Performance improvement of MoS2/graphene heterostructures based FET by tuning mobility and threshold voltage using APTES

Abstract

2D materials have been intensively explored because of their remarkable electrical properties, with a special focus devoted to the fabrication of lateral heterostructures. Two-dimensional materials like molybdenum disulphide (MoS₂) have been shown to make field effect transistors (FETs) with high current on–off ratios. However, carrier mobility in back gate MoS₂ FETs is often low (0.5–20 cm²/Vs), which limits the overall device performance. Here, we report a novel low Schottky barrier transistor based on graphene, MoS2 and Self-assembled monolayer (SAMS) that utilizes vertical heterostructures in which the channel is composed of MoS₂/graphene vertical heterostructures that uses graphene as the electrodes. Self-assembled monolayers of Aminopropyltriethoxysilane (APTES) serve a dual purpose, used for passivation and as an n-type dopant for MoS₂, significantly improving the electrical properties.

Our experimental and theoretical results show that, with the deposition of APTES on the substrate, there is an increase in mobility from 103 to 135 cm²/Vs, along with the reduction in the threshold voltage from 5.04 to 1.05 V, which is attributed to APTES passivation, which prevents electron trapping and de-trapping, a significant factor determining variation in threshold voltage (ΔV_TH). Density functional theory (DFT) calculations support the experimental results and demonstrate that the introduction of APTES doping in MoS₂ induces n-type doping in the material, hence improving the performance of the device. The combination of graphene electrodes along with the APTES passivation on substrate holds the promise for reliable and efficient synaptic applications in neuromorphic computing technologies, as well as next-generation complementary logic devices.