Vertical Charge Transport and Negative Transconductance in Multilayer Molybdenum Disulfides

Abstract

Negative transconductance (NTC) devices have been heavily investigated for their potential in low power logical circuit, memory, oscillating, and high-speed switching applications. Previous NTC devices are largely attributed to two working mechanisms: quantum mechanical tunneling, and mobility degradation at high electrical field. Herein we report a systematic investigation of charge transport in multilayer two-dimensional semiconductors (2DSCs) with optimized van der Waals contact and for the first time demonstrate NTC and antibipolar characteristics in multilayer 2DSCs (such as MoS, WSe). By varying the measurement temperature, bias voltage, and body thickness, we found the NTC behavior can be attributed to a vertical potential barrier in the multilayer 2DSCs and the competing mechanisms between intralayer lateral transport and interlayer vertical transport, thus representing a new working mechanism for NTC operation. Importantly, this vertical potential barrier arises from inhomogeneous carrier distribution in 2DSC from the near-substrate region to the bulk region, which is in contrast to conventional semiconductors with homogeneous doping defined by bulk dopants. We further show that the unique NTC behavior can be explored for creating frequency doublers and phase shift keying circuits with only one transistor, greatly simplifying the circuit design compared to conventional technology.

High efficiency and fast van der Waals hetero-photodiodes with a unilateral depletion region

“…15 and Note 4). The light p-type conduction of thick MoS 2 here may be attributed to the impurities-induced doping effect or the defect-induced doping effect (e.g., S adatoms) 41,42 . The weak gate control is likely due to the thick MoS 2 channel.…”

Impact of Thickness on Contact Issues for Pinning Effect in Black Phosphorus Field‐Effect Transistors

“…Third, as BP thickness exceeds ≈10 nm, interlayer screening should be considered, which induces a interlayer resistant and forces the current flow in top layers. The current in top layer cannot be modulated by gate voltage, resulting in the reduction of mobility . Accordingly, there is a turning point at ≈10 nm BP in mobility‐thickness curve .…”

Black phosphorus electronics

“…Second, for BP thicknesses between $ 5 and 10 nm, the mobility seems to vary only slightly because the Fermi energy pinning effect dominates the contact resistance. Lastly, when the thickness of BP exceeds $10 nm, the trend of decresing mobility with increasing layer thickness begin to appear; that is, the interlayer resistance becomes a critical factor in current transport and limits the current flow in the top layers [45]. To further reveal the variation of SBH with BP thickness, the experimentally extracted SBH for different thickness BP FETs are presented in Fig.…”