electrodes. The intramolecular proton transfer completely changes the parity of the electronic wave functions of the core molecule, and the electron tunneling channels around the Fermi energy are thus largely modified, resulting in a significant ON/OFF switching ratio. This work develops a strategy for designing high-performance single-molecule switches