Construction and electrical performance improvement of MoS2 FET with graphene/metal contact

Abstract

A field effect transistor (FET) device of a MoS2/graphene vertical heterostructure material combined with the high carrier mobility of graphene material with a permanent band gap of monolayer MoS2 material, can realize the application of digital circuit. In this paper, the high-quality MoS2/graphene vertical heterostructure material can be synthesized by chemical vapor deposition (CVD) and wet transfer methods. The electron transfer, photoluminescence (PL) spectrum and carrier transport of MoS2/graphene heterostructure material can be characterized by microscope, Raman spectrometer, SEM, AFM and XPS, which can be used to judge the quality of the material. Besides, monolayer MoS2 and MoS2/graphene FETs can be prepared by lithography and electron beam evaporation, and the electrical performance is also tested and analyzed. The results show that the Schottky barrier height can be adjusted by the gate voltage and doped graphene. The photoexcited electron-hole pairs of monolayer MoS2 material can be separated by MoS2/graphene heterojunction when the gate voltage is zero, which would greatly decrease the PL characteristics. Compared to the MoS2/metal FET, the on-state current, switching ratio ,and drain current of MoS2/graphene FET are increased by an order of magnitude, the mobility and transconductance can also be increased, which can be explained by the smaller Schottky barrier height and the energy band rearrangement. Meanwhile, drain current exceeds 4×10−6A, which can also confirm the enhanced electronic characteristics of MoS2/graphene FET. Therefore, MoS2/graphene vertical heterostructure material can be applied to the ultra-high electronic device fields.