Improved contact resistivity and enhanced mobility of metal-graphene FET by inserting ultra-thin MoOx layer at source/drain region

Achieving low resistance contacts and high carrier mobility are common concerns for obtaining high performance of graphene devices. In graphene FETs (GFETs), the work functions (WF) of electrode materials and metal-graphene (M-G) contact configurations have remarkable influences on contact properties of M-G. In this work, the contact properties of Cu-G are improved prominently by inserting a nanoscale MoOx (x<3) ultra-thin layer formed by annealing Mo film in the air atmosphere at 150°C between the electrode and graphene in GFETs. Results show that MoOx can not only induce the p-doping, but also induce end contact to graphene characterized by Mo-C carbide formation from the XPS and TEM results. The relationship between the improvement of contact properties of M-G and the thickness of MoOx layer inserted at source/drain region was further investigated. It is shown that, within 0-3 nm thickness of MoOx, the thicker the MoOx deposited, the better the output characteristics and the greater the field mobilities are. The mechanism of that MoOx deposited at source-drain helps improving the carrier mobility is discussed and is related to improved interface between graphene and SiO2. This study provides a simple and important way to improve contact properties of M-G and carrier mobility of contact and graphene FET.