Substitutional W Doping of MoS2 for Threshold Voltage Control of Field Effect Transistor

Abstract

Two dimensional (2D) layered transition metal dichalcogenides (TMDCs) have attracted great attention owing to its excellent properties such as superior mechanical flexibility, transparency thermal stability, and compatibility to silicon CMOS processes. In particular, molybdenum disulfide (MoS2) has been extensively studied in recent years. MoS2 has been considered as attractive channel material for electronic switch device applications in the form of field-effect transistors (FETs) due to superior electrical properties such as thickness-dependent bandgap, high field-effect mobility, high current on/off ratio (>108), nearly ideal subthreshold swing (SS). Despite all the advantages of MoS2 as a promising candidate to replace silicon in such devices, large variations in the threshold voltage (Vth) of FET makes difficult it in practical application. The Vth of silicon-based semiconductor technology at the 22 nm technology node is 0.289 V for high performance logic and 0.413 V for low operating power logic. In contrast, values of Vth of back-gated MoS2 FETs being reported vary from −30 V to 40 V. In the case of Si-based FET, Vth can be easily tuned by doping through ion implantation. However, this method cannot be applied to MoS2 because energetic processes such as implantation, plasma easily cause damage to MoS2. In this study, we developed one-step doping process during chemical vapor deposition (CVD) of MoS2. electrical properties such as carrier density, bandgap and chemical composition tuned according to dopant concentration. In addition, Vth modulation of MoS2 was carried out by using substitutional doping of W. Vth of MoS2 FET has decreased by more than 10 V after doping.