Evaluation of Transport Parameters in MoS₂/Graphene Junction Devices Fabricated by Chemical Vapor Deposition

Abstract

We demonstrated imaging of the depletion layer in a MoS/graphene heterojunction fabricated by chemical vapor deposition and obtained their transport parameters such as diffusion length, lifetime, and mobility by using scanning photocurrent microscopy (SPCM). The device exhibited a n-type operation, which was determined by the MoS layer with a lower mobility. The SPCM revealed the presence of the depletion layer at the heterojunction, whereas graphene provided an excellent electrical contact for the MoS layer without resulting in a rectifying behavior, even if they were anchored within a very short range. The polarity of the photocurrent signal switched when we applied a drain-source bias voltage, from which we extracted the potential barrier at the junction. More importantly, a bias-dependent SPCM allowed us to simultaneously record the diffusion lengths of both majority and minority carriers for the respective MoS and graphene layers. By combining the diffusion lengths with the lifetimes measured by femtosecond SPCM, we determined the electron and hole mobilities in each layer, from which we found that the electron mobility (160 cm V s) was higher than the hole mobility (80 cm V s) in MoS, whereas the hole mobility (15 000 cm V s) was relatively higher in graphene.

Gate-tunable photodetector and ambipolar transistor implemented using a graphene/MoSe2 barristor

“…S4 and S5, respectively). Our device shows a high on/off ratio of 3.3 × 10 4 , which substantially exceeds those reported for pure graphene transistors (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). The barristor exhibits distinct ambipolar behavior and remarkably high carrier mobility values, specifically, an electron mobility of 247 cm 2 /V s and a hole mobility of 182 cm 2 /V s at room temperature.…”

“…The graphene/MoSe 2 junction was formed between the source and drain electrodes. A polydimethylsiloxane well was located between the side gate and the graphene/MoSe 2 channel and filled with an ion-gel dielectric for the SPCM measurements 19,20 .…”

Unconventional van der Waals heterostructures beyond stacking

“…In this way, the self-passivated synthetic GeS is superior to exfoliated GeS flakes; in addition, the functional properties of the GeS- a GeS 2 flakes are at least on par with materials derived from high-quality single crystals. For example, nanometer-scale CL spectroscopy shows minority carrier (electron) diffusion lengths in the p-type GeS core of ∼0.27 μm ( Sutter et al., 2019b ), comparable to the diffusion lengths in the highest-quality layered TMD semiconductors ( Cadiz et al., 2018 ; Kim et al., 2018b ).…”

Research on the Preparation and Spectral Characteristics of Graphene/TMDs Hetero-structures

“…The following describes the transfer-specific processes of monolayer graphene material to SiO 2 /Si substrate [29]. First, PMMA solution with a mass fraction of 4% was uniformly spin-coated on the surface of monolayer graphene material with a size of 1 cm × 1 cm, the rotation speed and time were 3000 R/min and 1 min, respectively.…”