Ultrafast van der Waals diode using graphene quantum capacitance and Fermi-level depinning

Abstract

Graphene, with superior electrical tunabilities, has arisen as a multifunctional insertion layer in vertically stacked devices. Although the role of graphene inserted in metal-semiconductor junctions has been well investigated in quasi-static charge transport regime, the implication of graphene insertion at ultrahigh frequencies has rarely been considered. Here, we demonstrate the diode operation of vertical Pt/n-MoSe 2 /graphene/Au assemblies at ~200-GHz cutoff frequency (f C ). The electric charge modulation by the inserted graphene becomes essentially frozen above a few GHz frequencies due to graphene quantum capacitance–induced delay, so that the Ohmic graphene/MoSe 2 junction may be transformed to a pinning-free Schottky junction. Our diodes exhibit much lower total capacitance than devices without graphene insertion, deriving an order of magnitude higher f C , which clearly demonstrates the merit of graphene at high frequencies.

High-Field Electron Transport and High Saturation Velocity in Multilayer Indium Selenide Transistors

“…By contrast, 2D materials can retain their intrinsic electrical properties without compromising mobility, even at the ultimate scaling limit, due to their atomically thin nature. , The high-field transport properties and current saturation behavior of van der Waals (vdW) semiconductors have been rigorously studied for application to next-generation communication systems. − Graphene shows a high υ sat of up to 6 × 10 7 cm/s at room temperature (RT) and is a promising candidate for ultrahigh radio frequency (RF) transistors, but the zero band gap nature of graphene causes high off-current, limiting its application in integrated circuit technology. , 2D transition metal dichalcogenides (TMDCs), such as molybdenum disulfide (MoS 2 ) and tungsten disulfide (WS 2 ), show relatively low υ sat values of 3–6 × 10 6 and 3.8 × 10 6 cm/s, respectively, at RT, due to the high impurity scattering rates and corresponding low mobilities (generally <100 cm 2 /(V s)). − …”

Sachharomyces Cerevisae Dry Powder-Mediated Exfoliation of Graphite Chunks into Functionalized Few-Layer Graphene

“…Graphene is the simplest 2D material and owing to its exceptional properties, such as high thermal and electrical conductivity, large surface area, and mechanical stability, promises several potential applications, such as green energy production and storage. − However, to utilize graphene for large-scale applications, its synthesis/processing methods are of high importance and are constantly being examined for their scalability, ecofriendliness, and cost efficiency. , There are several reports on the green reduction of exfoliated graphene oxide to fabricate few-layer graphene sheets utilizing tea solution, plant extracts, and saccharides as reducing agents . Other sustainable approaches have been devised to prepare graphene-based materials derived from lignocellulosic biomass, industrial molasses waste, and fuel coke .…”

High Performance Indium–Tin–Oxide Schottky Diodes for Terahertz Band Operation

“…As a result, the pursuit of high-performance thin-film Schottky diodes, characterized by affordability and minimal thermal requirements, has emerged as a promising and focused area of research. Investigations have been undertaken employing a diverse range of thin-film semiconductor materials, including organic semiconductors, Si microparticles, two-dimensional (2D) materials, and oxide semiconductors (OSs). − However, the performance of these proposed technologies has thus far been constrained by various challenges, such as the limited mobility of thin-films, suboptimal contact due to the absence of efficient doping methods, and pronounced nonuniformity stemming from randomly distributed grain sizes. To surmount these obstacles, there exists a pressing need for ground-breaking advancements in material enhancement, process optimization, and innovative device architectures to realize thin-film Schottky diodes to meet future performance demands.…”